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Caving

Caving, also known as spelunking (United States and Canada) and potholing (United Kingdom and Ireland), is the recreational pastime of exploring wild cave systems (as distinguished from show caves). In contrast, speleology is the scientific study of caves and the cave environment.

The challenges involved in caving vary according to the cave being visited; in addition to the total absence of light beyond the entrance, negotiating pitches, squeezes, and water hazards can be difficult. Cave diving is a distinct, and more hazardous, sub-speciality undertaken by a small minority of technically proficient cavers. In an area of overlap between recreational pursuit and scientific study, the most devoted and serious-minded cavers become accomplished at the surveying and mapping of caves and the formal publication of their efforts. These are usually published freely and publicly, especially in the UK and other European countries, although in the US, these are generally private.

Although caving is sometimes categorized as an "extreme sport," cavers do not commonly use this terminology and typically dislike the term being used in reference to caving, as it implies a disregard for safety.

Many caving skills overlap with those involved in canyoning and mine and urban exploration.

Motivation
Caving is often undertaken for the enjoyment of the outdoor activity or for physical exercise, as well as original exploration, similar to mountaineering or diving. Physical or biological science is also an important goal for some cavers, while others are engaged in cave photography. Virgin cave systems comprise some of the last unexplored regions on Earth and much effort is put into trying to locate, enter and survey them. In well-explored regions (such as most developed nations), the most accessible caves have already been explored, and gaining access to new caves often requires cave digging or cave diving.

Caving, in certain areas, has also been utilized as a form of eco and adventure tourism, for example in New Zealand. Tour companies have established an industry leading and guiding tours into and through caves. Depending on the type of cave and the type of tour, the experience could be adventure-based or ecological-based. There are tours led through lava tubes by a guiding service (e.g. Lava River Cave, the oceanic islands of Tenerife, Iceland and Hawaii).

Caving has also been described as an "individualist's team sport" by some, as cavers can often make a trip without direct physical assistance from others but will generally go in a group for companionship or to provide emergency help if needed. Some however consider the assistance cavers give each other as a typical team sport activity.

Etymology
The term Potholing refers to the act of exploring potholes, a word originating in the north of England for predominantly vertical caves. Clay Perry, an American caver of the 1940s, wrote about a group of men and boys who explored and studied caves throughout New England. This group referred to themselves as spelunkers, a term derived from the Latin spēlunca ("cave, cavern, den"), itself from the Greek σπῆλυγξ spēlynks ("cave"). This is regarded as the first use of the word in the Americas. Throughout the 1950s, spelunking was the general term used for exploring caves in US English. It was used freely, without any positive or negative connotations, although only rarely outside the US.

In the 1960s, the terms spelunking and spelunker began to be considered déclassé among experienced enthusiasts. In 1985, Steve Knutson – editor of the National Speleological Society (NSS) publication American Caving Accidents – made the following distinction:

"…Note that (in this case) the term 'spelunker' denotes someone untrained and unknowledgeable in current exploration techniques, and 'caver' is for those who are."

This sentiment is exemplified by bumper stickers and T-shirts displayed by some cavers: "Cavers rescue spelunkers". Nevertheless, outside the caving community, "spelunking" and "spelunkers" predominately remain neutral terms referring to the practice and practitioners, without any respect to skill level.

History
In the mid-nineteenth century, John Birkbeck explored potholes in England, notably Gaping Gill in 1842 and Alum Pot in 1847–8, returning there in the 1870s. In the mid-1880s, Herbert E. Balch began exploring Wookey Hole Caves and in the 1890s, Balch was introduced to the caves of the Mendip Hills. One of the oldest established caving clubs, Yorkshire Ramblers' Club, was founded in 1892.

Caving as a specialized pursuit was pioneered by Édouard-Alfred Martel (1859–1938), who first achieved the descent and exploration of the Gouffre de Padirac, in France, as early as 1889 and the first complete descent of a 110-metre wet vertical shaft at Gaping Gill in 1895. He developed his own techniques based on ropes and metallic ladders. Martel visited Kentucky and notably Mammoth Cave National Park in October 1912. In the 1920s famous US caver Floyd Collins made important explorations in the area and in the 1930s, as caving became increasingly popular, small exploration teams both in the Alps and in the karstic high plateaus of southwest France (Causses and Pyrenees) transformed cave exploration into both a scientific and recreational activity. Robert de Joly, Guy de Lavaur  and Norbert Casteret were prominent figures of that time, surveying mostly caves in Southwest France. During World War II, an alpine team composed of Pierre Chevalier, Fernand Petzl, Charles Petit-Didier and others explored the Dent de Crolles cave system near Grenoble, which became the deepest explored system in the world (-658m) at that time. The lack of available equipment during the war forced Pierre Chevalier and the rest of the team to develop their own equipment, leading to technical innovation. The scaling-pole (1940), nylon ropes (1942), use of explosives in caves (1947) and mechanical rope-ascenders (Henri Brenot's "monkeys", first used by Chevalier and Brenot in a cave in 1934) can be directly associated to the exploration of the Dent de Crolles cave system.

