Karst is a topography formed from the dissolution of soluble rocks such as limestone, dolomite, and gypsum. It is characterized by underground drainage systems with sinkholes and caves. It has also been documented for more weathering-resistant rocks, such as quartzite, given the right conditions. Subterranean drainage may limit surface water, with few to no rivers or lakes. However, in regions where the dissolved bedrock is covered (perhaps by debris) or confined by one or more superimposed non-soluble rock strata, distinctive karst features may occur only at subsurface levels and be totally missing above ground.
The English word karst was borrowed from German Karst in the late 19th century, which entered German much earlier. According to one interpretation the term is derived from the German name for a number of geological, geomorphological, and hydrological features found within the range of the Dinaric Alps, stretching from the northeastern corner of Italy above the city of Trieste (at the time part of the Austrian Littoral), across the Balkan peninsula along the coast of the eastern Adriatic to Kosovo and North Macedonia, where the massif of the Šar Mountains begins, and more specifically the karst zone at the northwestern-most section, described in early topographical research as a plateau, between Italy and Slovenia.
In the local South Slavic languages, all variations of the word are derived from a Romanized Illyrian base (yielding Latin: carsus, Dalmatian Romance carsus), later metathesized from the reconstructed form *korsъ into forms such as Bosnian: krš, kras, Croatian: krš, kraš, Serbian: kras, and Slovene: kras. Languages preserving the older, non-metathesized form include Italian: Carso, German: Karst, and Albanian: karsti; the lack of metathesis precludes borrowing from any of the South Slavic languages, specifically Slovene. The Slovene common noun kras was first attested in the 18th century, and the adjective form kraški in the 16th century. As a proper noun, the Slovene form Grast was first attested in 1177.
Ultimately, the word is of Mediterranean origin. It has been suggested that the word may derive from the Proto-Indo-European root karra- 'rock'. The name may also be connected to the oronym Kar(u)sádios oros cited by Ptolemy, and perhaps also to Latin Carusardius.
Johann Weikhard von Valvasor, a pioneer of the study of karst in Slovenia and a fellow of the Royal Society for Improving Natural Knowledge, London, introduced the word karst to European scholars in 1689, describing the phenomenon of underground flows of rivers in his account of Lake Cerknica.
Jovan Cvijić greatly advanced the knowledge of karst regions, so much that he became known as the "father of karst geomorphology". Primarily discussing the karstic regions of the Balkans, Cvijić's 1893 publication Das Karstphänomen describes landforms such as karren, dolines and poljes. In a 1918 publication, Cvijić proposed a cyclical model for karstic landscape development. Karst hydrology emerged as a discipline in the late 1950s and early 1960s in France. Previously, the activities of cave explorers, called speleologists, had been dismissed as more of a sport than a science, meaning that underground karstic caves and their associated watercourses were, from a scientific perspective, understudied.
The development of karst occurs whenever acidic water starts to break down the surface of bedrock near its cracks, or bedding planes. As the bedrock (typically limestone or dolostone) continues to degrade, its cracks tend to get bigger. As time goes on, these fractures will become wider, and eventually a drainage system of some sort may start to form underneath. If this underground drainage system does form, it will speed up the development of karst formations there because more water will be able to flow through the region, giving it more erosive power.
The carbonic acid that causes karstic features is formed as rain passes through Earth's atmosphere picking up carbon dioxide (CO2), which dissolves in the water. Once the rain reaches the ground, it may pass through soil that can provide much more CO2 to form a weak carbonic acid solution, which dissolves calcium carbonate. The primary reaction sequence in limestone dissolution is the following:
In particular and very rare conditions such as encountered in the past in Lechuguilla Cave in New Mexico (and more recently in the Frasassi Caves in Italy), other mechanisms may also play a role. The oxidation of sulfides leading to the formation of sulfuric acid can also be one of the corrosion factors in karst formation. As oxygen (O2)-rich surface waters seep into deep anoxic karst systems, they bring oxygen, which reacts with sulfide present in the system (pyrite or hydrogen sulfide) to form sulfuric acid (H2SO4). Sulfuric acid then reacts with calcium carbonate, causing increased erosion within the limestone formation. This chain of reactions is:
|H2S||+||2 O2||→||H2SO4||(sulfide oxidation)|
|+||2 H3O+||(sulfuric acid dissociation)|
|CaCO3||+||2 H3O+||→||Ca2+||+||H2CO3||+||2 H2O||(calcium carbonate dissolution)|
|Ca2+||+||SO42-||→||CaSO4||(formation of calcium sulfate)|
|CaSO4||+||2 H2O||→||CaSO4 · 2 H2O||(formation of gypsum)|
The karstification of a landscape may result in a variety of large- or small-scale features both on the surface and beneath. On exposed surfaces, small features may include solution flutes (or rillenkarren), runnels, limestone pavement (clints and grikes), collectively called karren or lapiez. Medium-sized surface features may include sinkholes or cenotes (closed basins), vertical shafts, foibe (inverted funnel shaped sinkholes), disappearing streams, and reappearing springs. Large-scale features may include limestone pavements, poljes, and karst valleys. Mature karst landscapes, where more bedrock has been removed than remains, may result in karst towers, or haystack/eggbox landscapes. Beneath the surface, complex underground drainage systems (such as karst aquifers) and extensive caves and cavern systems may form.
