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Glacier

A glacier is a persistent body of dense ice that is constantly moving downhill under its own weight. A glacier forms where the accumulation of snow exceeds its ablation over many years, often centuries. It acquires distinguishing features, such as crevasses and seracs, as it slowly flows and deforms under stresses induced by its weight. As it moves, it abrades rock and debris from its substrate to create landforms such as cirques, moraines, or fjords. Although a glacier may flow into a body of water, it forms only on land and is distinct from the much thinner sea ice and lake ice that form on the surface of bodies of water.

On Earth, 99% of glacial ice is contained within vast ice sheets (also known as "continental glaciers") in the polar regions, but glaciers may be found in mountain ranges on every continent other than the Australian mainland, including Oceania's high-latitude oceanic island countries such as New Zealand. Between latitudes 35°N and 35°S, glaciers occur only in the Himalayas, Andes, and a few high mountains in East Africa, Mexico, New Guinea and on Zard-Kuh in Iran. With more than 7,000 known glaciers, Pakistan has more glacial ice than any other country outside the polar regions. Glaciers cover about 10% of Earth's land surface. Continental glaciers cover nearly 5 e6sqmi or about 98% of Antarctica's 5.1 e6sqmi, with an average thickness of ice 7,000 ft. Greenland and Patagonia also have huge expanses of continental glaciers. The volume of glaciers, not including the ice sheets of Antarctica and Greenland, has been estimated at 170,000 km3.

Glacial ice is the largest reservoir of fresh water on Earth, holding with ice sheets about 69 percent of the world's freshwater. Many glaciers from temperate, alpine and seasonal polar climates store water as ice during the colder seasons and release it later in the form of meltwater as warmer summer temperatures cause the glacier to melt, creating a water source that is especially important for plants, animals and human uses when other sources may be scant. However, within high-altitude and Antarctic environments, the seasonal temperature difference is often not sufficient to release meltwater.

Since glacial mass is affected by long-term climatic changes, e.g., precipitation, mean temperature, and cloud cover, glacial mass changes are considered among the most sensitive indicators of climate change and are a major source of variations in sea level.

A large piece of compressed ice, or a glacier, appears blue, as large quantities of water appear blue, because water molecules absorb other colors more efficiently than blue. The other reason for the blue color of glaciers is the lack of air bubbles. Air bubbles, which give a white color to ice, are squeezed out by pressure increasing the created ice's density.

Etymology and related terms
The word glacier is a loanword from French and goes back, via Franco-Provençal, to the Vulgar Latin glaciārium, derived from the Late Latin glacia, and ultimately Latin glaciēs, meaning "ice". The processes and features caused by or related to glaciers are referred to as glacial. The process of glacier establishment, growth and flow is called glaciation. The corresponding area of study is called glaciology. Glaciers are important components of the global cryosphere.

Classification by size, shape and behavior
Glaciers are categorized by their morphology, thermal characteristics, and behavior. Alpine glaciers form on the crests and slopes of mountains. A glacier that fills a valley is called a valley glacier, or alternatively, an alpine glacier or mountain glacier. A large body of glacial ice astride a mountain, mountain range, or volcano is termed an ice cap or ice field. Ice caps have an area less than 50,000 km2 by definition.

Glacial bodies larger than 50,000 km2 are called ice sheets or continental glaciers. Several kilometers deep, they obscure the underlying topography. Only nunataks protrude from their surfaces. The only extant ice sheets are the two that cover most of Antarctica and Greenland. They contain vast quantities of freshwater, enough that if both melted, global sea levels would rise by over 70 m. Portions of an ice sheet or cap that extend into water are called ice shelves; they tend to be thin with limited slopes and reduced velocities. Narrow, fast-moving sections of an ice sheet are called ice streams. In Antarctica, many ice streams drain into large ice shelves. Some drain directly into the sea, often with an ice tongue, like Mertz Glacier.

Tidewater glaciers are glaciers that terminate in the sea, including most glaciers flowing from Greenland, Antarctica, Baffin, Devon, and Ellesmere Islands in Canada, Southeast Alaska, and the Northern and Southern Patagonian Ice Fields. As the ice reaches the sea, pieces break off or calve, forming icebergs. Most tidewater glaciers calve above sea level, which often results in a tremendous impact as the iceberg strikes the water. Tidewater glaciers undergo centuries-long cycles of advance and retreat that are much less affected by climate change than other glaciers.

Classification by thermal state
Thermally, a temperate glacier is at a melting point throughout the year, from its surface to its base. The ice of a polar glacier is always below the freezing threshold from the surface to its base, although the surface snowpack may experience seasonal melting. A subpolar glacier includes both temperate and polar ice, depending on the depth beneath the surface and position along the length of the glacier. In a similar way, the thermal regime of a glacier is often described by its basal temperature. A cold-based glacier is below freezing at the ice-ground interface and is thus frozen to the underlying substrate. A warm-based glacier is above or at freezing at the interface and is able to slide at this contact. This contrast is thought to a large extent to govern the ability of a glacier to effectively erode its bed, as sliding ice promotes plucking at rock from the surface below. Glaciers which are partly cold-based and partly warm-based are known as polythermal.

Formation
Glaciers form where the accumulation of snow and ice exceeds ablation. A glacier usually originates from a cirque landform (alternatively known as a corrie or as a cwm) – a typically armchair-shaped geological feature (such as a depression between mountains enclosed by arêtes) – which collects and compresses through gravity the snow that falls into it. This snow accumulates and the weight of the snow falling above compacts it, forming névé (granular snow). Further crushing of the individual snowflakes and squeezing the air from the snow turns it into "glacial ice". This glacial ice will fill the cirque until it "overflows" through a geological weakness or vacancy, such as a gap between two mountains. When the mass of snow and ice reaches sufficient thickness, it begins to move by a combination of surface slope, gravity, and pressure. On steeper slopes, this can occur with as little as 15 m of snow-ice.

In temperate glaciers, snow repeatedly freezes and thaws, changing into granular ice called firn. Under the pressure of the layers of ice and snow above it, this granular ice fuses into denser firn. Over a period of years, layers of firn undergo further compaction and become glacial ice. Glacier ice is slightly more dense than ice formed from frozen water because glacier ice contains fewer trapped air bubbles.

Glacial ice has a distinctive blue tint because it absorbs some red light due to an overtone of the infrared OH stretching mode of the water molecule. (Liquid water appears blue for the same reason. The blue of glacier ice is sometimes misattributed to Rayleigh scattering of bubbles in the ice.)

Structure
A glacier originates at a location called its glacier head and terminates at its glacier foot, snout, or terminus.

Glaciers are broken into zones based on surface snowpack and melt conditions. The ablation zone is the region where there is a net loss in glacier mass. The upper part of a glacier, where accumulation exceeds ablation, is called the accumulation zone. The equilibrium line separates the ablation zone and the accumulation zone; it is the contour where the amount of new snow gained by accumulation is equal to the amount of ice lost through ablation. In general, the accumulation zone accounts for 60–70% of the glacier's surface area, more if the glacier calves icebergs. Ice in the accumulation zone is deep enough to exert a downward force that erodes underlying rock. After a glacier melts, it often leaves behind a bowl- or amphitheater-shaped depression that ranges in size from large basins like the Great Lakes to smaller mountain depressions known as cirques.

The accumulation zone can be subdivided based on its melt conditions.
 * 1) The dry snow zone is a region where no melt occurs, even in the summer, and the snowpack remains dry.
 * 2) The percolation zone is an area with some surface melt, causing meltwater to percolate into the snowpack. This zone is often marked by refrozen ice lenses, glands, and layers. The snowpack also never reaches the melting point.
 * 3) Near the equilibrium line on some glaciers, a superimposed ice zone develops. This zone is where meltwater refreezes as a cold layer in the glacier, forming a continuous mass of ice.
 * 4) The wet snow zone is the region where all of the snow deposited since the end of the previous summer has been raised to 0 °C.

The health of a glacier is usually assessed by determining the glacier mass balance or observing terminus behavior. Healthy glaciers have large accumulation zones, more than 60% of their area is snow-covered at the end of the melt season, and they have a terminus with a vigorous flow.

Following the Little Ice Age's end around 1850, glaciers around the Earth have retreated substantially. A slight cooling led to the advance of many alpine glaciers between 1950 and 1985, but since 1985 glacier retreat and mass loss has become larger and increasingly ubiquitous.

Motion
Glaciers move downhill by the force of gravity and the internal deformation of ice. At the molecular level, ice consists of stacked layers of molecules with relatively weak bonds between layers. When the amount of strain (deformation) is proportional to the stress being applied, ice will act as an elastic solid. Ice needs to be at least 30 m thick to even start flowing, but once its thickness exceeds about 50 m (160 ft), stress on the layer above will exceeds the inter-layer binding strength, and then it'll move faster than the layer below. This means that small amounts of stress can result in a large amount of strain, causing the deformation to become a plastic flow rather than elastic. Then, the glacier will begin to deform under its own weight and flow across the landscape. According to the Glen–Nye flow law, the relationship between stress and strain, and thus the rate of internal flow, can be modeled as follows:

\Sigma = k \tau^n,\, $$

where:
 * $$\Sigma\,$$ = shear strain (flow) rate
 * $$\tau\,$$ = stress
 * $$n\,$$ = a constant between 2–4 (typically 3 for most glaciers)
 * $$k\,$$ = a temperature-dependent constant

The lowest velocities are near the base of the glacier and along valley sides where friction acts against flow, causing the most deformation. Velocity increases inward toward the center line and upward, as the amount of deformation decreases. The highest flow velocities are found at the surface, representing the sum of the velocities of all the layers below.