In 1941, American cavers organized themselves into the National Speleological Society (NSS) to advance the exploration, conservation, study and understanding of caves in the United States. American caver Bill Cuddington, known as "Vertical Bill", further developed the single-rope technique (SRT) in the late 1950s. In 1958, two Swiss alpinists, Juesi and Marti teamed together, creating the first rope ascender known as the Jumar. In 1968 Bruno Dressler asked Fernand Petzl, who worked as a metals machinist, to build a rope-ascending tool, today known as the Petzl Croll, that he had developed by adapting the Jumar to vertical caving. Pursuing these developments, Petzl started in the 1970s a caving equipment manufacturing company named Petzl. The development of the rappel rack and the evolution of mechanical ascension systems extended the practice and safety of vertical exploration to a wider range of cavers.

Practice and equipment

Hard hats are worn to protect the head from bumps and falling rocks. The caver's primary light source is usually mounted on the helmet in order to keep the hands free. Electric LED lights are most common. Many cavers carry two or more sources of light – one as primary and the others as backup in case the first fails. More often than not, a second light will be mounted to the helmet for quick transition if the primary fails. Carbide lamp systems are an older form of illumination, inspired by miner's equipment, and are still used by some cavers, particularly on remote expeditions where electric charging facilities are not available.

The type of clothes worn underground varies according to the environment of the cave being explored, and the local culture. In cold caves, the caver may wear a warm base layer that retains its insulating properties when wet, such as a fleece ("furry") suit or polypropylene underwear, and an oversuit of hard-wearing (e.g., cordura) or waterproof (e.g., PVC) material. Lighter clothing may be worn in warm caves, particularly if the cave is dry, and in tropical caves thin polypropylene clothing is used, to provide some abrasion protection while remaining as cool as possible. Wetsuits may be worn if the cave is particularly wet or involves stream passages. On the feet boots are worn – hiking-style boots in drier caves, or rubber boots (such as wellies) often with neoprene socks ("wetsocks") in wetter caves. Knee-pads (and sometimes elbow-pads) are popular for protecting joints during crawls. Depending on the nature of the cave, gloves are sometimes worn to protect the hands against abrasion or cold. In pristine areas and for restoration, clean oversuits and powder-free, non-latex surgical gloves are used to protect the cave itself from contaminants. Ropes are used for descending or ascending pitches (single rope technique or SRT) or for protection. Knots commonly used in caving are the figure-of-eight- (or figure-of-nine-) loop, bowline, alpine butterfly, and Italian hitch. Ropes are usually rigged using bolts, slings, and carabiners. In some cases cavers may choose to bring and use a flexible metal ladder.

In addition to the equipment already described, cavers frequently carry packs containing first-aid kits, emergency equipment, and food. Containers for securely transporting urine are also commonly carried. On longer trips, containers for securely transporting feces out of the cave are carried.

During very long trips, it may be necessary to camp in the cave – some cavers have stayed underground for many days, or in particularly extreme cases, for weeks at a time. This is particularly the case when exploring or mapping extensive cave systems, where it would be impractical to retrace the route back to the surface regularly. Such long trips necessitate the cavers carrying provisions, sleeping, and cooking equipment.

Safety

Caves can be dangerous places; hypothermia, falling, flooding, falling rocks and physical exhaustion are the main risks. Rescuing people from underground is difficult and time-consuming, and requires special skills, training, and equipment. Full-scale cave rescues often involve the efforts of dozens of rescue workers (often other long-time cavers who have participated in specialized courses, as normal rescue staff are not sufficiently experienced in cave environments), who may themselves be put in jeopardy in effecting the rescue. This said, caving is not necessarily a high-risk sport (especially if it does not involve difficult climbs or diving). As in all physical sports, knowing one's limitations is key.

Caving in warmer climates carries the risk of contracting histoplasmosis, a fungal infection that is contracted from bird or bat droppings. It can cause pneumonia and can disseminate in the body to cause continued infections.

In many parts of the world, leptospirosis ("a type of bacterial infection spread by animals" including rats ) is a distinct threat, owing to the presence of rat urine in rainwater or precipitation that enters the caves water system. Complications are uncommon, but can be serious. Safety risks while caving can be minimized by using a number of techniques:

 * Checking that there is no danger of flooding during the expedition. Rainwater funneled underground can flood a cave very quickly, trapping people in cut-off passages and drowning them. In the UK, drowning accounts for almost half of all caving fatalities (see List of UK caving fatalities).
 * Using teams of several cavers, preferably at least four. If an injury occurs, one caver stays with the injured person while the other two go out for help, providing assistance to each other on their way out.
 * Notifying people outside the cave as to the intended return time. After an appropriate delay without a return, these will then organize a search party (usually made up by other cavers trained in cave rescues, as even professional emergency personnel are unlikely to have the skills to effect a rescue in difficult conditions).
 * Use of helmet-mounted lights (hands-free) with extra batteries. American cavers recommend a minimum of three independent sources of light per person, but two lights is common practice among European cavers.
 * Sturdy clothing and footwear, as well as a helmet, are necessary to reduce the impact of abrasions, falls, and falling objects. Synthetic fibers and woolens, which dry quickly, shed water, and are warm when wet, are vastly preferred to cotton materials, which retain water and increase the risk of hypothermia. It is also helpful to have several layers of clothing, which can be shed (and stored in the pack) or added as needed. In watery cave passages, polypropylene thermal underwear or wetsuits may be required to avoid hypothermia.
 * Cave passages look different from different directions. In long or complex caves, even experienced cavers can become lost. To reduce the risk of becoming lost, it is necessary to memorize the appearance of key navigational points in the cave as they are passed by the exploring party. Each member of a cave party shares responsibility for being able to remember the route out of the cave. In some caves it may be acceptable to mark a small number of key junctions with small stacks or "cairns" of rocks, or to leave a non-permanent mark such as high-visibility flagging tape tied to a projection.
 * Vertical caving uses ladders or single rope technique (SRT) to avoid the need for climbing passages that are too difficult. SRT is a complex skill and requires proper training and well-maintained equipment. Some drops that are abseiled down may be as deep as several hundred meters (for example Harwoods Hole).