Erosion along limestone shores, notably in the tropics, produces karst topography that includes a sharp makatea surface above the normal reach of the sea, and undercuts that are mostly the result of biological activity or bioerosion at or a little above mean sea level. Some of the most dramatic of these formations can be seen in Thailand's Phangnga Bay and at Halong Bay in Vietnam.
Calcium carbonate dissolved into water may precipitate out where the water discharges some of its dissolved carbon dioxide. Rivers which emerge from springs may produce tufa terraces, consisting of layers of calcite deposited over extended periods of time. In caves, a variety of features collectively called speleothems are formed by deposition of calcium carbonate and other dissolved minerals.
Farming in karst areas must take into account the lack of surface water. The soils may be fertile enough, and rainfall may be adequate, but rainwater quickly moves through the crevices into the ground, sometimes leaving the surface soil parched between rains.
A karst fenster (karst window) occurs when an underground stream emerges onto the surface between layers of rock, cascades some distance, and then disappears back down, often into a sinkhole. Rivers in karst areas may disappear underground a number of times and spring up again in different places, usually under a different name (like Ljubljanica, the river of seven names). An example of this is the Popo Agie River in Fremont County, Wyoming. At a site simply named "The Sinks" in Sinks Canyon State Park, the river flows into a cave in a formation known as the Madison Limestone and then rises again 800 m (1⁄2 mi) down the canyon in a placid pool. A turlough is a unique type of seasonal lake found in Irish karst areas which are formed through the annual welling-up of water from the underground water system.
Water supplies from wells in karst topography may be unsafe, as the water may have run unimpeded from a sinkhole in a cattle pasture, through a cave and to the well, bypassing the normal filtering that occurs in a porous aquifer. Karst formations are cavernous and therefore have high rates of permeability, resulting in reduced opportunity for contaminants to be filtered. Groundwater in karst areas is just as easily polluted as surface streams. Sinkholes have often been used as farmstead or community trash dumps. Overloaded or malfunctioning septic tanks in karst landscapes may dump raw sewage directly into underground channels.
The karst topography also poses difficulties for human inhabitants. Sinkholes can develop gradually as surface openings enlarge, but progressive erosion is frequently unseen until the roof of an underground cavern suddenly collapses. Such events have swallowed homes, cattle, cars, and farm machinery. In the United States, sudden collapse of such a cavern-sinkhole swallowed part of the collection of the National Corvette Museum in Bowling Green, Kentucky in 2014.
Interstratal karst is a karstic landscape which is developed beneath a cover of insoluble rocks. Typically this will involve a cover of sandstone overlying limestone strata undergoing solution. In the United Kingdom extensive doline fields developed at Mynydd Llangynidr across a plateau of Twrch Sandstone overlying concealed Carboniferous Limestone.
Kegelkarst is a type of tropical karst terrain with numerous cone-like hills, formed by cockpits, mogotes, and poljes and without strong fluvial erosion processes. This terrain is found in Cuba, Jamaica, Indonesia, Malaysia, the Philippines, Puerto Rico, southern China, Myanmar, Thailand, Laos and Vietnam.
Pseudokarsts are similar in form or appearance to karst features but are created by different mechanisms. Examples include lava caves and granite tors—for example, Labertouche Cave in Victoria, Australia—and paleocollapse features. Mud Caves are an example of pseudokarst.
The world's largest limestone karst is Australia's Nullarbor Plain. Slovenia has the world's highest risk of sinkholes, while the western Highland Rim in the eastern United States is at the second-highest risk of karst sinkholes.
Many karst-related terms derive from South Slavic languages, entering scientific vocabulary through early research in the Western Balkan Dinaric Alpine karst.
