PhD Abigail Metcalfe
email: abigail.metcalfe@uca.fr

Séverine Moune

Jean-Christophe Komorowski

Robert Robertson

EP Thomas E Christopher

R Joseph

Moretti

Severine Moune

Jean-Christophe Komorowski

Richard Robertson

Erouscilla P Joseph

Roberto Moretti

Elena Melekhova
email: elena.melekhova@earth.ox.ac.uk

Steve Sparks
email: steve.sparks@bristol.ac.uk

Jenni Barclay
email: j.barclay@uea.ac.uk

S Moune

J-C Komorowski

R Robertson

EP Joseph

J-C Komorowski

Diverse Magma Storage and Major and Volatile Magma Composition: What are the implications on the Eruptive Style Across a Volcanic Arc? An Example of the Lesser Antilles Arc

Keywords: Lesser Antilles, Geochemistry, Magma Storage, Eruption Style, Arc Volcanism, Melt Inclusions, Magma Mush, Volcanic Unrest, Volcanic Eruption Lesser Antilles, Geochemistry, Magma Storage, Eruption Style, Arc Volcanism, Melt Inclusions, Magma Mush, Volcanic Unrest, Volcanic Eruption Lesser Antilles, Geochemistry, Magma Storage, Eruption Style, Arc Volcanism, Melt 16 Inclusions, Magma Mush, Volcanic Unrest, Volcanic Eruption 17

ou non, émanant des établissements d'enseignement et de recherche français ou étrangers, des laboratoires publics ou privés.

magmas are likely to erupt explosively in the near future, given the unrest observed at many systems in the central arc. Despite the fact that advancements in science, technology and our understanding of volcanoes in the arc undoubtedly prevented large numbers of casualties in the late 20 th and 21 st centuries, large evacuations of people remain unavoidable. In some cases, evacuation becomes long term displacement and results in major socio-economic impacts. This highlights the need for future crises to be effectively managed so as to limit the socio-economic impacts and maintain the relationship between scientists, authorities and the population.

Declaration of interests ☒ The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.

☐ The authors declare the following financial interests/personal relationships which may be considered as potential competing interests:

13 geochemical signatures in comparison to the active Soufrière Hills Volcano. This indicates that isolated 398 melt bodies within the crystal mush result in a heterogenous system, which is vertically and laterally 399 extensive (Devine et al., 2003;[START_REF] Edmonds | Extensive, water-rich magma reservoir beneath southern Montserrat[END_REF].

400

As well as being chemically heterogenous, the Soufrière Hills system is thought to be composed of 401 layers of mush (solid and crystalline), liquid (sub-solidus, eruptible magma) and exsolved fluid layers

402

(volatiles exsolved from the magma on saturation; Christopher et al., 2015;[START_REF] Edmonds | Extensive, water-rich magma reservoir beneath southern Montserrat[END_REF]. The

403

presence of fluid layers with exsolved fluids, resulting from magma recharge, may lead to instabilities 404 in the mush system and may result in overpressures that could fuel explosive eruptions (Christopher 405 et al., 2015;[START_REF] Edmonds | Extensive, water-rich magma reservoir beneath southern Montserrat[END_REF]. The cyclicity observed in the vulcanian eruptions was thought to 406 be related to the ascent of different magma batches. The ascent of magma to the surface was 407 calculated to take 5 -13 hours, consistent with the 12-hour cyclicity of the Vulcanian eruptions.

408

Geochemistry, petrology (e.g., Christopher et al., 2015;[START_REF] Edmonds | Extensive, water-rich magma reservoir beneath southern Montserrat[END_REF] and geophysical studies

409

(e.g., Paulatto et al., 2012) show the mush system extends from <4 to 16 km, with the main active 410 reservoir between 8 -12 km (Paulatto et al., 2012;Christopher et al., 2015;[START_REF] Edmonds | Extensive, water-rich magma reservoir beneath southern Montserrat[END_REF]; Fig

413

In the Central Arc (Guadeloupe to Dominica) andesites are dominant, with some basalts and dacites 414 (Fig. 3; 4). St Lucia is more commonly included in the Southern Arc based on seismic data (Wadge and 415 [START_REF] Wadge | Segmentation of the Lesser Antilles subduction zone[END_REF], but fits into the Central Arc based on geochemistry and volcanology, so is also 416 discussed in this section. 417

Guadeloupe

418

The whole rock composition of La Soufrière de Guadeloupe eruption products have also remained 419 consistent, though they do span a wide range of compositions (51 -61 wt% SiO2;[START_REF] Touboul | 238U-230Th-226Ra disequilibria in andesitic lavas of the last magmatic eruption of Guadeloupe Soufrièrre, French Antilles: processes and timescales of differentiation[END_REF] 420 [START_REF] Boudon | A new scenario for the last magmatic eruption of La Soufrière of Guadeloupe (Lesser Antilles) in 1530 AD Evidence from stratigraphy radiocarbon dating and magmatic evolution of erupted products[END_REF]Samper et al., 2009;Ricci et al., 2017;Pichavant et al., 2018;Metcalfe et al., 421 2022). The 1530 CE sub-Plinian eruption (Komorowski et al., 2008;[START_REF] Boudon | A new scenario for the last magmatic eruption of La Soufrière of Guadeloupe (Lesser Antilles) in 1530 AD Evidence from stratigraphy radiocarbon dating and magmatic evolution of erupted products[END_REF]Esposti Ongaro 422 et al., 2020) shows black-and-white banded pumices with characteristic mixing and mingling textures 423 between andesitic (ca. 62 wt% SiO2) and basaltic-andesite (55 wt% SiO2) compositions (Semet et al., 424 1981;Poussineau, 2005;[START_REF] Boudon | A new scenario for the last magmatic eruption of La Soufrière of Guadeloupe (Lesser Antilles) in 1530 AD Evidence from stratigraphy radiocarbon dating and magmatic evolution of erupted products[END_REF]Pichavant et al., 2018). Deposits from the Echelle scoria 425 cone also show a bimodal composition, with mixing textures between basaltic andesite and dacitc 426 compositions observed. To the south of La Soufrière de Guadeloupe, the Mont Caraïbes complex 427 erupted a basaltic composition (47 -50 wt% SiO2) and is often interpreted to represent the parental 428 magma for La Soufrière de Guadeloupe [START_REF] Bissainte-Lubino | Le complexe des Monts Caraïbes de Guadeloupe (Arc des Petites Antilles) Etude pétrographique, minéralogique et géochimique[END_REF][START_REF] Metcalfe | Insights into the Origin and Dynamics of Past Eruptions of La Soufrière de Guadeloupe from Melt Inclusions: Implications for Future Unrest and Environmental Impact[END_REF]. Eruption products Mont can lead to eruption (e.g., [START_REF] Gourgaud | Magmatology of Mt. Pelée (Martinique, FWI). I: Magma mixing and triggering of the 1902 and 1929 Pelean nuées ardentes[END_REF]Murphy et al., 1998Murphy et al., , 2000;;Pichavant et al., 2002).

463 Pichavant et al. (2018) suggest, based on melt inclusion volatile concentrations and experimental data,

464

a minimum depth of the La Soufrière Guadeloupe magma reservoir between 5.6 and 7.1 km (135 -465 170 MPa, based on a density of 2450 kg m -3 ; [START_REF] Barnoud | 3-D linear inversion of gravity data: method and application to Basse-Terre volcanic island, Guadeloupe, Lesser Antilles[END_REF], and a maximum depth of 8.5 km 466

given the absence of amphibole phenocrysts in the juvenile eruptive products .

467 Moretti et al. (2020a) proposed a deep gas supply from a crystal mush conceptual model as used at 468 many similar systems to explain observations and activity (e.g., Cashman et al., 2017). This was refined

469

by Metcalfe et al. (2021Metcalfe et al. ( , 2022) ) to a vertically and laterally extensive mush system extending 6 -9 km 470 in depth (190 -220 MPa, based on a density of 2450 kg m -3 ; [START_REF] Barnoud | 3-D linear inversion of gravity data: method and application to Basse-Terre volcanic island, Guadeloupe, Lesser Antilles[END_REF], which hosts evolved 471 magmas (Fig 2). Remobilization of this mush system to produce eruptible magma may occur through 472 the injection of mafic magma from depth into the shallow system, resulting in magma mixing.

473

Alternatively, in eruptions where no mixing textures are observed (e.g., 1657 CE), exsolved fluids and

474

heat from magma at depth may allow remobilization with no interaction with a mafic magma.

475

Investigation of major and volatile elements of melt inclusions across several Holocene eruptions

476

shows the composition of the storage zone has remained stable during this time period (Metcalfe et 477 al., 2022). There is some evidence for a deeper storage zone, hosting less -evolved compositions based 478 on the presence of a basaltic parental magma (Monts Caraibes) and the basalt produced by the Echelle

479

and Citerne scoria cones (Bissante, 1999;[START_REF] Legendre | Reconstruction fine de l'histoire éruptive et scenarii éruptifs à la soufrière de Guadeloupe: vers un modèle intégré de fonctionnement du volcan[END_REF]Metcalfe et al., 2022). Bissainte (1999) 480 calculated crystallization pressures of 400 -900 MPa for Mont Caraïbes cumulates, which is equivalent 482 Moretti et al. (2020) show the mush system is the source of heat and deep magmatic fluids that rise

483

and contribute to the hydrothermal system. The heat and fluids supplied by intrusions into the mush 484 system below 5 km are considered to be one possible cause of seismic activity (White and McCausland,485 2016) and unrest episodes, as well as the potential cause of some of the more violent and long-lasting 486 historical non-magmatic phreatic activity produced from the long-lived hydrothermal system 487 [START_REF] Feuillard | The 1975-1977 crisis of La Soufrière de Guadeloupe (FWI): a still-born magmatic eruption[END_REF]Komorowski et al., 2005;Villemant et al., 2005;Rosas-Carbajal et al., 2015, 488 Moretti et al., 2020a). 489

Dominica 490

The whole rock composition of eruption products from Dominica ranges from 50 -67 wt% SiO2 491 (Lindsay et al., 2005;Howe et al., 2015;[START_REF] Boudon | Revised chronostratigraphy of recurrent ignimbritic eruptions in Dominica (Lesser Antilles arc): Implications on the behavior of the magma plumbing system[END_REF]d'Augustin et al., 2020), with no large-492 scale magma mixing or mingling textures reported (e.g., Howe et al., 2015;[START_REF] Boudon | Revised chronostratigraphy of recurrent ignimbritic eruptions in Dominica (Lesser Antilles arc): Implications on the behavior of the magma plumbing system[END_REF]Solaro 493 et al., 2020). The eruption products are relatively evolved within the LAA whole rock trend (Fig 3),

494

which is typical of the eruption products in the central arc. In comparison, the composition of MIs

808

Following the end of lava extrusion and the last collapse event which occurred on 11th February 2010,

809

the Hazard Level was lowered from Level 4 to Level 3 and a pause in the eruption began (MVO 810 Scientific Updates, 2010-21). This followed the previous pattern in the eruption where activity was 811 minimal between eruption phases. However, it is unclear how long this pause in activity will last.

812

Through 2010 seismicity and SO2 emissions continued, as well as minor incandescence on the dome 813 related to hot gasses from a deep source passing through fractures. The observed deformation pattern

814

showed slow inflation of the volcano, with ash venting and degradation of the lava dome observed 817

Activity remained at a low level in 2012 and was characterized by spots of incandescence on the lava 818 dome and continued fumarolic activity and seismic swarms. Peaks in activity were often associated 819 with ash venting, with significant ash venting observed in March 2012, resulting in the formation of a 820 new crater. Large VT events associated with the venting are interpreted to be related to increasing 821 pressure below the volcano from uprising magma, while the ash venting was interpreted to be 822 phreatic in origin (MVO Scientific Updates, 2010-21).

emissions. However, no changes to fumarolic activity or the dome were observed and in August 2014

825

the Hazard Level was lowered again to Level 1 (MVO Scientific Updates, 2010-21). Since 2017, activity 826 has remained low and consistent with short-lived seismic swarms and SO2 output generally at 200 -presence of new magma close to the surface and that the eruption was escalating rapidly (Marinelli, 858 1976;Brousse et al., 1977;Heiken et al., 1980). This observation had a major influence on the scientific 859 management of the crisis, though ultimately the material was identified as non-juvenile clasts 860 removed from a pumice fallout deposited during the 1530 CE eruption [START_REF] Boudon | A new scenario for the last magmatic eruption of La Soufrière of Guadeloupe (Lesser Antilles) in 1530 AD Evidence from stratigraphy radiocarbon dating and magmatic evolution of erupted products[END_REF] 861 Komorowski et al., 2008).

862

There is also some debate on the cause of this eruption with two models proposed. The more widely 863 accepted model relates the phreatic eruption to a 'still-born' magmatic event [START_REF] Feuillard | The 1975-1977 crisis of La Soufrière de Guadeloupe (FWI): a still-born magmatic eruption[END_REF].

864

Evidence for this model is provided by the depth of seismicity at ca. 6 km, consistent with the depth 865 of the magma reservoir and SO2 and Cl signatures which were magmatic in origin. The migration of 866 earthquake hypocentres from depth towards the shallower system over a few hours was also 867 observed and considered to support this model [START_REF] Feuillard | The 1975-1977 crisis of La Soufrière de Guadeloupe (FWI): a still-born magmatic eruption[END_REF]Villemant et al., 2005;Boichu 868 et al., 2011;Li et al., 2016). Ruzié et al. (2012) suggest new magma is being continuously injected into 869 a shallow magma reservoir at ca. 6 km based on modelling of the flux of noble gas isotopes ( 4 He/ 3 He; 870 R/Ra) in hydrothermal fluids and on petrological analysis of the 1530 CE eruption deposits (Semet et 871 al., 1981;Pichavant et al., 2018). Magmatic gases are buffered by the hydrothermal system but an 872 increase in heat flux and migration of chemically reactive fluids in the hydrothermal system are 873 responsible for the sealing of the host-rock and resulting pressurization of the system leading to the 874 phreatic activity observed. The injection of magma into the reservoir is interpreted as the triggering 875 source of several unrest episodes in La Soufrière de Guadeloupe's history including new pulses in 876 1992, 1997-1998 (Villemant et al., 2014) and 2018 (Moretti et al., 2020).

877

However, Zlotnicki et al. (1992) proposed that new magma arrival is not required for a phreatic 878 eruption to occur. Therefore, hydrothermal activity alone, with deposition of impermeable clay 879 minerals that seal of fractures combined with high fluid circulation can result in pressurization of 880 aquifers and phreatic eruption. Moune et al. (2022) also discuss this model for generating phreatic 881 eruptions in the context of the more recent unrest. Independent of the exact mechanism required to 882 generate the phreatic event of 1976-77, all gas data and the hydrothermal fluid C, He and Cl isotopic 883 ratios indicate a persistent magma reservoir degassing and supplying fluids and heat to the shallow 884 hydrothermal system (Brombach et al., 2000;Ruzié et al., 2012;2013;[START_REF] Allard | Steam and gas emission rate from La Soufriere volcano, Guadeloupe (Lesser Antilles): implications for the magmatic supply during degassing unrest[END_REF]; Jean-Baptiste 885 et al., 2014;Villemant et al., 2014;Tamburello et al., 2019;Inostroza et al., 2022a, b;Moretti et al., 886 2020a, b;Moune et al., 2022).

887

Following the 1976-77 eruption, monitoring of this volcano was increased to include continuous 888 seismic and geodetic monitoring (using global navigation satellite system; GNSS), gas plume 889 monitoring, meteorological networks, periodic extensometric surveys of lava dome fractures, 890 fumarole gas and thermal spring sampling and thermal monitoring (OVSG-IPGP, 1999[START_REF] Joseph | 14 submarine eruptions have also occurred from Kick[END_REF] five years fumarolic activity extended at the summit, and then more recently along its eastern flanks,

897

and to the top of the lava dome with the reactivation of three fumaroles (OVSG-IPGP, 1999-2021; 898 Komorowski et al., 2005;Tamburello et al., 2019;Jessop et al., 2021). Late 1997 and early 1998 marked 899 the onset of highly acidic chlorine-rich fluids degassing, which has continued till present day 900 (Komorowski et al., 2005;OVSG-IPGP, 1999[START_REF] Joseph | 14 submarine eruptions have also occurred from Kick[END_REF]Villemant et al., 2014;Moretti et al., 2020a,b).

901

Seismic activity is characterised by numerous, low magnitude (M <1), high-frequency volcano-tectonic 902 earthquakes which have been observed to increase in frequency and rate with twenty felt volcanic 903 earthquakes since 1992, including ten since 2013 (Komorowski et al., 2005;Moretti et al., 2020a).

904

Between April 2017-December 2018 unrest reached the highest level since 1976-77 (Moretti et al.,

908

Changes in gas chemistry were also detected before and after the April 2018 earthquake. Low CO2/H2S 909 and SO2/H2S ratios were observed until November 2017 when a strong chemical perturbation 910 occurred. Perturbations at the time of the earthquake resulted in high SO 2 /H2S, CO2/CH 4 , H2 /H2O and

911

CO/CO 2 and He/CH 4 recorded by MultiGas and Giggenbach bottles (Moretti et al., 2020a,b;Moune et 912 al., 2022). From June to December 2018 a decrease in SO2/H2S and CO2/H2S ratios was then observed.

913

These ratios indicate a pulse of fluid with deep hydrothermal/magmatic origin heated and pressurised 914 the hydrothermal system (Moretti et al., 2020a).

915

This episode period of accelerating unrest is interpreted as a failed phreatic eruption triggered by the 916 ascent of heat and fluids from the deep hydrothermal and magmatic system to shallow depths 917 (Moretti et al. 2020). Two hypotheses are formulated by Moretti et al. (2020a): [START_REF] Wallace | Melt inclusion CO2 contents, pressures of olivine crystallization, and the problem of shrinkage bubbles[END_REF] The deep magmatic

918

fluids, stored at mid-to low-crustal depths in the mush system, generated an upstreaming of 919 magmatic gases through the mush system and the crystallizing magma reservoir. This process leads 920 to cyclic rejuvenation of the magma and exsolution of dissolved volatiles that are released into the

921

hydrothermal system and cause heating and pressurisation.

[2] Episodic fresh injections of basaltic 922 magma from mid-crustal depths into the shallow magma reservoir of La Soufrière de Guadeloupe,

29

pressure magmatic fluids into the hydrothermal system. This causes heating and pressurisation that 925 may exceed the tensile strength of the rocks and lead to a phreatic eruption.

926

However, for both hypotheses, Moretti et al. (2020a) show that the multiparameter unrest data

933

below the summit) resulting from stalled small intrusions (Villemant et al., 2014), or injections of fresh

934

undegassed magma from depth resupplying the shallow magma storage zone of the upper mush

935

system.

936

Measurements of temperature and mass flux at fumaroles and thermal springs and ground

937

temperature measurements shows that between 2010 and 2020 widespread ground heating of the

938

summit occurred with an increase of the heat output from 0.2 ± 0.1 MW to 5.7 ± 0.9 MW (Jessop et

945

Guadeloupe is one of the most intense heat emitters globally among volcanic domes with an active

946

hydrothermal system (Jessop et al., 2021).

947

Looking more closely at the long term unrest at La Soufrière de Guadeloupe, particularly at the rate

948

of fracture opening and evolution of the permeability of the system through degassing and gas ratios,

952

the release of the seal which prevented escalation to a phreatic eruption (Zlotnicki et al., 1992;Moune 953 et al., 2022). Despite this, the cycle of sealing and reopening of fractures and transfer of heat from a 954 lower aquifer, to an upper one (with high fluid circulation) raises concerns for a future phreatic 955 eruption (Zlotnicki et al., 1992;Moune et al., 2022). As the shallow hydrothermal system is hosted in

956

the hydrothermally altered core of the dome (Heap et al., 2021a;2021b;2022a;2022b), any

957

pressurisation may reduce friction and increase pore pressure along mechanically weak pre-existing 958 consequences (e.g., Peruzzetto et al., 2019;Heap et al., 2021b). Such edifice collapses could occur 960 without the involvement of magma, as observed in the La Soufrière de Guadeloupe stratigraphic 961 record (Komorowski et al., 2005;Rosas-Carbajal et al., 2016). These collapses are associated with 962 moderate laterally directed explosions (up to VEI2) that can generate turbulent pyroclastic density 963 currents of limited extension (< 5 km) as described for the 1797-1798, 1836-1837, and 1976-1977 964 phreatic eruptions (Komorowski et al., 2005;Rosas-Carbajal et al., 2016).

967

the highest concentrations of active volcanoes in the world (Lindsay et al. 2005;Mayer et al., 2017).

968

These volcanoes have produced the highest erupted magma volume in the LAA (40 km 3 ; Wadge 1984; 969 1986; Macdonald et al., 2000; Di Napoli et al. 2014; Mayer et al., 2017). Only one recent eruption is 970 recorded on Dominica, but unrest in the form of seismicity and hydrothermal activity has been

971

recorded for the nine volcanic centres. The Valley of Desolation-Boiling Lake area is one of the more

972

active centres and experiences vigorous hydrothermal activity (Sapper 1903;Robson and Wilmore 973 1955;Lindsay et al., 2005;Mayer et al., 2017) and is monitored regularly by UWI-SRC.

974

The two most recent eruptions on Dominica have occurred from the Valley of Desolation-Boiling Lake

975

area in 1880 and 1997, with neither eruption witnessed (Lindsay et al., 2005;Fig 1). The 1880 eruption

976

was a large phreatic eruption with ash covering 55 km 2 , resulting in a slight ash fall 19 km out to sea

977

and the generation of lahars (Nicholls et al., 1880b). In comparison, the phreatic eruption occurring 978 on 8 th -9 th July 1997 was very small magnitude, however, as this eruption was unobserved little is 979 known about the dynamics. Subsequent investigation reported non-altered lava, hydrothermally 980 altered igneous minerals and hydrothermal minerals present [START_REF] Komorowski | Analytical results and report on the current activity of the Soufrière area as of December 8-9 1998[END_REF].

981

This eruption may have been triggered by the occurrence of several landslides. Fumarolic vents were

982

observed to be covered by landslide deposits, which has been hypothesised to have resulted in

983

pressurization of the hydrothermal system and produced a phreatic eruption (James, 1997; 984 [START_REF] Komorowski | Analytical results and report on the current activity of the Soufrière area as of December 8-9 1998[END_REF]Lindsay et al. 2005;Mayer 2017). The Boiling Lake itself 985 experiences considerable water level and temperature variations and experienced a small explosion 986 of CO2 and other gases in 1901, killing two people (Ober 1880;James 1988).

987

Activity at the other complexes varies greatly, with the majority of seismic and hydrothermal activity

988

occurring on the south of the island (Lindsay et al., 2005;Fig 1). The Plat Pays volcanic complex, which 989 is mainly comprised of lava domes, experiences a high number of seismic swarms and fumarolic 990 activity, this complex was active as recently as 450 years ago. Also, in the south of the island are the Morne Anglais and Morne Watt complexes which have a history of explosive eruptions and experience 992 regular seismic swarms (Lindsay et al., 2005;Fig 1). One of the potentially most dangerous complexes 993 is the Wotten Waven complex, which has a history of large explosive eruptions and produced the 994 Roseau Tuff. This complex experiences hydrothermal and fumarolic activity and a future explosive 995 eruption has the potential to affect most of Dominica (Lindsay et al., 2005).

996

In the north of the island the Morne Diablotins and Morne Aux Diables complexes also experience 997 considerable periods of unrest (Fig 1). Though no historical eruptions are recorded from these 998 complexes, and the majority of seismicity occurs in the south of the island, several periods of increased 999 seismic activity have been recorded in 1841, 1893, 2000and 2003(Lindsay et al., 2005)).

Finally, the Trois Pitons and Grand Soufriere Hills complexes are the least active complexes and have no evidence for recent eruptions (Lindsay et al., 2005;Fig 1). However, they are poorly studied and do still experience periods of increased seismic activity. The eruptive record is poorly understood, particularly at Grand Soufriere Hills, and until new data is available on the eruptive history, the complex is considered active (Lindsay et al., 2005).

All of Dominica's volcanoes are at the green volcanic alert level and continue to be monitored (UWI

SRC

Montagne Pelée, Martinique

The eruptive record of Montagne Pelée shows a history of sub-Plinian to Plinian and dome-forming eruptions (Westercamp and Traineau, 1983;Carazzo et al., 2012;Michaud-Dubuy, 2019;[START_REF] Michaud-Dubuy | Impact of wind direction variability on hazard assessment in Martinique (Lesser Antilles): The example of the 13.5 ka cal BP Bellefontaine Plinian eruption of Mount Pelée volcano[END_REF][START_REF] Boudon | What factors control superficial lava dome explosivity?[END_REF][START_REF] Boudon | Volcanological evolution of Montagne Pelée (Martinique): A textbook case of alternating Plinian and dome-forming eruptions[END_REF]. Many of the 8 Plinian eruptions of the last 9000 years at Montagne Pelée (e.g., P1 eruption at ca. 1350 CE; P2 eruption at ca. 330 CE, P3 eruption at ca. 79 CE) are thought to be associated with 20 -30 km high columns which underwent collapse and produced pyroclastic density currents (Carazzo et al., 2012(Carazzo et al., , 2019(Carazzo et al., , 2020;;[START_REF] Michaud-Dubuy | Impact of wind direction variability on hazard assessment in Martinique (Lesser Antilles): The example of the 13.5 ka cal BP Bellefontaine Plinian eruption of Mount Pelée volcano[END_REF]. At least 5 of the numerous phases of eruptions in the last 2000 years are associated with lava dome growth and collapse (Carazzo et al., 2019(Carazzo et al., , 2020;;Michaud-Dubuy, 2019;[START_REF] Boudon | Volcanological evolution of Montagne Pelée (Martinique): A textbook case of alternating Plinian and dome-forming eruptions[END_REF] along with violent laterally directed explosions at the base of the dome. These explosions produced devastating, highly energetic and mobile pyroclastic density currents with a laterally spreading, dilute flow, as well as valley-channelled denser flows [START_REF] Lacroix | La Montagne Pelée et ses éruptions[END_REF]Perret, 1935;[START_REF] Boudon | Martinique[END_REF][START_REF] Boudon | Volcanological evolution of Montagne Pelée (Martinique): A textbook case of alternating Plinian and dome-forming eruptions[END_REF] as exemplified by one of the world's most devastating eruptions that occurred on 8 th May 1902.

Prior to this eruption, a repose period of three centuries was observed. This was then interrupted by two short-lived phreatic eruptions in 1792 and 1851-52 (Tanguy, 1994;[START_REF] Boudon | Martinique[END_REF]. Following these minor eruptions activity, a new period of unrest began in 1889 in the form of renewed fumarolic activity reaching a peak in 1902 (Chrétien, 1983;Chrétien and Brousse, 1988;[START_REF] Boudon | Martinique[END_REF].

Seismic activity also increased, inferred from the breaking of submarine cables due to submarine landslides and mudflows and the increasing number of earthquakes felt by the population of St Pierre.

The onset of eruptive activity began with phreatic eruptions on 23 rd -25 th April 1902 which increased in intensity and transitioned to phreatomagmatic activity, perhaps as early as the 2 nd or 3 rd May.

Activity transitioned to magmatic activity on the night of 5 th May, and a large glowing dome was seen on the night of 6 th -7 th May 1902, and continued to grow rapidly [START_REF] Lacroix | La Montagne Pelée et ses éruptions[END_REF]Tanguy, 1994;Tanguy, 2004;[START_REF] Boudon | Martinique[END_REF][START_REF] Boudon | Volcanological evolution of Montagne Pelée (Martinique): A textbook case of alternating Plinian and dome-forming eruptions[END_REF].

The rapid rise of pressurized hot hydrothermal fluids and groundwater led to the sudden drainage of the summit crater lake, causing devastating lahars that killed 23 people on 5 th May 1902 in St Pierre.