Cave conservation
Many cave environments are very fragile. Many speleothems can be damaged by even the slightest touch and some by impacts as slight as a breath. Research suggests that increased carbon dioxide levels can lead to "a higher equilibrium concentration of calcium within the drip waters feeding the speleothems, and hence causes dissolution of existing features." In 2008, researchers found evidence that respiration from cave visitors may generate elevated carbon dioxide concentrations in caves, leading to increased temperatures of up to 3 °C and a dissolution of existing features.

Pollution is also of concern. Since water that flows through a cave eventually comes out in streams and rivers, any pollution may ultimately end up in someone's drinking water, and can even seriously affect the surface environment, as well. Even minor pollution such as dropping organic material can have a dramatic effect on the cave biota.

Cave-dwelling species are also very fragile, and often, a particular species found in a cave may live within that cave alone, and be found nowhere else in the world, such as Alabama cave shrimp. Cave-dwelling species are accustomed to a near-constant climate of temperature and humidity, and any disturbance can be disruptive to the species' life cycles. Though cave wildlife may not always be immediately visible, it is typically nonetheless present in most caves.

Bats are one such fragile species of cave-dwelling animal. Bats which hibernate are most vulnerable during the winter season, when no food supply exists on the surface to replenish the bat's store of energy should it be awakened from hibernation. Bats which migrate are most sensitive during the summer months when they are raising their young. For these reasons, visiting caves inhabited by hibernating bats is discouraged during cold months; and visiting caves inhabited by migratory bats is discouraged during the warmer months when they are most sensitive and vulnerable. Due to an affliction affecting bats in the northeastern US known as white nose syndrome (WNS), the US Fish & Wildlife Service has called for a moratorium effective March 26, 2009, on caving activity in states known to have hibernacula (MD, NY, VT, NH, MA, CT, NJ, PA, VA, and WV) affected by WNS, as well as adjoining states.

Some cave passages may be marked with flagging tape or other indicators to show biologically, aesthetically, or archaeologically sensitive areas. Marked paths may show ways around notably fragile areas such as a pristine floor of sand or silt which may be thousands of years old, dating from the last time water flowed through the cave. Such deposits may easily be spoiled forever by a single misplaced step. Active formations such as flowstone can be similarly marred with a muddy footprint or handprint, and ancient human artifacts, such as fiber products, may even crumble to dust under all but the most gentle touch.

In 1988, concerned that cave resources were becoming increasingly damaged through unregulated use, Congress enacted the Federal Cave Resources Protection Act, giving land management agencies in the United States expanded authority to manage cave conservation on public land.

Caving organizations
Cavers in many countries have created organizations for the administration and oversight of caving activities within their nations. The oldest of these is the French Federation of Speleology (originally Société de spéléologie) founded by Édouard-Alfred Martel in 1895, which produced the first periodical journal in speleology, Spelunca. The first University-based speleological institute in the world was founded in 1920 in Cluj-Napoca, Romania, by Emil Racovita, a Romanian biologist, zoologist, speleologist and explorer of Antarctica.

The British Speleological Association was established in 1935 and the National Speleological Society in the US was founded in 1941 (originally formed as the Speleological Society of the District of Columbia on May 6, 1939).

An international speleological congress was proposed at a meeting in Valence-sur-Rhone, France in 1949 and first held in 1953 in Paris. The International Union of Speleology (UIS) was founded in 1965.

title: Caving


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Cave

A cave or cavern is a natural void in the ground, specifically a space large enough for a human to enter. Caves often form by the weathering of rock and often extend deep underground. The word cave can refer to smaller openings such as sea caves, rock shelters, and grottos, that extend a relatively short distance into the rock and they are called exogene caves. Caves which extend further underground than the opening is wide are called endogene caves.

Speleology is the science of exploration and study of all aspects of caves and the cave environment. Visiting or exploring caves for recreation may be called caving, potholing, or spelunking.

Formation types
The formation and development of caves is known as speleogenesis; it can occur over the course of millions of years. Caves can range widely in size, and are formed by various geological processes. These may involve a combination of chemical processes, erosion by water, tectonic forces, microorganisms, pressure, and atmospheric influences. Isotopic dating techniques can be applied to cave sediments, to determine the timescale of the geological events which formed and shaped present-day caves.