An aquifer is an underground layer of water-bearing permeable rock, rock fractures or unconsolidated materials (gravel, sand, or silt). Groundwater can be extracted using a water well. The study of water flow in aquifers and the characterization of aquifers is called hydrogeology. Related terms include aquitard, which is a bed of low permeability along an aquifer, and aquiclude (or aquifuge), which is a solid, impermeable area underlying or overlying an aquifer. If the impermeable area overlies the aquifer, pressure could cause it to become a confined aquifer.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 also refer to much smaller openings such as sea caves, rock shelters, and grottos, though strictly speaking a cave is exogene, meaning it is deeper than its opening is wide, and a rock shelter is endogene.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.Coastal–Karst Statistical Region
The Coastal–Karst Statistical Region (Slovene: Obalno-kraška statistična regija, Italian: Litorale-Carso) is a statistical region in southwest Slovenia. It covers the traditional and historical regions of Slovenian Istria and most of the Karst Plateau, which traditionally belonged to the County of Gorizia and Gradisca. The region has a sub-Mediterranean climate and is Slovenia's only statistical region bordering the sea. Its natural features enable the development of tourism, transport, and special agricultural crops. More than two-thirds of gross value added are generated by services (trade, accommodation, and transport); most was generated by activities at the Port of Koper and through seaside and spa tourism. The region recorded almost a quarter of all tourist nights in the country in 2013; slightly less than half by domestic tourists. Among foreign tourists, Italians, Austrians, and Germans predominated. In 2012 the region was one of four regions with a positive annual population growth rate (8.1‰). However, the age structure of the population was less favourable: in mid-2013 the ageing index was 133.3, which means that for every 100 inhabitants under 15 there were 133 inhabitants 65 or older. The farms in this region are among the smallest in Slovenia in terms of average utilised agricultural area per farm and in terms of the number of livestock on farms.Estavelle
In karst geology, estavelle or inversac is a ground orifice which, depending on weather conditions and season, can serve either as a sink or as a source of fresh water. It is a type of sinkhole.Karst Plateau (Italy-Slovenia)
The Karst Plateau or the Karst region (Slovene: Kras, Italian: Carso), also locally called Karst, is a karst plateau region extending across the border of southwestern Slovenia and northeastern Italy.
It lies between the Vipava Valley, the low hills surrounding the valley, the westernmost part of the Brkini Hills, northern Istria, and the Gulf of Trieste. The western edge of the plateau also marks the traditional ethnic border between Italians and Slovenes. The region gave its name to the karst topography. For this reason, it is also referred to as the Classical Karst.Karst Shepherd
The Karst Shepherd (Slovene: kraški ovčar listen or kraševec listen ) is a breed of dog of the livestock guardian type, originating in Slovenia. This mountain dog breed is recognised by the Fédération Cynologique Internationale.Karst spring
A karst spring is a spring that is part of a karst system. That includes the underground drainage of a much larger area, which means that karst springs often have a very large discharge. Because of their often conical or bowl shape, such water sources are also known in German-speaking lands as a Topf ("pot") which is reflected in names such as Aachtopf (the source of the Radolfzeller Aach) or Blautopf (the source of the Blau river in Blaubeuren).
Karst springs are usually the end of a cave system at the place where a river cave reaches the Earth's surface. Thus, it is often possible to enter the caves at a karst spring and explore them. Large karst springs are located in many parts of the world. The world's largest karst springs are believed to be in Papua New Guinea, with others located in Mediterranean countries including Bosnia, Turkey, Slovenia and Italy.Littoral–Inner Carniola Statistical Region
The Littoral–Inner Carniola Statistical Region (Slovene: Primorsko-notranjska statistična regija) is a statistical region in southwest Slovenia. Until January 1, 2015 it was named the Inner Carniola–Karst Statistical Region (Slovene: Notranjsko-kraška statistična regija).The karst terrain, with Postojna Cave and intermittent Lake Cerknica, is the most important natural feature of this statistical region. This is one of the smallest statistical regions in Slovenia, and it is the least densely populated, with a population density six times lower than the Central Slovenia Statistical Region. The region is among the economically less developed ones in the country because in 2012 it contributed only 1.8% of Slovenia’s GDP. With an average of four employees per company, the enterprises in the region are among the smallest in Slovenia. In 2012, agriculture in this region generated around 6% of gross value added, which is one of the highest shares of gross value added by agriculture per individual region. In 2013, the average utilised agricultural area per farm was the highest in this region. The region has the highest employment rate in Slovenia (it was 59.9% in 2013), and the registered unemployment rate is among the lowest. The region also has the highest share of women in tertiary education (151 female students per 100 male students).Luobi Cave
Luobi Cave (simplified Chinese: 落笔洞; traditional Chinese: 落筆洞; pinyin: Luòbĭ Dòng; literally: 'hanging pen cave') is a karst cave under the west face of Yin Ridge (印岭) located 7 km (4.3 mi) north east of Lizhigou Town (荔枝沟镇), 15 km (9.3 mi) from Sanya City, Hainan Province, People's Republic of China.Petter Adolf Karsten
Petter Adolf Karsten (16 February 1834 – 22 March 1917) was a Finnish mycologist, the foremost expert on the fungi of Finland in his day, and known in consequence as the "father of Finnish mycology".