Because ice can flow faster where it is thicker, the rate of glacier-induced erosion is directly proportional to the thickness of overlying ice. Consequently, pre-glacial low hollows will be deepened and pre-existing topography will be amplified by glacial action, while nunataks, which protrude above ice sheets, barely erode at all – erosion has been estimated as 5 m per 1.2 million years. This explains, for example, the deep profile of fjords, which can reach a kilometer in depth as ice is topographically steered into them. The extension of fjords inland increases the rate of ice sheet thinning since they are the principal conduits for draining ice sheets. It also makes the ice sheets more sensitive to changes in climate and the ocean.

Although evidence in favor of glacial flow was known by the early 19th century, other theories of glacial motion were advanced, such as the idea that meltwater, refreezing inside glaciers, caused the glacier to dilate and extend its length. As it became clear that glaciers behaved to some degree as if the ice were a viscous fluid, it was argued that "regelation", or the melting and refreezing of ice at a temperature lowered by the pressure on the ice inside the glacier, was what allowed the ice to deform and flow. James Forbes came up with the essentially correct explanation in the 1840s, although it was several decades before it was fully accepted.

Fracture zone and cracks

The top 50 m of a glacier are rigid because they are under low pressure. This upper section is known as the fracture zone and moves mostly as a single unit over the plastic-flowing lower section. When a glacier moves through irregular terrain, cracks called crevasses develop in the fracture zone. Crevasses form because of differences in glacier velocity. If two rigid sections of a glacier move at different speeds or directions, shear forces cause them to break apart, opening a crevasse. Crevasses are seldom more than 150 ft deep but, in some cases, can be at least 1000 ft deep. Beneath this point, the plasticity of the ice prevents the formation of cracks. Intersecting crevasses can create isolated peaks in the ice, called seracs. Crevasses can form in several different ways. Transverse crevasses are transverse to flow and form where steeper slopes cause a glacier to accelerate. Longitudinal crevasses form semi-parallel to flow where a glacier expands laterally. Marginal crevasses form near the edge of the glacier, caused by the reduction in speed caused by friction of the valley walls. Marginal crevasses are largely transverse to flow. Moving glacier ice can sometimes separate from the stagnant ice above, forming a bergschrund. Bergschrunds resemble crevasses but are singular features at a glacier's margins. Crevasses make travel over glaciers hazardous, especially when they are hidden by fragile snow bridges.

Below the equilibrium line, glacial meltwater is concentrated in stream channels. Meltwater can pool in proglacial lakes on top of a glacier or descend into the depths of a glacier via moulins. Streams within or beneath a glacier flow in englacial or sub-glacial tunnels. These tunnels sometimes reemerge at the glacier's surface.

Subglacial processes

Most of the important processes controlling glacial motion occur in the ice-bed contact—even though it is only a few meters thick. The bed's temperature, roughness and softness define basal shear stress, which in turn defines whether movement of the glacier will be accommodated by motion in the sediments, or if it'll be able to slide. A soft bed, with high porosity and low pore fluid pressure, allows the glacier to move by sediment sliding: the base of the glacier may even remain frozen to the bed, where the underlying sediment slips underneath it like a tube of toothpaste. A hard bed cannot deform in this way; therefore the only way for hard-based glaciers to move is by basal sliding, where meltwater forms between the ice and the bed itself. Whether a bed is hard or soft depends on the porosity and pore pressure; higher porosity decreases the sediment strength (thus increases the shear stress τB).

Porosity may vary through a range of methods.
 * Movement of the overlying glacier may cause the bed to undergo dilatancy; the resulting shape change reorganises blocks. This reorganises closely packed blocks (a little like neatly folded, tightly packed clothes in a suitcase) into a messy jumble (just as clothes never fit back in when thrown in  in a disordered fashion).  This increases the porosity.  Unless water is added, this will necessarily reduce the pore pressure (as the pore fluids have more space to occupy).
 * Pressure may cause compaction and consolidation of underlying sediments. Since water is relatively incompressible, this is easier when the pore space is filled with vapour; any water must be removed to permit compression. In soils, this is an irreversible process.
 * Sediment degradation by abrasion and fracture decreases the size of particles, which tends to decrease pore space. However, the motion of the particles may disorder the sediment, with the opposite effect. These processes also generate heat.

Bed softness may vary in space or time, and changes dramatically from glacier to glacier. An important factor is the underlying geology; glacial speeds tend to differ more when they change bedrock than when the gradient changes. Further, bed roughness can also act to slow glacial motion. The roughness of the bed is a measure of how many boulders and obstacles protrude into the overlying ice. Ice flows around these obstacles by melting under the high pressure on their stoss side; the resultant meltwater is then forced into the cavity arising in their lee side, where it re-freezes.

As well as affecting the sediment stress, fluid pressure (pw) can affect the friction between the glacier and the bed. High fluid pressure provides a buoyancy force upwards on the glacier, reducing the friction at its base. The fluid pressure is compared to the ice overburden pressure, pi, given by ρgh. Under fast-flowing ice streams, these two pressures will be approximately equal, with an effective pressure (pi – pw) of 30 kPa; i.e. all of the weight of the ice is supported by the underlying water, and the glacier is afloat.

Basal melting and sliding
Glaciers may also move by basal sliding, where the base of the glacier is lubricated by the presence of liquid water, reducing basal shear stress and allowing the glacier to slide over the terrain on which it sits. Meltwater may be produced by pressure-induced melting, friction or geothermal heat. The more variable the amount of melting at surface of the glacier, the faster the ice will flow. Basal sliding is dominant in temperate or warm-based glaciers.

 * τD = ρgh sin α
 * where τD is the driving stress, and α the ice surface slope in radians.

 * τB is the basal shear stress, a function of bed temperature and softness.

 * τF, the shear stress, is the lower of τB and τD. It controls the rate of plastic flow.

The presence of basal meltwater depends on both bed temperature and other factors. For instance, the melting point of water decreases under pressure, meaning that water melts at a lower temperature under thicker glaciers. This acts as a "double whammy", because thicker glaciers have a lower heat conductance, meaning that the basal temperature is also likely to be higher. Bed temperature tends to vary in a cyclic fashion. A cool bed has a high strength, reducing the speed of the glacier. This increases the rate of accumulation, since newly fallen snow is not transported away. Consequently, the glacier thickens, with three consequences: firstly, the bed is better insulated, allowing greater retention of geothermal heat.

Secondly, the increased pressure can facilitate melting. Most importantly, τD is increased. These factors will combine to accelerate the glacier. As friction increases with the square of velocity, faster motion will greatly increase frictional heating, with ensuing melting – which causes a positive feedback, increasing ice speed to a faster flow rate still: west Antarctic glaciers are known to reach velocities of up to a kilometre per year. Eventually, the ice will be surging fast enough that it begins to thin, as accumulation cannot keep up with the transport. This thinning will increase the conductive heat loss, slowing the glacier and causing freezing. This freezing will slow the glacier further, often until it is stationary, whence the cycle can begin again. The flow of water under the glacial surface can have a large effect on the motion of the glacier itself. Subglacial lakes contain significant amounts of water, which can move fast: cubic kilometres can be transported between lakes over the course of a couple of years. This motion is thought to occur in two main modes: pipe flow involves liquid water moving through pipe-like conduits, like a sub-glacial river; sheet flow involves motion of water in a thin layer. A switch between the two flow conditions may be associated with surging behaviour. Indeed, the loss of sub-glacial water supply has been linked with the shut-down of ice movement in the Kamb ice stream. The subglacial motion of water is expressed in the surface topography of ice sheets, which slump down into vacated subglacial lakes.

Speed
The speed of glacial displacement is partly determined by friction. Friction makes the ice at the bottom of the glacier move more slowly than ice at the top. In alpine glaciers, friction is also generated at the valley's sidewalls, which slows the edges relative to the center.

Mean glacial speed varies greatly but is typically around 1 m per day. There may be no motion in stagnant areas; for example, in parts of Alaska, trees can establish themselves on surface sediment deposits. In other cases, glaciers can move as fast as 20 – per day, such as in Greenland's Jakobshavn Isbræ. Glacial speed is affected by factors such as slope, ice thickness, snowfall, longitudinal confinement, basal temperature, meltwater production, and bed hardness.

A few glaciers have periods of very rapid advancement called surges. These glaciers exhibit normal movement until suddenly they accelerate, then return to their previous movement state. These surges may be caused by the failure of the underlying bedrock, the pooling of meltwater at the base of the glacier — perhaps delivered from a supraglacial lake — or the simple accumulation of mass beyond a critical "tipping point". Temporary rates up to 300 ft per day have occurred when increased temperature or overlying pressure caused bottom ice to melt and water to accumulate beneath a glacier.

In glaciated areas where the glacier moves faster than one km per year, glacial earthquakes occur. These are large scale earthquakes that have seismic magnitudes as high as 6.1. The number of glacial earthquakes in Greenland peaks every year in July, August, and September and increased rapidly in the 1990s and 2000s. In a study using data from January 1993 through October 2005, more events were detected every year since 2002, and twice as many events were recorded in 2005 as there were in any other year.

Ogives
Ogives or Forbes bands are alternating wave crests and valleys that appear as dark and light bands of ice on glacier surfaces. They are linked to seasonal motion of glaciers; the width of one dark and one light band generally equals the annual movement of the glacier. Ogives are formed when ice from an icefall is severely broken up, increasing ablation surface area during summer. This creates a swale and space for snow accumulation in the winter, which in turn creates a ridge. Sometimes ogives consist only of undulations or color bands and are described as wave ogives or band ogives.