It is estimated that a cave cannot be more than 3000 m vertically beneath the surface due to the pressure of overlying rocks. This does not, however, impose a maximum depth for a cave which is measured from its highest entrance to its lowest point, as the amount of rock above the lowest point is dependent on the topography of the landscape above it. For karst caves the maximum depth is determined on the basis of the lower limit of karst forming processes, coinciding with the base of the soluble carbonate rocks. Most caves are formed in limestone by dissolution.

Caves can be classified in various other ways as well, including a contrast between active and relict: active caves have water flowing through them; relict caves do not, though water may be retained in them. Types of active caves include inflow caves ("into which a stream sinks"), outflow caves ("from which a stream emerges"), and through caves ("traversed by a stream").

Solutional
Solutional caves or karst caves are the most frequently occurring caves. Such caves form in rock that is soluble; most occur in limestone, but they can also form in other rocks including chalk, dolomite, marble, salt, and gypsum. Except for salt caves, solutional caves result when rock is dissolved by natural acid in groundwater that seeps through bedding planes, faults, joints, and comparable features. Over time cracks enlarge to become caves and cave systems.

The largest and most abundant solutional caves are located in limestone. Limestone dissolves under the action of rainwater and groundwater charged with H2CO3 (carbonic acid) and naturally occurring organic acids. The dissolution process produces a distinctive landform known as karst, characterized by sinkholes and underground drainage. Limestone caves are often adorned with calcium carbonate formations produced through slow precipitation. These include flowstones, stalactites, stalagmites, helictites, soda straws and columns. These secondary mineral deposits in caves are called speleothems.

The portions of a solutional cave that are below the water table or the local level of the groundwater will be flooded.

Lechuguilla Cave in New Mexico and nearby Carlsbad Cavern are now believed to be examples of another type of solutional cave. They were formed by H2S (hydrogen sulfide) gas rising from below, where reservoirs of oil give off sulfurous fumes. This gas mixes with groundwater and forms H2SO4 (sulfuric acid). The acid then dissolves the limestone from below, rather than from above, by acidic water percolating from the surface.

Primary
Caves formed at the same time as the surrounding rock are called primary caves.

Lava tubes are formed through volcanic activity and are the most common primary caves. As lava flows downhill, its surface cools and solidifies. Hot liquid lava continues to flow under that crust, and if most of it flows out, a hollow tube remains. Such caves can be found in the Canary Islands, Jeju-do, the basaltic plains of Eastern Idaho, and in other places. Kazumura Cave near Hilo, Hawaii is a remarkably long and deep lava tube; it is 65.6 km.

Lava caves include but are not limited to lava tubes. Other caves formed through volcanic activity include rifts, lava molds, open vertical conduits, inflationary, blisters, among others.

Sea or littoral
Sea caves are found along coasts around the world. A special case is littoral caves, which are formed by wave action in zones of weakness in sea cliffs. Often these weaknesses are faults, but they may also be dykes or bedding-plane contacts. Some wave-cut caves are now above sea level because of later uplift. Elsewhere, in places such as Thailand's Phang Nga Bay, solutional caves have been flooded by the sea and are now subject to littoral erosion. Sea caves are generally around 5 to 50 m in length, but may exceed 300 m.

Corrasional or erosional
Corrasional or erosional caves are those that form entirely by erosion by flowing streams carrying rocks and other sediments. These can form in any type of rock, including hard rocks such as granite. Generally there must be some zone of weakness to guide the water, such as a fault or joint. A subtype of the erosional cave is the wind or aeolian cave, carved by wind-born sediments. Many caves formed initially by solutional processes often undergo a subsequent phase of erosional or vadose enlargement where active streams or rivers pass through them.

Glacier
Glacier caves are formed by melting ice and flowing water within and under glaciers. The cavities are influenced by the very slow flow of the ice, which tends to collapse the caves again. Glacier caves are sometimes misidentified as "ice caves", though this latter term is properly reserved for bedrock caves that contain year-round ice formations.

Fracture
Fracture caves are formed when layers of more soluble minerals, such as gypsum, dissolve out from between layers of less soluble rock. These rocks fracture and collapse in blocks of stone.

Talus
Talus caves are formed by the openings among large boulders that have fallen down into a random heap, often at the bases of cliffs. These unstable deposits are called talus or scree, and may be subject to frequent rockfalls and landslides.

Anchialine
Anchialine caves are caves, usually coastal, containing a mixture of freshwater and saline water (usually sea water). They occur in many parts of the world, and often contain highly specialized and endemic fauna.

Physical patterns

 * Branchwork caves resemble surface dendritic stream patterns; they are made up of passages that join downstream as tributaries. Branchwork caves are the most common of cave patterns and are formed near sinkholes where groundwater recharge occurs. Each passage or branch is fed by a separate recharge source and converges into other higher order branches downstream.
 * Angular network caves form from intersecting fissures of carbonate rock that have had fractures widened by chemical erosion. These fractures form high, narrow, straight passages that persist in widespread closed loops.
 * Anastomotic caves largely resemble surface braided streams with their passages separating and then meeting further down drainage. They usually form along one bed or structure, and only rarely cross into upper or lower beds.
 * Spongework caves are formed when solution cavities are joined by mixing of chemically diverse water. The cavities form a pattern that is three-dimensional and random, resembling a sponge.
 * Ramiform caves form as irregular large rooms, galleries, and passages. These randomized three-dimensional rooms form from a rising water table that erodes the carbonate rock with hydrogen-sulfide enriched water.
 * Pit caves (vertical caves, potholes, or simply "pits") consist of a vertical shaft rather than a horizontal cave passage. They may or may not be associated with one of the above structural patterns.