Continuing explosive phreatomagmatic activity triggered new lahars during the night of 7 -8 th May that destroyed the town of Le Prêcheur killing another 400 people (Tanguy, 1994). Sudden

decompression of the over-pressurised and rapidly growing lava dome resulted in a small vertical column but a large laterally-directed explosion on 8th May 1902 [START_REF] Lacroix | La Montagne Pelée et ses éruptions[END_REF]Tanguy, 1994;[START_REF] Boudon | The 1902 péléean deposits in the Fort Cemetery of St. Pierre, Martinique: A model for the accumulation of turbulent nu´ees ardentes[END_REF][START_REF] Boudon | Reply. The May 1902 eruptions of Mount Pelée: high-velocity directed blasts or column-collapse nu´ees ardentes ?[END_REF][START_REF] Boudon | Martinique[END_REF][START_REF] Boudon | Volcanological evolution of Montagne Pelée (Martinique): A textbook case of alternating Plinian and dome-forming eruptions[END_REF]. This produced a very mobile pyroclastic density current which expanded rapidly and moved across topographic ridges as a high-energy, low-density pyroclastic surge [START_REF] Boudon | The 1902 péléean deposits in the Fort Cemetery of St. Pierre, Martinique: A model for the accumulation of turbulent nu´ees ardentes[END_REF][START_REF] Boudon | Reply. The May 1902 eruptions of Mount Pelée: high-velocity directed blasts or column-collapse nu´ees ardentes ?[END_REF][START_REF] Bourdier | Stratigraphy of the 1902 and 1929 nuée ardente deposits, Montagne Pelée, Martinique[END_REF]. More concentrated block-and-ash pyroclastic flows rich in solid material from the dome were channelled in numerous valleys down to the coast. These high-velocity and highly turbulent surges caused the complete destruction of St Pierre and the death of 28,000 people on 8 th May 1902 [START_REF] Lacroix | La Montagne Pelée et ses éruptions[END_REF]Tanguy, 1994;Tanguy, 2004;[START_REF] Bourdier | Stratigraphy of the 1902 and 1929 nuée ardente deposits, Montagne Pelée, Martinique[END_REF][START_REF] Boudon | The 1902 péléean deposits in the Fort Cemetery of St. Pierre, Martinique: A model for the accumulation of turbulent nu´ees ardentes[END_REF][START_REF] Boudon | Reply. The May 1902 eruptions of Mount Pelée: high-velocity directed blasts or column-collapse nu´ees ardentes ?[END_REF][START_REF] Boudon | Martinique[END_REF][START_REF] Brown | Volcanic fatalities database: analysis of volcanic threat with distance and victim classification[END_REF]Gueugneau et al., 2020;[START_REF] Boudon | Volcanological evolution of Montagne Pelée (Martinique): A textbook case of alternating Plinian and dome-forming eruptions[END_REF].

Following this deadly phase, activity remained high but intermittent with strong vertical eruptions and further concentrated, high-energy, turbulent pyroclastic density currents which again affected St Pierre on 20 th and 26 th May, 6 th June, 9 th July and 30 th August 1902. The 30 th August flow destroyed the towns of Morne Rouge and Ajoupa Bouillon which caused an additional 1500 -2000 deaths [START_REF] Brown | Volcanic fatalities database: analysis of volcanic threat with distance and victim classification[END_REF]. During this explosive phase, a vertical Vulcanian explosion on 9th July occurred on the lava dome, producing a small volume pumiceous fallout and an eruption column that collapsed to generate a concentrated, channelised pyroclastic density current [START_REF] Boudon | The 1902 péléean deposits in the Fort Cemetery of St. Pierre, Martinique: A model for the accumulation of turbulent nu´ees ardentes[END_REF][START_REF] Bourdier | Stratigraphy of the 1902 and 1929 nuée ardente deposits, Montagne Pelée, Martinique[END_REF][START_REF] Boudon | Reply. The May 1902 eruptions of Mount Pelée: high-velocity directed blasts or column-collapse nu´ees ardentes ?[END_REF]2005;[START_REF] Boudon | Volcanological evolution of Montagne Pelée (Martinique): A textbook case of alternating Plinian and dome-forming eruptions[END_REF]. Following this initial explosive phase, the eruption proceeded until 1905 with effusive dome and lava spine growth (Tanguy, 1994;[START_REF] Boudon | Martinique[END_REF][START_REF] Boudon | Volcanological evolution of Montagne Pelée (Martinique): A textbook case of alternating Plinian and dome-forming eruptions[END_REF]. This continued to produce numerous block-and-ash pyroclastic density currents from gravitational dome collapse. The currents were channelled in valleys to the south and south-west of the volcano without overflowing.

This 1902-1905 eruption highlights the long periods of unrest which can be observed preceding an eruption, in this case unrest began in 1889 and continued to build to a magmatic eruption in 1902, 13 years after the onset of phreatic unrest. In comparison, the less destructive eruption of 1929 had only a couple of months of felt unrest, yet followed a similar sequence of events as the 1902 eruption. The 1929 eruption began with phreatic eruptions followed by the main explosive magmatic phase, which was followed by dome building activity and then a decrease in activity until the eruption ended in 1932 [START_REF] Bourdier | Stratigraphy of the 1902 and 1929 nuée ardente deposits, Montagne Pelée, Martinique[END_REF]. This eruption was less powerful compared to the 1902 eruption, and as a result the impact on Martinique was much less severe [START_REF] Bourdier | Stratigraphy of the 1902 and 1929 nuée ardente deposits, Montagne Pelée, Martinique[END_REF].

As with the current Soufrière Hills Volcano, Montserrat eruption (1995 -ongoing), the 20 th century eruptions of Montagne Pelée eruption also provides an account of transition in styles with phreatic and explosive and effusive magmatic activity observed during one eruption. Finally, the 1902 eruption in particular, reminds us of the continuing hazards posed by active LAA volcanoes.

Montagne Pelée is currently experiencing a new phase of volcanic unrest which began in late December 2018. This was observed by the network which recorded a swarm of 17 deep, distal, volcano-tectonic (VT) earthquakes (the hypocentral distance is ≤ 25 km, depth between 10-20 km below sea level) as well as a swarm of shallow-depth (down to 4 km depth) volcano-tectonic earthquakes located on the volcano [START_REF] Fontaine | Report on Pelee (France)[END_REF]2022). At the time the distal VT seismicity had not been entirely recognized as being of volcanic origin. Therefore the shallow-depth VT seismicity was interpreted as evidence for a reactivation of the hydrothermal systems, which is not necessarily associated with the arrival at depth of magmatic fluids.

In November 2020, the seismic unrest accelerated with respect to the rate and energy of shallowdepth, proximal VT seismicity but also, for the first time, of low frequency, volcanic seismicity.

Together this indicated the onset of an increased circulation of pressurized hydrothermal fluids. This unprecedented volcanic unrest prompted the Observatoire Volcanaologique et Sismologique de Martinique (OVSM-IPGP) to recommend an increase to the yellow volcanic alert level to the authorities in charge of civil protection. This was implemented by the authorities on 4 th December 2020 (OVSM-IPGP, 2020-2022). In addition, 41 hybrid and 25 long-period seismic signals have been recorded up to the time of writing on 1 st September 2022 (OVSM, 2020(OVSM, -2022;;[START_REF] Fontaine | Report on Pelee (France)[END_REF]2022).

Signs of the current unrest have been detailed in OVSM, 2020-2022and Fontaine et al., (2021;2022), these signals are as follows: [START_REF] Wallace | Melt inclusion CO2 contents, pressures of olivine crystallization, and the problem of shrinkage bubbles[END_REF] an ongoing perturbation of the hydrothermal system, perhaps related to the circulation of hot and pressurized fluids of hydrothermal and/or magmatic origin, observed via the seismicity with high and low frequencies content. No felt earthquakes have been reported since the onset of unrest, though the number of VTs is above the base level recorded between 1 st January 1999 and 1 st January 2019; [2] strongly degraded, browned and dead vegetation zones observed in 2021 on the southwest flank of the volcano which show a pulsatory increase and decrease in size; [3] a minor deformation from June 2021 to June 2022 is revealed by continuous GNSS data, best modelled as a source of inflation located about 1 km below and slightly SW of the summit, above the hydrothermal system; [4] the detection of an area of underwater gas emission at shallow depths since June 2021.

The ongoing unrest features most likely reflect the ascent of a limited volume of deep magmatic fluids which reinvigorated the shallow hydrothermal circulation. Though no surface fumarolic activity is observed, extensive monitoring of this system is still required given the fact that there is no preeruptive unrest monitored by a multiparameter network. Although an extended period of 13 years preceded the major eruption of Montagne Pelée in 1902, we cannot expect that this is a characteristic of magmatic eruptions at Montagne Pelée after extensive times of quiescence.

Soufrière St Vincent

Soufrière St Vincent is the most active subaerial volcano in the Lesser Antilles due to numerous recent eruptions (Table 1). The major historic eruptions of 1440, 1580, 1718 and 1812, and recent eruptions of 1902-03, 1971-72, 1979 and 2020 -21 are well documented, however, the prehistoric eruptive history is less well known. The recent eruptive history reveals a range of activity from major explosive phases to periods of completely effusive dome growth (e.g., [START_REF] Anderson | IX. Report on the eruptions of the soufrière, St. Vincent, 1902, and on a visit to Montagne Pelèe, in Martinique.-Part I[END_REF][START_REF] Aspinall | Eruption of Soufrière volcano on St. Vincent island, 1971-1972[END_REF][START_REF] Shepard | Robertson[END_REF]Robertson, 1992;Robertson, 1995;Cole et al, 2019;[START_REF] Fedele | Petrological insights on the last 1000 years of explosive activity at La Soufrière volcano, St. Vincent (Lesser Antilles)[END_REF]Joseph et al., 2022). Two additional prehistoric eruptions (1580 and 1440 CE) suggest a cyclicity with repose period ranging between 77 and 140 years that appears to be systematically decreasing (Cole et al 2019).

The 1902-3 eruption was the deadliest eruption recorded for St Vincent with 1500 deaths [START_REF] Pyle | The 1902-3 eruptions of the Soufrière, St Vincent: Impacts, relief and response[END_REF]; Table 1). As with the 1902 Montagne Pelée eruption, unrest prior to the 1902 Soufrière St

Vincent began with an increase in seismic activity. However, unlike Montagne Pelée's extended period of unrest, increases in seismic activity are only reported from 1901, one year prior to the eruption (though a longer period of unrest, with earthquakes going unfelt by the population, cannot be discounted [START_REF] Pyle | The 1902-3 eruptions of the Soufrière, St Vincent: Impacts, relief and response[END_REF]). Seismic activity culminated in phreatic eruptions which transitioned into a violent magmatic eruption producing pyroclastic density currents and lahars [START_REF] Anderson | IX. Report on the eruptions of the soufrière, St. Vincent, 1902, and on a visit to Montagne Pelèe, in Martinique.-Part I[END_REF]Roobol and Smith, 1975;[START_REF] Pyle | The 1902-3 eruptions of the Soufrière, St Vincent: Impacts, relief and response[END_REF]. The eruption continued with intermittent vulcanian explosions until March 1903 (Roobol and Smith, 1975;[START_REF] Pyle | The 1902-3 eruptions of the Soufrière, St Vincent: Impacts, relief and response[END_REF].

In comparison, a completely effusive eruption was observed in 1971-72. This eruption saw the aseismic emplacement of a basaltic-andesite dome, a direct contrast to the major explosive eruption observed in 1902 [START_REF] Aspinall | Eruption of Soufrière volcano on St. Vincent island, 1971-1972[END_REF][START_REF] Shepard | Robertson[END_REF]Robertson, 1992). Explosive activity began 13 th April 1979 following elevated seismicity and lasted for 13 days until 26 April. The explosive phase of the eruption consisted of 11 vulcanian explosions that produced eruptions columns up to 18 km.

Pyroclastic flows affected several valleys surrounding the volcano, but only reached the sea at Larikai valley. The explosive phase of the eruption was followed by six months of effusive dome growth [START_REF] Shepard | Robertson[END_REF]Robertson, 1995).

The most recent eruption of Soufrière St Vincent began in December 2020, making this the most recent period of volcanic activity in the Lesser Antilles (Global Volcanism Program, 2021;Joseph et al., 2022). This eruption began with an effusive phase on 27 th December 2020 with dome growth in the south-west sector of the crater floor, adjacent to the 1979 dome. Increasing seismicity culminated in April 2021 with a transition from effusive to explosive behaviour, following three months of dome growth. On recommendation from the scientists from the Seismic Research Center (UWI Trinidad) the volcanic alert level was raised by the authorities from orange to red on the afternoon of 8th April 2021. This is the highest level on a four-level scale (UWI-SRC Scientific Updates, 2020-21). The increase in alert level was followed that day by the onset of rapid evacuations from the red zone (Joseph et al., 2022). The first explosion occurred on the morning of 9th April and was vulcanian in nature. This was then followed by a pause of roughly 5 hours after which sub-Plinian activity began, lasting until the 11 th of April, when the first pyroclastic density currents appeared. This was followed by a period of pulsing, explosive activity that continued for the next 20 hours. The latest update on the volcano was in March 2022 when seismic activity was reported to have reached a minimum, no significant change in deformation signal had been observed and no change in gas composition has been observed in the plume. This activity is considered to be at levels similar to background activity recorded prior to the 2020 -2021 eruption and the alert level was lowered to green.

Kick 'em Jenny

The submarine volcano Kick 'em Jenny has erupted 14 times in the 20 th and 21 st centuries, making this the most active volcano in the LAA (Figure 5). The most recent eruption occurred in 2017, following this eruption the alert level was reduced to yellow (UWI SRC scientific updates 2020). This alert level has remained at yellow due to periods of seismic unrest being recorded (UWI SRC scientific updates 2020).

Prior to the 2001 eruption, Kick 'em Jenny eruptions were not associated with precursory seismicity, as far as is known (UWI SRC scientific updates 2020). The 2001 eruption marked a change in behaviour, with this and the following 2015 and 2017 eruptions associated with precursory seismicity. Following the 2017 eruption several periods of high level seismic unrest have been recorded. The most recent period of unrest occurred from April to June 2020, which included >1000 volcanic earthquakes with a maximum magnitude 3.1 earthquake recorded (UWI SRC scientific updates 2020).

This period of unrest is interpreted to relate to magma intrusion or pressure changes (due to crystallisation or degassing) (UWI SRC scientific updates 2020). It is also hypothesised the system may have experienced sufficient magma recharge to generate eruptions without further high level seismicity, as observed for the pre-2001 eruptions. However, further periods of seismic unrest without eruption are also considered likely (UWI SRC scientific updates 2020).

Discussion

How Reliable is the Melt Inclusion Data?

MIs can undergo significant post entrapment modifications (PEM) which can result in changes to the composition of the MI (e.g., Steele-Macinnis et al., 2011;Wallace et al., 2015;Cannatelli et al., 2016).

In order to ensure the MIs are representative of the original melt care must be taken when choosing the MIs and also when processing the data.

The majority of studies have avoided or discarded MIs with obvious signs of post entrapment crystallization (PEC), cracks or bubbles (e.g., [START_REF] Mann | Phenocryst-hosted melt inclusions record stalling of magma during ascent in the conduit and upper magma reservoir prior to vulcanian explosions, Soufrière Hills volcano, Montserrat, West Indies[END_REF][START_REF] Cooper | Variable water input controls evolution of the Lesser Antilles volcanic arc[END_REF]Metcalfe et al., 2022; Supplementary datasheet 2). This ensures the MIs have experienced minimal PEMs and the composition has not been altered. For studies which report PEC, MIs with >10% PEC have been discarded (e.g., Camejo-Harry et al., 2019;d'Augustin et al., 2020). This leaves some MIs in the dataset presented here which have experienced <10% PEC, however, PEC has been shown to have negligible effects on both major and volatile elements for up to 11% PEC (Moretti et al., 2018). (Supplementary datasheet 2). Bubbles can also have a major impact on the volatile content, particularly CO2 with up to 90% CO2 sequestered in th bubble (e.g., Moore et al., 2015;Venugopal et al., 2020). In most studies, mis with bubbles were not analysed (e.g., [START_REF] Balcone-Boissard | Deep pre-eruptive storage of silicic magmas feeding Plinian and domeforming eruptions of central and northern Dominica (Lesser Antilles) inferred from volatile contents of melt inclusions[END_REF]d'Augustin et al., 2020). In cases where they were analysed, care has been taken to ensure the bubble size and volatile concentration did not correlate and the volatile contents were comparable to MIs without bubbles present (Supplementary datasheet 2).

Many studies have also included additional checks on the MIs to ensure the MI has experienced minimal PEM. For example, studies which report bubbles in the MIs ensure lower H2O and CO2 values are not associated with larger bubbles (e.g., Melekhova et al., 2017). [START_REF] Balcone-Boissard | Deep pre-eruptive storage of silicic magmas feeding Plinian and domeforming eruptions of central and northern Dominica (Lesser Antilles) inferred from volatile contents of melt inclusions[END_REF] ensure their MIs were volatile saturated by comparing CO 2 content of melt inclusions with increasing crystallization, shown through increasing contents of incompatible trace elements (Wallace et al., 1999;Blundy andCashman, 2008). d'Augustin et al. (2020) also show minimum H+ diffusion by comparing H2O content with Li content. The effect of H+ diffusion has also been ensured to be minimal through analysis of deuterium (e.g., Metcalfe et al., 2022;Bouvier et al., 2010b), with MIs outside the accepted range of δD values discarded. Finally, ensuring the MIs fall in the same liquid line of descent can provide assurance that there has been minimal PEM affecting the inclusions.

Corrections and checks to the MIs have been applied by : Toothill et al., 2007, Bouvier et al., 2010a,b, Melekhova et al., 2017[START_REF] Balcone-Boissard | Deep pre-eruptive storage of silicic magmas feeding Plinian and domeforming eruptions of central and northern Dominica (Lesser Antilles) inferred from volatile contents of melt inclusions[END_REF], Camejo-Harry et al., 2019[START_REF] Cooper | Time scales and temperatures of crystal storage in magma reservoirs: implications for magma reservoir dynamics[END_REF]d'Augustin et al., 2020, and Metcalfe et al., 2022 (Supplementary dataset 2). However, for the Martel et al., 1998[START_REF] Mann | Phenocryst-hosted melt inclusions record stalling of magma during ascent in the conduit and upper magma reservoir prior to vulcanian explosions, Soufrière Hills volcano, Montserrat, West Indies[END_REF][START_REF] Cooper | Variable water input controls evolution of the Lesser Antilles volcanic arc[END_REF] may have a higher error on pressure estimates (Supplementary dataset 2). Based on the checks performed by the studies included here, and the fact that MIs have minimal PEC and are not associated with cracks or Fe-Ti oxides we can be confident that the MI dataset presented here have experienced minimal PEM. This indicates the MIs provide good preservation of the original major and volatile composition.

Controls on Along Arc Variations

Slab structure controls are also hypothesised to influence the central portion of the LAA. Slab age does not vary greatly along strike [START_REF] Cooper | Variable water input controls evolution of the Lesser Antilles volcanic arc[END_REF]Braszus et al., 2021) and instead: (1) sediment input (Plank and Langmuir, 1998;[START_REF] Carpentier | Pb-Nd isotopic constraints on sedimentary input into the Lesser Antilles arc system[END_REF], (2) subduction of the Tiburon and Baracuda bathymetric ridges (Bouysse and Westercamp, 1990) and, ( 3) subduction of strongly hydrated fracture zones (Schlaphorst et al., 2019;[START_REF] Cooper | Variable water input controls evolution of the Lesser Antilles volcanic arc[END_REF][START_REF] Bie | Imaging slab-transported fluids and their deep dehydration from seismic velocity tomography in the Lesser Antilles subduction zone[END_REF] have been hypothesised to control along arc variations (e.g., [START_REF] Allen | The role of arc migration in the development of the Lesser Antilles: A new tectonic model for the Cenozoic evolution of the eastern Caribbean[END_REF]. The increased presence of water in the subduction zone lowers the melting point of the rocks promoting melt genesis. Fracture zones have recently been proposed to have a primary control on along arc variations in various subduction zones (e.g., Venugopal et al. 2020), but also in the LAA, in particular the Marathon and Mercurius fracture zones which underlay the Northern and Central LAA (Müller et al., 2019;[START_REF] Cooper | Variable water input controls evolution of the Lesser Antilles volcanic arc[END_REF][START_REF] Bie | Along-arc heterogeneity in local seismicity across the Lesser Antilles subduction zone from a dense ocean-bottom seismometer network[END_REF]Fig. 6). [START_REF] Cooper | Variable water input controls evolution of the Lesser Antilles volcanic arc[END_REF] These fracture zones most likely host the serpentine and supply substantial volumes of fluid to the Central Arc (Fig 6). This suggests that the along arc compositional variation and magmatic productivity is controlled by the distribution of subducted serpentine [START_REF] Cooper | Variable water input controls evolution of the Lesser Antilles volcanic arc[END_REF]. In turn, these variations, will result in variations in magma storage due to changes in density contrasts and influence the ascent of the magma, volatiles exsolving will reduce the density further until the neutral buoyancy point is reached. This is particularly important when considering the Central Arc which has the highest magma productivity, shallowest storage depths and the largest number of volcanoes in a state of unrest (Fig

6).

The distribution of serpentine in the slab is hypothesised to control magma productivity and crustal thickness (Fig 6). This could also relate to the variation in composition observed along the arc with the Northern and Central (including St Lucia) arcs erupting generally more evolved compositions and the Southern Arc producing less evolved compositions and dominated by basalts and basaltic andesites (Fig 6). The correlation between the eruption of evolved magmas and the thicker crust is hypothesised to occur due to basaltic magmas becoming more likely to pond as the crust thickens, allowing further fractionation to more evolved compositions (Baker, 1982;Devine, 1995;[START_REF] Macdonald | The Lesser Antilles volcanic chain: a study in arc magmatism[END_REF]Fig 6). This suggests that the homogenous composition produced from a narrow range of shallow storage depths in the central arc, is due to the thicker crust which is allowing for the ponding and fractionation of basaltic magmas (Fig 6). Subsequently, magma composition, which is at least partly controlled by density contrasts, crustal thickness, magma productivity and serpentine distribution, is a first order control on eruption style. This is observed in the Central arc which produce evolved compositions and large volume, explosive, caldera eruptions, dome building eruptions and associated voluminous pyroclastic density current deposits from stratovolcanoes [START_REF] Macdonald | The Lesser Antilles volcanic chain: a study in arc magmatism[END_REF]Lindsay et al., 2013;Smith et al., 2013;[START_REF] Bezard | Assimilation of sediments embedded in the oceanic arc crust: Myth or reality?[END_REF]Howe et al., 2015a;Lindsay and Robertson, 2018;Fig 6).

In contrast, the thinner crust in the Southern Arc which allows the eruption of more basaltic magmas erupting in explosion craters and mafic lava flows, with large dome-forming eruptions being less common (e.g., [START_REF] Arculus | Geology and geochemistry of the alkali basalt-andesite association of Grenada, Lesser Antilles island arc[END_REF]Brown et al., 1977;Thirlwall and Graham, 1984;Robertson, 2003;Lindsay and Robertson, 2018;[START_REF] Fedele | Petrological insights on the last 1000 years of explosive activity at La Soufrière volcano, St. Vincent (Lesser Antilles)[END_REF].

Magma Composition, Storage and Controls on Eruption Style

Magma Chemistry

The Grenada magmas are the most primitive and are particularly silica-poor and could represent a potential parental magma composition which would fractionate to produce the suites of magma observed across the Arc. The whole rock compositions in equilibrium with a primitive magma are shown on Figure 3, and plot below the FeO/MgO ratio corresponding to olivine Fo 90 , using Kd ol-liq = 0.3 (e.g., Melekhova et al., 2019). Using the compositions of the primitive Grenada whole rock we provide two models of fractional crystallisation starting at pressures of 300 MPa (White et al., 2017) using RhyoliteMELTS v1.2. 0 (Fig 3;Ghiorso and Sack, 1995;Gualda et al., 2012).

In the first model (A), the starting composition is the average of the most primitive whole rock compositions (FeO/MgO <0.7; Fig 3). In the second model (B), we used the average of the most primitive whole rock compositions with the highest CaO/Al2O3 ratio. The same input parameters were used for both starting compositions which included a starting pressure of 300 MPa, a starting temperature of 1200 o C (liquidus calculated by MELTS) and an oxygen fugacity buffered at NNO (stamper et al., 2014). The melt was then cooled and decompressed in three iterations due to failed convergence. The iterations were completed at increasing dP/dT (details in supplementary datasheet [START_REF] Cooper | Variable water input controls evolution of the Lesser Antilles volcanic arc[END_REF]. Lower water contents are generally observed in melt inclusions from the central arc, with higher water contents observed in the northern and southern arcs (Fig 6). However, the fact that melt inclusion water contents can often be affected by processes including: magma differentiation, degassing and post-entrapment crystallization or diffusion, suggests that the observed trend may be the result of additional processes following magma differentiation. Therefore, the highest water content recorded at a given volcano is considered the best estimate of the water content (Rasmussen et al., 2022).

Magma Storage

At many systems along the arc the mush model is now the accepted storage model, with a transcrustal mush system often described. Looking closer at the individual systems, we can hypothesise that across the arc there are generally three levels of the mush storage system which varies in depth across the northern, central and southern arcs. Storage depths are often considered to be the depths at which the magma is at neutral buoyancy (Sparks et al., 2019), and due to the rheological properties of the magma (e.g., composition, crystal content, volatile abundance, gas/liquid ratios and temperature)

which drive magma emplacement at different depths (e.g., Burov et al., 2003). However, more recently magma H2O concentration has been hypothesised as a major control on the storage depth (Rasmussen et al., 2022). Storage depths have in some cases been shown to be consistent with the predicted depths of water degassing and related processes (Rasmussen et al., 2022). The variations in storage depths in the LAA are not reflected in magma storage temperature variations (Fig 6), with temperature remaining consistent across the arc. This may be due to the different methods and techniques used across the arc to calculate temperature. Bias towards measurement of one phase (e.g., cpx+liquid) and crystal rims + matrix glass, may exacerbate this and contribute to the homogenous temperature profile (Higgins et al., 2022). Melekhova et al. (2019) use an inversion approach which combines xenolith petrology and seismic receiver functions to present crustal structure along the LAA. This model shows four crustal layers which vary laterally (Figure 2). The magma system depths presented in the literature generally fit within layers 2 (6 -15 km) and 3 (12 -32 km), except for St Lucia where the lower crust system fits into layer 4 (26 -38 km).

5.3.2.a

Lower Crust (ca. >18 km, ca. >400 MPa) Melekhova et al. (2017) infer a depth of 25 km from primitive cumulate composition of ol+cpx+sp from St Kitts which are in equilibrium with the most primitive magmas. This is in agreement with the estimates for cumulates from other islands (>15 ->30 km; e.g., Bissante, 1999;Parkinson and Arculus, 1999;Stamper et al., 2014;Fig 6). Fractionation occurs to produce magmas which ascend into the middle crustal storage zone. However, as cumulates from this lower storage level are rarely observed it is unclear whether this is applicable across the arc. Despite this, this does provide a good estimation for the deepest part of the LAA system.

5.3.2.b Mid Crust (ca. 10 -18 km, ca. 200 -400 MPa)

Above the lower crustal zone is a zone of mafic-intermediate magma which, depending on the system, is generally described as basalt to basaltic-andesite in composition and associated cumulates [START_REF] Tollan | Cumulate xenoliths from St. Vincent, Lesser Antilles Island Arc: a window into upper crustal differentiation of mantle-derived basalts[END_REF]Stamper et al., 2014;Melekhova et al., 2019). The magmas stored here are often described as the parental magmas for the more evolved magmas stored in the shallow system. Again, this mid crustal part of the system is less well studied than shallower parts but is commonly reported between 10 -18 km (Pichavant et al., 2002;[START_REF] Edmonds | Extensive, water-rich magma reservoir beneath southern Montserrat[END_REF][START_REF] Boudon | Volcanological evolution of Montagne Pelée (Martinique): A textbook case of alternating Plinian and dome-forming eruptions[END_REF]e.g., Melekhova et al., 2017;[START_REF] Balcone-Boissard | Deep pre-eruptive storage of silicic magmas feeding Plinian and domeforming eruptions of central and northern Dominica (Lesser Antilles) inferred from volatile contents of melt inclusions[END_REF][START_REF] Fedele | Petrological insights on the last 1000 years of explosive activity at La Soufrière volcano, St. Vincent (Lesser Antilles)[END_REF]Fig 6). Within the transcrustal mush system, the parental magmas can migrate into the shallow part of the system and undergo processes including fractional crystallisation and magma mixing. For example, during the most recent eruption of Soufriere St Vincent seismicity indicates the initial activity during the explosive phase (23 -24 March 2021) involved the shallow system (~6 km). This was then followed by deeper seismicity (~10 km depth; 5-6 April 2021) interpreted as fresh magma migrating from the mid system up into the shallow system (Joseph et al., 2022).