Geography
Glaciers are present on every continent and in approximately fifty countries, excluding those (Australia, South Africa) that have glaciers only on distant subantarctic island territories. Extensive glaciers are found in Antarctica, Argentina, Chile, Canada, Pakistan, Alaska, Greenland and Iceland. Mountain glaciers are widespread, especially in the Andes, the Himalayas, the Rocky Mountains, the Caucasus, Scandinavian Mountains, and the Alps. Snezhnika glacier in Pirin Mountain, Bulgaria with a latitude of 41°46′09″ N is the southernmost glacial mass in Europe. Mainland Australia currently contains no glaciers, although a small glacier on Mount Kosciuszko was present in the last glacial period. In New Guinea, small, rapidly diminishing, glaciers are located on Puncak Jaya. Africa has glaciers on Mount Kilimanjaro in Tanzania, on Mount Kenya, and in the Rwenzori Mountains. Oceanic islands with glaciers include Iceland, several of the islands off the coast of Norway including Svalbard and Jan Mayen to the far north, New Zealand and the subantarctic islands of Marion, Heard, Grande Terre (Kerguelen) and Bouvet. During glacial periods of the Quaternary, Taiwan, Hawaii on Mauna Kea and Tenerife also had large alpine glaciers, while the Faroe and Crozet Islands were completely glaciated.

The permanent snow cover necessary for glacier formation is affected by factors such as the degree of slope on the land, amount of snowfall and the winds. Glaciers can be found in all latitudes except from 20° to 27° north and south of the equator where the presence of the descending limb of the Hadley circulation lowers precipitation so much that with high insolation snow lines reach above 6500 m. Between 19˚N and 19˚S, however, precipitation is higher, and the mountains above 5000 m usually have permanent snow. Even at high latitudes, glacier formation is not inevitable. Areas of the Arctic, such as Banks Island, and the McMurdo Dry Valleys in Antarctica are considered polar deserts where glaciers cannot form because they receive little snowfall despite the bitter cold. Cold air, unlike warm air, is unable to transport much water vapor. Even during glacial periods of the Quaternary, Manchuria, lowland Siberia, and central and northern Alaska, though extraordinarily cold, had such light snowfall that glaciers could not form.

In addition to the dry, unglaciated polar regions, some mountains and volcanoes in Bolivia, Chile and Argentina are high (4500 to 6900 m) and cold, but the relative lack of precipitation prevents snow from accumulating into glaciers. This is because these peaks are located near or in the hyperarid Atacama Desert.

Erosion
Glaciers erode terrain through two principal processes: plucking and abrasion.

As glaciers flow over bedrock, they soften and lift blocks of rock into the ice. This process, called plucking, is caused by subglacial water that penetrates fractures in the bedrock and subsequently freezes and expands. This expansion causes the ice to act as a lever that loosens the rock by lifting it. Thus, sediments of all sizes become part of the glacier's load. If a retreating glacier gains enough debris, it may become a rock glacier, like the Timpanogos Glacier in Utah.

Abrasion occurs when the ice and its load of rock fragments slide over bedrock and function as sandpaper, smoothing and polishing the bedrock below. The pulverized rock this process produces is called rock flour and is made up of rock grains between 0.002 and 0.00625 mm in size. Abrasion leads to steeper valley walls and mountain slopes in alpine settings, which can cause avalanches and rock slides, which add even more material to the glacier. Glacial abrasion is commonly characterized by glacial striations. Glaciers produce these when they contain large boulders that carve long scratches in the bedrock. By mapping the direction of the striations, researchers can determine the direction of the glacier's movement. Similar to striations are chatter marks, lines of crescent-shape depressions in the rock underlying a glacier. They are formed by abrasion when boulders in the glacier are repeatedly caught and released as they are dragged along the bedrock.The rate of glacier erosion varies. Six factors control erosion rate: When the bedrock has frequent fractures on the surface, glacial erosion rates tend to increase as plucking is the main erosive force on the surface; when the bedrock has wide gaps between sporadic fractures, however, abrasion tends to be the dominant erosive form and glacial erosion rates become slow. Glaciers in lower latitudes tend to be much more erosive than glaciers in higher latitudes, because they have more meltwater reaching the glacial base and facilitate sediment production and transport under the same moving speed and amount of ice.
 * Velocity of glacial movement
 * Thickness of the ice
 * Shape, abundance and hardness of rock fragments contained in the ice at the bottom of the glacier
 * Relative ease of erosion of the surface under the glacier
 * Thermal conditions at the glacier base
 * Permeability and water pressure at the glacier base

Material that becomes incorporated in a glacier is typically carried as far as the zone of ablation before being deposited. Glacial deposits are of two distinct types:

 * Glacial till: material directly deposited from glacial ice. Till includes a mixture of undifferentiated material ranging from clay size to boulders, the usual composition of a moraine.
 * Fluvial and outwash sediments: sediments deposited by water. These deposits are stratified by size.

Larger pieces of rock that are encrusted in till or deposited on the surface are called "glacial erratics". They range in size from pebbles to boulders, but as they are often moved great distances, they may be drastically different from the material upon which they are found. Patterns of glacial erratics hint at past glacial motions.

Moraines
Glacial moraines are formed by the deposition of material from a glacier and are exposed after the glacier has retreated. They usually appear as linear mounds of till, a non-sorted mixture of rock, gravel, and boulders within a matrix of fine powdery material. Terminal or end moraines are formed at the foot or terminal end of a glacier. Lateral moraines are formed on the sides of the glacier. Medial moraines are formed when two different glaciers merge and the lateral moraines of each coalesce to form a moraine in the middle of the combined glacier. Less apparent are ground moraines, also called glacial drift, which often blankets the surface underneath the glacier downslope from the equilibrium line. The term moraine is of French origin. It was coined by peasants to describe alluvial embankments and rims found near the margins of glaciers in the French Alps. In modern geology, the term is used more broadly and is applied to a series of formations, all of which are composed of till. Moraines can also create moraine-dammed lakes.

Drumlins
Drumlins are asymmetrical, canoe-shaped hills made mainly of till. Their heights vary from 15 to 50 meters, and they can reach a kilometer in length. The steepest side of the hill faces the direction from which the ice advanced (stoss), while a longer slope is left in the ice's direction of movement (lee). Drumlins are found in groups called drumlin fields or drumlin camps. One of these fields is found east of Rochester, New York; it is estimated to contain about 10,000 drumlins. Although the process that forms drumlins is not fully understood, their shape implies that they are products of the plastic deformation zone of ancient glaciers. It is believed that many drumlins were formed when glaciers advanced over and altered the deposits of earlier glaciers.

Glacial valleys, cirques, arêtes, and pyramidal peaks

Before glaciation, mountain valleys have a characteristic "V" shape, produced by eroding water. During glaciation, these valleys are often widened, deepened and smoothed to form a U-shaped glacial valley or glacial trough, as it is sometimes called. The erosion that creates glacial valleys truncates any spurs of rock or earth that may have earlier extended across the valley, creating broadly triangular-shaped cliffs called truncated spurs. Within glacial valleys, depressions created by plucking and abrasion can be filled by lakes, called paternoster lakes. If a glacial valley runs into a large body of water, it forms a fjord.

Typically glaciers deepen their valleys more than their smaller tributaries. Therefore, when glaciers recede, the valleys of the tributary glaciers remain above the main glacier's depression and are called hanging valleys.

At the start of a classic valley glacier is a bowl-shaped cirque, which have escarped walls on three sides but is open on the side that descends into the valley. Cirques are where ice begins to accumulate in a glacier. Two glacial cirques may form back to back and erode their backwalls until only a narrow ridge, called an arête is left. This structure may result in a mountain pass. If multiple cirques encircle a single mountain, they create pointed pyramidal peaks; particularly steep examples are called horns.

Roches moutonnées
Passage of glacial ice over an area of bedrock may cause the rock to be sculpted into a knoll called a roche moutonnée, or "sheepback" rock. Roches moutonnées may be elongated, rounded and asymmetrical in shape. They range in length from less than a meter to several hundred meters long. Roches moutonnées have a gentle slope on their up-glacier sides and a steep to vertical face on their down-glacier sides. The glacier abrades the smooth slope on the upstream side as it flows along, but tears rock fragments loose and carries them away from the downstream side via plucking.

Alluvial stratification
As the water that rises from the ablation zone moves away from the glacier, it carries fine eroded sediments with it. As the speed of the water decreases, so does its capacity to carry objects in suspension. The water thus gradually deposits the sediment as it runs, creating an alluvial plain. When this phenomenon occurs in a valley, it is called a valley train. When the deposition is in an estuary, the sediments are known as bay mud. Outwash plains and valley trains are usually accompanied by basins known as "kettles". These are small lakes formed when large ice blocks that are trapped in alluvium melt and produce water-filled depressions. Kettle diameters range from 5 m to 13 km, with depths of up to 45 meters. Most are circular in shape because the blocks of ice that formed them were rounded as they melted.

Glacial deposits
When a glacier's size shrinks below a critical point, its flow stops and it becomes stationary. Meanwhile, meltwater within and beneath the ice leaves stratified alluvial deposits. These deposits, in the forms of columns, terraces and clusters, remain after the glacier melts and are known as "glacial deposits". Glacial deposits that take the shape of hills or mounds are called kames. Some kames form when meltwater deposits sediments through openings in the interior of the ice. Others are produced by fans or deltas created by meltwater. When the glacial ice occupies a valley, it can form terraces or kames along the sides of the valley. Long, sinuous glacial deposits are called eskers. Eskers are composed of sand and gravel that was deposited by meltwater streams that flowed through ice tunnels within or beneath a glacier. They remain after the ice melts, with heights exceeding 100 meters and lengths of as long as 100 km.

Loess deposits
Very fine glacial sediments or rock flour is often picked up by wind blowing over the bare surface and may be deposited great distances from the original fluvial deposition site. These eolian loess deposits may be very deep, even hundreds of meters, as in areas of China and the Midwestern United States. Katabatic winds can be important in this process.

Retreat of glaciers due to climate change
Glaciers, which can be hundreds of thousands of years old, are used to track climate change over long periods of time. Researchers melt or crush samples from glacier ice cores whose progressively deep layers represent respectively earlier times in Earth's climate history. The researchers apply various instruments to the content of bubbles trapped in the cores' layers in order to track changes in the atmosphere's composition. Temperatures are deduced from differing relative concentrations of respective gases, confirming that for at least the last million years, global temperatures have been linked to carbon dioxide concentrations.