Geographic distribution
Caves are found throughout the world, although the distribution of documented cave system is heavily skewed towards those countries where caving has been popular for many years (such as France, Italy, Australia, the UK, the United States, etc.). As a result, explored caves are found widely in Europe, Asia, North America and Oceania, but are sparse in South America, Africa, and Antarctica.

This is a rough generalization, as large expanses of North America and Asia contain no documented caves, whereas areas such as the Madagascar dry deciduous forests and parts of Brazil contain many documented caves. As the world's expanses of soluble bedrock are researched by cavers, the distribution of documented caves is likely to shift. For example, China, despite containing around half the world's exposed limestone—more than 1000000 km2—has relatively few documented caves.

Records and superlatives

 * The cave system with the greatest total length of surveyed passage is Mammoth Cave in Kentucky, US, at 675.9 km.
 * The longest surveyed underwater cave, and second longest overall, is Sistema Ox Bel Ha in Yucatán, Mexico at 436 km.
 * The deepest known cave—measured from its highest entrance to its lowest point—is Veryovkina Cave in Abkhazia, Georgia, with a depth of 2,204 m. This was the first cave to be explored to a depth of more than 2000 m. (The first cave to be descended below 1000 m was Gouffre Berger in France.) The Sarma and Illyuzia-Mezhonnogo-Snezhnaya caves in Georgia, (1830 m, and 1753 m respectively) are the current second- and third-deepest caves. The deepest outside Georgia is Lamprechtsofen Vogelschacht Weg Schacht in Austria, which is 1,623 m deep.
 * The deepest vertical shaft in a cave is 603 m in Vrtoglavica Cave in Slovenia. The second deepest is Ghar-e-Ghala at 562 m in the Parau massif near Kermanshah in Iran.
 * The deepest underwater cave bottomed by a remotely operated underwater vehicle at 450 m, is the Hranice Abyss in the Czech Republic.
 * The Miao Room is the world's largest known room by volume, with a measured volume of 10780000 m3. The largest known room by surface is Sarawak Chamber, in the Gunung Mulu National Park (Miri, Sarawak, Borneo, Malaysia), a sloping, boulder strewn chamber with an area of 154500 m2. The largest room in a show cave is the Salle de la Verna in the French Pyrenees.
 * The largest passage ever discovered is in the Son Doong Cave in Phong Nha-Kẻ Bàng National Park in Quảng Bình Province, Vietnam. It is 4.6 km in length, 80 m high and wide over most of its length, but over 140 m high and wide for part of its length.

Five longest surveyed

 * 1) Mammoth Cave, Kentucky, US
 * 2) Sistema Ox Bel Ha, Mexico
 * 3) Sistema Sac Actun/Sistema Dos Ojos, Mexico
 * 4) Jewel Cave, South Dakota, US
 * 5) Shuanghedong Cave Network, China

Ecology
Cave-inhabiting animals are often categorized as troglobites (cave-limited species), troglophiles (species that can live their entire lives in caves, but also occur in other environments), trogloxenes (species that use caves, but cannot complete their life cycle fully in caves) and accidentals (animals not in one of the previous categories). Some authors use separate terminology for aquatic forms (for example, stygobites, stygophiles, and stygoxenes).

Of these animals, the troglobites are perhaps the most unusual organisms. Troglobitic species often show a number of characteristics, termed troglomorphic, associated with their adaptation to subterranean life. These characteristics may include a loss of pigment (often resulting in a pale or white coloration), a loss of eyes (or at least of optical functionality), an elongation of appendages, and an enhancement of other senses (such as the ability to sense vibrations in water). Aquatic troglobites (or stygobites), such as the endangered Alabama cave shrimp, live in bodies of water found in caves and get nutrients from detritus washed into their caves and from the feces of bats and other cave inhabitants. Other aquatic troglobites include cave fish, and cave salamanders such as the olm and the Texas blind salamander.

Cave insects such as Oligaphorura (formerly Archaphorura) schoetti are troglophiles, reaching 1.7 mm in length. They have extensive distribution and have been studied fairly widely. Most specimens are female, but a male specimen was collected from St Cuthberts Swallet in 1969.

Bats, such as the gray bat and Mexican free-tailed bat, are trogloxenes and are often found in caves; they forage outside of the caves. Some species of cave crickets are classified as trogloxenes, because they roost in caves by day and forage above ground at night.

Because of the fragility of cave ecosystems, and the fact that cave regions tend to be isolated from one another, caves harbor a number of endangered species, such as the Tooth cave spider, liphistius trapdoor spider, and the gray bat.

Caves are visited by many surface-living animals, including humans. These are usually relatively short-lived incursions, due to the lack of light and sustenance.