5.3.2.c Upper Crust (ca. <10 km, ca. <200 MPa)

The most well-defined parts of the magma systems across the arc are the shallow zones. The shallow area of the system contains evolved magmas which are often described as homogenous (e.g., Dominica, St Vincent, Guadeloupe; e.g., [START_REF] Fedele | Petrological insights on the last 1000 years of explosive activity at La Soufrière volcano, St. Vincent (Lesser Antilles)[END_REF]Metcalfe et al., 2022). Magmas from this system can display homogeneity from one eruption to the next, even with considerable repose periods (e.g., Martinique, Guadeloupe). Evolved magmas are reported to extend to the mid-crust in the Northern Arc (down to 15 km), but is consistent in the Central Arc, between 6 -9 km (e.g., Pichavant et al., 2002;d'Augustin et al., 2020;[START_REF] Fedele | Petrological insights on the last 1000 years of explosive activity at La Soufrière volcano, St. Vincent (Lesser Antilles)[END_REF]Metcalfe et al., 2022;Fig 6). Less data exists for the Southern Arc, but in St Vincent there is some evidence that the shallow system may extend up to <3.5 km [START_REF] Fedele | Petrological insights on the last 1000 years of explosive activity at La Soufrière volcano, St. Vincent (Lesser Antilles)[END_REF]. However, we do acknowledge that more data is required in order to conclusively observe this trend. The upper crust system (<10 km) presented here fits into the layer 2 (6 -15 km) proposed by Melekhova et al. (2019). This is particularly well defined in ). This highlights that the magma storage structure which is defined by magma chemistry and petrology provides a snapshot of the crustal structure along the arc.

Processes Occurring in the Storage Zone

The shallow systems are hypothesised to contain an 'active region' with eruptible magma which supplies recent eruptions (e.g., [START_REF] Montserrat | [END_REF]Christopher et al., 2015;[START_REF] Edmonds | Extensive, water-rich magma reservoir beneath southern Montserrat[END_REF]. The active region of mush within the shallow system is generally hypothesised to be remobilised by recharge from the middle basalt to basaltic andesite region (12 -18 km). Evidence for this is observed in the textures exhibited in lavas and pumices (e.g., banded pumices from Guadeloupe and enclaves from

Montserrat; e.g., [START_REF] Boudon | A new scenario for the last magmatic eruption of La Soufrière of Guadeloupe (Lesser Antilles) in 1530 AD Evidence from stratigraphy radiocarbon dating and magmatic evolution of erupted products[END_REF]Wadge et al., 2014), which are present in recent eruption products showing this is an active process in triggering eruptions. However, it is important to note mixing textures are generally not consistent through a system's eruptive history (e.g., Guadeloupe; Metcalfe et al., 2022). This suggests that though recharge by the parental magma from the middle region may occur it does not always result in the eruption of mixed magma compositions. Instead, this may result in the remobilisation of the shallow system and eruption of homogenous magmas and dominantly more evolved liquids in the form of melt inclusions. Also suggested as a hypothesis for remobilisation of the shallow system, is mixing of magmas with a similar composition (Solaro et al., 2019). Or alternatively, through volatiles and heat released from the parental magma migrating up through the system and resulting in remobilisation in the shallower system, with no need for direct mixing (Christopher et al., 2010;Metcalfe et al., 2022).

However, we cannot discount the effect of the well-developed hydrothermal systems present. The hydrothermal systems present at the active volcanoes, including Montserrat, Guadeloupe, Dominica, Martinique and St Vincent. This often complicates the interpretation of monitoring signals due to the scrubbing of magmatic gases, in particular SO2, which often buffers and suppresses the magmatic signal (Moune et al., 2022). Recent research highlights the potential importance of the hydrothermal systems in generating eruptions (Zlotnicki et al., 1992;Mayer et al., 2017;Moune et al., 2022).

Phreatic eruptions in particular, which can be generated without any change in the magma recharge zone at depth, can be generated due to the sealing of fractures in the hydrothermal system which increases the pressure in deep aquifers to potentially generate an eruption (e.g., Moune et al., 2022).

This has been discussed as a potential cause of the 1976-77 La Soufrière phreatic eruption (Zlotnicki et al., 1992) and given the build-up of hydrothermal pressure observed in 2018, it may have led to a phreatic eruption if the fractured state, hence the high permeability of the dome had not allowed for release of the pressure (Moretti et al., 2020a;Moune et al., 2022). The effect of the upper system has also been discussed in the context of magmatic eruptions from La Soufriere Guadeloupe, where the eruption style of magma ascending from the active region of the storage zone is affected by the state of the upper system. Though ultimately the main driver of an explosive eruption is the supersaturation of volatiles in the magma and brittle failure of a magma. Metcalfe et al. (2022) hypothesise that eruption style at La Soufriere de Guadeloupe is controlled by magma ascent rate, with faster magma ascents resulting in larger, more explosive eruptions. Along with magma composition and ascent rate, the state of the hydrothermal system can also influence eruption style and could be responsible for the range of eruption styles produced by each individual system. A slow ascending magma experiencing feedbacks between degassing and crystallization will be expected to erupt with low explosivity or effusively, however, sealing of the hydrothermal system and a reduction in permeability may favour the accumulation of gas, leading to over pressurisation and an explosive eruption (e.g., Cassidy et al., 2018;Metcalfe et al., 2022).

In order to provide an appraisal of the prevalent degassing process (decompression degassing vs CO2infiltration), integrated into a fast and comprehensive visualization of the volcano plumbing systems from their source to the surface, we provide pressure vs CO2 (gas) diagrams (Fig 7). This has been used in literature to: [START_REF] Wallace | Melt inclusion CO2 contents, pressures of olivine crystallization, and the problem of shrinkage bubbles[END_REF] identify degassing processes such as decompression degassing and CO2-fluxing (Mangiacapra et al., 2008;[START_REF] Barsanti | Heterogeneous large total CO2 abundance in the shallow magmatic system of Kilauea volcano, Hawaii[END_REF][START_REF] Arienzo | The feeding system of Agnano-Monte Spina eruption (Campi Flegrei, Italy): Dragging the past into present activity and future scenarios[END_REF]Moretti et al., 2013Moretti et al., , 2019;;Caricchi et al., 2018;Papale et al., 2022), and [2] provide a straightforward petrologic/geochemical image of volcano plumbing systems which integrates geophysical information and highlights depth intervals of magma storage. The accuracy of this representation is highly dependent on the performance of the adopted model for volatile melt-saturation, in particular, the model's sensitivity to compositional variations from deep to shallow regions [START_REF] Barsanti | Heterogeneous large total CO2 abundance in the shallow magmatic system of Kilauea volcano, Hawaii[END_REF]Papale et al., 2022). Among compositional variations, the redox-induced partitioning of iron between FeO and Fe2O3 plays a major role in shifting the equilibrium pressure of H2O-CO2 saturation by a factor comparable, or even superior to, that of analytical errors on dissolved H2O and especially CO2 contents measured in melt inclusions (Moretti, 2022).

For given fO2 values we calculated the iron oxidation state of each MI by means of the Ottonello et al.

Perspectives and Limitations

Despite the wealth of knowledge and understanding of the LAA there is still much to be learned about each magmatic system and about the LAA as a whole. In particular, we need to improve our understanding of the geometry of the deeper parts of the LAA magma storage systems to provide a more complete picture of this system. Understanding the variations in pressure, temperature and depth of the deep magma storage system may help provide links with the variations in mineralogy and chemical composition observed through the system. This could be done, for example, through seismic imaging across larger areas and and over longer seismic lines which would extend the data collected by the VOILA project (refs). In addition, deep penetration multichannel seismic (e.g., [START_REF] Laigle | Seismic structure and activity of the north-central Lesser Antilles subduction zone from an integrated approach: Similarities with the Tohoku forearc[END_REF], gravity surveys and magnetotellurics imaging at sea using ocean bottom stations (e.g., [START_REF] Darnet | Mapping the geometry of volcanic systems with magnetotelluric soundings: Results from a land and marine magnetotelluric survey performed during the 2018-2019 Mayotte seismovolcanic crisis[END_REF] may help to resolve and provide additional information on the structure of the magmatic reservoir. This should include understanding the lateral extent of the storage systems and 'active regions' of mush, with particular focus on Dominica which appears to have a much more laterally extensive system in comparison to the other islands [START_REF] Balcone-Boissard | Deep pre-eruptive storage of silicic magmas feeding Plinian and domeforming eruptions of central and northern Dominica (Lesser Antilles) inferred from volatile contents of melt inclusions[END_REF]d'Augustin et al., 2020).

To understand the role of the parental magmas in the different systems and how this varies along the arc could include refining our understanding of how the parental magma remobilises the shallow system. Though remobilisation by a parental magma has been proven in many cases, there are many eruption products, which show no evidence for mixing a less evolved magma demonstrating the parental magma is not always erupted. This creates a bias in the geochemistry dataset as the evolved magmas from the shallow system are more often erupted, with fewer examples of the parental and primitive magmas. This along with the homogenous compositions observed in magmas erupted from the shallow system requires detailed investigation of eruption deposits to better understand if finescale mixing textures are present. This will allow us to better understand how the parental magma interacts with the shallow system and why it is not consistently erupted.

Understanding the volatile processes occurring, and in particular how degassing from various depths across the vertically extended magma system contributes to the gas ratios measured at the surface (e.g., [START_REF] Metcalfe | Volatile Emissions from Past Eruptions at La Soufrière de Guadeloupe (Lesser Antilles): Insights into Degassing Processes and Atmospheric Impacts[END_REF][START_REF] Moretti | The geochemistry of magmatic solicitations on volcanic-hydrothermal systems: the long-standing unrest of La Soufrière de Guadeloupe dissected via non-condensable gases[END_REF]. This requires an integration of melt inclusion volatile data and gas monitoring data which is available for many systems which have long-term monitoring.

In addition, understanding the presence and accumulation of exsolved fluids in the system as the abundance of exsolved volatiles can affect the evolution and growth of the magma reservoir (e.g., Degruyter et al., 2017;Rasmussen et al., 2022). Understanding the relationship between the presence of exsolved volatiles to the depth and growth of the magmatic systems in the LAA, may be key to understanding along arc variations in the magmatic systems.

The majority of eruptive activity in the 20 th century has occurred in the Central and Southern arcs, with the only eruption in the northern arc being in Montserrat. The majority of eruptions in this period have been vulcanian eruptions, dome eruptions and phreatic eruptions (Fig 5) and it would be reasonable to assume any future activity will also take this form, with less frequent sub-Plinian to Plinian size eruptions interspersed. However, it is also important to consider the large pumiceous pyroclastic flow deposits of Guadeloupe, Dominica and St Lucia. The Roseau and Layou tuffs in Dominica (Howe et al., 2014), the Belfond Unit on St Lucia (Lindsay et al., 2013) and large Plinian eruptions from Grande-Découverte and Carmichaël volcanoes on Guadeloupe (Komorowski et al., 2005;[START_REF] Legendre | Reconstruction fine de l'histoire éruptive et scenarii éruptifs à la soufrière de Guadeloupe: vers un modèle intégré de fonctionnement du volcan[END_REF] and though much less frequent in the eruptive record, these large Plinian eruptions are important to consider, as such eruptions would impact the entire region (Lindsay and Robertson, 2018) Volcano monitoring has shown major advancements over the last fifty years, however, the period of monitorable unrest can vary greatly even within the same system. In the case of St Vincent, the two most recent explosive eruptions have had very short periods of monitorable unrest (on the order of days for the 1979 eruption and 2 months for the 2020 eruption (onset in November 2020; Joseph et al., 2022; UWI SRC scientific updates 2020-21). In the case of the St Vincent 2020 eruption, the 2 months of unrest was followed by an effusive phase of eruption with evacuation not taking place until the explosive phase of eruption had begun (Joseph et al., 2022). Other systems such as La Soufrière de Guadeloupe could also potentially have short periods of monitorable unrest prior to eruption, as

shown by diffusion timescales (e.g., Metcalfe et al., 2021 a,b). Diffusion timescales allow the calculation of the time between the last magmatic process that destabilizes the magma in the storage zone and eruption, for La Soufrière de Guadeloupe, this is calculated to be on the order of weeks for even large explosive eruptions at this system (Metcalfe et al., 2021a,b). The short time frames of escalation from monitorable unrest to eruption and then an explosive phase requires efficient and effective monitoring plans, to allow for timely and successful crisis management and evacuation, as was demonstrated by the remarkable crisis response to the Soufrière of St Vincent eruption in 2020 (Joseph et al., 2022). Much can be learnt from the handling of the 2020 Soufrière St Vincent eruption and the support that has been provided for the evacuated people. However, though people begun to return to their homes a few months after the eruption, some people remain displaced and support had to be continued over years after the eruption in order to facilitate social and economic recovery (Joseph et al., 2022). This is highlighted by the 1995 Soufrière Hills eruption on Montserrat, where following the evacuation of >6,000 people and a population reduction from ca. 11,000 pre-eruption to ca. 4,000 post-eruption, only 1000 people have returned (Kokelaar, 2002;[START_REF] Aspinall | Risk assessment at the Soufrière Hills volcano, Montserrat[END_REF][START_REF] Barclay | Livelihoods, Wellbeing and the Risk to Life During Volcanic Eruptions[END_REF].

As previously discussed, a wide variation in eruption styles is observed across the arc as exemplified by the eruptions in the 20 th century (Fig 5). The hazards posed by eruptions need to be clearly conveyed to the populations with volcanoes in a state of unrest, particularly on islands where volcanic risk is not necessarily considered high by the population (e.g., Guadeloupe; Chenet et al., 2014).

Though the eruptions occurring in the early 20 th century (e.g., Montagne Pelée 1902 and Soufrière St

Vincent 1902) resulted in a large number of casualties (>30,000 deaths), advancements in science and technology have allowed a better understanding and monitoring of the volcanoes of the LAA. This has undoubtedly prevented large numbers of casualties in eruptions in the later 20 th century, however, in most cases, evacuations of people remain unavoidable (Table 1). In some cases, evacuation becomes long term displacement and results in major socio-economic impacts and in the case of the La Soufrière de Guadeloupe 1976 eruption, a loss of trust in scientists and authorities (Hincks et al., 2014;Chenet et al., 2014;[START_REF] Komorowski | Challenges of volcanic crises on small islands states[END_REF]. This highlights the need for future crises to be managed with care and transparency to limit the socio-economic impacts and maintain the relationship between scientists, authorities and the population.

Conclusions

In this review of the LAA we have focused on the magma storage system, geochemistry and recent eruptive history. We have highlighted investigating trends across the arc can be useful to provide more context for each system. The distribution of subducted serpentine has a first order control on magmatic productivity (Fig 6), compositional variation and variation in magma storage depth as serpentine can supply substantial volumes of fluid to the arc [START_REF] Cooper | Variable water input controls evolution of the Lesser Antilles volcanic arc[END_REF]. This is particularly important to consider in the Central Arc where evolved magmas are stored at shallow depths and are likely to erupt explosively in the near future, given the unrest observed at many systems in LAA.

Through this review we show that there appears to be three different levels of magma storage within a vertical and laterally extensive, transcrustal magma mush. The deepest storage area is the least well defined but is most likely at >18 km depth. Above this, at ca. 10 -18 km are the parental magmas which undergo fractional crystallization to produce more evolved magmas which are stored in the shallow system at ca. <10 km. Within the shallow mush system there is an 'active region' which has supplied the most recent eruptions, and is most likely remobilised by magma, heat and volatiles from the parental magmas at 10 -18 km. Eruption products from recent eruptions are often described as having restricted bulk compositions with few systematic compositional changes. This indicates the 'active region' of the magma systems supplying eruptions can remain homogenous in composition and also stable over long periods of time, perhaps by buffering recharge from depth.

Relating the sub-surface processes occurring leading up to an eruption, and the monitorable surface observables remains a challenge. Adapting current monitoring strategies to detect, in a timely manner, the entire eruption timeline from the point at which sub-surface processes effectively generate recordable signals on the surface would greatly enhance monitoring and crisis management strategies. However, many uncertainties must be addressed within this including understanding the surface observables in terms of the sub-surface processes, timescales, and dynamics. In addition, understanding the modulation, abortion and escalation of sub-surface processes and the probability it can lead to an eruption are also important and complicated factors to consider for unrest thresholds, Laterally and vertically extensive mush systems are now proposed for many systems across the arc, which can be divided broadly into three levels: (1) >18 km;

(2) 10 -18 km; (3) <10 km. The location of the mush systems, generally fit with the location of crustal layers (e.g., Guadeloupe, Martinique, St Vincent). The majority of research has focused on the shallow and middle systems. Many systems are hypothesised to have an active region of mush which has supplied recent eruptions in the shallow area of the system (<10 km). The shallow system is remobilised by less evolved magmas from >10 km.

This highlights the need to refine storage models, particularly at depths greater than 10 km. Magmas may be produced from parental magmas fractionating at >18 km, as hypothesised for St Kitts, Guadeloupe and St Lucia. (Bissante, 1999 ;Melekhova et al., 2015 ;Melekovha et al., 2017 ;Paulatto et al., 2012 ;Christopher et al., 2015 ;[START_REF] Edmonds | Extensive, water-rich magma reservoir beneath southern Montserrat[END_REF]Pichavant et al., 2018 ;Metcalfe et al., 2022 ;[START_REF] Balcone-Boissard | Deep pre-eruptive storage of silicic magmas feeding Plinian and domeforming eruptions of central and northern Dominica (Lesser Antilles) inferred from volatile contents of melt inclusions[END_REF]d'Augustin et al., 2020 ;Martel et al., 1998 ;[START_REF] Fedele | Petrological insights on the last 1000 years of explosive activity at La Soufrière volcano, St. Vincent (Lesser Antilles)[END_REF]Camejo-Harry et al., 2019 ;Boudon and. Balcone-Boissard, 2021).

Figure 3 Plot of CaO/Al2O3 vs FeO(total)/MgO using whole rock data compilation from across the arc. As well as data from the northern (circle symbols), central (square symbols) and southern (diamond symbol) arcs, we present two MELTS models of fractional crystallisation (see discussion). This shows that the whole rock data is related through factional crystallisation, with the variability observed related to mixing. (Saba [START_REF] Defant | Evidence suggests slab melting in arc magmas[END_REF]Roobol and Smith, 2004); Statia (Roobol and Smith, 2004);

St Kitts (Baker, 1968[START_REF] Baker | Geology and geochemistry of the Mansion pyroclast fall succession[END_REF][START_REF] Baker | Geochemical evolution of St Kitts and Montserrat, Lesser Antilles[END_REF][START_REF] Toothill | A complex petrogenesis for an arc magmatic suite, St Kitts, Lesser Antilles[END_REF]Higgins et al., 2021); Montserrat (Murphy et al., 2000;[START_REF] Zellmer | [END_REF]Christopher et al., 2015;Plail et al., 2018); Guadeloupe (including La Soufrière and Mont Caraïbes, Toubol et al., 2007;[START_REF] Boudon | A new scenario for the last magmatic eruption of La Soufrière of Guadeloupe (Lesser Antilles) in 1530 AD Evidence from stratigraphy radiocarbon dating and magmatic evolution of erupted products[END_REF]Samper et al., 2009;Ricci et al., 2017;Pichavant et al., 2018;Metcalfe et al., 2021Metcalfe et al., , 2022)); Dominica (Lindsay et al., 2005;Howe et al., 2015;[START_REF] Boudon | Revised chronostratigraphy of recurrent ignimbritic eruptions in Dominica (Lesser Antilles arc): Implications on the behavior of the magma plumbing system[END_REF][START_REF] Balcone-Boissard | Deep pre-eruptive storage of silicic magmas feeding Plinian and domeforming eruptions of central and northern Dominica (Lesser Antilles) inferred from volatile contents of melt inclusions[END_REF]d'Augustin et al., 2020); Martinique (Gourgand et al., 1989;Pichavant et al., 2002); St Lucia (Wright et al., 1984;Vidal et al., 1991;Lindsay et al., 2013;[START_REF] Bezard | Seeing through the effects of crustal assimilation to assess the source composition beneath the southern Lesser Antilles Arc[END_REF]; St Vincent (Graham and Thirwall, 1981;Heath et al., 1988;[START_REF] Fedele | [END_REF]Cole et al., 2019;Joseph et al., 2022); Kick 'em Jenny (Devine and Sigurdsson, 1996;Camejo-Harry et al., 2019); Grenada [START_REF] Arculus | Geology and geochemistry of the alkali basalt-andesite association of Grenada, Lesser Antilles island arc[END_REF][START_REF] Arculus | Mineralogy and petrology of Grenada, Lesser Antilles island arc[END_REF]Cawthorn et al., 1973;Thirwall and Grahm, 1984;Thirwall et al., 1994Thirwall et al., , 1996;;Woodland et al., 2002;Rojas-Agramonte et al., 2017). (Saba (Roobol and Smith, 2004); Statia [START_REF] Cooper | Variable water input controls evolution of the Lesser Antilles volcanic arc[END_REF]; St Kitts [START_REF] Toothill | A complex petrogenesis for an arc magmatic suite, St Kitts, Lesser Antilles[END_REF]Melekhova et al., 2017;[START_REF] Cooper | Variable water input controls evolution of the Lesser Antilles volcanic arc[END_REF]; Redonda [START_REF] Cooper | Variable water input controls evolution of the Lesser Antilles volcanic arc[END_REF]; Montserrat (Devine et al., 1998;Humphreys et al., 2010;Mann et aal., 2013;[START_REF] Cooper | Variable water input controls evolution of the Lesser Antilles volcanic arc[END_REF]; Guadeloupe (Poussineau,2005;[START_REF] Boudon | A new scenario for the last magmatic eruption of La Soufrière of Guadeloupe (Lesser Antilles) in 1530 AD Evidence from stratigraphy radiocarbon dating and magmatic evolution of erupted products[END_REF]Pichavant et al., 2018;[START_REF] Cooper | Variable water input controls evolution of the Lesser Antilles volcanic arc[END_REF]Metcalfe et al., 2022;[START_REF] Metcalfe | Insights into the Origin and Dynamics of Past Eruptions of La Soufrière de Guadeloupe from Melt Inclusions: Implications for Future Unrest and Environmental Impact[END_REF]; Dominica (Baalcone-Boissard et al., 2018;[START_REF] Cooper | Variable water input controls evolution of the Lesser Antilles volcanic arc[END_REF]d'Augustin et al., 2020;[START_REF] Ostorero | Timewindow into the transcrustal plumbing system dynamics of Dominica (Lesser Antilles)[END_REF]; Martinique (Martel et al., 1998;[START_REF] Cooper | Variable water input controls evolution of the Lesser Antilles volcanic arc[END_REF]; St Lucia [START_REF] Cooper | Variable water input controls evolution of the Lesser Antilles volcanic arc[END_REF]; St Vincent (Devine and Sigurdsson, 1983;Heath et al., 1998;Bouvier et al., 2010b;[START_REF] Cooper | Variable water input controls evolution of the Lesser Antilles volcanic arc[END_REF]; Petite Mustique [START_REF] Cooper | Variable water input controls evolution of the Lesser Antilles volcanic arc[END_REF]; Kick 'em Jenny (Camejo-Harry et al., 2019); Grenada (Bouvier et al., 2010a;[START_REF] Cooper | Variable water input controls evolution of the Lesser Antilles volcanic arc[END_REF]. and Smith, 2004); Statia [START_REF] Cooper | Variable water input controls evolution of the Lesser Antilles volcanic arc[END_REF]; St Kitts [START_REF] Toothill | A complex petrogenesis for an arc magmatic suite, St Kitts, Lesser Antilles[END_REF]Melekhova et al., 2017;[START_REF] Cooper | Variable water input controls evolution of the Lesser Antilles volcanic arc[END_REF]; Redonda [START_REF] Cooper | Variable water input controls evolution of the Lesser Antilles volcanic arc[END_REF]; Montserrat (Devine et al., 1998;Humphreys et al., 2010;Mann et aal., 2013;[START_REF] Cooper | Variable water input controls evolution of the Lesser Antilles volcanic arc[END_REF]; Guadeloupe (Poussineau,2005;[START_REF] Boudon | A new scenario for the last magmatic eruption of La Soufrière of Guadeloupe (Lesser Antilles) in 1530 AD Evidence from stratigraphy radiocarbon dating and magmatic evolution of erupted products[END_REF]Pichavant et al., 2018;[START_REF] Cooper | Variable water input controls evolution of the Lesser Antilles volcanic arc[END_REF]Metcalfe et al., 2022;[START_REF] Metcalfe | Insights into the Origin and Dynamics of Past Eruptions of La Soufrière de Guadeloupe from Melt Inclusions: Implications for Future Unrest and Environmental Impact[END_REF]; Dominica (Baalcone- et al., 2018;[START_REF] Cooper | Variable water input controls evolution of the Lesser Antilles volcanic arc[END_REF]d'Augustin et al., 2020;[START_REF] Ostorero | Timewindow into the transcrustal plumbing system dynamics of Dominica (Lesser Antilles)[END_REF]; Martinique (Martel et al., 1998;[START_REF] Cooper | Variable water input controls evolution of the Lesser Antilles volcanic arc[END_REF]; St Lucia [START_REF] Cooper | Variable water input controls evolution of the Lesser Antilles volcanic arc[END_REF]; St Vincent (Devine and Sigurdsson, 1983;Heath et al., 1998;Bouvier et al., 2010b;[START_REF] Cooper | Variable water input controls evolution of the Lesser Antilles volcanic arc[END_REF]; Petite Mustique [START_REF] Cooper | Variable water input controls evolution of the Lesser Antilles volcanic arc[END_REF]; Kick 'em Jenny (Camejo-Harry et al., 2019); Grenada (Bouvier et al., 2010a;[START_REF] Cooper | Variable water input controls evolution of the Lesser Antilles volcanic arc[END_REF].

Boissard
Table 1 Sub-aerial eruptions in the LAA occurring in the 20 th and 21 st centuries [START_REF] Lacroix | La Montagne Pelée et ses éruptions[END_REF][START_REF] Jolivet | La crise volcanique de 1956 à la Soufrière de la Guadeloupe[END_REF][START_REF] Aspinall | Eruption of Soufrière volcano on St. Vincent island, 1971-1972[END_REF][START_REF] Shepard | Robertson[END_REF][START_REF] Feuillard | The 1975-1977 crisis of La Soufrière de Guadeloupe (FWI): a still-born magmatic eruption[END_REF][START_REF] Fournier | Boiling Lake of Dominica, West Indies: High-temperature volcanic crater lake dynamics[END_REF] impacts, which have had profound impacts on the people living in this region. Through this review we 28 highlight the variations observed in magma storage, which is described as a vertically extensive trans 29 crustal mush system. We hypothesise that across the arc there are generally three levels of the mush 30 storage system. First, a deep system at 25 km (ca. >400 MPa). This system is poorly constrained and Revised Manuscript with Changes Marked second mid-crustal system at 10 -18 km (ca. 3200 -400 MPa). The mid-crust stores basalt to basaltic 33 andesite which supplies and remobilises the third and last shallow system at <10 km (ca. <200 MPa)

34

which hosts evolved dacitic -rhyolitic magmas. This is the most well-defined part of the magma

35

system and is the region supplying eruptions. The remobilisation of the shallow system and the 36 production of eruptible magma can result in eruption, with magma composition considered a first 37 order control on eruption style. This is observed with the northern and central arcs, which produce 38 evolved compositions, large explosive and dome-forming eruptions, with associated hazards.

39

Magmatic productivity compositional variation and variation in magma storage depth is controlled by 40 the distribution of subducted serpentine. This is particularly important to consider in the central arc

41

which has the highest magma productivity and evolved magmas stored at shallow depths. These al., 2016). An explosive eruption is the result of brittle failure of a melt phase when the volume fraction 70 of exsolved volatiles is sufficiently large (Sparks, 1978;Woods and Koyaguchi, 1994;Carr et al., 2020),

71
when the strain rate is sufficiently high (Papale, 1999;[START_REF] Gonnermann | Explosive volcanism may not be an inevitable con-sequence of magma fragmentation[END_REF]

). Such variations are often linked to processes occurring in the magma storage system including 76 magma mixing and magma recharge (Sparks et al., 1977;Murphy et al., 2000;Plail et al., 2018).