Human activities in the industrial era have increased the concentration of carbon dioxide and other heat-trapping greenhouse gases in the air, causing current global warming. Human influence is the principal driver of changes to the cryosphere of which glaciers are a part.

Global warming creates positive feedback loops with glaciers. For example, in ice–albedo feedback, rising temperatures increase glacier melt, exposing more of earth's land and sea surface (which is darker than glacier ice), allowing sunlight to warm the surface rather than being reflected back into space. Reference glaciers tracked by the World Glacier Monitoring Service have lost ice every year since 1988. A study that investigated the period 1995 to 2022 showed that the flow velocity of glaciers in the Alps accelerates and slows down to a similar extent at the same time, despite large distances. This clearly shows that their speed is controlled by the climate change.

Water runoff from melting glaciers causes global sea level to rise, a phenomenon the IPCC terms a "slow onset" event. Impacts at least partially attributable to sea level rise include for example encroachment on coastal settlements and infrastructure, existential threats to small islands and low-lying coasts, losses of coastal ecosystems and ecosystem services, groundwater salinization, and compounding damage from tropical cyclones, flooding, storm surges, and land subsidence.

Isostatic rebound
Large masses, such as ice sheets or glaciers, can depress the crust of the Earth into the mantle. The depression usually totals a third of the ice sheet or glacier's thickness. After the ice sheet or glacier melts, the mantle begins to flow back to its original position, pushing the crust back up. This post-glacial rebound, which proceeds very slowly after the melting of the ice sheet or glacier, is currently occurring in measurable amounts in Scandinavia and the Great Lakes region of North America.

A geomorphological feature created by the same process on a smaller scale is known as dilation-faulting. It occurs where previously compressed rock is allowed to return to its original shape more rapidly than can be maintained without faulting. This leads to an effect similar to what would be seen if the rock were hit by a large hammer. Dilation faulting can be observed in recently de-glaciated parts of Iceland and Cumbria.

On other planets
The polar ice caps of Mars show geologic evidence of glacial deposits. The south polar cap is especially comparable to glaciers on Earth. Topographical features and computer models indicate the existence of more glaciers in Mars' past. At mid-latitudes, between 35° and 65° north or south, Martian glaciers are affected by the thin Martian atmosphere. Because of the low atmospheric pressure, ablation near the surface is solely caused by sublimation, not melting. As on Earth, many glaciers are covered with a layer of rocks which insulates the ice. A radar instrument on board the Mars Reconnaissance Orbiter found ice under a thin layer of rocks in formations called lobate debris aprons (LDAs).

In 2015, as New Horizons flew by the Pluto-Charon system, the spacecraft discovered a massive basin covered in a layer of nitrogen ice on Pluto. A large portion of the basin's surface is divided into irregular polygonal features separated by narrow troughs, interpreted as convection cells fuelled by internal heat from Pluto's interior. Glacial flows were also observed near Sputnik Planitia's margins, appearing to flow both into and out of the basin.

General references

 * A less-technical treatment of all aspects, with photographs and firsthand accounts of glaciologists' experiences. All images of this book can be found online (see Weblinks: Glaciers-online)
 * An undergraduate-level textbook.
 * A textbook for undergraduates avoiding mathematical complexities
 * A textbook devoted to explaining the geography of our planet.
 * A comprehensive reference on the physical principles underlying formation and behavior.
 * A textbook devoted to explaining the geography of our planet.
 * A comprehensive reference on the physical principles underlying formation and behavior.

title: Glacier


text:
Gylfaginning

Gylfaginning (Old Norse: 'The Beguiling of Gylfi' or 'The Deluding of Gylfi'; 13th century Old Norse pronunciation ) is the first main part of the 13th century Prose Edda, after the initial Prologue. The Gylfaginning takes the form of a dialogue between a Swedish King Gylfi and three men on thrones in Asgard called High, Just-As-High, and Third. Gylfi asks many questions of the three men on the history and future of the Æsir. The creation and eventual destruction of the world are described, as are many other aspects of Norse mythology. While the Gylfaginning never makes it explicit, the three are often presumed to be guises of Odin.

The second part of the Prose Edda is the Skáldskaparmál and the third Háttatal. The work is often attributed to or considered to have been compiled by Snorri Sturluson.

Summary
The Gylfaginning tells the story of Gylfi, a king of "the land that men now call Sweden". He is tricked by one of the goddesses of the Æsir, and wonders if all Æsir use magic and tricks for their will to be done. To find out more, he takes the "path of the serpent" to journey to Asgard. The Æsir realize he is coming and prepare illusions to deceive him; he finds a great palace. Inside the palace he encounters a man who asks Gylfi's name; Gylfi introduces himself as Gangleri. "Gangleri" then is taken to the king of the palace and comes upon three men on thrones: High, Just-As-High, and Third (Hár, Jafnhár, and Þriði).

Gangleri is then challenged to show his wisdom by asking questions, as is the custom in many sagas. Each question made to High, Just-As-High, and Third is about an aspect of the Norse mythology or its gods, and also about the creation and destruction of the world (Ragnarök). In the end, the palace and its people vanish, presumably as they were illusions to begin with. Gylfi is left standing on empty ground. Gylfi then returns to his nation and retells the tales he was told.

It can be argued that the author used this narrative device as a means of being able to safely document a vanishing and largely oral tradition within a Christian context. In the same way, a line continues the idea raised in the Prologue that Asgard is another name for the city of Troy, another way to make stories of the Norse gods acceptable as describing a lost ancient history rather than rival deities to the Christian god. The very final section of the Gylfaginning is also related to the Trojan connection to the Æsir, but is discarded as a later addition written by a separate author than the rest of the work by some scholars. According to this final section, the human descendants of the Trojans took on the same names told in the stories that had been told to Gylfi, presumably to endow themselves with additional authority.

The work as a whole is around 20,000 words.

license: Creative Commons - Attribution Share-Alike - https://creativecommons.org/licenses/by-sa/4.0/

title: Gylfaginning


text:
Glorious Revolution

The Glorious Revolution is the sequence of events that led to the deposition of James II and VII in November 1688. He was replaced by his daughter Mary II and her Dutch husband, William III of Orange, who was also his nephew. The two ruled as joint monarchs of England, Scotland, and Ireland until Mary's death in 1694. The Revolution itself was relatively bloodless, but pro-Stuart revolts between 1689 and 1746 caused significant casualties, while the political movement known as Jacobitism persisted into the late 18th century. William's invasion was the last successful invasion of England.

Despite his own Catholicism, for various reasons James became king in February 1685 with widespread backing from the Protestant majorities in England and Scotland, as well as largely Catholic Ireland. Although his policies quickly eroded this support, it was not until June 1688 that dissatisfaction became a political crisis. The birth of James Francis Edward on 10 June displaced his Protestant elder sister Mary as the heir presumptive. The prospect of a Catholic dynasty destroyed James's political authority, and led a few of his domestic opponents to seek external support in removing him.

Although there was little sign of armed English domestic resistance, both William and the Dutch States General were concerned James would support Louis XIV of France in the Nine Years' War. Claiming to be responding to an Invitation asking him to "protect the Protestant religion", William landed in Devon with 20,000 men on 5 November 1688. As he advanced on London, James' army disintegrated, and he went into exile in France on 23 December. In April 1689, Parliament made William and Mary joint monarchs of England and Ireland. A separate but similar Scottish settlement was made in June.

Domestically, the Revolution confirmed the primacy of Parliament over the Crown in both England and Scotland. In terms of external policy, until his death in 1702, William combined the roles of Dutch stadholder and British monarch. Both states thus became allies in resisting French expansion, an alliance which persisted for much of the 18th century, despite differing objectives. Under William's leadership, Dutch resources were focused on the land war with France, with the Royal Navy taking the lead at sea. This was a significant factor in the Dutch Republic being overtaken as the leading European maritime power by Britain during the War of the Spanish Succession.

Background
Despite his Catholicism, James became king in 1685 with widespread backing in all three of his kingdoms. In June 1685, he quickly crushed Protestant risings in Scotland and England, but was forced into exile less than four years later. Modern historians argue James failed to appreciate how much Royal power relied on support from the landed gentry, and the loss of that support fatally damaged his regime. The vast majority of the gentry in England and Scotland were Protestant, while even in largely Catholic Ireland a disproportionate number were members of the Protestant Church of Ireland. Although willing to accept James's personal religious beliefs, his backers did so only so long as he maintained the primacy of the Protestant Church of England and Church of Scotland. When his policies appeared to undermine the existing political and religious order, the result was to alienate his English and Scottish supporters and destabilise Ireland.

Stuart political ideology derived from James VI and I, who in 1603 had created a vision of a centralised state, run by a monarch whose authority came from God, and where the function of Parliament was simply to obey. Disputes over the relationship between king and Parliament led to the War of the Three Kingdoms and continued after the 1660 Stuart Restoration. Charles II came to rely on the Royal Prerogative since measures passed in this way could be withdrawn when he decided, rather than Parliament. However, it could not be used for major legislation or taxation.

Concern that Charles II intended to create an absolute monarchy led to the 1679 to 1681 Exclusion Crisis, dividing the English political class into those who wanted to 'exclude' James from the throne, mostly Whigs, and their opponents, mostly Tories. However, in 1685 many Whigs feared the consequences of bypassing the 'natural heir', while Tories were often strongly anti-Catholic, and their support assumed the continued primacy of the Church of England. Most importantly, it was seen as a short-term issue; James was 52, his marriage to Mary of Modena remained childless after 11 years, and the heirs were his Protestant daughters, Mary and Anne.