Cave entrances often have typical florae. For instance, in the eastern temperate United States, cave entrances are most frequently (and often densely) populated by the bulblet fern, Cystopteris bulbifera.

Archaeological and cultural importance

People have made use of caves throughout history. The earliest human fossils found in caves come from a series of caves near Krugersdorp and Mokopane in South Africa. The cave sites of Sterkfontein, Swartkrans, Kromdraai B, Drimolen, Malapa, Cooper's D, Gladysvale, Gondolin and Makapansgat have yielded a range of early human species dating back to between three and one million years ago, including Australopithecus africanus, Australopithecus sediba and Paranthropus robustus. However, it is not generally thought that these early humans were living in the caves, but that they were brought into the caves by carnivores that had killed them.

The first early hominid ever found in Africa, the Taung Child in 1924, was also thought for many years to come from a cave, where it had been deposited after being predated on by an eagle. However, this is now debated (Hopley et al., 2013; Am. J. Phys. Anthrop.). Caves do form in the dolomite of the Ghaap Plateau, including the Early, Middle and Later Stone Age site of Wonderwerk Cave; however, the caves that form along the escarpment's edge, like that hypothesised for the Taung Child, are formed within a secondary limestone deposit called tufa. There is numerous evidence for other early human species inhabiting caves from at least one million years ago in different parts of the world, including Homo erectus in China at Zhoukoudian, Homo rhodesiensis in South Africa at the Cave of Hearths (Makapansgat), Homo neanderthalensis and Homo heidelbergensis in Europe at Archaeological Site of Atapuerca, Homo floresiensis in Indonesia, and the Denisovans in southern Siberia.

In southern Africa, early modern humans regularly used sea caves as shelter starting about 180,000 years ago when they learned to exploit the sea for the first time. The oldest known site is PP13B at Pinnacle Point. This may have allowed rapid expansion of humans out of Africa and colonization of areas of the world such as Australia by 60–50,000 years ago. Throughout southern Africa, Australia, and Europe, early modern humans used caves and rock shelters as sites for rock art, such as those at Giant's Castle. Caves such as the yaodong in China were used for shelter; other caves were used for burials (such as rock-cut tombs), or as religious sites (such as Buddhist caves). Among the known sacred caves are China's Cave of a Thousand Buddhas and the sacred caves of Crete.

Paleolithic cave paintings have been found throughout the world dating from 64,800 years old for non-figurative art and 43,900 years old for figurative art.

Caves and acoustics
The importance of sound in caves predates a modern understanding of acoustics. Archaeologists have uncovered relationships between paintings of dots and lines, in specific areas of resonance, within the caves of Spain and France, as well as instruments depicting paleolithic motifs, indicators of musical events and rituals. Clusters of paintings were often found in areas with notable acoustics, sometimes even replicating the sounds of the animals depicted on the walls. The human voice was also theorized to be used as an echolocation device to navigate darker areas of the caves where torches were less useful. Dots of red ochre are often found in spaces with the highest resonance, where the production of paintings was too difficult.

Caves continue to provide usage for modern-day explorers of acoustics. Today Cumberland Caverns provides one of the best examples for modern musical usages of caves. Not only are the caves utilized for reverberation, but for the dampening qualities of their abnormal faces as well. The irregularities in the walls of the Cumberland Caverns diffuse sounds bouncing off the walls and give the space an almost recording studio-like quality. During the 20th century musicians began to explore the possibility of using caves as locations as clubs and concert halls, including the likes of Dinah Shore, Roy Acuff, and Benny Goodman. Unlike today, these early performances were typically held in the mouths of the caves, as the lack of technology made depths of the interior inaccessible with musical equipment. In Luray Caverns, Virginia, a functioning organ has been developed that generates sound by mallets striking stalactites, each with a different pitch.

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

title: Cave


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Chinese numerals

Chinese numerals are words and characters used to denote numbers in written Chinese.

Today, speakers of Chinese languages use three written numeral systems: the system of Arabic numerals used worldwide, and two indigenous systems. The more familiar indigenous system is based on Chinese characters that correspond to numerals in the spoken language. These may be shared with other languages of the Chinese cultural sphere such as Korean, Japanese, and Vietnamese. Most people and institutions in China primarily use the Arabic or mixed Arabic-Chinese systems for convenience, with traditional Chinese numerals used in finance, mainly for writing amounts on cheques, banknotes, some ceremonial occasions, some boxes, and on commercials.

The other indigenous system consists of the Suzhou numerals, or huama, a positional system, the only surviving form of the rod numerals. These were once used by Chinese mathematicians, and later by merchants in Chinese markets, such as those in Hong Kong until the 1990s, but were gradually supplanted by Arabic numerals.

Characters used as numerals
The Chinese character numeral system consists of the Chinese characters used by the Chinese written language to write spoken numerals. Similar to spelling-out numbers in English (e.g., "one thousand nine hundred forty-five"), it is not an independent system per se. Since it reflects spoken language, it does not use the positional system as in Arabic numerals, in the same way that spelling out numbers in English does not.