77

However, recent studies also stress the importance of processes occurring external to the magmatic 78 system (e.g., Hlinka et al., 2021;Metcalfe et al., 2022).

79

In recent years the effects of bottom-up vs top-down vs external forces has been shown to play an [START_REF] Marsh | On the crystallinity, probability of occurrence, and rheology of lava and magma[END_REF][START_REF] Rosenberg | Experimental deformation of partially melted granite revisited: implications for the continental crust[END_REF].

103

Geophysical methods identify laterally and vertically elongated low-velocity zones with <10% melt 104 more consistent with a crystal mush system [START_REF] Koulakov | Rapid changes in magma storage beneath the Klyuchevskoy group of volcanoes inferred from time-dependent seismic tomography[END_REF]Ward et al., 2013;Sinton, 1992; 105 [START_REF] Lees | Seismic tomography of magmatic systems[END_REF][START_REF] Farrell | Tomography from 26 years of seismicity revealing that the spatial extent of the Yellowstone crustal magma reservoir extends well beyond the Yellowstone caldera[END_REF][START_REF] Huang | The Yellowstone magmatic system from the mantle plume to the upper crust[END_REF]Kiser et al., 2016;[START_REF] Pritchard | Geophysical evidence for silicic crustal melt in the continents: where, what kind, and how much?[END_REF] the close crystal contacts and the high viscosity which prevents convection and thereby limits most 108 heat lost through conduction [START_REF] Balmforth | Weakly nonlinear viscoplastic convection[END_REF]Dufek et al 2010;[START_REF] Blundy | Crustal magmatic systems from the perspective of heat transfer[END_REF].

109

The heat loss prevents large volumes of eruptible magma from forming but allows the mush system 110 to be maintained over long periods of time [START_REF] Blundy | Crustal magmatic systems from the perspective of heat transfer[END_REF]Cashman et al., 2017;Karakas 111 et al., 2017;[START_REF] Glazner | Thermal constraints on the longevity, depth, and vertical extent of magmatic systems[END_REF]. Periodic injections of recharge magma have also been shown by numerical 112 models to be sufficiently high or long enough to maintain some eruptible melt within a crystal mush 113 [START_REF] Huber | Crystal-poor versus crystal-rich ignimbrites: A competition between stirring and reactivation[END_REF][START_REF] Annen | Construction and evolution of igneous bodies: Towards an integrated perspective of crustal magmatism[END_REF][START_REF] Cooper | What does a magma reservoir look like? The "Crystal's-Eye" view[END_REF]. Long-lived, trans-crustal mush systems are 114 consistent with many of the features of arc volcanoes and the long-lived volcanic activity observed in 115 the arc (e.g., [START_REF] Balcone-Boissard | Deep pre-eruptive storage of silicic magmas feeding Plinian and domeforming eruptions of central and northern Dominica (Lesser Antilles) inferred from volatile contents of melt inclusions[END_REF]Metcalfe et al., 2022;Higgins et al., 2022).

116

The transition from crystal mush to an eruptible magma occurs over a narrow crystal content (Shaw, 117 1969;Caricchi et al., 2007;[START_REF] Costa | Time scales and petrogenesis of silicic magmas[END_REF]Burgisser and Bergantz, 2011;Sparks et al., 2019). The 118 energy required to remobilize a crystal mush depends on the initial melt content; mushes with a higher 119 initial melt content requirie less energy to remobilise [START_REF] Bachmann | Gas percolation in upper-crustal silicic crystal mushes as a mechanism for upward heat advection and rejuvenation of near-solidus magma bodies[END_REF]Bergantz et al., 120 2017;Sparks et al., 2019). Magma recharge and addition of volatiles are considered the main drivers 121 of remobilization (Scandone et al., 2007;[START_REF] Costa | Time scales and petrogenesis of silicic magmas[END_REF][START_REF] Mader | The rheology of two-phase magmas: A review and analysis[END_REF][START_REF] Rubin | Rapid cooling and cold storage in a silicic magma reservoir recorded in individual crystals[END_REF] 122 [START_REF] Cooper | Rapid remobilization of magmatic crystals kept in cold storage[END_REF]Sparks and Cashman, 2017;Jackson et al 2018). There are several hypotheses 123 on how a mush is remobilised. Many models involve a reduction in crystallinity through, for example,

124

reactive melt flow (Jackson et al., 2018) and the growth of a buoyant mobile layer (Burgisser and 125 Bergantz, 2011). This increases the melt fraction and leads to remobilization of the cold mush system 126 through overturn or unzipping of the mush system (Burgisser and Bergantz, 2011;Bergantz et al., 127 2015Bergantz et al., 127 , 2017;;Schleicher et al., 2016;Schleicher and Bergantz 2017;Carrara et al., 2019) The different 128 proposed mechanisms of remobilisation indicate that this is a complex process and may involve a 129 combination of mechanisms.

130

The Lesser Antilles Arc (LAA) is a good example of an active island arc, with a range of eruption styles 131 recorded and a wealth of geochemical data available, making it an excellent arc to investigate links 1 km -1 for the past 300 years (Wadge, 1984).

152

To the north of Martinique, the arc bifurcates into an inactive eastern limb and an active western limb 153 (Schlaphorst et al., 2018). The older eastern arc is composed of several islands which are now covered 161

Each island has at least one active volcanic complex except for Dominica, which has nine potentially 162 active volcanoes (e.g., Brown et al., 2015;[START_REF] Leone | Integrating spatial accessibility in the design of "volcano" evacuation plans: application in the French West Indies (Guadeloupe and Martinique)[END_REF]Fig 1) and Guadeloupe which has two 163 active volcanoes (Komorowski et al., 2005;[START_REF] Komorowski | European Catalogue of Volcanoes[END_REF]. Eruptions range from small 164 phreatic to effusive dome forming (ca. 9 -47 x 10 6 m 3 ; e.g., Shepard and Sigurdsson, 1982;Loughlin Palmer et al., 2016;Carazzo et al., 2020;Joseph et al., 2022). The twenty-three eruptions that have 167 occurred in the LAA since 1900 provide examples of how devastating an eruption in the LAA can be impacts (e.g., La Soufrière de Guadeloupe, 1976;Soufrière Hills, Montserrat, 1995-present;Lepointe, 174 1999;[START_REF] Blérald | Histoire économique de la Guadeloupe et de la Martinique: du XVIIe siècle à nos jours[END_REF]Kokelaar, 2002), all of which have profound impacts on the lives and livelihoods 175 of people in the LAA. Approximately one million people are threatened by the direct effect of volcanic is the variation in Wadati-Benioff zone dip, which diverges from 50 o -60 o in the Northern Arc to sub-182 vertical in the Southern Arc (e.g., Wadge and Shepard, 1984;Schlaphorst et al., 2018). In the Central

183

Arc the slab dips at ca. 20 o until 50 km depth where it increases to 45 o -55 o (Paulatto et al., 2017). et al., 2016;Melekhova et al., 2019;Schlaphorst et al., 2021). The range of crustal 189 thickness (20 -37 km) is considered to relate to long-term variations in magma productivity (Melekova 190 et al., 2019;[START_REF] Cooper | Variable water input controls evolution of the Lesser Antilles volcanic arc[END_REF]. Another contributing factor to the variation in magma production is

194

Two crustal layers are observed using seismic discontinuities (Boynton et al., 1979). The first 195 discontinuity is the upper crust, which extends to a variable depth of 2 -30 km along the arc and is a 196 plutonic igneous layer (Wadge, 1986;Schlaphorst et al., 2018). Below this is a layer of dense mafic 197 igneous rocks including cumulates directly overlying the mantle (the Moho), estimated between 30 -

7

Arnaiz-Rodrígues et al., 2016;Schlaphorst et al., 2021). Both discontinuities are found at greater 200 depths in the northern part of the arc, with the along arc variation in the discontinuities being

201

unusually strong (Schlaphorst et al., 2018). The strong variation in the nature of the discontinuities 202 results from variation in melt generation and differentiation (Schlaphorst et al., 2018).

203

Variations in upper plate mantle seismic velocities are also observed, seismicity is shown to be closely 204 related to hydration and dehydration processes and are controlled by thermal structure, composition

205

and state of stress (Paulatto et al., 2017;[START_REF] Ezenwaka | Thermally-constrained fluid circulation and seismicity in the Lesser Antilles subduction zone[END_REF]. Three main phases of dehydration two major fracture zones to the north (Paulatto et al., 2017;[START_REF] Cooper | Variable water input controls evolution of the Lesser Antilles volcanic arc[END_REF]Harmon et al., 2019; 211 Schlaphorst et al., 2021). The anomalies are thought to be related to either the upwelling of hot mantle 212 material or partial melt and fluids. A high δ 11 B anomaly is also observed in the Guadeloupe and

213

Dominica melt inclusions thought to be related to dewatering of serpentinised oceanic crust, occurring

214

close to the fracture zone to the north of the Central Arc [START_REF] Cooper | Variable water input controls evolution of the Lesser Antilles volcanic arc[END_REF]. Alternatively, the redistribution of fluids (Ha et al., 2020) or along-strike variability in the subducted plate morphology 217 could also account for the velocity anomalies observed.

3 Magma Composition and Magma Storage Across the Lesser Antilles Arc

219

A crystal mush is often described to be vertically extensive and consist of melt-rich lenses and solid 220 crystals (Cashman and Blundy, 2013;Cashman and Sparks, 2013;Cashman et al., 2017;Blundy et al., 221 2019). The mush exists under sub-solidus conditions for long timescales before remobilisation (e.g.,

222

Bachmann [START_REF] Bachmann | Gas percolation in upper-crustal silicic crystal mushes as a mechanism for upward heat advection and rejuvenation of near-solidus magma bodies[END_REF]Bergantz et al., 2015;Burgisser and Bergantz, 2011;Parmigiani et al 231 Blundy and Cashman, 2008;Putirka, 2008;Ridolfi et al., 2010); [3] Equilibrium experiments with the 232 Formatted: Font: +Body (Calibri), 11 pt Formatted: Font: +Body (Calibri), 11 pt [START_REF] Defant | Evidence suggests slab melting in arc magmas[END_REF]Roobol and Smith, 2004). Evidence of magma mixing in banded pumices and 306 rounded enclaves is observed [START_REF] Defant | Evidence suggests slab melting in arc magmas[END_REF]. However, no compositional differences between 307 the enclaves and other magmas are discussed [START_REF] Defant | Evidence suggests slab melting in arc magmas[END_REF].

324

Cumulates from Statia have mineral assemblages and textures that are similar to those observed in 325 xenoliths from Martinique [START_REF] Cooper | Time scales and temperatures of crystal storage in magma reservoirs: implications for magma reservoir dynamics[END_REF] with plagioclase, olivine, clinopyroxene,

326

orthopyroxene, amphibole and spinel interstitial melt also present (Cooper et al., 2016[START_REF] Cooper | Time scales and temperatures of crystal storage in magma reservoirs: implications for magma reservoir dynamics[END_REF]. Cooper

346

Bubbles are reported in the St Kitts MIs [START_REF] Toothill | A complex petrogenesis for an arc magmatic suite, St Kitts, Lesser Antilles[END_REF]Melekhova et al., 2017), however, MIs

347

with lower H2O or CO2 are not associated with larger bubbles (Melekhova et al., 2017). Xenoliths from

348

St Kitts are reported to be rich in plagioclase and amphibole.

349

An extensive, transcrustal magmatic mush system has been proposed by Melekhova et al. (2017) and [START_REF] Cooper | What does a magma reservoir look like? The "Crystal's-Eye" view[END_REF]Higgins et al., 2022). Though many magmas correspond to shallow depths, some melts are

361

362

shown to bypass equilibration with the shallower mush system and so preserve evidence of their studies to be conducted on the eruption products. Soufrière Hills Volcano on Montserrat, has 367 produced a restricted bulk composition of andesite (56 -62 wt% SiO2; e.g., Murphy et al., 2000

370

banded lava and pumice observed, however no significant difference in composition is noted between 371 layers (Murphy et al., 2000).

372

Mafic enclaves are hosted throughout the andesite, with the proportion of mafic enclaves increasing 373 from the Phase 1 (1995) deposits to the Phase 5 ( 2010) deposits (Barclay et al. 2010). The mafic understanding of this system is based on the key hypothesis that an andesitic magma body is

395

recharged by an intruding basaltic magma, which releases heat and volatiles and drives eruption (e.g.,

13

geochemical signatures in comparison to the active Soufrière Hills Volcano. This indicates that isolated 398 melt bodies within the crystal mush result in a heterogenous system, which is vertically and laterally 399 extensive (Devine et al., 2003;[START_REF] Edmonds | Extensive, water-rich magma reservoir beneath southern Montserrat[END_REF].

400

As well as being chemically heterogenous, the Soufrière Hills system is thought to be composed of 401 layers of mush (solid and crystalline), liquid (sub-solidus, eruptible magma) and exsolved fluid layers

402

(volatiles exsolved from the magma on saturation; Christopher et al., 2015;[START_REF] Edmonds | Extensive, water-rich magma reservoir beneath southern Montserrat[END_REF]. The

403

presence of fluid layers with exsolved fluids, resulting from magma recharge, may lead to instabilities 404 in the mush system and may result in overpressures that could fuel explosive eruptions (Christopher 405 et al., 2015;[START_REF] Edmonds | Extensive, water-rich magma reservoir beneath southern Montserrat[END_REF]. The cyclicity observed in the vulcanian eruptions was thought to 406 be related to the ascent of different magma batches. The ascent of magma to the surface was 407 calculated to take 5 -13 hours, consistent with the 12-hour cyclicity of the Vulcanian eruptions.

408

Geochemistry, petrology (e.g., Christopher et al., 2015;[START_REF] Edmonds | Extensive, water-rich magma reservoir beneath southern Montserrat[END_REF] and geophysical studies

409

(e.g., Paulatto et al., 2012) show the mush system extends from <4 to 16 km, with the main active 410 reservoir between 8 -12 km (Paulatto et al., 2012;Christopher et al., 2015;[START_REF] Edmonds | Extensive, water-rich magma reservoir beneath southern Montserrat[END_REF]; Fig

418

The whole rock composition of La Soufrière de Guadeloupe eruption products have also remained 419 consistent, though they do span a wide range of compositions (51 -61 wt% SiO2;[START_REF] Touboul | 238U-230Th-226Ra disequilibria in andesitic lavas of the last magmatic eruption of Guadeloupe Soufrièrre, French Antilles: processes and timescales of differentiation[END_REF] 420 [START_REF] Boudon | A new scenario for the last magmatic eruption of La Soufrière of Guadeloupe (Lesser Antilles) in 1530 AD Evidence from stratigraphy radiocarbon dating and magmatic evolution of erupted products[END_REF]Samper et al., 2009;Ricci et al., 2017;Pichavant et al., 2018;Metcalfe et al., 421 2022). The 1530 CE sub-Plinian eruption (Komorowski et al., 2008;[START_REF] Boudon | A new scenario for the last magmatic eruption of La Soufrière of Guadeloupe (Lesser Antilles) in 1530 AD Evidence from stratigraphy radiocarbon dating and magmatic evolution of erupted products[END_REF]Esposti Ongaro 422 et al., 2020) shows black-and-white banded pumices with characteristic mixing and mingling textures 423 between andesitic (ca. 62 wt% SiO2) and basaltic-andesite (55 wt% SiO2) compositions (Semet et al., 424 1981;Poussineau, 2005;[START_REF] Boudon | A new scenario for the last magmatic eruption of La Soufrière of Guadeloupe (Lesser Antilles) in 1530 AD Evidence from stratigraphy radiocarbon dating and magmatic evolution of erupted products[END_REF]Pichavant et al., 2018). Deposits from the Echelle scoria 425 cone also show a bimodal composition, with mixing textures between basaltic andesite and dacitc 426 compositions observed. To the south of La Soufrière de Guadeloupe, the Mont Caraïbes complex 427 erupted a basaltic composition (47 -50 wt% SiO2) and is often interpreted to represent the parental 428 magma for La Soufrière de Guadeloupe [START_REF] Bissainte-Lubino | Le complexe des Monts Caraïbes de Guadeloupe (Arc des Petites Antilles) Etude pétrographique, minéralogique et géochimique[END_REF][START_REF] Metcalfe | Insights into the Origin and Dynamics of Past Eruptions of La Soufrière de Guadeloupe from Melt Inclusions: Implications for Future Unrest and Environmental Impact[END_REF]. Eruption products Mont

429

Formatted: Font: +Body (Calibri), 11 pt Formatted: Font: +Body (Calibri), 11 pt maximum of 5.6 wt% H2O (Fig 4D;Pichavant et al., 2018;[START_REF] Cooper | Variable water input controls evolution of the Lesser Antilles volcanic arc[END_REF]Metcalfe et al., 2022).

445

The CO2 contents from Guadeloupe are much higher than those recorded in the Northern arc ranging 446 from <50 -1500 ppm (Fig 4E;[START_REF] Cooper | Variable water input controls evolution of the Lesser Antilles volcanic arc[END_REF]Metcalfe et al., 2022). MIs from from La Soufrière 447 de Guadeloupe are reported to be bubble-free (Metcalfe et al., 2022).

448

Most models of the current La Soufrière de Guadeloupe magma storage system have been based on 449 data collected for the 1530 CE eruption (Semet et al., 1981;[START_REF] Touboul | 238U-230Th-226Ra disequilibria in andesitic lavas of the last magmatic eruption of Guadeloupe Soufrièrre, French Antilles: processes and timescales of differentiation[END_REF][START_REF] Boudon | A new scenario for the last magmatic eruption of La Soufrière of Guadeloupe (Lesser Antilles) in 1530 AD Evidence from stratigraphy radiocarbon dating and magmatic evolution of erupted products[END_REF] 450 Pichavant et al., 2018). The observation of the compositionally banded 1530 CE eruption products 451 imply that the La Soufrière de Guadeloupe reservoir is chemically and physically heterogenous.

452

However, the relative compositional homogeneity of mineral phases observed in the 1530 CE eruption

453

products is difficult to reconcile with this scenario.

454

In the absence of any geophysical evidence for a deep long-lived magma reservoir, early 455 interpretations hypothesise the presence of an andesite magma body formed from fractional 456 crystallisation of a basaltic-andesite parental melt [START_REF] Touboul | 238U-230Th-226Ra disequilibria in andesitic lavas of the last magmatic eruption of Guadeloupe Soufrièrre, French Antilles: processes and timescales of differentiation[END_REF]Pichavant et al., 2018). The 457 shallow andesite body must be remobilised by a magma, as the andesite body is considered to be 458 homogenous until remobilisation caused by the arrival of basaltic magma (Semet et al., 1981;Touboul 459 et al., 2007;Pichavant et al., 2018). With the arrival of a mafic recharge magma chemical and physical 460 changes occur in the magma storage zone. A hybrid magma may also be formed through incomplete 461 mixing (Pichavant et al., 2018). The magma mixing and development of instabilities in the reservoir heat from magma at depth may allow remobilization with no interaction with a mafic magma.

475

Investigation of major and volatile elements of melt inclusions across several Holocene eruptions

476

shows the composition of the storage zone has remained stable during this time period (Metcalfe et

al., 2022

). There is some evidence for a deeper storage zone, hosting less -evolved compositions based 478 on the presence of a basaltic parental magma (Monts Caraibes) and the basalt produced by the Echelle

479

and Citerne scoria cones (Bissante, 1999;[START_REF] Legendre | Reconstruction fine de l'histoire éruptive et scenarii éruptifs à la soufrière de Guadeloupe: vers un modèle intégré de fonctionnement du volcan[END_REF]Metcalfe et al., 2022). Bissainte (1999)

486

historical non-magmatic phreatic activity produced from the long-lived hydrothermal system 487 [START_REF] Feuillard | The 1975-1977 crisis of La Soufrière de Guadeloupe (FWI): a still-born magmatic eruption[END_REF]Komorowski et al., 2005;Villemant et al., 2005;Rosas-Carbajal et al., 2015, 488 Moretti et al., 2020a). 489

Dominica 490

The whole rock composition of eruption products from Dominica ranges from 50 -67 wt% SiO2 491 (Lindsay et al., 2005;Howe et al., 2015;[START_REF] Boudon | Revised chronostratigraphy of recurrent ignimbritic eruptions in Dominica (Lesser Antilles arc): Implications on the behavior of the magma plumbing system[END_REF]d'Augustin et al., 2020), with no large-492 scale magma mixing or mingling textures reported (e.g., Howe et al., 2015;[START_REF] Boudon | Revised chronostratigraphy of recurrent ignimbritic eruptions in Dominica (Lesser Antilles arc): Implications on the behavior of the magma plumbing system[END_REF]; Solaro

539

Most studies on Martinique focus on the homogeneity of the composition of eruption products in the 540 last 13,500 years of activity, though a wide range of compositions are recorded (51 -66 wt% SiO2;

541 Gourgand et al., 1989;Smith and Roobol, 1990;Pichavant et al., 2002;[START_REF] Annen | Conditions for the growth of a longlived shallow crustal magma chamber below Mount Pelee volcano (Martinique, Lesser Antilles Arc)[END_REF]. The 542 majority of eruption products appear to be evolved in comparison to the Northern and Southern Arc

543

eruption products (Fig 3). Mafic lavas, mafic enclaves, and mingled/mixed products are also reported 544 in the eruptive history of the volcano [START_REF] Bourdier | Magma mixing in a main stage of formation of Montagne Pelée: the Saint Vincent-type scoria flow sequence (Martinique, FWI)[END_REF]Fichaut et al., 1989aFichaut et al., , 1989b comparable to St Lucia [START_REF] Cooper | Variable water input controls evolution of the Lesser Antilles volcanic arc[END_REF]. Vapour bubbles are not reported by [START_REF] Cooper | Variable water input controls evolution of the Lesser Antilles volcanic arc[END_REF].

556

The main andesitic magma reservoir beneath Montagne Pelée is inferred using the petrology of 557 erupted rocks as well as results from experimental petrology to be at pressures of 6 -9 km, ca. 200 ± 558 50 MPa (based on a density of 2650 kg m 3 ; Martel et al., 1998;Fig 2). Mafic magmas have been

559

experimentally determined to be stored at > 16 km (400 to 500 MPa), suggesting that the magmatic 560 transcrustal system below Montagne Pelée also has a similar deeper component, like magmatic density of 2660 kg/m (Christeson et al., 2008). Magma from the mid-crustal chamber recharges the 596 shallow chamber with mixing hypothesised between the two magmas, shown by resorption textures 597 observed in plagioclase.

601

basalt to andesite compositions (47 -62 wt% SiO2; Graham and Thirlwall, 1981;Heath et al., 1998; 602 Cole et al., 2019;[START_REF] Fedele | Petrological insights on the last 1000 years of explosive activity at La Soufrière volcano, St. Vincent (Lesser Antilles)[END_REF]Joseph et al., 2022). The majority of eruption deposits are basalt

603

to basaltic andesite, with andesite mainly found in mixed magma deposits as the more evolved 604 component. For example, banded and mingled textures are observed in the 1902-03 and 1979 605 eruption deposits (Carey and Sigurdsson, 1978;Graham and Thirlwall, 1981;Heath et al., 1998a). The 606 greatest compositional variation is observed in samples from the 1902-03 eruption (50 -55 wt% SiO2;

610

MIs hosted in plagioclase, orthopyroxene, clinopyroxene and titano-magnetite from Soufrière St

611

Vincent (55 -77 wt% SiO2; Heath et al., 1998;[START_REF] Cooper | Variable water input controls evolution of the Lesser Antilles volcanic arc[END_REF], are more comparable to those 612 from the Central Arc, spanning a similar range to the MIs from La Soufrière de Guadeloupe (Fig 4A).

613

As with the systems in the Central Arc (e.g., La Soufrière de Guadeloupe and Dominica) the MIs from

614

Soufrière St Vincent generally, indicate the system is fed by homogenous magmas with episodic 615 rejuvenation events [START_REF] Fedele | Petrological insights on the last 1000 years of explosive activity at La Soufrière volcano, St. Vincent (Lesser Antilles)[END_REF]. Devine and Sigurdsson (1982) and Bouvier et al. (2010b) 616 measured MIs in olivine from basaltic-andesite eruption products (43 -60 wt% SiO2). St Vincent

617

xenoliths lack orthopyroxene and are rich in olivine (Melekhova et al., 2019).

618

The majority of MIs from St Vincent record Cl contents ranging from 0.08 -0.29 wt%, with a few MIs

693

from the submarine volcano Kick 'em Jenny (Lindsay et al., 2005a; Table 1; Fig. 5). Most islands have 694 a single volcano from which Holocene eruptions have occurred, and which are likely to erupt again in can produce large explosive eruptions generating pyroclastic flows as well as lava domes and 708 associated block and ash-flows (e.g., [START_REF] Macdonald | The Lesser Antilles volcanic chain: a study in arc magmatism[END_REF]Lindsay et al., 2013;Smith et al., 709 2013;[START_REF] Bezard | Assimilation of sediments embedded in the oceanic arc crust: Myth or reality?[END_REF]Howe et al., 2015). Volcanoes of the Central Arc (Soufrière of Guadeloupe

714

of Soufrière of Guadeloupe [START_REF] Boudon | A new scenario for the last magmatic eruption of La Soufrière of Guadeloupe (Lesser Antilles) in 1530 AD Evidence from stratigraphy radiocarbon dating and magmatic evolution of erupted products[END_REF]Komorowski et al.? 2008;Esposti Ongaro et al., 715 2020). Larger magnitude VEI 5 Plinian eruptions have also been recorded, for example in Guadeloupe

716

(e.g., the Pintade eruption ca. 42 ka from the Grande Découverte-La Soufrière volcanic complex, 717 Komorowski et al., 2005), Dominica (e.g., the Roseau Tuff; Carey and Sigurdsson, 1980;Solaro et al., 718 2020) and St Lucia (e.g., the Belfond unit; Lindsay et al., 2013). However, such activity occurred 20,000

719

to 45,000 years ago, and Plinian eruptions of this scale are not recorded in recent history. As well as 720 stratovolcanoes, the Southern Arc activity has produced a diversity of eruptive phenomena including small explosion craters and lava flows, whereas large dome-forming eruptions are rare due to the 722 magma chemistry (Lindsay and Robertson, 2018).

and lasted until 15 November 1995. At this point the onset of dome growth was observed marking 744 the transition into the magmatic phases of the eruption.

745

Phase 1 (15 November 1995 -10 March 1998) began with a cycle of dome extrusion and Vulcanian

746

explosions leading to dome collapse and pyroclastic density current surges [START_REF] Voight | Remarkable cyclic ground deformation monitored in real-time on Montserrat, and its use in eruption forecasting[END_REF]Sparks 747 et al., 1998;Cole et al., 1998Cole et al., , 2002;;Robertson et al., 1998;Calder et al., 2002;Kokelaar, 2002;Wadge 748 et al., 2014). The explosion on 17 September 1996 produced a column that reached up to 15 km and 749 may have been of Sub-Plinian magnitude and intensity (Robertson et al., 1998). A noticeable pumice 750 deposit was produced with ashfall in the Caribbean region, which was particularly heavy in 751

Guadeloupe. In 1997 activity changed and two series of Vulcanian explosions occurred with a sub-

752

daily cyclic pattern that produced a total of 88 explosions (Druitt et al., 2002b). On 26 December 1997,

753

this phase of the eruption ended with partial edifice collapse of the old pre-eruption crater wall and 754 part of the growing dome. This led to the emplacement of a debris avalanche deposit that reached 755 the South-West coast and triggered a small tsunami with a maximum wave run-up height of 1 m on 756 the western shores of Montserrat (Sparks et al., 2002). The partial edifice collapse also resulted in a observed, these eruptions resulted in additional fracturing of the shallow regions of the volcanic 773 edifice which facilitated magma transport (Wadge et al., 2014)

785

eruption column and dome collapses (Chardot et al., 2010;Komorowski et al., 2010). Additional

786

Vulcanian explosions that produced pumice fallout deposits and small pumice-rich pyroclastic density 787 currents occurred on 3 December 2008, and 3 January 2009 (Komorowski et al., 2010). Phase 4 was

788

short but was characterised by a high degree of explosivity leading to pyroclastic density currents.