There was much greater sympathy in Scotland for a 'Stuart heir', and the 1681 Succession Act confirmed the duty of all to support him, 'regardless of religion.' Over 95 percent of Scots belonged to the national church or kirk; even other Protestant sects were banned, and by 1680, Catholics were a tiny minority confined to parts of the aristocracy and the remote Highlands. Episcopalians had regained control of the kirk in 1660, leading to a series of Presbyterian uprisings, but memories of the bitter religious conflicts of the Civil War period meant the majority preferred stability.

In England and Scotland, most of those who backed James in 1685 wanted to retain existing political and religious arrangements, but this was not the case in Ireland. While he was guaranteed support from the Catholic majority, James was also popular among Irish Protestants, since the Church of Ireland depended on Royal support for its survival, while Ulster was dominated by Presbyterians who supported his tolerance policies. However, religion was only one factor; of equal concern for Catholics were laws barring them from serving in the military or holding public office, and land reform. In 1600, 90% of Irish land was owned by Catholics but following a series of confiscation during the 17th century, this had dropped to 22% in 1685. Catholic and Protestant merchants in Dublin and elsewhere objected to commercial restrictions placing them at a disadvantage to their English competitors.

The political background in England

While James's supporters viewed hereditary succession as more important than his personal Catholicism, they opposed his policies of 'Tolerance' under which Catholics would be allowed to hold public office and engage in public life. Opposition was led by devout Anglicans who argued that the measures he proposed were incompatible with the oath he had sworn as king to uphold the supremacy of the Church of England. In an age when oaths were seen as fundamental to a stable society, by demanding that Parliament approve his measures James was seen not only to be breaking his own word but requiring others to do the same. Parliament refused to comply, despite being "the most Loyal Parliament a Stuart ever had".

Although historians generally accept James wished to promote Catholicism, not establish an Absolute monarchy, his stubborn and inflexible reaction to opposition had the same result. When the English and Scottish Parliaments refused to repeal the 1678 and 1681 Test Acts, he suspended them in November 1685 and ruled by decree. Attempts to form a 'King's party' of Catholics, English Dissenters and dissident Scottish Presbyterians was politically short-sighted, since it rewarded those who joined the 1685 rebellions and undermined his supporters.

Demanding tolerance for Catholics was also badly timed. In October 1685 Louis XIV of France issued the Edict of Fontainebleau revoking the 1598 Edict of Nantes which had given French Protestants the right to practise their religion; over the next four years, an estimated 200,000 to 400,000 went into exile, 40,000 of whom settled in London. Combined with Louis's expansionist policies and the killing of 2,000 Vaudois Protestants in 1686, it led to fears Protestant Europe was threatened by a Catholic counter-reformation. These concerns were reinforced by events in Ireland; the Lord Deputy, the Earl of Tyrconnell, wanted to create a Catholic establishment able to survive James's death, which meant replacing Protestant officials at a pace that was inherently destabilising.

Timeline of events: 1686 to 1688

The majority of those who backed James in 1685 did so because they wanted stability and the rule of law, qualities frequently undermined by his actions. After suspending Parliament in November 1685, he sought to rule by decree; although the principle was not disputed, the widening of its scope caused considerable concern, particularly when judges who disagreed with its application were dismissed. He then alienated many by perceived attacks on the established church; Henry Compton, Bishop of London, was suspended for refusing to ban John Sharp from preaching after he gave an anti-Catholic sermon.

He often made things worse by political clumsiness; to general fury, the Ecclesiastical Commission of 1686 established to discipline the Church of England included suspected Catholics like the Earl of Huntingdon. This was combined with an inability to accept opposition; in April 1687, he ordered Magdalen College, Oxford, to elect a Catholic sympathiser named Anthony Farmer as president, but as he was ineligible under the college statutes, the fellows elected John Hough instead. Both Farmer and Hough withdrew in favour of another candidate selected by James, who then demanded the fellows personally apologise on their knees for 'defying' him; when they refused, they were replaced by Catholics.

Attempts to create an alternative 'Kings Party' were never likely to succeed, as English Catholics made up only 1.1% of the population and Nonconformists 4.4%. Both groups were divided; since private worship was generally tolerated, Catholic moderates feared greater visibility would provoke a backlash. Among Nonconformists, while Quakers and Congregationalists supported repeal of the Test Acts, the majority wanted to amend the 1662 Act of Uniformity and be allowed back into the Church of England. When James ensured the election of the Presbyterian John Shorter as Lord Mayor of London in 1687, he insisted on complying with the Test Act, reportedly because of a 'distrust of the King's favour...thus encouraging that which His Majesties whole Endeavours were intended to disannull.'

To ensure a compliant Parliament, James required potential MPs to be approved by their local Lord Lieutenant; eligibility for both offices required positive answers in writing to the 'Three Questions', one being a commitment to repeal of the Test Act. In addition, local government and town corporations were purged to create an obedient electoral machine, further alienating the county gentry who had formed the majority of those who backed James in 1685. On 24 August 1688, writs were issued for a general election.

The expansion of the military caused great concern, particularly in England and Scotland, where memories of the Civil War left huge resistance to standing armies. In Ireland, Talbot replaced Protestant officers with Catholics; James did the same in England, while basing the troops at Hounslow appeared a deliberate attempt to overawe Parliament. In April 1688, he ordered his Declaration of Indulgence read in every church; when the Archbishop of Canterbury and six other bishops refused, they were charged with seditious libel and confined in the Tower of London. Two events turned dissent into a crisis; the birth of James Francis Edward Stuart on 10 June created the prospect of a Catholic dynasty, while the acquittal of the Seven Bishops on 30 June destroyed James's political authority.

Prelude: 1685 to June 1688

In 1677, James's elder daughter and heir Mary married her Protestant cousin William III of Orange, stadtholder of the main provinces of the Dutch Republic. The two initially shared common objectives in wanting Mary to succeed her father, while French ambitions in the Spanish Netherlands threatened both English and Dutch trade. Although William sent James troops to help suppress the 1685 Monmouth Rebellion, their relationship deteriorated thereafter.

The Franco-Dutch War, continued French expansion, and expulsion of the Huguenots meant William assumed another war was inevitable, and although the States General of the Netherlands preferred peace, the majority accepted he was correct. This view was widely shared throughout Protestant Europe; in October 1685, Frederick William, Elector of Brandenburg renounced his French alliance for one with the Dutch. In July 1686, other Protestant states formed the anti-French League of Augsburg, with Dutch support; securing or neutralising English resources, especially the Royal Navy, now became key to both sides.

Following a skirmish between French and Dutch naval vessels in July 1686, William concluded English neutrality was not enough and he needed their active support in the event of war. His relationship with James was affected by the fact both men relied on advisors with relatively limited views; in William's case, mainly English and Scots Presbyterian exiles, the latter with close links to the Protestant minority in Ireland, who saw Tyrconnell's policies as a threat to their existence. Having largely alienated his Tory support base, James depended on a small circle of Catholic converts like Sunderland, Melfort and Perth.

Suspicions increased when James sought William's backing for repealing the Test Acts; he predictably refused, further damaging their relationship. Having previously assumed he was guaranteed English support in a war with France, William now worried he might face an Anglo-French alliance, despite assurances by James he had no intention of doing so. Historians argue these assurances were genuine, but James did not appreciate the distrust caused by his domestic policies. In August 1687, William's cousin de Zuylestein travelled to England with condolences on the death of Mary of Modena's mother, allowing him to make contact with the political opposition. Throughout 1688, his English supporters provided William detailed information on public opinion and developments, very little of which was intercepted.

In October 1687, after fourteen years of marriage and multiple miscarriages, it was announced the Queen was pregnant, Melfort immediately declaring it was a boy. When James then wrote to Mary urging her to convert to Catholicism, it convinced many he was seeking a Catholic heir, one way or the other and may have been a deciding factor in whether to invade. Early in 1688, a pamphlet circulated in England written by Dutch Grand Pensionary Gaspar Fagel; this guaranteed William's support for freedom of worship for Dissenters and retaining the Test Acts, unlike James who offered tolerance in return for repeal.

In April 1688, Louis XIV announced tariffs on Dutch herring imports, along with plans to support the Royal Navy in the English Channel. James immediately denied making any such request, but fearing it was the prelude to a formal alliance, the Dutch began preparing a military intervention. On the pretext of needing additional resources to deal with French privateers, in July the States General authorised an additional 9,000 sailors and 21 new warships.

Invitation to William

The success of William's invasion would partly depend on domestic support, and at the end of April William met with Edward Russell, unofficial envoy for the Whig opposition. In a conversation recorded by Gilbert Burnet, he requested a formal invitation asking him to "rescue the nation and the religion", with a projected date of end September. William subsequently claimed he was 'forced' to take control of the conspiracy when Russell warned him the English would rise against James even without his help, and he feared this would lead to a republic, depriving his wife of her inheritance.

Although this version is strongly disputed, Zuylestein returned to England in June, ostensibly to congratulate James on his new son, in reality to co-ordinate with William's supporters. Spurred by the prospect of a Catholic successor, the "Invitation to William" was quickly drafted by Henry Sydney, later described by Whig historians as "the great wheel on which the Revolution rolled". The signatories provided no considerable political power and were not representative, but they were selected to make it seem like they represented a broad spectrum, and provided William with an essential propaganda tool. Danby, a Tory, and Devonshire, a Whig; Henry Compton, Bishop of London, for the church; Shrewsbury and Lumley for the army, and finally Russell and Sydney for the navy. They promised to support a Dutch landing, but stressed the importance of acting quickly.

The Invitation was carried to The Hague on 30 June by Rear Admiral Herbert, disguised as a common sailor. Meanwhile, William's ally Bentinck launched a propaganda campaign in England, which presented him as a "true Stuart", but one without the faults of either James or Charles II. Much of the "spontaneous" support for William on his landing was organised by Bentinck and his agents.