Ordinary numerals
There are characters representing the numbers zero through nine, and other characters representing larger numbers such as tens, hundreds, thousands, ten thousands and hundred millions. There are two sets of characters for Chinese numerals: one for everyday writing, known as, and one for use in commercial, accounting or financial contexts, known as. The latter arose because the characters used for writing numerals are geometrically simple, so simply using those numerals cannot prevent forgeries in the same way spelling numbers out in English would. A forger could easily change the everyday characters (30) to  (5000) just by adding a few strokes. That would not be possible when writing using the financial characters (30) and  (5000). They are also referred to as "banker's numerals", "anti-fraud numerals", or "banker's anti-fraud numerals". For the same reason, rod numerals were never used in commercial records.

Large numbers
For numbers larger than 10,000, similarly to the long and short scales in the West, there have been four systems in ancient and modern usage. The original one, with unique names for all powers of ten up to the 14th, is ascribed to the Yellow Emperor in the 6th century book by Zhen Luan,. In modern Chinese, only the second system is used, in which the same ancient names are used, but each represents a myriad, times the previous: In practice, this situation does not lead to ambiguity, with the exception of, which means 1012 according to the system in common usage throughout the Chinese communities as well as in Japan and Korea, but has also been used for 106 in recent years (especially in mainland China for megabyte). To avoid problems arising from the ambiguity, the PRC government never uses this character in official documents, but uses ) or instead. Partly due to this, combinations of  and  are often used instead of the larger units of the traditional system as well, for example  instead of . The ROC government in Taiwan uses  to mean 1012 in official documents.

Large numbers from Buddhism
Numerals beyond zǎi come from Buddhist texts in Sanskrit, but are mostly found in ancient texts. Some of the following words are still being used today, but may have transferred meanings.

Small numbers
The following are characters used to denote small order of magnitude in Chinese historically. With the introduction of SI units, some of them have been incorporated as SI prefixes, while the rest have fallen into disuse.

SI prefixes
In the People's Republic of China, the early translation for the SI prefixes in 1981 was different from those used today. The larger and smaller Chinese numerals  were defined as translation for the SI prefixes as mega, giga, tera, peta, exa, micro, nano, pico, femto, atto, resulting in the creation of yet more values for each numeral.

The Republic of China (Taiwan) defined as the translation for mega and  as the translation for tera. This translation is widely used in official documents, academic communities, informational industries, etc. However, the civil broadcasting industries sometimes use to represent "megahertz".

Today, the governments of both China and Taiwan use phonetic transliterations for the SI prefixes. However, the governments have each chosen different Chinese characters for certain prefixes. The following table lists the two different standards together with the early translation.

Whole numbers
Multiple-digit numbers are constructed using a multiplicative principle; first the digit itself (from 1 to 9), then the place (such as 10 or 100); then the next digit.

In Mandarin, the multiplier (liǎng) is often used rather than  for all numbers 200 and greater with the "2" numeral (although as noted earlier this varies from dialect to dialect and person to person). Use of both or  are acceptable for the number 200. When writing in the Cantonese dialect, is used to represent the "2" numeral for all numbers. In the southern Min dialect of Chaozhou (Teochew), (no6) is used to represent the "2" numeral in all numbers from 200 onwards. Thus:

For the numbers 11 through 19, the leading 'one' is usually omitted. In some dialects, like Shanghainese, when there are only two significant digits in the number, the leading 'one' and the trailing zeroes are omitted. Sometimes, the one before "ten" in the middle of a number, such as 213, is omitted. Thus:

Notes:
 * 1) Nothing is ever omitted in large and more complicated numbers such as this.

In certain older texts like the Protestant Bible, or in poetic usage, numbers such as 114 may be written as [100] [10] [4].

Outside of Taiwan, digits are sometimes grouped by myriads instead of thousands. Hence it is more convenient to think of numbers here as in groups of four, thus 1,234,567,890 is regrouped here as 12,3456,7890. Larger than a myriad, each number is therefore four zeroes longer than the one before it, thus 10000 × =. If one of the numbers is between 10 and 19, the leading 'one' is omitted as per the above point. Hence (numbers in parentheses indicate that the number has been written as one number rather than expanded):

In Taiwan, pure Arabic numerals are officially always and only grouped by thousands. Unofficially, they are often not grouped, particularly for numbers below 100,000. Mixed Arabic-Chinese numerals are often used in order to denote myriads. This is used both officially and unofficially, and come in a variety of styles:

Interior zeroes before the unit position (as in 1002) must be spelt explicitly. The reason for this is that trailing zeroes (as in 1200) are often omitted as shorthand, so ambiguity occurs. One zero is sufficient to resolve the ambiguity. Where the zero is before a digit other than the units digit, the explicit zero is not ambiguous and is therefore optional, but preferred. Thus:

Fractional values
To construct a fraction, the denominator is written first, followed by, then the literary possessive particle , and lastly the numerator. This is the opposite of how fractions are read in English, which is numerator first. Each half of the fraction is written the same as a whole number. For example, to express "two thirds", the structure "three parts of-this two" is used. Mixed numbers are written with the whole-number part first, followed by, then the fractional part.

Percentages are constructed similarly, using as the denominator. (The number 100 is typically expressed as, like the English 'one hundred'. However, for percentages, is used on its own.)