789

Lava extrusion rates were also high and there was a different cyclicity than observed in the previous 790 phases (Wadge et al., 2014).

and pyroclastic density currents. This was followed by large Vulcanian explosions and the termination

793

of phase 5 with a major dome collapse on 11 February 2010 (Stinton et al., 2014b). This generated the 794 second laterally directed explosion of the eruption, which directed high-energy, high-velocity,

795

turbulent, dilute pyroclastic density currents northward. This resulted in significant damage on areas

796

previously affected by pyroclastic density currents in 1997. This paroxysmal event, the last of the 797 ongoing eruption so-far, also generated widespread ashfalls in the Caribbean region from Guadeloupe

798

to Saint-Lucia (Komorowski et al., 2011;Cadelis et al., 2013). Since 11 th February 2010, a pause in the 799 dome growth began, which has continued up to the time of writing, making it the longest pause so far 800 in the eruption.

801

Overall, the eruption at Soufrière Hills has been characterised by periods of dome-growth, dome 802 collapse and a diversity of Vulcanian to Sub-Plinian explosions, with the eruption becoming 803 increasingly vigorous (Druitt and Kokelaar, 2002;Fig 5). In particular, the cyclicities of this eruption

804

have provided important observations on the nature of eruptions and have allowed a better 805 understanding of the drivers and behaviour of this volcano (Odbert et al., 2014). The cyclicity in

806

eruptive styles and the unique longevity of the eruption, highlight the importance of the continuous 807 monitoring of this system, which remains active and hazardous even during quiescence periods.

808

Following the end of lava extrusion and the last collapse event which occurred on 11th February 2010,

809

the Hazard Level was lowered from Level 4 to Level 3 and a pause in the eruption began (MVO

810

Scientific Updates, 2010-21). This followed the previous pattern in the eruption where activity was 811 minimal between eruption phases. However, it is unclear how long this pause in activity will last.

812

Through 2010 seismicity and SO2 emissions continued, as well as minor incandescence on the dome 817

Activity remained at a low level in 2012 and was characterized by spots of incandescence on the lava 818 dome and continued fumarolic activity and seismic swarms. Peaks in activity were often associated 819 with ash venting, with significant ash venting observed in March 2012, resulting in the formation of a 820 new crater. Large VT events associated with the venting are interpreted to be related to increasing 821 pressure below the volcano from uprising magma, while the ash venting was interpreted to be observed during this eruption, with escalation in activity possible as the eruption has not been

833

declared to be officially over. For the eruption to be considered over, the seismic activity, gas 834 emissions and deformation must all return to substantially lower levels than have so far been

835

observed.

838

-1977 phreatic eruption demonstrates the impact a limited VEI 2, non-magmatic, explosive eruption 839 can have (Komorowski et al., 2005;[START_REF] Legendre | Reconstruction fine de l'histoire éruptive et scenarii éruptifs à la soufrière de Guadeloupe: vers un modèle intégré de fonctionnement du volcan[END_REF]Komorowski et al., 2012;Rosas-Carbajal et al., 840 2016;Metcalfe et al., 2021a, b;[START_REF] Komorowski | European Catalogue of Volcanoes[END_REF]. This eruption also highlights the importance 841 of clear, effective and efficient crisis response management, and risk reduction plans. The eruption 842 posed a significant risk to the population of Guadeloupe and resulted in severe socio-economic

843

difficulties associated with the evacuation of >70,000 people from Basse-Terre, and had a lasting 844 influence on the population of Guadeloupe [START_REF] Le Guern | Soufriere of Guadeloupe 1976-1977 eruption-Mass and energy transfer and volcanic health hazards[END_REF][START_REF] Feuillard | The 1975-1977 crisis of La Soufrière de Guadeloupe (FWI): a still-born magmatic eruption[END_REF]Komorowski 845 et al., 2005;Hincks et al., 2014;Chenet et al., 2014;Komorowski et al., 2015). One year prior to the 846 1976 -77 event, volcanic seismicity began to increase with three distinct earthquake swarms (Feuillard 847 et al., 1983;Komorowski et al., 2005;Hincks et al., 2014). Despite this increase in seismicity, no large 848 changes in fumarolic activity were observed (Dorel and Feuillard, 1980;[START_REF] Feuillard | The 1975-1977 crisis of La Soufrière de Guadeloupe (FWI): a still-born magmatic eruption[END_REF]. One 849 month prior to the eruption a minor landslide occurred and new fractures formed [START_REF] Feuillard | La Soufrière de la Guadeloupe : un volcan et un peuple[END_REF]. 853 Some controversy has surrounded the scientific management of this eruption and the resulting crisis 854 response decisions made by authorities [START_REF] Feuillard | La Soufrière de la Guadeloupe : un volcan et un peuple[END_REF]Komorowski et al., 2005;[START_REF] Beauducel | Surveillance opérationnelle des volcans français: développements récents à la Guadeloupe[END_REF] 855 Hincks et al., 2014: Chenet et al., 2014;Komorowski et al., 2015;[START_REF] Komorowski | Challenges of volcanic crises on small islands states[END_REF]. Particularly 1997-1998(Villemant et al., 2014) ) and 2018 (Moretti et al., 2020).

877

However, Zlotnicki et al. (1992) proposed that new magma arrival is not required for a phreatic

884

hydrothermal system (Brombach et al., 2000;Ruzié et al., 2012;2013;[START_REF] Allard | Steam and gas emission rate from La Soufriere volcano, Guadeloupe (Lesser Antilles): implications for the magmatic supply during degassing unrest[END_REF]Jean-Baptiste 885 et al., 2014;Villemant et al., 2014;Tamburello et al., 2019;Inostroza et al., 2022a, b;Moretti et al., 886 2020a, b;Moune et al., 2022).

887

Following the 1976-77 eruption, monitoring of this volcano was increased to include continuous 888 seismic and geodetic monitoring (using global navigation satellite system; GNSS), gas plume five years fumarolic activity extended at the summit, and then more recently along its eastern flanks,

897

and to the top of the lava dome with the reactivation of three fumaroles (OVSG-IPGP, 1999-2021;

898 Komorowski et al., 2005;Tamburello et al., 2019;Jessop et al., 2021). Late 1997 and early 1998 marked 899 the onset of highly acidic chlorine-rich fluids degassing, which has continued till present day 900 (Komorowski et al., 2005;OVSG-IPGP, 1999[START_REF] Joseph | 14 submarine eruptions have also occurred from Kick[END_REF]Villemant et al., 2014;Moretti et al., 2020a,b).

901

Seismic activity is characterised by numerous, low magnitude (M <1), high-frequency volcano-tectonic 902 earthquakes which have been observed to increase in frequency and rate with twenty felt volcanic 903 earthquakes since 1992, including ten since 2013 (Komorowski et al., 2005;Moretti et al., 2020a). al., 2022). From June to December 2018 a decrease in SO2/H2S and CO2/H2S ratios was then observed.

912

913

These ratios indicate a pulse of fluid with deep hydrothermal/magmatic origin heated and pressurised 914 the hydrothermal system (Moretti et al., 2020a).

915

This episode period of accelerating unrest is interpreted as a failed phreatic eruption triggered by the 916 ascent of heat and fluids from the deep hydrothermal and magmatic system to shallow depths 917 (Moretti et al. 2020). Two hypotheses are formulated by Moretti et al. (2020a): [START_REF] Wallace | Melt inclusion CO2 contents, pressures of olivine crystallization, and the problem of shrinkage bubbles[END_REF] The deep magmatic 918 fluids, stored at mid-to low-crustal depths in the mush system, generated an upstreaming of 919 magmatic gases through the mush system and the crystallizing magma reservoir. This process leads 920 to cyclic rejuvenation of the magma and exsolution of dissolved volatiles that are released into the 921 hydrothermal system and cause heating and pressurisation.

[2] Episodic fresh injections of basaltic 922 magma from mid-crustal depths into the shallow magma reservoir of La Soufrière de Guadeloupe, However, for both hypotheses, Moretti et al. (2020a) show that the multiparameter unrest data

945

Guadeloupe is one of the most intense heat emitters globally among volcanic domes with an active

946

hydrothermal system (Jessop et al., 2021).

947

Looking more closely at the long term unrest at La Soufrière de Guadeloupe, particularly at the rate 948 of fracture opening and evolution of the permeability of the system through degassing and gas ratios, eruption (Zlotnicki et al., 1992;Moune et al., 2022). As the shallow hydrothermal system is hosted in pressurisation may reduce friction and increase pore pressure along mechanically weak pre-existing

958

Formatted: Font: +Body (Calibri), 11 pt Formatted: Font: +Body (Calibri), 11 pt consequences (e.g., Peruzzetto et al., 2019;Heap et al., 2021b). Such edifice collapses could occur 960 without the involvement of magma, as observed in the La Soufrière de Guadeloupe stratigraphic 961 record (Komorowski et al., 2005;Rosas-Carbajal et al., 2016). These collapses are associated with 962 moderate laterally directed explosions (up to VEI2) that can generate turbulent pyroclastic density 963 currents of limited extension (< 5 km) as described for the 1797-1798, 1836-1837, and 1976-1977 964 phreatic eruptions (Komorowski et al., 2005;Rosas-Carbajal et al., 2016).

967

the highest concentrations of active volcanoes in the world (Lindsay et al. 2005;Mayer et al., 2017).

968

These volcanoes have produced the highest erupted magma volume in the LAA (40 km 3 ; Wadge 1984; 969 1986; Macdonald et al., 2000; Di Napoli et al. 2014; Mayer et al., 2017)

974

The two most recent eruptions on Dominica have occurred from the Valley of Desolation-Boiling Lake 975 area in 1880 and 1997, with neither eruption witnessed (Lindsay et al., 2005;Fig 1). The 1880 eruption 976 was a large phreatic eruption with ash covering 55 km 2 , resulting in a slight ash fall 19 km out to sea 977 and the generation of lahars (Nicholls et al., 1880b). In comparison, the phreatic eruption occurring 978 on 8 th -9 th July 1997 was very small magnitude, however, as this eruption was unobserved little is 979 known about the dynamics. Subsequent investigation reported non-altered lava, hydrothermally 980 altered igneous minerals and hydrothermal minerals present [START_REF] Komorowski | Analytical results and report on the current activity of the Soufrière area as of December 8-9 1998[END_REF].

981

This eruption may have been triggered by the occurrence of several landslides. Fumarolic vents were 982 observed to be covered by landslide deposits, which has been hypothesised to have resulted in 983 pressurization of the hydrothermal system and produced a phreatic eruption (James, 1997; 984 [START_REF] Komorowski | Analytical results and report on the current activity of the Soufrière area as of December 8-9 1998[END_REF]Lindsay et al. 2005;Mayer 2017). The Boiling Lake itself 985 experiences considerable water level and temperature variations and experienced a small explosion 986 of CO2 and other gases in 1901, killing two people (Ober 1880;James 1988).

987

Activity at the other complexes varies greatly, with the majority of seismic and hydrothermal activity 988 occurring on the south of the island (Lindsay et al., 2005;Fig 1). The Plat Pays volcanic complex, which 989 is mainly comprised of lava domes, experiences a high number of seismic swarms and fumarolic 990 activity, this complex was active as recently as 450 years ago. Also, in the south of the island are the Morne Anglais and Morne Watt complexes which have a history of explosive eruptions and experience 992 regular seismic swarms (Lindsay et al., 2005;Fig 1). One of the potentially most dangerous complexes 993 is the Wotten Waven complex, which has a history of large explosive eruptions and produced the 994 Roseau Tuff. This complex experiences hydrothermal and fumarolic activity and a future explosive 995 eruption has the potential to affect most of Dominica (Lindsay et al., 2005).

996

In the north of the island the Morne Diablotins and Morne Aux Diables complexes also experience 997 considerable periods of unrest (Fig 1). Though no historical eruptions are recorded from these 998 complexes, and the majority of seismicity occurs in the south of the island, several periods of increased 999 seismic activity have been recorded in 1841, 1893, 2000and 2003(Lindsay et al., 2005)).

1000

Finally, the Trois Pitons and Grand Soufriere Hills complexes are the least active complexes and have 1001 no evidence for recent eruptions (Lindsay et al., 2005;Fig 1). However, they are poorly studied and do 1002 still experience periods of increased seismic activity. The eruptive record is poorly understood,

1003

particularly at Grand Soufriere Hills, and until new data is available on the eruptive history, the 1004 complex is considered active (Lindsay et al., 2005).

1005

All of Dominica's volcanoes are at the green volcanic alert level and continue to be monitored (UWI eruptions (Westercamp and Traineau, 1983;Carazzo et al., 2012;Michaud-Dubuy, 2019 underwent collapse and produced pyroclastic density currents (Carazzo et al., 2012(Carazzo et al., , 2019(Carazzo et al., , 2020;; these signals are as follows: [START_REF] Wallace | Melt inclusion CO2 contents, pressures of olivine crystallization, and the problem of shrinkage bubbles[END_REF] an ongoing perturbation of the hydrothermal system, perhaps related [START_REF] Aspinall | Eruption of Soufrière volcano on St. Vincent island, 1971-1972[END_REF][START_REF] Shepard | Robertson[END_REF]Robertson, 1992)

1135

Pyroclastic flows affected several valleys surrounding the volcano, but only reached the sea at Larikai 1136 valley. The explosive phase of the eruption was followed by six months of effusive dome growth 1137 [START_REF] Shepard | Robertson[END_REF]Robertson, 1995).

1138

The et al., 2011;Wallace et al., 2015;Cannatelli et al., 2016).

1201

In order to ensure the MIs are representative of the original melt care must be taken when choosing

1202

the MIs and also when processing the data.

1203

The majority of studies have avoided or discarded MIs with obvious signs of post entrapment 1204 crystallization (PEC), cracks or bubbles (e.g., [START_REF] Mann | Phenocryst-hosted melt inclusions record stalling of magma during ascent in the conduit and upper magma reservoir prior to vulcanian explosions, Soufrière Hills volcano, Montserrat, West Indies[END_REF][START_REF] Cooper | Variable water input controls evolution of the Lesser Antilles volcanic arc[END_REF]Metcalfe et al., 1205 2022; Supplementary datasheet 2). This ensures the MIs have experienced minimal PEMs and the 1206 composition has not been altered. For studies which report PEC, MIs with >10% PEC have been 1207

discarded (e.g., Camejo-Harry et al., 2019;d'Augustin et al., 2020). This leaves some MIs in the dataset 1208 presented here which have experienced <10% PEC, however, PEC has been shown to have negligible 1209 effects on both major and volatile elements for up to 11% PEC (Moretti et al., 2018). (Supplementary 1210 datasheet 2). Bubbles can also have a major impact on the volatile content, particularly CO2 with up 1211 to 90% CO2 sequestered in th bubble (e.g., Moore et al., 2015;Venugopal et al., 2020). In most studies, 1212 mis with bubbles were not analysed (e.g., [START_REF] Balcone-Boissard | Deep pre-eruptive storage of silicic magmas feeding Plinian and domeforming eruptions of central and northern Dominica (Lesser Antilles) inferred from volatile contents of melt inclusions[END_REF]d'Augustin et al., 2020) through analysis of deuterium (e.g., Metcalfe et al., 2022;Bouvier et al., 2010b), with MIs outside the to occur due to basaltic magmas becoming more likely to pond as the crust thickens, allowing further 1266 fractionation to more evolved compositions (Baker, 1982;Devine, 1995;[START_REF] Macdonald | The Lesser Antilles volcanic chain: a study in arc magmatism[END_REF]; Fig 1270 Subsequently, magma composition, which is at least partly controlled by density contrasts, crustal 1271 thickness, magma productivity and serpentine distribution, is a first order control on eruption style.

1272

This is observed in the Central arc which produce evolved compositions and large volume, explosive, 1273 caldera eruptions, dome building eruptions and associated voluminous pyroclastic density current 1274 deposits from stratovolcanoes [START_REF] Macdonald | The Lesser Antilles volcanic chain: a study in arc magmatism[END_REF]Lindsay et al., 2013;Smith et al., 2013;Bezard 1275[START_REF] Bezard | Assimilation of sediments embedded in the oceanic arc crust: Myth or reality?[END_REF]Howe et al., 2015a;Lindsay and Robertson, 2018;Fig 6).

1276

In contrast, the thinner crust in the Southern Arc which allows the eruption of more basaltic magmas 1277 erupting in explosion craters and mafic lava flows, with large dome-forming eruptions being less 1278 common (e.g., [START_REF] Arculus | Geology and geochemistry of the alkali basalt-andesite association of Grenada, Lesser Antilles island arc[END_REF]Brown et al., 1977;Thirlwall and Graham, 1984;Robertson, 2003; 1279 Lindsay and Robertson, 2018;[START_REF] Fedele | Petrological insights on the last 1000 years of explosive activity at La Soufrière volcano, St. Vincent (Lesser Antilles)[END_REF]. magma ascent rate, with faster magma ascents resulting in larger, more explosive eruptions. Along

1422

with magma composition and ascent rate, the state of the hydrothermal system can also influence 1423 eruption style and could be responsible for the range of eruption styles produced by each individual 1424 system. A slow ascending magma experiencing feedbacks between degassing and crystallization will 1425 be expected to erupt with low explosivity or effusively, however, sealing of the hydrothermal system 1426 and a reduction in permeability may favour the accumulation of gas, leading to over pressurisation 1427 and an explosive eruption (e.g., Cassidy et al., 2018;Metcalfe et al., 2022).

1428

In order to provide an appraisal of the prevalent degassing process (decompression degassing vs CO2-1429 infiltration), integrated into a fast and comprehensive visualization of the volcano plumbing systems 1430 from their source to the surface, we provide pressure vs CO2 (gas) diagrams (Fig 7). This has been used 1431 in literature to: [START_REF] Wallace | Melt inclusion CO2 contents, pressures of olivine crystallization, and the problem of shrinkage bubbles[END_REF] identify degassing processes such as decompression degassing and CO2-fluxing 1432 (Mangiacapra et al., 2008;[START_REF] Barsanti | Heterogeneous large total CO2 abundance in the shallow magmatic system of Kilauea volcano, Hawaii[END_REF][START_REF] Arienzo | The feeding system of Agnano-Monte Spina eruption (Campi Flegrei, Italy): Dragging the past into present activity and future scenarios[END_REF]Moretti et al., 2013Moretti et al., , 2019; Caricchi

1436

The accuracy of this representation is highly dependent on the performance of the adopted model for 1437 volatile melt-saturation, in particular, the model's sensitivity to compositional variations from deep to 1438 shallow regions [START_REF] Barsanti | Heterogeneous large total CO2 abundance in the shallow magmatic system of Kilauea volcano, Hawaii[END_REF]Papale et al., 2022). Among compositional variations, the redox-1439 induced partitioning of iron between FeO and Fe2O3 plays a major role in shifting the equilibrium 1440 pressure of H2O-CO2 saturation by a factor comparable, or even superior to, that of analytical errors 1441 on dissolved H2O and especially CO2 contents measured in melt inclusions (Moretti, 2022).

1442

For given fO2 values we calculated the iron oxidation state of each MI by means of the Ottonello et al.

1443

(2001) model extended to P> 1 bar and hydrous conditions, as in Moretti (2005). We first computed 1444

Fe 3+ /Fe(tot) of MIs, and therefore FeO and Fe2O3 contents, by using guess pressure values. Saturation 1536 months of unrest was followed by an effusive phase of eruption with evacuation not taking place until 1537 the explosive phase of eruption had begun (Joseph et al., 2022). Other systems such as La Soufrière 1538 de Guadeloupe could also potentially have short periods of monitorable unrest prior to eruption, as 1539

shown by diffusion timescales (e.g., Metcalfe et al., 2021 a,b). Diffusion timescales allow the 1540 calculation of the time between the last magmatic process that destabilizes the magma in the storage 1541 zone and eruption, for La Soufrière de Guadeloupe, this is calculated to be on the order of weeks for 1542 even large explosive eruptions at this system (Metcalfe et al., 2021a,b). The short time frames of Table 1 Sub-aerial eruptions in the LAA occurring in the 20 th and 21 st centuries [START_REF] Lacroix | La Montagne Pelée et ses éruptions[END_REF]Jolivet, 1733[START_REF] Jolivet | La crise volcanique de 1956 à la Soufrière de la Guadeloupe[END_REF][START_REF] Aspinall | Eruption of Soufrière volcano on St. Vincent island, 1971-1972[END_REF][START_REF] Shepard | Robertson[END_REF][START_REF] Feuillard | The 1975-1977 crisis of La Soufrière de Guadeloupe (FWI): a still-born magmatic eruption[END_REF][START_REF] Fournier | Boiling Lake of Dominica, West Indies: High-temperature volcanic crater lake dynamics[END_REF]Wadge et

Figure 1 Figure

 1 Figure 1

Figure 4

 4 Figure 4Click here to access/download;Figure;FIG4.pdf

481

  to ca. 16 to 30 km depth (Fig 2).

815

  along with occasional, small pyroclastic flows. This low level of activity continued into 2011, with the 816 Hazard Level reduced again to Level 2 in November 2011 (MVO Scientific Updates, 2010-21).

  with a peak in seismicity observed on 27 April 2018 when a M 4.1 earthquake was felt by the 906 Basse-Terre population, the largest earthquake in 42 years (OVSG-IPGP, 1999-2023; Moretti et al., 907 2020a).

927

  recorded prior to and after the M 4.1 earthquake, indicate that the high degree of fracturing and 928 permeability of the dome allowed fluid pressure to be released laterally, on pre-existing deep tectonic 929 discontinuities of the upper regions of the Grande-Découverte-La Soufrière volcanic complex(Moretti 930 et al., 2020a). Moreover,Moretti et al. (2020a) concluded, regardless of which of these hypotheses is 931 more realistic, the reoccurrence of unrest sequences could escalate to a magmatic eruption. This 932 scenario would result from the presence of either; a rejuvenated magma at shallow depth (ca. 3 km

  939 al., 2021). The total heat flux density has also increased over the 2010 -2020 period from 326 ± 69 940 W/m 2 -403 ± 24 W/m 2 , indicating an increase in thermal intensity at the summit. These changes are 941 related to the spread of fumarolic sites over the dome and also the propagation of thermal anomalies 942 on the summit. The observed increases in temperature, mass and heat flux correlate well with the 943 observed accelerating seismic and degassing unrest of La Soufrière de Guadeloupe over the last 944 decade. On the basis of this measured heat loss per unit (heat flux density, W/m 2 ), La Soufrière de

949

  could be interpreted as cycles of sealing and reopening of the hydrothermal system (Moune et al., 950 2022) For example, in March 2017 during a phase of increased permeability, liberation of native S and 951 sulphate and resulting increase of H2S degassing and a decrease in the CO2/H2S ratio could indicate

  active Holocene volcanic centres spread across the island which makes it one of

  Scientific Updates, 2001-22). A background level of seismicity is recorded with occasional swarms of elevated seismicity which, though significant, are considered part of the normal pattern of activity (UWI SRC Scientific Updates, 2001-22). Volcanic unrest has in the past been observed in northern (Morne aux Diables) and southern Dominica (Plat Pays Volcanic Centre). Swarms occurring in the southern complexes, particularly Morne Plat Pays and Morne Anglais, which are the youngest volcanoes on the island, are particularly significant as this is considered the most likely site of the next eruption (UWI SRC Scientific Updates, 2001-22).

  Fig.6).[START_REF] Cooper | Variable water input controls evolution of the Lesser Antilles volcanic arc[END_REF] demonstrated this through δ 11 B studies of melt inclusions across the arc with higher δ 11 B values observed in the Central Arc (Fig 6) related to fluids from serpentine dehydration. In comparison, δ 11 B values in the Northern and Southern arc are related to fluids from altered oceanic crust and sediment dehydration. The higher δ 11 B values in the Central Arc coincide with the location of the Marathon and Mercurius fracture zones subducted beneath the Central Arc.

3 )

 3 , determined by the decompression and cooling intervals. This simulated fractional crystallisation involving phases including olivine, plagioclase, orthopyroxene, clinopyroxene, amphibole, hornblende and spinel (supplementary datasheet 3). This modelled assemblage is coherent with the observed assemblage in whole rock samples across the LAA. The fractional crystallisation models predict nonlinear liquid lines of descent which both reproduce the general trend of the LAA whole rock data. This indicates the LAA magmas are related to one another by fractional crystallisation, and the differentiation trend observed can be explained by fractionation of a primitive melt with a composition similar to the most primitive Grenada eruption products (Fig3). However, there is a large spread of data, indicating magma mixing and crustal contamination are also occurring to produce the trends within the individual systems. For example, minor assimilation of crust or sediments is observed in St Lucia and Martinique magmas (e.g.,[START_REF] Bezard | Seeing through the effects of crustal assimilation to assess the source composition beneath the southern Lesser Antilles Arc[END_REF] and mixing textures observed in Guadeloupe (e.g.,[START_REF] Boudon | A new scenario for the last magmatic eruption of La Soufrière of Guadeloupe (Lesser Antilles) in 1530 AD Evidence from stratigraphy radiocarbon dating and magmatic evolution of erupted products[END_REF].The magmas from individual volcanoes are often compositionally homogenous across long lasting eruptions (e.g., Montserrat) and across several eruptions (e.g., Guadeloupe). For the volcanoes which have been most recently active (i.e., those in the central arc, Montserrat and St Vincent) the eruption products are described as having restricted bulk compositions and few systematic compositional changes. Together this indicates the 'active region' of the magma mush system being tapped and supplying eruptions has remained consistent in composition and also stable. Indeed, in their study of CO2-SO2-H2S gas emissions from Soufrière Hills inMontserrat, Edmonds et al. (2010) demonstrated that released gases must result from the mixing of shallow volatile-depleted rhyolitic gases with deep volatiles supplied by unerupted underplating mafic magma (basaltic andesite). Water content across the LAA from melt inclusions varies greatly, with large ranges observed at individual systems(Fig 6;

  Guadeloupe,Martinique and St Vincent (Fig 2). Layer 3 (12 -32 km) proposed byMelekhova et al. (2019) spans a wide range of depths and encompasses both the mid-crust (10 -18 km) and lower crust (>18 km) systems presented here. This means, for example, in Guadeloupe the lower crust system fits into theMelekhova et al. (2019) layer 3 (fig 2

(

  2001) model extended to P> 1 bar and hydrous conditions, as inMoretti (2005). We first computed Fe 3+ /Fe(tot) of MIs, and therefore FeO and Fe2O3 contents, by using guess pressure values. Saturation pressures (P(fluid)) from thePapale et al. (2006) model were then used to update Fe 3+ /Fe(tot) values via the redox model ofMoretti (2005) and the new FeO and Fe2O3 values were entered into thePapale et al. (2006) computation for pressure. Two to three iterations were sufficient to obtain consistent sets of fO2-Fe 3+ /Fe(tot)-P(fluid) values for the two models combined and solve the mutual effects played by FeO-Fe2O3 partitioning on equilibrium fluid pressures at H2O-CO2 saturation and the role of dissolved water on iron oxidation state(Moretti and Papale, 2004; Papale et al., 2006; Moretti, 2022, Moretti and Ottonello, 2022; Papale et al., 2022 for detailed discussions and examples on different melt compositions including basalt and andesite.When we begin to consider data from across the arc, the P vs CO2 data (Fig 7) shows the processes of decompression and fluxing are occuring above the Moho, and between ca. 200 and 100 MPa (ca. 4 -8 km). The data is spread over the whole H2O-CO2 range, giving us an estimate of the main levels of emplacement in the crust. Further spread in the gas composition may occur at this crustal level (ca. 200 -100 MPa, ca. 4 -8 km) due to magma differentiation and magma mixing. There are two main scenarios: (1) the first scenario is a 'static' scenario, wherethe data is spread over a large XCO2(gas) domain for a pressure interval. This is indicative of magma ponding at a given depth interval where H2O and CO2 fractionate due to fractional crystallization or CO2-driven dehydration processes. (2) the second scenario is a 'dynamic' scenario where we identify paths of magma ascent with either XCO2 increase (CO2-fluxing) or XCO2 decrease (decompression degassing). The P vs CO2 data indicates in the Northern Arc, St Kitts and Montserrat MI CO2 decreases with decompression of the magma across pressures of ca. 240 -100 MPa (Fig 7A). However, MIs from Statia are experiencing CO2 fluxing, shown by the CO2 increasing with decompression across the same pressure range of ca. 240 -100 MPa (Fig 7A). There are also a small cluster of St Kitts MIs at a higher pressure (>300 MPa) which are affected by CO2 fluxing (Fig 7A). In the Central arc decreasing with decompression is affecting the CO2 content in the majority of the MIs, this generally occurs across pressures of ca. <200 MPa (Fig 7B). Martinique and St Lucia MIs experience decompression over a narrower range (ca. <130 MPa) (Fig 7B). The Dominica MIs form a bimodal distribution, the data from Balcone-Boissard et al. (2018) (Fig 7B), has a very hydrous source and experiences CO2 fluxing over pressures from 375 -150 MPa. In comparison, the data from d'Augustin et al. (2020) is comparatively CO2-rich, with CO2 decreasing with decompression. The majority of these MIs from d'Augustin et al. (2020) experience decompression at <200 MPa, however, there are some MIs which are deeper at >500 MPa. In the Southern Arc, decompression and CO2 fluxing are affecting MIs, generally these processes occur at < 200 MPa, however, Grenada has a deeper source down to ca. 400 MPa (Fig 7C). Though there are only a few MIs data points for St Vincent, MI CO2 is decreasing with decompression across a narrow pressure range (150 -180 MPa; Fig 7C), however, with more data this range may be extended. The Kick 'em Jenny MIs show a wide spread of data, which also shows CO2 decreasing with decompression. There are also two high pressure (ca.600 MPa), CO2-rich data points which are outliers from the distribution (Fig 7C). Grenada has a very hydrous source and experiences CO2 fluxing over a wide range of pressures (60 -400 MPa; Fig 7C).

  alert levels and early-warning systems.Each island in the LAA has an active volcano with eruptions occurring in the Holocene, and 24 eruptions since 1900. Recent eruptions demonstrate the volcanoes of the LAA can result in thousands of deaths, large scale and long-term displacements and severe economic impacts. Though advancements in science, technology and our understanding of LAA volcanoes has undoubtedly prevented large numbers of casualties in the late 20 th and 21 st centuries, large evacuations of people remain unavoidable. Long term displacements of people require continued support to facilitate social and economic recovery. The majority of recent eruptive activity has occurred in the Central and Southern arcs, and though the northern arc should not be neglected, research focus should be based on where the next eruption is most likely to occur. This should include understanding the lateral extent of the storage systems and 'active regions' of mush, and as mentioned previously, with particular focus on Dominica which appears to have a much more laterally extensive system in comparison to the other islands. This also provides an area where monitoring efforts should be concentrated, in particular renewed unrest in Martinique and ongoing unrest in Guadeloupe should continue to be monitored carefully. This should include further studies of past eruptions to provide further constraints on the magma storage and behaviour and also careful monitoring of the hydrothermal systems. Overall, further research on the LAA must continue to be underpinned by the hazardous nature of the system and the tens of thousands of people that can be affected by even a small eruption. Continuing our advancement in understanding of the LAA is essential to continue to improve monitoring techniques, reduce the impact of eruption and provide clear crisis management. volcanic unrest" (coord.: R. Moretti), the project "Vers la Plateforme Régionale de Surveillance Tellurique du 50 uture" (PREST) co-funded by INTERREG Caraïbes V for the European Regional Development Fund, and the European Union's Horizon 2020 research and innovation programme, under grant agreement No 731070 (EUROVOLC project). This work was supported by the Institut National des Sciences de l'Univers (INSU-CNRS) and the CASAVA Project funded by the French Agence Nationale de la Recherche, 2009-2015 (ANR-09-RISK-02). The authors thank the OVSG-IPGP team for logistical support and help with data collection. We are grateful for help and information from Laurence and E. Barret (Vert Intense, Guadeloupe), we are grateful to P. Cole for providing St Vincent whole rock data and to T. Druitt for encouraging this review. We thank O. Higgins and two other anonymous reviewers for their constructive reviews which helped improved the manuscript. This study contributes to the IdEx Université Paris Cité ANR-18-IDEX-0001 and is Laboratory of excellence ClerVolc contribution number XX.