Dutch preparations: July to September 1688

William's key strategic purpose was creating a defensive coalition that would block further French expansion in Europe, an objective not shared by the majority of his English supporters. In 1672, an alliance with the Electorate of Cologne had enabled France to bypass Dutch forward defences and nearly over-run the Republic, so ensuring an anti-French ruler was vital to prevent a repetition. As an ecclesiastical principality of the Holy Roman Empire, Cologne's ruler was nominated by Pope Innocent XI, in conjunction with Emperor Leopold I. Both Louis and James were in dispute with Innocent over the right to appoint Catholic bishops and clergy; when the old Elector died in June 1688, Innocent and Leopold ignored the French candidate in favour of Joseph Clemens of Bavaria.

After 1678, France continued its expansion into the Rhineland, including the 1683 to 1684 War of the Reunions, additional territorial demands in the Palatinate, and construction of forts at Landau and Traben-Trarbach. This presented an existential threat to Habsburg dominance, guaranteeing Leopold's support for the Dutch, and negating French attempts to build German alliances. William's envoy Johann von Görtz assured Leopold English Catholics would not be persecuted and intervention was to elect a free Parliament, not depose James, a convenient fiction that allowed him to remain neutral.

Although his English supporters considered a token force sufficient, William assembled 260 transport ships and 15,000 men, nearly half the 30,000 strong Dutch States Army. With France on the verge of war, their absence was of great concern to the States General and Bentinck hired 13,616 German mercenaries to man Dutch border fortresses, freeing elite units like the Scots Brigade for use in England. The increase could be presented as a limited precaution against French aggression, as the Dutch would typically double or triple their army strength in wartime; William instructed his experienced deputy Schomberg to prepare for a campaign in Germany.

Decision to invade

At the beginning of September, an invasion remained in the balance, with the States General fearing a French attack via Flanders while their army was in England. However, the surrender of Belgrade on 6 September seemed to presage an Ottoman collapse and release Austrian resources for use in Germany. Hoping to act before Leopold could respond and relieve pressure on the Ottomans, Louis attacked Philippsburg. With France now committed in Germany, this greatly reduced the threat to the Dutch.

Instead, Louis attempted to intimidate the States General, and on 9 September, his envoy D'Avaux handed them two letters. The first warned an attack on James meant war with France, the second any interference with French operations in Germany would end with the destruction of the Dutch state. Both misfired; convinced Louis was trying to drag him into war, James told the Dutch there was no secret Anglo-French alliance against them, although his denials only increased their suspicions. By confirming France's primary objective was the Rhineland, the second allowed William to move troops from the eastern border to the coast, even though most of the new mercenaries had yet to arrive.

On 22 September, the French seized over 100 Dutch ships, many owned by Amsterdam merchants; in response, on 26 September the Amsterdam City Council agreed to back William. This was a significant decision since the Council dominated the States of Holland, the most powerful political body in the Dutch Republic which contributed nearly 60% of its budget. French troops entered the Rhineland on 27 September and in a secret session held on 29th, William argued for a pre-emptive strike, as Louis and James would "attempt to bring this state to its ultimate ruin and subjugation, as soon as they find the occasion". This was accepted by the States, with the objective left deliberately vague, other than making the English "King and Nation live in a good relation, and useful to their friends and allies, and especially to this State".

Following their approval, the Amsterdam financial market raised a loan of four million guilders in only three days, with further financing coming from various sources, including two million guilders from the banker Francisco Lopes Suasso. The biggest concern for Holland was the potential impact on the Dutch economy and politics of William becoming ruler of England; the claim he had no intention of "removing the King from the throne" was not believed. These fears were arguably justified; William's access to English resources permanently diminished Amsterdam's power within the Republic and its status as the world's leading commercial and financial centre.

English defensive strategy

Neither James nor Sunderland trusted Louis, correctly suspecting that his support would continue only so long as it coincided with French interests, while Mary of Modena claimed his warnings were simply an attempt to drag England into an unwanted alliance. As a former naval commander, James appreciated the difficulties of a successful invasion, even in good weather, and as autumn approached, the likelihood seemed to diminish. With the Dutch on the verge of war with France, he did not believe the States General would allow William to make the attempt; if they did, his army and navy were strong enough to defeat it.

Reasonable in theory, his reliance on the loyalty and efficiency of the military proved deeply flawed. Both the army and the navy remained overwhelmingly Protestant and anti-Catholic; in July, only personal intervention by James prevented a naval mutiny when a Catholic captain held Mass on his ship. The transfer of 2,500 Catholics from the Royal Irish Army to England in September led to clashes with Protestant troops, some of his most reliable units refused to obey orders, and many of their officers resigned.

When James demanded the repatriation of all six regiments of the Scots Brigade in January 1688, William refused but used the opportunity to purge those considered unreliable, a total of 104 officers and 44 soldiers. Some may have been Williamite agents, such as Colonel Belasyse, a Protestant with over 15 years of service who returned to his family estates in Yorkshire and made contact with Danby. The promotion of Catholic former Brigade officers like Thomas Buchan and Alexander Cannon to command positions led to the formation of the Association of Protestant Officers, which included senior veterans like Charles Trelawny, Churchill, and Percy Kirke.

On 14 August, Churchill offered his support to William, helping convince him it was safe to risk an invasion; although James was aware of the conspiracy, he took no action. One reason may have been fears over the impact on the army; with a notional strength of 34,000, it looked impressive on paper but morale was brittle while many were untrained or lacked weapons. It also had to fill policing roles previously delegated to the militia, which had been deliberately allowed to decay; most of the 4,000 regular troops brought from Scotland in October had to be stationed in London to keep order. In October, attempts were made to restore the militia but many members were reportedly so angry at the changes made to local corporations, James was advised it was better not to raise them.

Widespread discontent and growing hostility to the Stuart regime were particularly apparent in North-East and South-West England, the two landing places identified by William. A Tory whose brother Jonathan was one of the Seven Bishops, Trelawny's commitment confirmed support from a powerful and well-connected West Country bloc, allowing access to the ports of Plymouth and Torbay. In the north, a force organised by Belasyse and Danby prepared to seize York, its most important city, and Hull, its largest port.

Herbert had been replaced by Dartmouth as commander of the fleet when he defected in June but many captains owed him their appointments and were of doubtful loyalty. Dartmouth suspected Berkeley and Grafton of plotting to overthrow him; to monitor them, he placed their ships next to his and minimised contact between the other vessels to prevent conspiracy. A lack of funds meant that excluding fireships and light scouting vessels, only 16 warships were available in early October, all third rates or fourth rates that were short of both men and supplies.

While the Downs was the best place to intercept a cross-Channel attack, it was also vulnerable to a surprise assault, even for ships fully manned and adequately provisioned. Instead, James placed his ships in a strong defensive position near Chatham Dockyard, believing the Dutch would seek to establish naval superiority before committing to a landing. While this had been the original plan, winter storms meant conditions deteriorated rapidly for those on the transports; William therefore decided to sail in convoy and avoid battle. The easterly winds that allowed the Dutch to cross prevented the Royal Navy leaving the Thames estuary and intervening.

The English fleet was outnumbered 2:1, undermanned, short of supplies, and in the wrong place. Key landing locations in the south-west and Yorkshire had been secured by sympathisers, while both army and navy were led by officers whose loyalty was questionable. Even early in 1686, foreign observers doubted the military would fight for James against a Protestant heir, and William claimed only to be securing the inheritance of his wife Mary. While still a dangerous undertaking, the invasion was less risky than it seemed.

Embarkation of the army and the Declaration of The Hague

The Dutch preparations, though carried out with great speed, could not remain secret. The English envoy Ignatius White, the Marquess d'Albeville, warned his country: "an absolute conquest is intended under the specious and ordinary pretences of religion, liberty, property and a free Parliament". Louis threatened an immediate declaration of war if William proceeded and sent James 300,000 livres.

Embarkations, begun on 22 September (Gregorian calendar), had been completed on 8 October, and the expedition was that day openly approved by the States of Holland; the same day James issued a proclamation to the English nation that it should prepare for a Dutch invasion to ward off conquest. On 30 September/10 October (Julian/Gregorian calendars) William issued the Declaration of The Hague (actually written by Fagel), of which 60,000 copies of the English translation by Gilbert Burnet were distributed after the landing in England, in which he assured that his only aim was to maintain the Protestant religion, install a free parliament and investigate the legitimacy of the Prince of Wales. He would respect the position of James.

William went on to condemn James's advisers for overturning the religion, laws, and liberties of England, Scotland, and Ireland by the use of the suspending and dispensing power; the establishment of the "manifestly illegal" commission for ecclesiastical causes and its use to suspend the Bishop of London and to remove the Fellows of Magdalen College, Oxford. William also condemned James's attempt to repeal the Test Acts and the penal laws through pressuring individuals and waging an assault on parliamentary boroughs, as well as his purging of the judiciary. James's attempt to pack Parliament was in danger of removing "the last and great remedy for all those evils".

"Therefore", William continued, "we have thought fit to go over to England, and to carry over with us a force sufficient, by the blessing of God, to defend us from the violence of those evil Counsellors ... this our Expedition is intended for no other design, but to have, a free and lawful Parliament assembled as soon as is possible". On 4/14 October, William responded to the allegations by James in a second declaration, denying any intention to become king or to conquer England, a claim which remains controversial.

The swiftness of the embarkations surprised all foreign observers. Louis had in fact delayed his threats against the Dutch until early September because he assumed it then would be too late in the season to set the expedition in motion anyway, if their reaction proved negative; typically, such an enterprise would take at least some months. Being ready after the last week of September / first week of October would normally have meant that the Dutch could have profited from the last spell of good weather, as the autumn storms tend to begin in the third week of that month. However, this year they came early. For three weeks, the invasion fleet was prevented by adverse south-westerly gales from departing from the naval port of Hellevoetsluis and Catholics all over the Netherlands and the British kingdoms held prayer sessions that this "popish wind" might endure. However, on 14/24 October, it became the famous "Protestant Wind" by turning to the east.