Because percentages and other fractions are formulated the same, Chinese are more likely than not to express 10%, 20% etc. as 'parts of 10' (or 1/10, 2/10, etc. i.e. 十分之一; shí fēnzhī yī, 十分之二; shí fēnzhī èr, etc.) rather than "parts of 100" (or 10/100, 20/100, etc. i.e. 百分之十; bǎi fēnzhī shí, 百分之二十; bǎi fēnzhī èrshí, etc.)

In Taiwan, the most common formation of percentages in the spoken language is the number per hundred followed by the word, a contraction of the Japanese パーセント; pāsento, itself taken from 'percent'. Thus 25% is 二十五趴; èrshíwǔ pā.

Decimal numbers are constructed by first writing the whole number part, then inserting a point, and finally the fractional part. The fractional part is expressed using only the numbers for 0 to 9, similarly to English.

functions as a number and therefore requires a measure word. For example:.

Ordinal numbers
Ordinal numbers are formed by adding before the number. The Heavenly Stems are a traditional Chinese ordinal system.

Negative numbers
Negative numbers are formed by adding  before the number.

Usage
Chinese grammar requires the use of classifiers (measure words) when a numeral is used together with a noun to express a quantity. For example, "three people" is expressed as, "three ( particle) person", where /  is a classifier. There exist many different classifiers, for use with different sets of nouns, although / is the most common, and may be used informally in place of other classifiers.

Chinese uses cardinal numbers in certain situations in which English would use ordinals. For example, (literally "three story/storey") means "third floor" ("second floor" in British ). Likewise, (literally "twenty-one century") is used for "21st century".

Numbers of years are commonly spoken as a sequence of digits, as in ("two zero zero one") for the year 2001. Names of months and days (in the Western system) are also expressed using numbers: ("one month") for January, etc.; and  ("week one") for Monday, etc. There is only one exception: Sunday is, or informally , both literally "week day". When meaning "week", "" and ""  are interchangeable. "" or ""  means "day of worship". Chinese Catholics call Sunday "" , "Lord's day".

Full dates are usually written in the format 2001年1月20日 for January 20, 2001 (using "year",  "month", and  "day") – all the numbers are read as cardinals, not ordinals, with no leading zeroes, and the year is read as a sequence of digits. For brevity the, and  may be dropped to give a date composed of just numbers. For example "6-4" in Chinese is "six-four", short for "month six, day four" i.e. June Fourth, a common Chinese shorthand for the 1989 Tiananmen Square protests (because of the violence that occurred on June 4). For another example 67, in Chinese is sixty seven, short for year nineteen sixty seven, a common Chinese shorthand for the Hong Kong 1967 leftist riots.

Counting rod and Suzhou numerals

In the same way that Roman numerals were standard in ancient and medieval Europe for mathematics and commerce, the Chinese formerly used the rod numerals, which is a positional system. The Suzhou numerals system is a variation of the Southern Song rod numerals. Nowadays, the huāmǎ system is only used for displaying prices in Chinese markets or on traditional handwritten invoices.

Hand gestures

There is a common method of using of one hand to signify the numbers one to ten. While the five digits on one hand can easily express the numbers one to five, six to ten have special signs that can be used in commerce or day-to-day communication.

Historical use of numerals in China

Most Chinese numerals of later periods were descendants of the Shang dynasty oracle numerals of the 14th century BC. The oracle bone script numerals were found on tortoise shell and animal bones. In early civilizations, the Shang were able to express any numbers, however large, with only nine symbols and a counting board though it was still not positional.

Some of the bronze script numerals such as 1, 2, 3, 4, 10, 11, 12, and 13 became part of the system of rod numerals.

In this system, horizontal rod numbers are used for the tens, thousands, hundred thousands etc. It is written in Sunzi Suanjing that "one is vertical, ten is horizontal".

The counting rod numerals system has place value and decimal numerals for computation, and was used widely by Chinese merchants, mathematicians and astronomers from the Han dynasty to the 16th century.

In 690 AD, Wu Zetian promulgated Zetian characters, one of which was 〇. The word is now used as a synonym for the number zero.

Alexander Wylie, Christian missionary to China, in 1853 already refuted the notion that "the Chinese numbers were written in words at length", and stated that in ancient China, calculation was carried out by means of counting rods, and "the written character is evidently a rude presentation of these". After being introduced to the rod numerals, he said "Having thus obtained a simple but effective system of figures, we find the Chinese in actual use of a method of notation depending on the theory of local value [i.e. place-value], several centuries before such theory was understood in Europe, and while yet the science of numbers had scarcely dawned among the Arabs."

During the Ming and Qing dynasties (after Arabic numerals were introduced into China), some Chinese mathematicians used Chinese numeral characters as positional system digits. After the Qing period, both the Chinese numeral characters and the Suzhou numerals were replaced by Arabic numerals in mathematical writings.

Cultural influences
Traditional Chinese numeric characters are also used in Japan and Korea and were used in Vietnam before the 20th century. In vertical text (that is, read top to bottom), using characters for numbers is the norm, while in horizontal text, Arabic numerals are most common. Chinese numeric characters are also used in much the same formal or decorative fashion that Roman numerals are in Western cultures. Chinese numerals may appear together with Arabic numbers on the same sign or document.

title: Chinese numerals