Figure Captions Figure 1

 Captions1 Figure Captions

Figure 2

 2 Figure 2 Schematic summary diagram of magma storage across the arc adapted from Melekohva et al. (2019). Storage models from along the arc are superimposed over the crustal structure (see key).

Figure 4

 4 Figure 4 Melt inclusion data from across the Lesser Antilles (A) SiO2; (B) Na2O + K2O; (C) Cl; (D) H2O; € CO2 vs volcano latitude. The most SiO2 rich magmas are observed in the Central Arc, while the least evolved magmas are found in the Southern Arc. Though the most evolved magmas are in the Central Arc, the most alkali rich magmas are found on Montserrat in the Northern Arc. Volatile content varies greatly across the arc, particularly H2O, however, magmas from the Central Arc notably more CO2 rich than the Northern and Southern Arcs. For full melt inclusion dataset see supplementary dataset 1.

Figure 5

 5 Figure 5 Timeline showing the distribution of LAA 20 th and 21 st Century eruption styles. Grey bars indicate years an eruption was occurring in the Lesser Antilles. For each eruption we show the main eruptive styles which occurred and indicate the maximum VEI. Where the data is available, we show the average bulk rock SiO2. Smaller and less explosive eruptions are more common (e.g., phreatic, vulcanian and dome) than larger explosive eruptions. Submarine eruptions are also common due to the high level of activity observed at Kick 'em Jenny.

Figure 6

 6 Figure 6 Panels showing: The Lesser Antilles and the location of the Marathon and Mercurius fault zones, 20 th century eruptions, crustal thickness, magma storage depth, magma temperature, MI SiO2 content, MI H2O content and MI δ 11 B content variation. Crustal thickness is highest in the central arc, which coincides with the shallow storage magma zones, the most evolved magma compositions, the highest MI δ 11 B content and the location of the Marathon and Mercurius fault zones.

Figure 7

 7 Figure 7 XCO2 in the gas phase v pressure for (A) The Northern Arc; (B) The Central Arc; (C) The Southern Arc. From this we can see the process of decompression and CO2 fluxing occurring across the arc, the direction of these processes are shown by the arrows. We highlight that in Dominica we see both process of CO2 fluxing (increasing CO2 with decreasing pressure) and decompression (decreasing CO2 with decreasing CO2). For full melt inclusion dataset see supplementary dataset 1. (Saba (Roobol

  23 along-arc. The Lesser Antilles Arc provides a perfect setting to investigate magma storage, magma 24 composition and eruptive style variations associated with arc volcanism. This arc is comprised of 25 eleven volcanically active islands. Since 1900, there have been 24 eruptions. Many eruptions have 26 resulted in thousands of deaths, large scale and long-term displacements and severe economic 27

42 magmas

 42 are likely to erupt explosively in the near future, given the unrest observed at many systems 43 in the central arc. Despite the fact that advancements in science, technology and our understanding 44 of volcanoes in the arc undoubtedly prevented large numbers of casualties in the late 20 th and 21 st observed at arc volcanoes within the same eruption (e.g., effusive to explosive and vice-versa; e.g.,

154

  in a carbonate platform -the Limestone Caribbees, which experienced active volcanism from the 155 Eocene to the mid-Oligocene. Activity on the arc has migrated westward forming the western arc, 156 which has been active since 20 Ma (Early Miocene to present (Fig 1);Westercamp and Tazieff, 1980).157Pleistocene to recent volcanism has occurred in narrow 10 km wide zones which are split into three 158 segments: the Northern Arc (Saba to Montserrat), the Central Arc (Guadeloupe to Martinique) and 159 the Southern Arc (St Lucia to Grenada(Sigurdsson and Carey, 1981;[START_REF] Wadge | Segmentation of the Lesser Antilles subduction zone[END_REF]

184

  Systematic variations in crustal thickness are observed along the Lesser Antilles Arc, with a greater 185 crustal thickness observed in the Northern and Central arcs. North of Martinique crustal thickness is 186 estimated between 30 -37 km (Arnaiz-Rodrígues et al., 2016; Melekhova et al., 2019; Schlaphorst et 187 al., 2021). South of Martinique the crust thins with crustal thickness estimated between 20 -30 km 188 (Arnaiz-Rodrígues

191

  the shift of the Marathon-Mercurius fracture zone from St Kitts (Northern Arc) to Dominica (Central 192 Arc), which is reflected in the greater crustal thickness in the Northern Arc (Paulatto et al., 2017; Bie 193 et al 2019; Cooper et al., 2020; Bie et al 2022).

206

  occur in the Atlantic slab: (1) 5 -20 km -compaction and draining of pore fluids from the sediments; 207 (2) 40 -100 km -chemical dehydration of the crust; (3) 120 -160 km lithospheric mantle 208 deserpentinization (van Keken et al., 2011; Paulatto et al., 2017). Notably slower seismic velocities are 209 observed below Guadeloupe, Dominica and Martinique where thicker crust occurs and is bound by

  210

  Fig 4C). A wide range of H2O is recorded (0.61 -5.93 wt%; Figure4D), and CO2 is comparable to other 322

327

  et al. (2019) calculate minimum volatile saturation pressures ranging from 0 -426 MPa, which 328 indicates storage at <15 km.

Formatted:

  Font: +Body (Calibri), 11 pt highest CO2 recorded in the northern Arc, this is still relatively low in comparison to the rest of the arc.

350

  Higgins et al. (2022) for the production of magmas at St Kitts. Depths are estimated from 351 thermobarometry of xenoliths and seismic modelling and range from 3 ->25 km. Though the deepest 352 part of the system is more difficult to distinguish as the cumulates are rarely observed, the deep 353 system is hypothesised to generate basalts -basaltic andesites through fractionation which ascend to 354 18 -25 km where they experience differentiation(Melekhova et al., 2017) (Fig 2). These basaltic-355andesites are considered the parental magmas for more evolved compositions which migrate upwards 356 and equilibrate with existing crystal mush(Melekhova et al., 2017; Fig 2). This means many eruption 357 products will have an equilibration pressure corresponding to shallow depths despite differentiation 358 beginning much deeper in the system. The majority of lavas erupted are supplied from the upper 359 portion of the transcrustal system, this is consistent with experimental data which indicates many 360 eruption products from St Kitts can be generated at 200 -550 MPa (ca. 3 km -15 km;Melekhova et

  Arc (Guadeloupe to Dominica) andesites are dominant, with some basalts and dacites 414 (Fig.3; 4). St Lucia is more commonly included in the Southern Arc based on seismic data (Wadge and 415[START_REF] Wadge | Segmentation of the Lesser Antilles subduction zone[END_REF], but fits into the Central Arc based on geochemistry and volcanology, so is also 416 discussed in this section.

480

  calculated crystallization pressures of 400 -900 MPa for Mont Caraïbes cumulates, which is equivalent 481 to ca. 16 to 30 km depth (Fig 2).482 Moretti et al. (2020) show the mush system is the source of heat and deep magmatic fluids that rise 483 and contribute to the hydrothermal system. The heat and fluids supplied by intrusions into the mush 484 system below 5 km are considered to be one possible cause of seismic activity (White and McCausland, 485 2016) and unrest episodes, as well as the potential cause of some of the more violent and long-lasting

493

  et al., 2020). The eruption products are relatively evolved within the LAA whole rock trend (Fig 3), 494 which is typical of the eruption products in the central arc. In comparison, the composition of MIs stored at ca. 16 km, ca. 400 MPa (based on a crustal density of 2450 g/m 3 ; Balcone-Boissard et al., 530 2018 and Solaro et al., 2019; Fig 2). In comparison, more recent Plinian eruptions (e.g., 8-18 ka) were 531 fed from magma that was sourced in shallower storage regions ≤ 7.3 km, ca. <200 MPa (based on a 532 mean crustal density of 2800 kg/m 3 ; d'Augustin et al., 2020), this is consistent with the system 533 described for Montserrat (Christopher et al., 2015; Edmonds et al., 2016; Fig 2). The similarities in 534 mineralogical and chemical composition, including comparable volatile element ratios for magma that 535 fed the ignimbritic eruption and the more recent Plinian eruptions indicate a common source. This 536 supports the existence of a transcrustal magmatic system extending from <7 -16 km (d'Augustin et 537 al., 2020; Fig 2).

  Fig 4A;[START_REF] Cooper | Variable water input controls evolution of the Lesser Antilles volcanic arc[END_REF] Martel et al., 1998). Na2O + K2O falls in the upper range observed in the 548

549

  Martinique xenoliths are comparable to those from St Kitts and are plagioclase-bearing(Cooper et al., 550 2016).551Volatiles from Martinique MI are reported by[START_REF] Cooper | Variable water input controls evolution of the Lesser Antilles volcanic arc[END_REF]. Cl contents(0.27 -0.30 wt% Cl; Fig 552 4C) fall into the range observed in the Central arc. H2O contents, however, are generally lower than 553 the others systems in the Central arc (<3.3 wt% H2O; Fig 4D) with one MI recording 5.2 wt% H2O. CO2 554 in Martinique MIs (<381 ppm; Fig 4E) is lower than observed in Guadeloupe and Dominica and is most 555

600

  Magmas from St Vincent have a narrow range of compositions, with Soufrière St Vincent producing

607

  Cole et al., 2019) with magmas from older eruptions generally being more homogenous and more 608 evolved (e.g., 1440 CE and 1580 CE;Cole et al., 2019). Despite the range of compositions, most of the 609 whole rock compositions appear relatively evolved within the LAA whole rock trend (Fig3).

619 extending the range to 0 .

 0 61 wt% Cl (Fig 4C; Heath et al., 1998; Bouvier et al., 2010b; Cooper et al., 620 2020;). H2O content is variable ranging from 1.50 -5.3 wt% (Fig 4D; Bouvier et al., 2010b; Cooper et 621 al., 2020), and CO2 contents are low (76 -103 ppm), however, this may be due to the small amount 622 of CO2 data available (Fig 4E; Cooper et al., 2020;). Vapour bubbles are reported by Heath et al. (1998) 623 and Bouvier et al. (2010b), therefore pressures must be considered minimum estimates. 624 Soufrière St Vincent experiences relatively steady-state behaviour, fed by homogenous magmas 625 initially stored at 7 km, ca. 200 MPa (based on a 2660 kg/m (Christeson et al., 2008)). Petrological and 626 geochemistry studies indicate magmas are stored in a shallow crustal reservoir at ca. 7 km (and including 9 from volcanoes on Guadeloupe, Martinique, St Vincent, Montserrat and Dominica and 14

710and

  Montagne Pelée) also have produced numerous explosive Plinian, VEI 4 eruptions (e.g., the P3 79 711 CE Plinian eruption of Montagne Pelée (Boudon and Balcone, 2021; Carazzo et al., 2020; Michaud-712 Dubuy et al., 2021), the 1010 CE GDS 3 eruption of La Soufrière (Legendre, 2012; Komorowski et al., 713 2012; Metcalfe et al., 2021a; 201b) as well as Subplinian VE3 eruptions such as the 1530 CE eruption

813

  related to hot gasses from a deep source passing through fractures. The observed deformation pattern 814 showed slow inflation of the volcano, with ash venting and degradation of the lava dome observed 815 along with occasional, small pyroclastic flows. This low level of activity continued into 2011, with the 816 Hazard Level reduced again to Level 2 in November 2011 (MVO Scientific Updates, 2010-21).

  de Guadeloupe has not experienced a magmatic eruption since 1657 CE, the 1976

850

  BetweenJuly 1976 and March 1977, 26 phreatic explosions occurred, which changed the mechanical 851 state of the dome through the opening of new major fractures and widening and deepening of existing 852 fractures and craters.

856

  concerning the report of fresh, unaltered, glassy andesite which was taken as evidence for the increase in heat flux and migration of chemically reactive fluids in the hydrothermal system are 873 responsible for the sealing of the host-rock and resulting pressurization of the system leading to the 874 phreatic activity observed. The injection of magma into the reservoir is interpreted as the triggering 875 source of several unrest episodes in La Soufrière de Guadeloupe's history including new pulses in 876 1992,

878

  eruption to occur. Therefore, hydrothermal activity alone, with deposition of impermeable clay 879 minerals that seal of fractures combined with high fluid circulation can result in pressurization of 880 aquifers and phreatic eruption. Moune et al. (2022) also discuss this model for generating phreatic 881 eruptions in the context of the more recent unrest. Independent of the exact mechanism required to 882 generate the phreatic event of 1976-77, all gas data and the hydrothermal fluid C, He and Cl isotopic 883 ratios indicate a persistent magma reservoir degassing and supplying fluids and heat to the shallow

904

  Between April 2017-December 2018 unrest reached the highest level since 1976-77 (Moretti et al., 905 2020a), with a peak in seismicity observed on 27 April 2018 when a M 4.1 earthquake was felt by the 906 Basse-Terre population, the largest earthquake in 42 years (OVSG-IPGP, 1999-2023; Moretti et al., chemistry were also detected before and after the April 2018 earthquake. Low CO2/H2S 909 and SO2/H2S ratios were observed until November 2017 when a strong chemical perturbation 910 occurred. Perturbations at the time of the earthquake resulted in high SO 2 /H2S, CO2/CH 4, H2 /H2O and 911 CO/CO 2 and He/CH 4 recorded by MultiGas and Giggenbach bottles(Moretti et al., 2020a,b; Moune et

927

  recorded prior to and after the M 4.1 earthquake, indicate that the high degree of fracturing and 928 permeability of the dome allowed fluid pressure to be released laterally, on pre-existing deep tectonic 929 discontinuities of the upper regions of the Grande-Découverte-La Soufrière volcanic complex(Moretti 930 et al., 2020a). Moreover,Moretti et al. (2020a) concluded, regardless of which of these hypotheses is 931 more realistic, the reoccurrence of unrest sequences could escalate to a magmatic eruption. This 932 scenario would result from the presence of either; a rejuvenated magma at shallow depth (ca. 3 km 933 below the summit) resulting from stalled small intrusions(Villemant et al., 2014), or injections of fresh 934 undegassed magma from depth resupplying the shallow magma storage zone of the upper mush 935 system.936Measurements of temperature and mass flux at fumaroles and thermal springs and ground 937 temperature measurements shows that between 2010 and 2020 widespread ground heating of the 938 summit occurred with an increase of the heat output from 0.2 ± 0.1 MW to 5.7 ± 0.9 MW(Jessop et 939 al., 2021). The total heat flux density has also increased over the 2010 -2020 period from 326 ± 69 940 W/m 2 -403 ± 24 W/m 2 , indicating an increase in thermal intensity at the summit. These changes are 941 related to the spread of fumarolic sites over the dome and also the propagation of thermal anomalies 942 on the summit. The observed increases in temperature, mass and heat flux correlate well with the 943 observed accelerating seismic and degassing unrest of La Soufrière de Guadeloupe over the last 944 decade. On the basis of this measured heat loss per unit (heat flux density, W/m 2 ), La Soufrière de

949

  could be interpreted as cycles of sealing and reopening of the hydrothermal system(Moune et al., 950 2022) For example, in March 2017 during a phase of increased permeability, liberation of native S and 951 sulphate and resulting increase of H2S degassing and a decrease in the CO2/H2S ratio could indicate 952 the release of the seal which prevented escalation to a phreatic eruption(Zlotnicki et al., 1992; Moune 953 et al., 2022). Despite this, the cycle of sealing and reopening of fractures and transfer of heat from a 954 lower aquifer, to an upper one (with high fluid circulation) raises concerns for a future phreatic 955

  active Holocene volcanic centres spread across the island which makes it one of

1006SRC

  Scientific Updates, 2001-22). A background level of seismicity is recorded with occasional swarms 1007 of elevated seismicity which, though significant, are considered part of the normal pattern of activity 1008 (UWI SRC Scientific Updates, 2001-22). Volcanic unrest has in the past been observed in northern 1009 (Morne aux Diables) and southern Dominica (Plat Pays Volcanic Centre). Swarms occurring in the 1010 southern complexes, particularly Morne Plat Pays and Morne Anglais, which are the youngest 1011 volcanoes on the island, are particularly significant as this is considered the most likely site of the next 1012 eruption (UWI SRC Scientific Updates, 2001-22).

1013 4 . 4

 44 Montagne Pelée, Martinique 1014 The eruptive record of Montagne Pelée shows a history of sub-Plinian to Plinian and dome-forming 1015

  most recent eruption of Soufrière St Vincent began in December 2020, making this the most 1139 recent period of volcanic activity in the Lesser Antilles (Global Volcanism Program, 2021; Joseph et al., 1140 2022). This eruption began with an effusive phase on 27 th December 2020 with dome growth in the 1141 south-west sector of the crater floor, adjacent to the 1979 dome. Increasing seismicity culminated in The latest update on the volcano was in March 2022 when seismic activity was reported to have 1175 reached a minimum, no significant change in deformation signal had been observed and no change in 1176 gas composition has been observed in the plume. This activity is considered to be at levels similar to 1177 background activity recorded prior to the 2020 -2021 eruption and the alert level was lowered to 1178 green.

  Kick 'em Jenny has erupted 14 times in the 20 th and 21 st centuries, making this 1181 the most active volcano in the LAA (Figure 5). The most recent eruption occurred in 2017, following 1182 this eruption the alert level was reduced to yellow (UWI SRC scientific updates 2020). This alert level 1183 has remained at yellow due to periods of seismic unrest being recorded (UWI SRC scientific updates 1184 2020). 1185 Prior to the 2001 eruption, Kick 'em Jenny eruptions were not associated with precursory seismicity, 1186 as far as is known (UWI SRC scientific updates 2020). The 2001 eruption marked a change in behaviour, 1187 with this and the following 2015 and 2017 eruptions associated with precursory seismicity. Following 1188 the 2017 eruption several periods of high level seismic unrest have been recorded. The most recent 1189 period of unrest occurred from April to June 2020, which included >1000 volcanic earthquakes with a have experienced sufficient magma recharge to generate eruptions without further high level 1194 seismicity, as observed for the pre-2001 eruptions. However, further periods of seismic unrest without 1195 eruption are also considered likely (UWI SRC scientific updates 2020). significant post entrapment modifications (PEM) which can result in changes to the 1200 composition of the MI (e.g., Steele-Macinnis

  1220 crystallization, shown through increasing contents of incompatible trace elements (Wallace et al., 1221 1999; Blundy and Cashman, 2008). d'Augustin et al. (2020) also show minimum H+ diffusion by 1222 comparing H2O content with Li content. The effect of H+ diffusion has also been ensured to be minimal 1223 Formatted: Font: +Body (Calibri), 11 pt Formatted: Normal (Web), Space Before: 0 pt, After: 0 pt Formatted: Font: (Default) +Body (Calibri) Formatted: Font: (Default) +Body (Calibri), 11 pt Formatted: Font: (Default) +Body (Calibri) Formatted: Font: (Default) +Body (Calibri)

1224

  Fig. 6).1247

  1265

  1267 6). This suggests that the homogenous composition produced from a narrow range of shallow storage 1268 depths in the central arc, is due to the thicker crust which is allowing for the ponding and fractionation 1269 of basaltic magmas (Fig 6).

  are the most primitive and are particularly silica-poor and could represent a 1283 potential parental magma composition which would fractionate to produce the suites of magma 1284 observed across the Arc. The whole rock compositions in equilibrium with a primitive magma are 1285 shown on Figure3, and plot below the FeO/MgO ratio corresponding to olivine Fo 90 , using Kd ol-liq = 1286 0.3 (e.g.,Melekhova et al., 2019). Using the compositions of the primitive Grenada whole rock we 1287 Formatted: Font: +Body (Calibri), 11 pt Formatted: Tab stops: Not at 2.01"

1433

  et al., 2018; Papale et al., 2022), and [2] provide a straightforward petrologic/geochemical image of 1434 volcano plumbing systems which integrates geophysical information and highlights depth intervals of 1435 magma storage.

  fluid)) from the Papale et al. (2006) model were then used to update Fe 3+ /Fe(tot) values via 1446 the redox model of Moretti (2005) and the new FeO and Fe2O3 values were entered into the Papale et 1447 al. (2006) computation for pressure. Two to three iterations were sufficient to obtain consistent sets 1448 of fO2-Fe 3+ /Fe(tot)-P(fluid) values for the two models combined and solve the mutual effects played by 1449 FeO-Fe2O3 partitioning on equilibrium fluid pressures at H2O-CO2 saturation and the role of dissolved 1450 Formatted: Normal, Tab stops: 2.01", Left Formatted: Font: +Body (Calibri), 11 pt, Not Highlight Formatted: Font: +Body (Calibri), 11 pt decompression. The majority of these MIs from d'Augustin et al. (2020) experience decompression at 1476 <200 MPa, however, there are some MIs which are deeper at >500 MPa. 1477 In the Southern Arc, decompression and CO2 fluxing are affecting MIs, generally these processes occur 1478 at < 200 MPa, however, Grenada has a deeper source down to ca. 400 MPa (Fig 7C). Though there are 1479 only a few MIs data points for St Vincent, MI CO2 is decreasing with decompression across a narrow 1480 pressure range (150 -180 MPa; Fig 7C), however, with more data this range may be extended. The 1481 Kick 'em Jenny MIs show a wide spread of data, which also shows CO2 decreasing with decompression. 1482 There are also two high pressure (ca.600 MPa), CO2-rich data points which are outliers from the 1483 Formatted: Font: +Body (Calibri), Not Bold Formatted: Font: +Body (Calibri), Not Bold Formatted: Font: +Body (Calibri), Not Bold Formatted: Font: +Body (Calibri), Not Bold Formatted: Font: +Body (Calibri) Formatted: Font: +Body (Calibri), Not Bold Formatted: Font: +Body (Calibri), Not Bold Formatted: Font: +Body (Calibri), Not Bold Formatted: Font: +Body (Calibri), Not Bold, Font color: Auto, English (United States), Pattern: Clear Formatted: Normal, Space Before: 6 pt, After: 6 pt, Tab stops: 2.01", Left Formatted: Font: (Default) +Body (Calibri), 11 pt Formatted: Normal (Web), Tab stops: Not at 2.01" monitorable unrest can vary greatly even within the same system. In the case of St Vincent, the two 1533 most recent explosive eruptions have had very short periods of monitorable unrest (on the order of 1534 days for the 1979 eruption and 2 months for the 2020 eruption (onset in November 2020; Joseph et 1535 al., 2022; UWI SRC scientific updates 2020-21). In the case of the St Vincent 2020 eruption, the 2

1543

  escalation from monitorable unrest to eruption and then an explosive phase requires efficient and 1544 effective monitoring plans, to allow for timely and successful crisis management and evacuation, as 1545 was demonstrated by the remarkable crisis response to the Soufrière of St Vincent eruption in 2020 1546(Joseph et al., 2022).1547Much can be learnt from the handling of the 2020 Soufrière St Vincent eruption and the support that 1548 has been provided for the evacuated people. However, though people begun to return to their homes 1549 a few months after the eruption, some people remain displaced and support had to be continued over under grant agreement No 731070 (EUROVOLC project). This work was supported by the Institut 1637 National des Sciences de l'Univers (INSU-CNRS) and the CASAVA Project funded by the French Agence 1638 Nationale de la Recherche, 2009-2015 (ANR-09-RISK-02). The authors thank the OVSG-IPGP team for 1639 logistical support and help with data collection. We are grateful for help and information from 1640 Laurence and E. Barret (Vert Intense, Guadeloupe), we are grateful to P. Cole for providing St Vincent

1641Figure Captions 1646 Figure 1 Figure 3 Figure 5 Figure 6

 16461356 Figure Captions1646

  Figures and Tables17401741 1742 1743 1744

  FIGURE 5 1755 1756 1757 1758

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  ; Wadge 368 et al., 2014). No systematic changes in bulk composition have been observed since the beginning of 369 the most recent eruption in 1995. Mixing and mingling textures are reported on Montserrat with rare,

  1096to the circulation of hot and pressurized fluids of hydrothermal and/or magmatic origin, observed via 1097 the seismicity with high and low frequencies content. No felt earthquakes have been reported since 1098 the onset of unrest, though the number of VTs is above the base level recorded between 1 st January 1099 1999 and 1 st January 2019; [2] strongly degraded, browned and dead vegetation zones observed in 1100 2021 on the southwest flank of the volcano which show a pulsatory increase and decrease in size;[3] 1101 a minor deformation from June 2021 to June 2022 is revealed by continuous GNSS data, best modelled 1102 as a source of inflation located about 1 km below and slightly SW of the summit, above the 1103 hydrothermal system;[4] the detection of an area of underwater gas emission at shallow depths since 1104

	1131	In comparison, a completely effusive eruption was observed in 1971-72. This eruption saw the
	1132	aseismic emplacement of a basaltic-andesite dome, a direct contrast to the major explosive eruption
		observed in 1902
		June 2021.