Crossing and landing

Although most of the warships were provided by the Admiralty of Amsterdam, the expedition was officially treated as a private affair, with the States General allowing William use of the Dutch army and fleet. For propaganda purposes, English admiral Arthur Herbert was nominally in command, but in reality, operational control remained with Lieutenant-Admiral Cornelis Evertsen the Youngest and Vice-Admiral Philips van Almonde. Accompanied by Willem Bastiaensz Schepers, the Rotterdam shipping magnate who provided financing, William boarded the frigate Den Briel on 16/26 October. The fleet contained 49 warships, 76 transports for the soldiers, 120 transports for the 5,000 horses required by the cavalry and supply train, and 40,000 men on board, of whom 9,500 were sailors of the Dutch States Navy. It was the largest fleet assembled in European waters up to that date.

Having departed on 19/29 October, the expedition was halfway across the North Sea when it was scattered by a gale, forcing the Brill back to Hellevoetsluis on 21/31 October. William refused to go ashore, and the fleet reassembled, having lost only one ship but nearly a thousand horses; press reports deliberately exaggerated the damage and claimed the expedition might be postponed until next spring. Dartmouth and his senior commanders considered taking advantage of this by blockading Hellevoetsluis, then decided against it, partly because the stormy weather made it dangerous but also because they could not rely on their men.

William replaced his losses and departed when the wind changed on 1/11 November, this time heading for Harwich where Bentinck had prepared a landing site. It has been suggested this was a feint to divert some of Dartmouth's ships north, which proved to be the case and when the wind shifted again, the Dutch armada sailed south into the Strait of Dover. In doing so, they twice passed the English fleet, which was unable to intercept because of the adverse winds and tides.

On 3/13 November, the invasion fleet entered the English Channel in an enormous formation 25 ships deep, the troops lined up on deck, firing musket volleys, colours flying and military bands playing. Intended to awe observers with its size and power, Rapin de Thoyras later described it as "the most magnificent and affecting spectacle...ever seen by human eyes". The same wind blowing the Dutch down the Channel kept Dartmouth confined in the Thames estuary; by the time he was able to make his way out, he was too far behind to stop William reaching Torbay on 5 November.

As anticipated, the French fleet remained in the Mediterranean, in order to support an attack on the Papal States if needed, while a south-westerly gale now forced Dartmouth to shelter in Portsmouth harbour and kept him there for two days, allowing William to complete his disembarkation undisturbed. The regular Dutch troops amounted to 14,000–15,000 men, consisting of around 11,000 infantry, including nearly 5,000 members of the elite Anglo-Scots Brigade and Dutch Blue Guards, 3,660 cavalry and an artillery train of twenty-one 24-pounder cannon.

Some 5,000 volunteers, consisting of British exiles and Huguenots, also accompanied the fleet, making a total army of over 20,000 men. William brought these volunteers along to accelerate English army reforms, because they could replace the soldiers who were loyal to James. William brought weapons to equip another 20,000 men, although the subsequent and rapid collapse of James's army meant the local volunteers who joined by 20 November were eventually dismissed.

The collapse of James's rule
James had considered himself safe from invasion, due to the French threat to the Spanish Netherlands, his navy and because it was late in the year for launching an expedition. He now panicked and met with the bishops on 28 September, offering them concessions. They responded five days later with demands that he restore the religious position to that prevailing in February 1685, and hold free elections for a new Parliament. Although they hoped this would allow James to remain king, in reality there was little chance of this. At a minimum, he would have to disinherit his son, enforce the Test Acts, and accept the supremacy of Parliament, all of which were unacceptable. In addition, by now his Whig opponents did not trust him to keep his promises, while Tories like Danby were too committed to William to escape punishment.

Although his veterans were superior to the largely untested recruits of the Royal Army, William and his English supporters preferred to avoid bloodshed. Torbay was sufficiently far from London to provide time for the regime to collapse on its own, while to avoid alienating the local population, his troops were well supplied and paid three months in advance. On 9 November, he entered Exeter and issued a proclamation claiming he sought only to secure the rights of his wife and a free Parliament. Despite this, there was little enthusiasm for either party, and the general mood was one of confusion and distrust. In Northern England, much of the gentry confirmed their backing for the invasion after Danby had the Declaration read out in York on 12 November.

On 19 November, James joined his main force of 19,000 at Salisbury, but morale was low and the loyalty of some of his commanders was doubtful. Officers of several regiments defected to William between 10 and 20 November, although only a few of them took any troops with them. Supply problems meanwhile left the Royal Army short of food and ammunition. On 20 November, dragoons led by Irish Catholic Patrick Sarsfield clashed with Williamite scouts at Wincanton; along with a minor skirmish at Reading on 9 December, also featuring Sarsfield, these were the only substantial military actions of the campaign. After securing his rear by taking Plymouth on 18 November, William began his advance on 21 November, while Danby and Belasyse captured York and Hull several days later.

Although only a tiny minority of James's army defected, the effect on the morale of his army was great. James's commander Feversham and other senior officers advised retreat. Lacking information on William's movements, suspicious of his own soldiers, worn out by lack of sleep and debilitating nose-bleeds, on 23 November James agreed. Because of its strategic implications, the withdrawal was a practical admission of defeat. The next day Churchill, Grafton and Princess Anne's husband George deserted to William, followed by Anne herself on 26 November. The next day, James held a meeting at Whitehall Palace with those peers still in London; with the exception of Melfort, Perth and other Catholics, they urged him to issue writs for a parliamentary election and negotiate with William.

On 8 December, Halifax, Nottingham and Godolphin met with William at Hungerford to hear his demands, which included the dismissal of Catholics from public office and funding for his army. Many viewed these as a reasonable basis for a settlement, but James decided to flee the country, convinced by Melfort and others that his life was threatened. This suggestion is generally dismissed by historians, since William made it clear he would not allow James to be harmed. Most Tories wanted him to retain his throne, while the Whigs simply wanted to drive him out of the country by imposing conditions he would refuse.

The Queen and Prince of Wales left for France on 9 December, James following separately on 10 December. Accompanied only by Edward Hales and Ralph Sheldon, he made his way to Faversham in Kent seeking passage to France, first dropping the Great Seal in the River Thames in a last-ditch attempt to prevent Parliament being summoned. In London, his flight and rumours of a "Papist" invasion led to riots and destruction of Catholic property, which quickly spread throughout the country. To fill the power vacuum, the Earl of Rochester set up a temporary government including members of the Privy Council and City of London authorities, but it took them two days to restore order.

When news arrived, James had been captured in Faversham on 11 December by local fishermen, Lord Ailesbury, one of his personal attendants, was sent to escort him back to London. On entering the city on 16 December, he was welcomed by cheering crowds. By making it seem that James remained in control, Tory loyalists hoped for a settlement which would leave them in government. To create an appearance of normality, he heard Mass and presided over a meeting of the Privy Council. James made it clear to the French ambassador Paul Barillon that he still intended to escape to France. His few remaining supporters viewed his flight as cowardice, and a failure to ensure law and order criminally negligent.

Happy to help him into exile, William recommended he relocate to Ham, largely because it was easy to escape from. James suggested Rochester instead, allegedly because his personal guard was there, in reality conveniently positioned for a ship to France. On 18 December, he left London with a Dutch escort as William entered, cheered by the same crowds who greeted his predecessor two days before. William occupied London and now effectively controlled the English government and the country's army, navy, and finances. On 22 December, Berwick arrived in Rochester with blank passports allowing them to leave England, while his guards were told that if James wanted to leave, "they should not prevent him, but allow him to gently slip through". Although Ailesbury and others begged him to stay, he left for France on 23 December.

The revolutionary settlement
James's departure significantly shifted the balance of power in favour of William, who took control of the provisional government on 28 December. Elections were held in early January for a Convention Parliament, which assembled on 22 January. The Whigs had a slight majority in the Commons and the Lords was dominated by the Tories, but both were led by moderates. Archbishop Sancroft and other Stuart loyalists wanted to preserve the line of succession; they recognised keeping James on the throne was no longer possible, so they preferred Mary either be appointed his regent or sole monarch.

The next two weeks were spent debating how to resolve this issue, much to the annoyance of William, who needed a swift resolution; the situation in Ireland was rapidly deteriorating, while the French had over-run large parts of the Rhineland and were preparing to attack the Dutch. At a meeting with Danby and Halifax on 3 February, he announced his intention to return home if the Convention did not appoint him joint monarch; Mary let it be known she would only rule jointly with her husband. Faced with this ultimatum, on 6 February Parliament declared that in deserting his people James had abdicated and thus vacated the Crown, which was therefore offered jointly to William and Mary.

Historian Tim Harris argues the most radical act of the 1688 Revolution was breaking the succession and establishing the idea of a "contract" between ruler and people, a fundamental rebuttal of the Stuart ideology of divine right. While this was a victory for the Whigs, other pieces of legislation were proposed by the Tories, often with moderate Whig support, designed to protect the Anglican establishment from being undermined by future monarchs, including the Calvinist William. The Declaration of Right was a tactical compromise, setting out where James had failed and establishing the rights of English citizens, without agreeing their cause or offering solutions. In December 1689, this was incorporated into the Bill of Rights.

However, there were two areas that arguably broke new constitutional ground, both responses to what were viewed as specific abuses by James. First, the Declaration of Right made keeping a standing army without parliamentary consent illegal, overturning the 1661 and 1662 Militia Acts and vesting control of the military in Parliament, not the Crown. The second was the Coronation Oath Act 1688; the result of James's perceived failure to comply with that taken in 1685, it established obligations owed by the monarchy to the people.