1105

The ongoing unrest features most likely reflect the ascent of a limited volume of deep magmatic fluids 1106 which reinvigorated the shallow hydrothermal circulation. Though no surface fumarolic activity is 1107 observed, extensive monitoring of this system is still required given the fact that there is no pre-1108 eruptive unrest monitored by a multiparameter network. Although an extended period of 13 years 1109 preceded the major eruption of Montagne Pelée in 1902, we cannot expect that this is a characteristic 1110 of magmatic eruptions at Montagne Pelée after extensive times of quiescence.

  . Explosive activity began 1133 13 th April 1979 following elevated seismicity and lasted for 13 days until 26 April. The explosive phase 1134 of the eruption consisted of 11 vulcanian explosions that produced eruptions columns up to 18 km.

Table 1

 1

									Unrest
	Island	Volcano	Summit Temperature ( o C) *	Eruption start	Eruption end	Main Eruptive Style	Maximum VEI	Eruptive Phases	Period Reported Prior to	Number of Deaths	People Evacuated
									Eruption
								-Dome growth
	St Vincent	Soufrière St Vincent	>95	2020	2021	Explosive	4	-Cyclic vulcanian explosions	~2 months**	0	>16,000
								-Sub-Plinian activity
	Dominica	Morne Watt	91 -99	1997	1997	Phreatic	1	-Unobserved phreatic explosion	N/A	0	0
								-Cyclic dome growth and
								collapse,
	Montserrat	Soufrière Hills	98 -99	1995	Ongoing Explosive	3 -4	-Cyclic vulcanian explosions	3 years	19	>6,000
								-Sub-Plinian activity
								-Lateral blasts
	St Vincent	Soufrière St Vincent	-	1979	1979	Explosive	3	-Vulcanian explosions -Dome growth	~days	2	20,000
	Guadeloupe	La Soufrière de Guadeloupe	~100	1976	1977	Phreatic	2	-26 phreatic explosions	13 months	0	70,000

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3.1.3 St Kitts

Guadeloupe are more typical of those observed (Fig3).

Analysis of MIs found in clinopyroxene, orthopyroxene and plagioclase from La Soufrière de

hosted in orthopyroxene, clinopyroxene and plagioclase from Dominica shows a narrower range (69

2020). This suggests the system is heterogeneous in temperature(Solaro et al., 2019(Solaro et al., , 2020)).

Harry et al., 2019). Bubble-free MIs were analysed byCamejo-Harry et al. (2019).

explosion. This generated a high-energy, high-velocity, turbulent, dilute pyroclastic density current,

and resulted in the most widespread destruction recorded during the eruption[START_REF] Young | Hazard implications of small-scale edifice instability and sector collapse : a case history from Soufriere Hills volcano, Montserrat[END_REF]

lava extrusion(Kokelaar, 2002).

Phase 2 (27 November 1999 -28 July 2003) was preceded by seismic swarms, ash venting and small

tons per day, though some short-lived peaks in seismic activity and SO2 output do occur (MVO

ScientificUpdates, 2010-21). In recent years, lahars, pyroclastic flows and rockfalls pose the most

Komorowski et al., 2005; Jacob et al., 2005;[START_REF] Beauducel | Surveillance opérationnelle des volcans français: développements récents à la Guadeloupe[END_REF] Villemant et al., 2005; 2014; Moretti et

al., 2020a,b; Jessop et al., 2021; Moune et al., 2022;[START_REF] Komorowski | European Catalogue of Volcanoes[END_REF]. This allowed decreasing

activity to be observed from 1984, with minimal activity observed through the 1980s until May 1992

when seismic swarms and a new degassing phase began with summit fumarole reactivation(Zlotnicki

et al, 1994; Komorowski et al., 2001;Komorowski et al., 2005; OVSG-IPGP, 1999[START_REF] Joseph | 14 submarine eruptions have also occurred from Kick[END_REF]. Over the next

located between a depth of 5.1 and 8 km triggers the pulsatory ascent of high-temperature and high-

centuries, large evacuations of people remain unavoidable. In some cases, evacuation becomes long

Formatted: Font: +Body (Calibri), 11 pt

and across several eruptions with an observed repose period(Cassidy et al., 2018). Magma

composition is often considered a first order control on eruption style (e.g.,Sides et al., 2014;[START_REF] Firth | Variable conditions of magma storage and differentiation with links to eruption style at Ambrym volcano, Vanuatu[END_REF]

[START_REF] Pritchard | Towards coordinated regional multi-satellite InSAR volcano observations: results from the Latin America pilot project[END_REF][START_REF] Cordell | Imaging the Laguna del Maule Volcanic Field, central Chile using magnetotellurics: Evidence for crustal melt regions laterally-offset from surface vents and lava flows[END_REF]. A magma mush can exist at a lower temperature due to

years in the LAA. In comparison, the Central American arc has a magma production rate of 62 km 3 Ma -

(Table1). Recent eruptions have resulted in thousands of deaths (e.g., 29,800 at Montagne Pelée in

[START_REF] Lacroix | La Montagne Pelée et ses éruptions[END_REF]; 1350 at La Soufrière St Vincent in 1902[START_REF] Brown | Volcanic fatalities database: analysis of volcanic threat with distance and victim classification[END_REF][START_REF] Pyle | The 1902-3 eruptions of the Soufrière, St Vincent: Impacts, relief and response[END_REF]

Table1), the short and long-term displacement of thousands more (e.g., La Soufrière de Guadeloupe,

1976; Soufrière Hills Volcano,Montserrat, 1995; Soufrière St. Vincent, 2021 (Lepointe, 1999;

Komorowski et al., 2005;[START_REF] Feuillard | La Soufrière de la Guadeloupe : un volcan et un peuple[END_REF] Joseph et al., 2022); Table1) and long-lasting economic

activity in the Lesser Antilles, and related phenomena threaten approximately two and a half million

people(Lindsay et al., 2005a;[START_REF] Leone | Integrating spatial accessibility in the design of "volcano" evacuation plans: application in the French West Indies (Guadeloupe and Martinique)[END_REF].

There are notable variations in geochemistry, volcanic activity, crustal structure and seismicity

observed along the LAA, including variations(Boynton et al., 1979; Macdonald et al., 2000, Melekhova

et al., 2019; Hayes et al., 2014; Schlaphorst et al., 2018; 2021;[START_REF] Cooper | Variable water input controls evolution of the Lesser Antilles volcanic arc[END_REF]. An example of this

km depth (e.g.,Boynton et al., 1979; Christeson et al., 2008;[START_REF] Kopp | Deep structure of the central Lesser Antilles Island Arc: Relevance for the formation of continental crust[END_REF][START_REF] Laigle | Seismic structure and activity of the north-central Lesser Antilles subduction zone from an integrated approach: Similarities with the Tohoku forearc[END_REF]

curvature of the arc (e.g.,Harris et al., 2018; Schlaphorst et al., 2017), ponding of melt and resulting

Cashman et al. (2017).

Conditions of the mush system are calculated through:[START_REF] Wallace | Melt inclusion CO2 contents, pressures of olivine crystallization, and the problem of shrinkage bubbles[END_REF] Melt inclusion volatile contents which are

Pichavant et al., 2002Pichavant et al., , 2018;; Solaro et al., 2019 Solaro et al., , 2020)).

(e.g.,Moretti et al., 2019;[START_REF] Boudon | Volcanological evolution of Montagne Pelée (Martinique): A textbook case of alternating Plinian and dome-forming eruptions[END_REF]. Despite this, the deeper system is

is available in Supplementary dataset 1 (built on compilation by DIGIS Team, 2022).

In the Northern Arc (Saba to Montserrat) the dominant rock type ranges from basalt to andesite (e.g.,

Rea and Baker, 1980; Fig 3). However, on several islands the compositional range can vary greatly,

from basalt to rhyolite.

3.1.1 Saba

Eruption deposit compositions from Saba range from basalts to andesites (49 -66 wt% SiO2), with the

basalts representing some of the least evolved compositions observed in the NorthernArc (Fig 3;

Melt inclusions (MIs) are also unevolved, particularly in comparison to other MIs in the Northern Arc,

and generally fall in the range 46 -56 wt% SIO2 (Fig 4A;Roobol and Smith, 2004). However, Na2O +

K2O contents(1.7 -4.6 wt% Na2O, 0.36 -0.45 wt% K2O; Fig 4B) fall into the range observed in the.

Northern Arc(Roobol and Smith, 2004). No volatile data or pressure data is reported for Saba.

3.1.2 St Eustatius (Statia)

Magmas erupted from The Quill on St Eustatius (Statia) are dominantly andesitic in composition,

however, a broader range of compositions are observed ranging from basalt to rhyolite (50 -72 wt%

SiO2;Roobol and Smith 2004). The compositions are generally relatively evolved, particularly in

[START_REF] Toothill | A complex petrogenesis for an arc magmatic suite, St Kitts, Lesser Antilles[END_REF] Melekohva et al., 2017; Higgins et al., 2021). The most recent active volcano on

St Kitts is Mt Liamuiga where basaltic-andesites and andesites are most common(42.1 -65.4 wt%

SiO2;[START_REF] Baker | Geochemical evolution of St Kitts and Montserrat, Lesser Antilles[END_REF][START_REF] Toothill | A complex petrogenesis for an arc magmatic suite, St Kitts, Lesser Antilles[END_REF] Melekhova et al., 2017; Higgins et al., 2021). Many Mt Liamuiga

eruption products are considered to be hybrid magmas from mixing of basalt, basaltic andesite and

andesite magmas, and are the product of open-system processes[START_REF] Toothill | A complex petrogenesis for an arc magmatic suite, St Kitts, Lesser Antilles[END_REF]. These magmas

cover nearly the whole range of compositions observed in the LAA (Fig3).

MIs hosted in plagioclase, clinopyroxene, orthopyroxene, ilmenite and amphibole from St Kitts range

Volatiles in MIs from St Kitts record Cl contents in the range 0.15 -0.43 wt%(Fig 4C; Toothill et al.,

2007;Melekhova et al., 2017;[START_REF] Cooper | Variable water input controls evolution of the Lesser Antilles volcanic arc[END_REF] with one MI recording 0.66 wt% Cl. H2O recorded

in the MI is variable ranging from 0.4 -8.2 wt%; Fig 4D;[START_REF] Toothill | A complex petrogenesis for an arc magmatic suite, St Kitts, Lesser Antilles[END_REF] Melekhova et al., 2017;

[START_REF] Cooper | Variable water input controls evolution of the Lesser Antilles volcanic arc[END_REF], this is the highest H2O content recorded in the Northern Arc. CO2 ranges from 15

-721 ppm(Fig 4E;[START_REF] Toothill | A complex petrogenesis for an arc magmatic suite, St Kitts, Lesser Antilles[END_REF] Melekhova et al., 2017;[START_REF] Cooper | Variable water input controls evolution of the Lesser Antilles volcanic arc[END_REF], though this is the

origin in the deeper system(Melekhova et al., 2017).

The ongoing, multiphase eruption of Soufrière Hills Volcano on Montserrat has allowed many in depth

enclaves are generally less evolved than the andesite they are hosted in (49 -56 wt% SiO2(Murphy et

al., 2000; Christopher et al., 2014; Plail et al., 2018)), and some overlap in composition is observed

with the South Soufrière Hills magmas found in the south of the island (e.g.,[START_REF] Baker | Geochemical evolution of St Kitts and Montserrat, Lesser Antilles[END_REF] Murphy et

al., 2000; Wadge et al., 2014). The eruption products are some of the most evolved in the Northern

Arc, and do not extend to the same unevolved compositions observed on Saba and St Kitts (Fig3).

Montserrat has a large amount of MI data available due to the large amount of work done on the 1995

This provides a snapshot of the magma system as it was directly prior to the eruption. Our

Murphy et al., 2000; Wadge et al., 2014). Studies of South Soufrière Hills Volcano reveal a distinct

Guadeloupe, and the neighbouring monogenetic cone of Echelle range from 58 -79 wt% SiO2 (Fig 4

the Central Arc[START_REF] Metcalfe | Insights into the Origin and Dynamics of Past Eruptions of La Soufrière de Guadeloupe from Melt Inclusions: Implications for Future Unrest and Environmental Impact[END_REF] Fig 4). Guadeloupe xenoliths are reported as plagioclase-rich,

isotropic and homogeneous, but texturally diverse. Bissainte (1999) describe gabbroic cumulates and

granodioritic enclaves which are interpreted as fragments of a granodioritic basement.

Guadeloupe MIs record variable Cl contents ranging from 0.06 -0.36 (Fig 4C;[START_REF] Cooper | Variable water input controls evolution of the Lesser Antilles volcanic arc[END_REF]

Metcalfe et al., 2022;[START_REF] Metcalfe | Insights into the Origin and Dynamics of Past Eruptions of La Soufrière de Guadeloupe from Melt Inclusions: Implications for Future Unrest and Environmental Impact[END_REF]. H2O generally falls in the range 1.85 -4.42 wt%, with a

a minimum depth of the La Soufrière Guadeloupe magma reservoir between 5.6 and 7.1 km (135 -

MPa, based on a density of 2450 kg m -3 ;[START_REF] Barnoud | 3-D linear inversion of gravity data: method and application to Basse-Terre volcanic island, Guadeloupe, Lesser Antilles[END_REF], and a maximum depth of 8.5 km

given the absence of amphibole phenocrysts in the juvenile eruptive products .

Moretti et al. (2020a) proposed a deep gas supply from a crystal mush conceptual model as used at

magmas(Fig 2). Remobilization of this mush system to produce eruptible magma may occur through

the injection of mafic magma from depth into the shallow system, resulting in magma mixing.

Alternatively, in eruptions where no mixing textures are observed (e.g., 1657 CE), exsolved fluids and

-79 wt% SiO2, 0.2 -4.5 wt% K2O, 1.1 -3.9 wt%; Fig4A, B) and is homogenous, regardless of eruption

[START_REF] Balcone-Boissard | Deep pre-eruptive storage of silicic magmas feeding Plinian and domeforming eruptions of central and northern Dominica (Lesser Antilles) inferred from volatile contents of melt inclusions[END_REF] d'Augustin et al., 2020;[START_REF] Cooper | Variable water input controls evolution of the Lesser Antilles volcanic arc[END_REF][START_REF] Ostorero | Timewindow into the transcrustal plumbing system dynamics of Dominica (Lesser Antilles)[END_REF].

Xenoliths from Dominica are dominated by olivine with well-equilibrated textures(Ziberna et al.,

2017;Melekhova et al., 2019).

MIs from Dominica record a similar range of Cl contents (0.15 -0.38 wt% Cl) as observed in

Guadeloupe and across the Central arc in general(Fig 4C;[START_REF] Balcone-Boissard | Deep pre-eruptive storage of silicic magmas feeding Plinian and domeforming eruptions of central and northern Dominica (Lesser Antilles) inferred from volatile contents of melt inclusions[END_REF][START_REF] Ostorero | Timewindow into the transcrustal plumbing system dynamics of Dominica (Lesser Antilles)[END_REF]

[START_REF] Moretti | UWI-SRC 2020-22[END_REF][START_REF] Cooper | Variable water input controls evolution of the Lesser Antilles volcanic arc[END_REF]. H2O contents from Dominica are the highest observed in the Central

The large ignimbrite eruptions observed on Dominica (e.g., 60 and 24 ka BP) were fed from magmas

feeding systems identified in Dominica and Montserrat(Pichavant et al., 2002;[START_REF] Edmonds | Extensive, water-rich magma reservoir beneath southern Montserrat[END_REF].

magmas evolve and undergo homogenisation, leading to the eruption of chemically homogeneous

magmas(Fedele et al., 2021) (Fig 2). The stored magmas exsolve volatiles which contribute to the

build-up of pressure in the shallow system which may trigger eruptions(Cole et al., 2019;[START_REF] Fedele | [END_REF]

al., 2021). The 2020 -2021 eruption is inferred to have begun with the remaining 1979 high-viscosity,

'em Jenny, suggesting the presence of a main storage region at ca.[7][8][9][10][11][12]

on densities of 2500 -2750 kg/m 3 ; Camejo-Harry et al., 2019), with some shallower networks of melt

Volcanism, Eruptive Style and Volcanic Unrest Across the Arc

the future (e.g., Saba, Statia, Nevis, Montserrat, Martinique, St Vincent). However, more complicated

systems are present with two active volcanoes in Guadeloupe (La Soufrière de Guadeloupe volcano,

and the Trois-Rivières-Madeleine volcanic complex;Komorowski et al., 2005; Samper et al., 2009;

[START_REF] Komorowski | FOR LA SOUFRIERE OF GUADELOUPE VOLCANO: INSIGHTS FROM A NEW ERUPTIVE CHRONOLOGY[END_REF] 2022) and nine potentially active volcanoes in Dominica(Lindsay et al.,

2003, 2005c). Since 1900, eruptions have varied in size and style ranging from subaerial phreatic (e.g.,

Guadeloupe 1956 and 1976-1977[START_REF] Le Guern | Soufriere of Guadeloupe 1976-1977 eruption-Mass and energy transfer and volcanic health hazards[END_REF][START_REF] Feuillard | The 1975-1977 crisis of La Soufrière de Guadeloupe (FWI): a still-born magmatic eruption[END_REF] Zlotnicki et al., 1992;

Komorowski et al., 2005; 2018; Hincks et al., 2014); Dominica 1997(Mayer et al., 2017; ; Global

Volcanism Program, 2023) to magmatic (e.g.,Montserrat 1995 -present (Wadge et al., 2014) and St

Vincent in 2020-2021(Joseph et al., 2022). Submarine eruptions have also occurred at Kick 'em Jenny

(Devine and Sigurdsson, 1995;[START_REF] Allen | 30 Years in the Life of an Active Submarine Volcano: A Time-Lapse Bathymetry Study of the Kick-'em-Jenny Volcano, Lesser Antilles[END_REF]; Table 1; Fig 5).

Most volcanoes in the LAA are stratovolcanoes which have often experienced lava domes eruptions,

particularly in the Northern and Central arcs (including St Lucia). The Northern and Central volcanoes

Some of the most recent sub-aerial, magmatic activity has occurred on the islands of Martinique (e.g.,

-1905;[START_REF] Brombach | Geochemistry of the thermal springs and fumaroles 1928 of Basse-Terre Island, Guadeloupe, Lesser Antilles[END_REF] -1932), St Vincent (e.g., 1902; 1971[START_REF] Camejo-Harry | Evolution in magma storage 1970 conditions beneath Kick-'em-Jenny and Kick-'em-Jack submarine volcanoes, Lesser Antilles 1971 arc[END_REF][START_REF] Shepard | Robertson[END_REF] and 2020 -2021) and Montserrat

(e.g., 1995 -present). These eruptions exemplify the multi-phase, transitional activity style that occurs

at volcanoes in the Lesser Antilles (Table1; Fig 5). Here, we discuss some of the most recent and

important eruptions in the Lesser Antilles. Therefore, we demonstrate the hazards the volcanoes

pose, and the potential impact for the people living on the islands. We also discuss recent unrest at

these systems and the implications for future eruptions.

4.1 Soufrière Hills Volcano, Montserrat

blasts and vulcanian explosions, [6] eruption transitions from effusive to explosive activity triggered

by dome collapse, and [7] sub-surface processes and structure of the system, amongst many others.

This eruption is split into five phases with intervals of minimal activity which escalated to the next

phase(Cole et al., 2014a). Phases 1 -3 were long-lived in comparison to Phases 4 -5 which were

shorter but more vigorous(Wadge et al., 2014a). The onset of the eruption was preceded by three

years of elevated local seismicity(Robertson et al., 2000;[START_REF] Young | Hazard implications of small-scale edifice instability and sector collapse : a case history from Soufriere Hills volcano, Montserrat[END_REF] Shepherd et al., 2002;

Odbert et al., 2014b) which was followed by an explosive phreatic phase that began on 18 July 1995

sudden decompression at the base of the growing dome, triggering a violent laterally-directed

explosions(Norton et al., 2002). This culminated in pumice-bearing explosions and later initiated the

block-and-ash flows into the sea (e.g.,[START_REF] Friant | Eruption of Soufrière Hills (1995-2009) from an offshore perspective: Insights from repeated swath bathymetry surveys[END_REF]. Phase 2 ended with a series of Vulcanian

explosions and a total dome collapse of ca. 2x10 6 m 3 of lava(Edmonds et al., 2006;[START_REF] Voight | Remarkable cyclic ground deformation monitored in real-time on Montserrat, and its use in eruption forecasting[END_REF]

2010b).

Prior to Phase 3 (1 August 2005 -20 April 2007) a 3.5 month-long series of phreatic episodes was

Wadge et al., 2014). Through the beginning of 2006 dome growth rate and direction varied and by

May 2006 a lava spine with an approximate diameter of 50 m had grown. Complete dome collapse,

Phase 5 (9th October 2009 -11 th February 2010) began with ash venting followed by lava extrusion

phreatic in origin (MVO Scientific Updates, 2010-21).

This low level of activity continued through 2013 and 2014 with periods of elevated seismicity and gas

emissions. However, no changes to fumarolic activity or the dome were observed and in August 2014

the Hazard Level was lowered again to Level 1 (MVO Scientific Updates, 2010-21). Since 2017, activity

has remained low and consistent with short-lived seismic swarms and SO2 output generally at 200 -

ScientificUpdates, 2010-21). The monitoring data is consistent with the previous pauses in activity

1976;Brousse et al., 1977; Heiken et al., 1980). This observation had a major influence on the scientific

management of the crisis, though ultimately the material was identified as non-juvenile clasts

removed from a pumice fallout deposited during the 1530 CE eruption[START_REF] Boudon | A new scenario for the last magmatic eruption of La Soufrière of Guadeloupe (Lesser Antilles) in 1530 AD Evidence from stratigraphy radiocarbon dating and magmatic evolution of erupted products[END_REF]

Komorowski et al., 2008).

There is also some debate on the cause of this eruption with two models proposed. The more widely

accepted model relates the phreatic eruption to a 'still-born' magmatic event[START_REF] Feuillard | The 1975-1977 crisis of La Soufrière de Guadeloupe (FWI): a still-born magmatic eruption[END_REF].

observed and considered to support this model[START_REF] Feuillard | The 1975-1977 crisis of La Soufrière de Guadeloupe (FWI): a still-born magmatic eruption[END_REF] Villemant et al., 2005;[START_REF] Boichu | Degassing at La Soufrière de Guadeloupe volcano (Lesser Antilles) since the last eruptive crisis in 1975-77: Result of a shallow magma intrusion?[END_REF]

et al., 2011; Li et al., 2016). Ruzié et al. (2012) suggest new magma is being continuously injected into

a shallow magma reservoir at ca. 6 km based on modelling of the flux of noble gas isotopes ( 4 He/ 3 He;

R/Ra) in hydrothermal fluids and on petrological analysis of the 1530 CE eruption deposits(Semet et

[START_REF] Marsh | On the crystallinity, probability of occurrence, and rheology of lava and magma[END_REF] Pichavant et al., 2018). Magmatic gases are buffered by the hydrothermal system but an

monitoring, meteorological networks, periodic extensometric surveys of lava dome fractures,

fumarole gas and thermal spring sampling and thermal monitoring(OVSG-IPGP, 1999[START_REF] Joseph | 14 submarine eruptions have also occurred from Kick[END_REF]

may exceed the tensile strength of the rocks and lead to a phreatic eruption.

the hydrothermally altered core of the dome(Heap et al., 2021a; 2021b; 2022a; 2022b), any

[START_REF] Michaud-Dubuy | Impact of wind direction variability on hazard assessment in Martinique (Lesser Antilles): The example of the 13.5 ka cal BP Bellefontaine Plinian eruption of Mount Pelée volcano[END_REF]. At least 5 of the numerous phases of eruptions in the last 2000 years are

associated with lava dome growth and collapse(Carazzo et al., 2019(Carazzo et al., , 2020;; Michaud-Dubuy, 2019;

[START_REF] Boudon | Volcanological evolution of Montagne Pelée (Martinique): A textbook case of alternating Plinian and dome-forming eruptions[END_REF] along with violent laterally directed explosions at the base of the

dome. These explosions produced devastating, highly energetic and mobile pyroclastic density

et al., 2017). During this explosive phase, a vertical Vulcanian explosion on 9th July occurred on the

authorities in charge of civil protection. This was implemented by the authorities on 4 th December

Signs of the current unrest have been detailed inOVSM, 2020-2022 and Fontaine et al., (2021; 2022),

Vincent began with an increase in seismic activity. However, unlike Montagne Pelée's extended period

(though a longer period of unrest, with earthquakes going unfelt by the population, cannot be

[START_REF] Anderson | IX. Report on the eruptions of the soufrière, St. Vincent, 1902, and on a visit to Montagne Pelèe, in Martinique.-Part I[END_REF] Roobol and Smith, 1975;[START_REF] Pyle | The 1902-3 eruptions of the Soufrière, St Vincent: Impacts, relief and response[END_REF]. The eruption continued with intermittent

vulcanian explosions until March 1903(Roobol and Smith, 1975;[START_REF] Pyle | The 1902-3 eruptions of the Soufrière, St Vincent: Impacts, relief and response[END_REF].

April 2021 with a transition from effusive to explosive behaviour, following three months of dome

growth. On recommendation from the scientists from the Seismic Research Center (UWI Trinidad)

maximum magnitude 3.1 earthquake recorded (UWI SRC scientific updates 2020).

This period of unrest is interpreted to relate to magma intrusion or pressure changes (due to

crystallisation or degassing) (UWI SRC scientific updates 2020). It is also hypothesised the system may

Corrections and checks to the MIs have been applied by: Toothill et al., 2007, Bouvier et al., 2010 a,b,

Melekhova et al., 2017[START_REF] Balcone-Boissard | Deep pre-eruptive storage of silicic magmas feeding Plinian and domeforming eruptions of central and northern Dominica (Lesser Antilles) inferred from volatile contents of melt inclusions[END_REF], Camejo-Harry et al., 2019[START_REF] Cooper | Time scales and temperatures of crystal storage in magma reservoirs: implications for magma reservoir dynamics[END_REF]

This has been discussed as a potential cause of the 1976-77 La Soufrière phreatic eruption(Zlotnicki

et al., 1992) and given the build-up of hydrothermal pressure observed in 2018, it may have led to a

phreatic eruption if the fractured state, hence the high permeability of the dome had not allowed for

release of the pressure(Moretti et al., 2020a; Moune et al., 2022).

Metcalfe et al. (2022) hypothesise that eruption style at La Soufriere de Guadeloupe is controlled by

When we begin to consider data from across the arc, the P vs CO2 data (Fig 7)shows the processes of

decompression and fluxing are occuring above the Moho, and between ca. 200 and 100 MPa (ca. 4 -

km). The data is spread over the whole H2O-CO2 range, giving us an estimate of the main levels of

MIs, this generally occurs across pressures of ca. <200 MPa (Fig 7B). Martinique and St Lucia MIs

experience decompression over a narrower range (ca. <130 MPa) (Fig7B). The Dominica MIs form a

bimodal distribution, the data from Balcone-Boissard et al. (2018) (Fig 7B, highlighted by the red

circle), has a very hydrous source and experiences CO2 fluxing over pressures from 375 -150 MPa. In

comparison, the data from d'Augustin et al. (2020) is comparatively CO2-rich, with CO2 decreasing with

et al., 2013), gravity surveys and magnetotellurics imaging at sea using ocean bottom stations (e.g.,

[START_REF] Darnet | Mapping the geometry of volcanic systems with magnetotelluric soundings: Results from a land and marine magnetotelluric survey performed during the 2018-2019 Mayotte seismovolcanic crisis[END_REF] may help to resolve and provide additional information on the structure of the

magmatic reservoir. This should include understanding the lateral extent of the storage systems and

'active regions' of mush, with particular focus on Dominica which appears to have a much more

Robertson, 2018)

Volcano monitoring has shown major advancements over the last fifty years, however, the period of

'active region' of the magma systems supplying eruptions can remain homogenous in composition

and also stable over long periods of time, perhaps by buffering recharge from depth.

Relating the sub-surface processes occurring leading up to an eruption, and the monitorable surface

Formatted: Font: (Default) +Body (Calibri), 11 pt Formatted: Default

1), along with the MELTS models (supplementary dataset 32).

PhD project and fieldwork this paper stemmed from. RM conceptualized the Pressure-CO2,gas

diagram, performed calculations and with AM discussed and interpreted the results. All authors

discussed the data, wrote and revised the manuscript and the figures.

France) and the IPGP Ecole Doctorale. We thank IPGP for general funding to the Observatoires

Volcanologiques et Sismologiques (OVS), the INSU-CNRS for funding provided by Service National

d'Observation en Volcanologie (SNOV), a Tellus-Aleas project to SM (2020), Insights into the dynamics

of the active hydrothermal system of La Soufrière de Guadeloupe from past eruptions), and the French

Ministère pour la Transition Ecologique et Solidaire (MTES) for financial support. This work has been

supported by the Clervolc (UCA-LMV), the AO-IPGP 2018 project "Depth to surface propagation of

fluid-related anomalies at La Soufrière de Guadeloupe volcano (FWI): timing and implications for

volcanic unrest" (coord.: R. Moretti), the project "Vers la Plateforme Régionale de Surveillance

Tellurique du 50 uture" _(PREST) co-funded by INTERREG Caraïbes V for the European Regional

Development Fund, and the European Union's Horizon 2020 research and innovation programme,

centres which are <2 Ma, are split into three areas of the arc: Northern, Central and Southern (Wadge

[START_REF] Wadge | Segmentation of the Lesser Antilles subduction zone[END_REF] including the submarine volcano Kick 'em Jenny. Also shown are the active

volcanoes which have had eruptions since 1270 CE (red triangles) and eruptions in the Holocene

(orange triangles). These twenty-one Holocene active volcanoes have the potential to impact tens of

thousands of people living in the Lesser Antilles. The photographs show the variation in morphology:

St Kitts -the northern flank of Mt Lliamuiga; Montserrat -Soufriere Hills Volcano morphology

following eruption, with collapse features and lahar deposits; Guadeloupe -the La Soufriere de

related to mixing. (Saba[START_REF] Defant | Evidence suggests slab melting in arc magmas[END_REF] Roobol and Smith, 2004); Statia(Roobol and Smith, 2004);

Soufrière and Mont Caraïbes, Toubol et al., 2007;[START_REF] Boudon | A new scenario for the last magmatic eruption of La Soufrière of Guadeloupe (Lesser Antilles) in 1530 AD Evidence from stratigraphy radiocarbon dating and magmatic evolution of erupted products[END_REF] Samper et al., 2009; Ricci et al.,

2017;Pichavant et al., 2018; Metcalfe et al., 2021 Metcalfe et al., , 2022)); Dominica(Lindsay et al., 2005; Howe et al.,

greatly across the arc, particularly H2O, however, magmas from the Central Arc notably more CO2 rich

than the Northern and Southern Arcs. For full melt inclusion dataset see supplementary dataset 1.

(Saba(Roobol and Smith, 2004); Statia[START_REF] Cooper | Variable water input controls evolution of the Lesser Antilles volcanic arc[END_REF]; St Kitts[START_REF] Toothill | A complex petrogenesis for an arc magmatic suite, St Kitts, Lesser Antilles[END_REF] Melekhova

et al., 2017;[START_REF] Cooper | Variable water input controls evolution of the Lesser Antilles volcanic arc[END_REF]; Redonda[START_REF] Cooper | Variable water input controls evolution of the Lesser Antilles volcanic arc[END_REF]; Montserrat(Devine et al., 1998;

Humphreys et al., 2010; Mann et aal., 2013;[START_REF] Cooper | Variable water input controls evolution of the Lesser Antilles volcanic arc[END_REF]; Guadeloupe(Poussineau,2005;

[START_REF] Boudon | A new scenario for the last magmatic eruption of La Soufrière of Guadeloupe (Lesser Antilles) in 1530 AD Evidence from stratigraphy radiocarbon dating and magmatic evolution of erupted products[END_REF] Pichavant et al., 2018;[START_REF] Cooper | Variable water input controls evolution of the Lesser Antilles volcanic arc[END_REF] Metcalfe et al., 2022;[START_REF] Metcalfe | Insights into the Origin and Dynamics of Past Eruptions of La Soufrière de Guadeloupe from Melt Inclusions: Implications for Future Unrest and Environmental Impact[END_REF];

Dominica(Baalcone-Boissard et al., 2018;[START_REF] Cooper | Variable water input controls evolution of the Lesser Antilles volcanic arc[END_REF] d'Augustin et al., 2020;[START_REF] Ostorero | Timewindow into the transcrustal plumbing system dynamics of Dominica (Lesser Antilles)[END_REF]

2021); Martinique(Martel et al., 1998;[START_REF] Cooper | Variable water input controls evolution of the Lesser Antilles volcanic arc[END_REF]; St Lucia[START_REF] Cooper | Variable water input controls evolution of the Lesser Antilles volcanic arc[END_REF]; St Vincent

(Devine and Sigurdsson, 1983; Heath et al., 1998; Bouvier et al., 2010b;[START_REF] Cooper | Variable water input controls evolution of the Lesser Antilles volcanic arc[END_REF]; Petite

Mustique[START_REF] Cooper | Variable water input controls evolution of the Lesser Antilles volcanic arc[END_REF]; Kick 'em Jenny(Camejo-Harry et al., 2019); Grenada(Bouvier et al.,

2010a;[START_REF] Cooper | Variable water input controls evolution of the Lesser Antilles volcanic arc[END_REF].

the average bulk rock SiO2. Smaller and less explosive eruptions are more common (e.g., phreatic,

vulcanian and dome) than larger explosive eruptions. Submarine eruptions are also common due to

the high level of activity observed at Kick 'em Jenny.

zones, 20 th century eruptions, crustal thickness, magma storage depth, magma temperature, MI SiO2

content, MI H2O content and MI δ 11 B content variation. Crustal thickness is highest in the central arc,

highest MI δ 11 B content and the location of the Marathon and Mercurius fault zones.

Figure 7 XCO2 in the gas phase v pressure for (A) The Northern Arc; (B) The Central Arc; (C) The

Southern Arc. From this we can see the process of decompression and CO2 fluxing occurring across the

arc, the direction of these processes are shown by the arrows. We highlight that in Dominica we see

both process of CO2 fluxing (increasing CO2 with decreasing pressure) and decompression (decreasing

CO2 with decreasing CO2). For full melt inclusion dataset see supplementary dataset 1. (Saba (Roobol

andSmith, 2004); Statia[START_REF] Cooper | Variable water input controls evolution of the Lesser Antilles volcanic arc[END_REF]; St Kitts[START_REF] Toothill | A complex petrogenesis for an arc magmatic suite, St Kitts, Lesser Antilles[END_REF] Melekhova et al., 2017;

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Acknowledgements

The PhD scholarship of AM was co-funded by the "Make our Planet Great Again" initiative (Campus France) and the IPGP Ecole Doctorale. We thank IPGP for general funding to the Observatoires Volcanologiques et Sismologiques (OVS), the INSU-CNRS for funding provided by Service National d'Observation en Volcanologie (SNOV), a Tellus-Aleas project to SM (2020), Insights into the dynamics of the active hydrothermal system of La Soufrière de Guadeloupe from past eruptions), and the French Ministère pour la Transition Ecologique et Solidaire (MTES) for financial support. This work has been supported by the Clervolc (UCA-LMV), the AO-IPGP 2018 project "Depth to surface propagation of fluid-related anomalies at La Soufrière de Guadeloupe volcano (FWI): timing and implications for Acknowledgements 1625

The PhD scholarship of AM was co-funded by the "Make our Planet Great Again" initiative (Campus

Data Availability

Our compiled whole rock and melt inclusion data set are available (supplementary material dataset 1), along with the MELTS models (supplementary dataset 3).

Data Availability

1617

Our compiled whole rock and melt inclusion data set are available (supplementary material dataset

Author Contribution Statement

AM collated the data and drafted the manuscript and figures. J-CK and SM supervised AM during the PhD project and fieldwork this paper stemmed from. RM conceptualized the Pressure-CO2,gas diagram, performed calculations and with AM discussed and interpreted the results. All authors discussed the data, wrote and revised the manuscript and the figures.

term displacement and results in major socio-economic impacts. This highlights the need for future 47 crises to be effectively managed so as to limit the socio-economic impacts and maintain the 48 relationship between scientists, authorities and the population.

50

Arc volcanism is often considered as one of the most hazardous types of volcanism due to the range 51 of eruption styles observed (e.g., Roobol and Smith, 1989;[START_REF] Brown | Volcanic fatalities database: analysis of volcanic threat with distance and victim classification[END_REF]. This variability makes 52 it difficult to define the processes, timescales and controls on eruptions and resulting hazards.

53

Understanding the drivers of changes in eruptive style is particularly important, as eruption style 54 dictates many of the hazards presented by a volcano (e.g., Komoroswki et al., 2005;Lindsay et al., 55 2005;Cassidy et al., 2018). Eruptions at arc volcanoes range from phreatic behaviour (generated in 56 the hydrothermal system and not resulting in magma extrusion, e.g., Kilgour et al., 2019) to effusive 57 eruptions in the form of lava domes and spines (e.g., Sheldrake et al., 2016), to explosive behaviour 58 ranging from small vulcanian eruptions (e.g., Druitt et al., 2002) to large Plinian eruptions (e.g., Vidal 59 et al., 2015). There are multiple ways to generate an eruption and processes are unlikely to occur in 60 isolation (Villemant and Boudon, 1998;Di Genova et al., 2017;Cassidy et al., 2018;Popa et al., 2021).

61

For magmatic eruptions, many mechanisms involve recharge of the system by magma from depth and 62 for explosive eruptions the supersaturation of volatiles in the magma and an increase in overpressure,

63

which exert a control on the flow rate into the conduit (e.g., Burnham, 1975). important for the production of more-evolved magmas through fractionation processes, the triggering 268 of eruption through recharge, and may also be evacuated in the more voluminous eruptions.

269

The active part of the systems supplying eruptions are located in the range of 5 -9 km (ca. 100 -200 270 ±50 MPa), with some evidence of melt at <5 km (e.g., Martel et al., 1998;Pichavant et al., 2002; 271 Christopher et al. 2015;[START_REF] Edmonds | Extensive, water-rich magma reservoir beneath southern Montserrat[END_REF]Pichavant et al., 2018;[START_REF] Balcone-Boissard | Deep pre-eruptive storage of silicic magmas feeding Plinian and domeforming eruptions of central and northern Dominica (Lesser Antilles) inferred from volatile contents of melt inclusions[END_REF] 272 Solaro et al., 2019;d'Augustin, et al., 2020;Metcalfe et al., 2021;Fig 2). These shallow storage regions 273 are typically formed of evolved magmas and are often the main zone from which magma is erupted.

274

Magma production rate is relatively low compared to the global range of subduction zones, with the 275 rate varying along the arc, the Central Arc produces the largest volumes of volcanic deposits,

276

particularly in the past 0.1 Ma (40 km 3 for Dominica and 8 km 3 for Guadeloupe and Martinique; Wadge 277 1984;1986;[START_REF] Macdonald | The Lesser Antilles volcanic chain: a study in arc magmatism[END_REF]. In comparison, the Northern and Southern parts of the arc have 278 produced smaller volumes (ca. 0 -5 km 3 ; Macdonald et al., 2000).

279

A wide range of magma types are observed across the arc, with variation in sediment input into the 280 arc playing a role in the changing chemistry of primitive parental magmas [START_REF] Carpentier | Pb-Nd isotopic constraints on sedimentary input into the Lesser Antilles arc system[END_REF]. In 281 the Southern Arc, the incoming plate is rich in clastic detritus, in comparison to the Northern Arc,

282

which has limited sediment supply and is richer in pelagic marine sediments [START_REF] Faugères | Quaternary sandy deposits and canyons on the Venezuelan margin and south Barbados accretionary prism[END_REF] 283 [START_REF] Carpentier | Pb-Nd isotopic constraints on sedimentary input into the Lesser Antilles arc system[END_REF]. The LAA magmas have fractionated from a parental magma hypothesised by 284 [START_REF] Macdonald | The Lesser Antilles volcanic chain: a study in arc magmatism[END_REF] as a picritic, silica-undersaturated magma, though due to the variation in 285 sediment input the trace element compositions is likely to vary across the arc.

286

The LAA magmas vary from tholeiitic suites in the Northern Arc, to calc-alkaline suites in the Central

287

Arc and silica-undersaturated, highly magnesian suites in the Southern Arc [START_REF] Macdonald | The Lesser Antilles volcanic chain: a study in arc magmatism[END_REF].

288

The trends observed in the geochemical data show the various magmas are the result of fractional 289 crystallisation (Fig 3;[START_REF] Macdonald | The Lesser Antilles volcanic chain: a study in arc magmatism[END_REF]. However, crustal contamination, and minor magma 290 mixing are also occurring, particularly in the Central Arc (MacDonald et al., 2000), minor assimilation 291 of crust or sediments is also observed in St Lucia and Martinique magmas [START_REF] Bezard | Seeing through the effects of crustal assimilation to assess the source composition beneath the southern Lesser Antilles Arc[END_REF].

292

Here, we provide a summary of the magma storage systems and a summary of the wealth of 293 geochemistry data available for the LAA.. This is important to understand any common depths of 294 magma storage, along arc variations and to eventually provide a coherent model of magma storage 295 along the arc. We note that, the geochemical dataset is biased towards both what is erupted and what 296 is analysed out of large amounts of samples, providing an incomplete view of the system. Our dataset from 59 -76 wt% SiO2, 1.3 -4.8 wt% Na2O and 0.6 -2.5 wt% K2O, which is within the range observed 339 in the Northern Arc (Fig 4A, B;[START_REF] Toothill | A complex petrogenesis for an arc magmatic suite, St Kitts, Lesser Antilles[END_REF]Melekhova et al., 2017;[START_REF] Cooper | Variable water input controls evolution of the Lesser Antilles volcanic arc[END_REF].

A; Poussineau, 2005;[START_REF] Boudon | A new scenario for the last magmatic eruption of La Soufrière of Guadeloupe (Lesser Antilles) in 1530 AD Evidence from stratigraphy radiocarbon dating and magmatic evolution of erupted products[END_REF]Pichavant et al., 2018;[START_REF] Cooper | Variable water input controls evolution of the Lesser Antilles volcanic arc[END_REF]Metcalfe et al., 434 2022). Major elements show no systematic changes across the Holocene eruptions (Poussineau, 2005; 435 [START_REF] Boudon | A new scenario for the last magmatic eruption of La Soufrière of Guadeloupe (Lesser Antilles) in 1530 AD Evidence from stratigraphy radiocarbon dating and magmatic evolution of erupted products[END_REF]Pichavant et al., 2018;Metcalfe et al., 2022;Fig 4). MIs hosted in clinopyroxene, 436 orthopyroxene, plagioclase and olivine from the basaltic parental magma from Mont Caraïbes have 437 also been measured for Guadeloupe. These MIs are notably less evolved in comparison to the MIs 438 from La Soufrière de Guadeloupe (49 -56 wt% SiO2) and are the least evolved inclusions observed in many similar systems to explain observations and activity (e.g., Cashman et al., 2017). This was refined 469 by Metcalfe et al. (2021Metcalfe et al. ( , 2022) ) to a vertically and laterally extensive mush system extending 6 -9 km 470 in depth (190 -220 MPa, based on a density of 2450 kg m -3 ; [START_REF] Barnoud | 3-D linear inversion of gravity data: method and application to Basse-Terre volcanic island, Guadeloupe, Lesser Antilles[END_REF], which hosts evolved Arc, with two distinct data clusters, one ranging from 4.5 -7.3 wt% H2O and the second from 1.4 -3.3 504 wt% H2O (Fig 4D;[START_REF] Balcone-Boissard | Deep pre-eruptive storage of silicic magmas feeding Plinian and domeforming eruptions of central and northern Dominica (Lesser Antilles) inferred from volatile contents of melt inclusions[END_REF]d'Augustin et al., 2020;[START_REF] Cooper | Variable water input controls evolution of the Lesser Antilles volcanic arc[END_REF]

509

A vertically and laterally extensive crystal mush system is also proposed for Dominica, with three 510 components: an underplating basalt, a basaltic-andesitic crystalline mush with a liquid hybrid layer, 511 and an interstitial rhyolitic melt which may accumulate at the top of the reservoir in a silicic cap (e.g., 512 Howe et al., 2015). This system is hypothesised to have formed through continuous fractionation, 513 accumulation, and disaggregation of the crystalline material of a crystal-mush along with interstitial 514 melt. This is highlighted by crystals with disequilibrium features indicating they have experienced 515 different histories (Howe et al., 2015). Volatile release from the underplating basalt is thought to 516 cause vigorous convection prior to eruption. Mafic phases observed in the Dominica eruption products 517 are remnants of incomplete mixing of basaltic material (Halama et al., 2006;Howe et al., 2015).

518

Following the eruption and the cessation of recharge of the underplating basalt, the liquid remaining 519 in the reservoir will begin to crystallise to ultimately remain in a crystalline state between eruptive 520 periods (Howe et al., 2015).

521

However, more recently the model of mafic recharge has been discarded for some eruptions (e.g.,

522

Layou and Roseau) due to the lack of evidence for mixing in groundmass glasses and melt inclusion 523 compositions [START_REF] Balcone-Boissard | Deep pre-eruptive storage of silicic magmas feeding Plinian and domeforming eruptions of central and northern Dominica (Lesser Antilles) inferred from volatile contents of melt inclusions[END_REF]Solaro et al., 2020). Instead, mixing of different parts of 524 the mush, without the need of a mafic magma, can explain many features observed for the Layou and 525 Roseau eruptions. The system prior to the eruption is considered as a cooling system which is 526 disturbed by a slightly hotter magma of a similar composition a decade prior to eruption (Solaro et al., The model proposes that magma rising from a depth > 16 km stalls and forms a deeper storage zone 563 located between 12 -16 km depth (Pichavant et al., 2018;[START_REF] Boudon | Volcanological evolution of Montagne Pelée (Martinique): A textbook case of alternating Plinian and dome-forming eruptions[END_REF].

564

The presence of mafic magmas with an andesite bulk composition leads to the interpretation of the 565 existence of a zoned magma storage system with a mafic zone below an andesitic zone (Pichavant et 566 al., 2002), similar to that presented for Guadeloupe by Pichavant et al. (2018). [START_REF] Annen | Conditions for the growth of a longlived shallow crustal magma chamber below Mount Pelee volcano (Martinique, Lesser Antilles Arc)[END_REF] 567 proposed a mush system for Montagne Pelée based on experimental determination of the thermal 568 evolution of the system. The formation of a long-lived persistent magma chamber was determined to 569 be unlikely based on realistic magma injection and cooling rates. Instead, the magma system is built 570 up by accreting sills. This injected magma then completely solidifies, existing as a highly crystalline 571 mush with only a small part (10-20 vol%) remaining as eruptible melt to feed eruptions (Annen et al., 572 2008). Magmas are calculated to ascend in < 1 day from a shallow reservoir of 6 km (ca. 200 ± 50 MPa) 573 (Martel, 2012). 574

St Lucia

575

In the Soufrière volcanic complex of St Lucia no large-scale mixing or mingling textures are reported 576 in the silica-rich deposits (62 -68 wt % SiO2; [START_REF] Bezard | Assimilation of sediments embedded in the oceanic arc crust: Myth or reality?[END_REF][START_REF] Bezard | Seeing through the effects of crustal assimilation to assess the source composition beneath the southern Lesser Antilles Arc[END_REF][START_REF] Bezard | Origin and evolution of silicic magmas in oceanic arcs; an in situ study from St Lucia, Lesser Antilles[END_REF]. A wider range of 577 compositions (basalt to rhyolite) are observed in older deposits extending this range to 50 -68 wt% 578 SiO2 (18 and 1.1 Ma; Briden et al., 1979;[START_REF] Aquater | Exploration of St. Lucia's Geothermal Resources[END_REF][START_REF] Guen De Kerneizon | L'Ile de Sainte-Lucie (Petites Antilles); distinction des principales séries magmatiques à partir des données pétrochimiques et géochronologiques[END_REF]Samper et 579 al., 2008;[START_REF] Bezard | Origin and evolution of silicic magmas in oceanic arcs; an in situ study from St Lucia, Lesser Antilles[END_REF]. The most differentiated eruption products in the central arc are found

592

Storage of basaltic-andesite to andesite magma is hypothesised to occur in the mid-crust, in a chamber 593 at 580 -720 MPa (ca. 20-26 km depth, based on a crustal density of 2660 kg/m (Christeson et al., degassed magma in the conduit being pushed up by the injection of new gas-rich magma (Joseph et 633 al., 2022). The injection of gas rich magma is thought to have occurred at ca. 6 km based on the depth 634 of seismic events (Joseph et al., 2022). The displacement of the high-viscosity magma cap by the new 635 lower viscosity gas-rich magma resulted in an acceleration in extrusion rate and on reaching the 636 surface experienced explosive fragmentation (Joseph et al., 2022).

670

Eruptions on Grenada produce basalt to basaltic-andesite from scoria cones and explosion craters 671 [START_REF] Arculus | Geology and geochemistry of the alkali basalt-andesite association of Grenada, Lesser Antilles island arc[END_REF]Van Soest, 2000;Stamper et al., 2014), with andesite and dacite much less common in 672 comparison to other islands [START_REF] Arculus | Geology and geochemistry of the alkali basalt-andesite association of Grenada, Lesser Antilles island arc[END_REF]. The most primitive compositions are observed on 673 Grenada (42 -67 wt% SiO2; Cawthorn et al., 1973;[START_REF] Arculus | Geology and geochemistry of the alkali basalt-andesite association of Grenada, Lesser Antilles island arc[END_REF]Thirwall and Graham, 1984; 674 Thirwall et al., 1996;Woodland et al., 2002;Rojas-Agramonte et al., 2017), the least evolved 675 compositions can be considered the primitive magmas of the LAA (Fig 3). The basalts in Grenada can 676 be split into two groups: the 'low-Sr' series which are Mg-rich olivine basalts, and the 'high-Sr' series 677 which are clinopyroxene-phyric series (Stamper et al., 2014).

678

The most primitive MI host in olivine are recorded in eruption deposits from Grenada however, more 679 evolved MIs are also present (42 -74 wt% SiO2;Fig 4A;Bouvier et al., 2010a;[START_REF] Cooper | Variable water input controls evolution of the Lesser Antilles volcanic arc[END_REF]. Na2O

688

Vapour bubbles are reported by Bouvier et al. (2010a), however, no relation between bubble size and 689 water content is observed.

Soufrière Hills volcano in Montserrat has experienced a long period of eruptive activity, beginning in 732 1995 and continuing to the present day. This eruption has provided insights into a range of 733 phenomena regarding andesite dome building eruptions including: [START_REF] Wallace | Melt inclusion CO2 contents, pressures of olivine crystallization, and the problem of shrinkage bubbles[END_REF] cyclicity of magma transport 734 linked with ground deformation, [2] shallow seismicity and eruptive activity, [3] growth and collapse 735 of andesite lava domes, [4] sector collapse and formation of debris avalanches, [5] dynamics of lateral longest period of continuous lava extrusion (Wadge et al., 2014). This phase was characterised by 765 major dome collapse events, with cyclic processes of magma flux and gas flux observed. Dome collapse 766 events in this phase resulted in ash columns up to 9 km high (Carn et al., 2004), which also caused 767 repeated minor ashfalls in the Caribbean region, with much of the collapse material deposited by significant threat, particularly following heavy rainfall. Some larger earthquakes continue to be felt by 830 the population, however, most felt earthquakes are now unrelated to Soufriere Hills Volcano (MVO Evidence for this model is provided by the depth of seismicity at ca. 6 km, consistent with the depth 865 of the magma reservoir and SO2 and Cl signatures which were magmatic in origin. The migration of 866 earthquake hypocentres from depth towards the shallower system over a few hours was also discounted [START_REF] Pyle | The 1902-3 eruptions of the Soufrière, St Vincent: Impacts, relief and response[END_REF]). Seismic activity culminated in phreatic eruptions which transitioned 1127 into a violent magmatic eruption producing pyroclastic density currents and lahars (Anderson and The effect of the upper system has also been discussed in the context of magmatic eruptions from La 1417 Soufriere Guadeloupe, where the eruption style of magma ascending from the active region of the 1418 storage zone is affected by the state of the upper system. Though ultimately the main driver of an 1419 explosive eruption is the supersaturation of volatiles in the magma and brittle failure of a magma.

water on iron oxidation state (Moretti and Papale, 2004;Papale et al., 2006;Moretti, 2022 eruptions are important to consider, as such eruptions would impact the entire region (Lindsay and years after the eruption in order to facilitate social and economic recovery (Joseph et al., 2022). This 1551 is highlighted by the 1995 Soufrière Hills eruption on Montserrat, where following the evacuation of 1552 >6,000 people and a population reduction from ca. 11,000 pre-eruption to ca. 4,000 post-eruption, 1553 only 1000 people have returned (Kokelaar, 2002;[START_REF] Aspinall | Risk assessment at the Soufrière Hills volcano, Montserrat[END_REF][START_REF] Barclay | Livelihoods, Wellbeing and the Risk to Life During Volcanic Eruptions[END_REF].

1554

As previously discussed, a wide variation in eruption styles is observed across the arc as exemplified 1555 by the eruptions in the 20 th century (Fig 5). The hazards posed by eruptions need to be clearly 1556 conveyed to the populations with volcanoes in a state of unrest, particularly on islands where volcanic 1557 risk is not necessarily considered high by the population (e.g., Guadeloupe; Chenet et al., 2014).

1558

Though the eruptions occurring in the early 20 th century (e.g., Montagne Pelée 1902 and Soufrière St

1559

Vincent 1902) resulted in a large number of casualties (>30,000 deaths), advancements in science and 1560 technology have allowed a better understanding and monitoring of the volcanoes of the LAA. This has 1561 undoubtedly prevented large numbers of casualties in eruptions in the later 20 th century, however, in 1562 most cases, evacuations of people remain unavoidable (Table 1). In some cases, evacuation becomes 1563 long term displacement and results in major socio-economic impacts and in the case of the La 1564 Soufrière de Guadeloupe 1976 eruption, a loss of trust in scientists and authorities (Hincks et al., 2014; 1565 Chenet et al., 2014;[START_REF] Komorowski | Challenges of volcanic crises on small islands states[END_REF]. This highlights the need for future crises to be managed 1566 with care and transparency to limit the socio-economic impacts and maintain the relationship 1567 between scientists, authorities and the population.

1569

In this review of the LAA we have focused on the magma storage system, geochemistry and recent 1570 eruptive history. We have highlighted investigating trends across the arc can be useful to provide more 1571 context for each system.

1572

The distribution of subducted serpentine has a first order control on magmatic productivity (Fig 6), 1573 compositional variation and variation in magma storage depth as serpentine can supply substantial 1574 volumes of fluid to the arc [START_REF] Cooper | Variable water input controls evolution of the Lesser Antilles volcanic arc[END_REF]. This is particularly important to consider in the Central

1575

Arc where evolved magmas are stored at shallow depths and are likely to erupt explosively in the near 1576 future, given the unrest observed at many systems in LAA.

1577

Through this review we show that there appears to be three different levels of magma storage within 1578 a vertical and laterally extensive, transcrustal magma mush. The deepest storage area is the least well 1579 defined but is most likely at >18 km depth. Above this, at ca. 10 -18 km are the parental magmas 1580 which undergo fractional crystallization to produce more evolved magmas which are stored in the 1581 shallow system at ca. <10 km. Within the shallow mush system there is an 'active region' which has 1582 supplied the most recent eruptions, and is most likely remobilised by magma, heat and volatiles from the parental magmas at 10 -18 km. Eruption products from recent eruptions are often described as

1612

Overall, further research on the LAA must continue to be underpinned by the hazardous nature of the 1613 system and the tens of thousands of people that can be affected by even a small eruption. Continuing 1614 our advancement in understanding of the LAA is essential to continue to improve monitoring 1615 techniques, reduce the impact of eruption and provide clear crisis management.

Author Contribution Statement

which coincides with the shallow storage magma zones, the most evolved magma compositions, the