At their coronation on 11 April, William and Mary swore to "govern the people of this kingdom of England, and the dominions thereunto belonging, according to the statutes in Parliament agreed on, and the laws and customs of the same". They were also to maintain the Protestant Reformed faith and "preserve inviolable the settlement of the Church of England, and its doctrine, worship, discipline and government as by law established".

Scotland and Ireland

While Scotland was not involved in the landing, by November 1688 only a tiny minority supported James. Many of those who accompanied William were Scots exiles, including the Earl of Melville, the Duke of Argyll, his personal chaplain William Carstares and Gilbert Burnet. News of James's flight led to celebrations and anti-Catholic riots in Edinburgh and Glasgow. Most members of the Scottish Privy Council went to London. On 7 January 1689, they asked William to take over government. Elections were held in March for a Scottish Convention, which was also a contest between Presbyterians and Episcopalians for control of the Kirk. While only 50 of the 125 delegates were classed as Episcopalian, they were hopeful of victory since William supported the retention of bishops.

On 16 March a Letter from James was read out to the convention, demanding obedience and threatening punishment for non-compliance. Public anger at its tone meant some Episcopalians stopped attending the convention, claiming to fear for their safety and others changed sides. The 1689–1691 Jacobite Rising forced William to make concessions to the Presbyterians, ended Episcopacy in Scotland and excluded a significant portion of the political class. Many later returned to the Kirk but Non-Juring Episcopalianism was the key determinant of Jacobite support in 1715 and 1745.

The English Parliament held that James 'abandoned' his throne. The Convention argued that he 'forfeited' it by his actions, as listed in the Articles of Grievances. On 11 April, the Convention ended James's reign and adopted the Articles of Grievances and the Claim of Right Act, making Parliament the primary legislative power in Scotland. On 11 May, William and Mary accepted the Crown of Scotland; after their acceptance, the Claim and the Articles were read aloud, leading to an immediate debate over whether or not an endorsement of these documents was implicit in that acceptance.

Anglo-Dutch alliance
Though he had carefully avoided making it public, William's main motive in organising the expedition had been the opportunity to bring England into an alliance against France. On 9 December 1688 he had already asked the States General to send a delegation of three to negotiate the conditions. On 18 February (Julian calendar) he asked the convention to support the Republic in its war against France. It refused, only consenting to pay £600,000 for the continued presence of the Dutch army in England. On 9 March (Gregorian calendar) the States General responded to Louis's earlier declaration of war by declaring war on France in return.

Before they could take part in the war, both the English and Scottish armies had to be rebuilt from scratch. Many officers who had supported James' removal were unwilling to continue under his successor, while William was reluctant to trust those who had not already served under him. In addition, according historian Jonathan Scott: 'The state and discipline of the rank and file was ‘deplorable’. There was a dire lack of experience and competence at every level.' For the purpose of reforming the English army on the Dutch model William appointed Dutch officers to key positions, which caused considerable resentment in England.

On 19 April (Julian calendar) the Dutch delegation signed a naval treaty with England. It stipulated that the combined Anglo-Dutch fleet would always be commanded by an Englishman, even when of lower rank. The Dutch agreed to this to make their dominance over the English army less painful for the British. The treaty also specified that the two parties would contribute in the ratio of five English vessels against three Dutch vessels, meaning in practice that the Dutch navy in the future would be smaller than the English. The Navigation Acts were not repealed. On 18 May, the new Parliament allowed William to declare war on France. On 9 September 1689, (Gregorian calendar), William as King of England joined the League of Augsburg against France.

The decline of the Dutch Republic
Having England as an ally meant that the military situation of the Republic was strongly improved, which allowed William to be uncompromising in his position towards France. The Dutch successfully secured their positions in the Spanish Netherlands, and halted French territorial expansion, but these military campaigns were very expensive. In 1712, at the end of the War of the Spanish Succession, the Republic was financially exhausted and was forced to let its fleet deteriorate, making what was by then the Kingdom of Great Britain the dominant maritime power of the world.

The Dutch economy, already burdened by the high national debt and concomitant high taxation, suffered from the other European states' protectionist policies, which its weakened fleet was no longer able to resist. To make matters worse, the main Dutch trading and banking houses moved much of their activity from Amsterdam to London after 1688. Between 1688 and 1720, world trade dominance shifted from the Republic to Great Britain.

Assessment and historiography
While the 1688 revolution was labeled "Glorious" by Protestant preachers two decades later, its historiography is complex, and its assessment disputed. Thomas Macaulay's account of the Revolution in The History of England from the Accession of James the Second exemplifies the "Whig history" narrative of the Revolution as a largely consensual and bloodless triumph of English common sense, confirming and strengthening its institutions of tempered popular liberty and limited monarchy. Edmund Burke set the tone for that interpretation when he proclaimed: "The Revolution was made to preserve our ancient indisputable laws and liberties, and that ancient constitution of government which is our only security for law and liberty."

An alternative narrative emphasizes William's successful foreign invasion from the Netherlands, and the size of the corresponding military operation. Several researchers have emphasized that aspect, particularly after the third centenary of the event in 1988. The historian J. R. Jones suggested that the invasion "should be seen ... as the first and arguably the only decisive phase of the Nine Years' War." John Childs added that "there was no natural political turmoil in England in 1688", or "at least not of sufficient consequence to produce the overthrow of a king." Jonathan Israel also stresses the importance of the Dutch aspect by arguing that, due the Dutch occupation of London, parliament was hardly free when they decided to accept William as their king.

It has been argued that the invasion aspect had been downplayed as a result of British pride and effective Dutch propaganda, trying to depict the course of events as a largely internal English affair. As the invitation was initiated by figures who had little influence, the legacy of the Glorious Revolution has been described as a successful propaganda act by William to cover up and justify his invasion. The claim that William was fighting for the Protestant cause in England was used to great effect to disguise the military, cultural and political impact that the Dutch regime had on England.

A third version, proposed by Steven Pincus, underplays the invasion aspect but unlike the Whig narrative views the Revolution as a divisive and violent event that involved all classes of the English population, not just the main aristocratic protagonists. Pincus argues that his interpretation echoes the widely held view of the Revolution in its aftermath, starting with its revolutionary labelling. Pincus argues that it was momentous especially when looking at the alternative that James was trying to enact – a powerful centralised autocratic state, using French-style "state-building". England's role in Europe and the country's political economy in the 17th century rebuts the view of many late-20th-century historians that nothing revolutionary occurred during the Glorious Revolution of 1688–89. Pincus says it was not a placid turn of events.

In diplomacy and economics William III transformed the English state's ideology and policies. This occurred not because William III was an outsider who inflicted foreign notions on England but because foreign affairs and political economy were at the core of the English revolutionaries' agenda. The revolution of 1688–89 cannot be fathomed in isolation. It would have been inconceivable without the changes resulting from the events of the 1640s and 1650s. The ideas accompanying the Glorious Revolution were rooted in the mid-century upheavals. The 17th century was a century of revolution in England, deserving of the same scholarly attention that 'modern' revolutions attract.

James II tried building a powerful militarised state on the mercantilist assumption that the world's wealth was necessarily finite, and empires were created by taking land from other states. The East India Company was thus an ideal tool to create a vast new English imperial dominion by warring with the Dutch and the Mughal Empire in India. After 1689 came an alternative understanding of economics, which saw Britain as a commercial rather than an agrarian society. It led to the foundation of the Bank of England, the creation of Europe's first widely circulating credit currency and the commencement of the "Age of Projectors". This subsequently gave weight to the view, advocated most famously by Adam Smith in 1776, that wealth was created by human endeavour and was thus potentially infinite.

Karl Marx viewed the revolution as essentially conservative in nature, writing that it was shaped by an alliance between English commercial and industrial bourgeoisie and increasingly commercialized large land owners.

Impact
As a coup, albeit largely bloodless, its legitimacy rests in the will expressed separately by the Scottish and English Parliaments according to their respective legal processes. On this point, the Earl of Shaftesbury declared in 1689, "The Parliament of England is that supreme and absolute power, which gives life and motion to the English government". The Revolution established the primacy of parliamentary sovereignty, a principle still relevant in consultation with the 15 Commonwealth realms regarding succession issues. The Bill of Rights 1689 formally established a system of constitutional monarchy and ended moves towards absolute monarchy by restricting the power of the monarch, who could no longer suspend laws, levy taxes, make royal appointments or maintain a standing army during peacetime without Parliament's consent. The British Army remains the military arm of Parliament, not the monarch, although the Crown is the source of all military executive authority.

Unlike the 1638 to 1651 Wars of the Three Kingdoms, most ordinary people in England and Scotland were relatively untouched by the "Glorious Revolution", the majority of the bloodshed taking place in Ireland. As a consequence, some historians suggest that in England at least it more closely resembles a coup d'état, rather than a social upheaval such as the French Revolution. This view is consistent with the original meaning of "revolution" as a circular process under which an old system of values is restored to its original position, with England's supposed "ancient constitution" being reasserted, rather than formed anew. Contemporary English political thought, as expressed in John Locke's then popular social contract theory, linked to George Buchanan's view of the contractual agreement between the monarch and their subjects, an argument used by the Scottish Parliament as justification for the Claim of Right.

Under the Coronation Oath Act 1688, William had sworn to maintain the primacy of the Church of England, which both his native Dutch Reformed Church and the Church of Scotland viewed as ideologically suspect in both doctrine and use of bishops. This required a certain degree of religious flexibility on his part, especially as he needed to placate his Catholic allies, Spain and Emperor Leopold. Despite promising legal toleration for Catholics in his Declaration of October 1688, William failed due to domestic opposition. The Act of Toleration 1689 granted relief to Nonconformists but Catholic emancipation would be delayed until 1829.

News of the Glorious Revolution reached the English colonies in North America in 1689, leading to a revolt in Boston and the dissolution of the Dominion of New England.

title: Glorious Revolution