Karsten was born in Merimasku near Turku, studied at the University of Helsinki, and then moved to the inland of Tammela, where he spent most of his life with teaching botany and doing research at the Mustiala Agriculture Institute (now the Faculty of Agriculture of the HAMK University of Applied Sciences).
He amassed a vast collection, both by his own efforts and those of his correspondents, and named about 200 new genera and 2,000 new species. In his mycological studies he extensively used the microscope and can be considered as the pioneer of fungal microscopy. Karstenia, the international journal of mycology published by the Finnish Mycological Society, is dedicated to Karsten.Pit cave
A pit cave, shaft cave or vertical cave—or often simply called a pit (in the US) or pot (in the UK); jama in South Slavic languages scientific and colloquial vocabulary (borrowed since early research in the Western Balkan Dinaric Alpine karst)—is a type of cave which contains one or more significant vertical shafts rather than being predominantly a conventional horizontal cave passage. Pit caves typically form in limestone as a result of long-term erosion by water. They can be open to the surface or found deep within horizontal caves. Among cavers, a pit is a vertical drop of any depth that cannot be negotiated safely without the use of ropes or ladders.Ponor
A ponor is a natural surface opening that may be found in landscapes where the geology and the geomorphology is characterized by some kind of karst, the international geological term for larger karst-induced surface water inlets.Sinkhole
A sinkhole, also known as a cenote, sink, sink-hole, swallet, swallow hole, or doline (the different terms for sinkholes are often used interchangeably), is a depression or hole in the ground caused by some form of collapse of the surface layer. Most are caused by karst processes – for example, the chemical dissolution of carbonate rocks or suffosion processes. Sinkholes vary in size from 1 to 600 m (3.3 to 2,000 ft) both in diameter and depth, and vary in form from soil-lined bowls to bedrock-edged chasms. Sinkholes may form gradually or suddenly, and are found worldwide.Solutional cave
A solutional cave or karst cave is a cave usually formed in the soluble rock limestone. It is the most frequently occurring type of cave. It can also form in other rocks, including chalk, dolomite, marble, salt beds, and gypsum.South China Karst
The South China Karst (simplified Chinese: 中国南方喀斯特; traditional Chinese: 中國南方喀斯特; pinyin: Zhōngguó Nánfāng Kāsītè), a UNESCO World Heritage Site since June 2007, spans the provinces of Chongqing, Guangxi, Guizhou, and Yunnan. It is noted for its karst features and landscapes as well as rich biodiversity. The site comprises seven clusters Phase I: Libo Karst, Shilin Karst, and Wulong Karst inscribed in 2007, and Phase II: Guilin Karst, Shibing Karst, Jinfoshan Karst, and Huanjiang Karst inscribed in 2014. UNESCO describes the South China Karst as "unrivalled in terms of the diversity of its karst features and landscapes."Speleology
Speleology is the scientific study of caves and other karst features, as well as their make-up, structure, physical properties, history, life forms, and the processes by which they form (speleogenesis) and change over time (speleomorphology). The term speleology is also sometimes applied to the recreational activity of exploring caves, but this is more properly known as caving or potholing, or (not usually by participants) by the uncommon American term spelunking. Speleology and caving are often connected, as the physical skills required for in situ study are the same.
Speleology is a cross-disciplinary field that combines the knowledge of chemistry, biology, geology, physics, meteorology, and cartography to develop portraits of caves as complex, evolving systems.Speleothem
Speleothems ( ; Ancient Greek: "cave deposit"), commonly known as cave formations, are secondary mineral deposits formed in a cave. Speleothems typically form in limestone or dolostone solutional caves. The term "speleothem" as first introduced by Moore (1952), is derived from the Greek words spēlaion "cave" + théma "deposit". The definition of "speleothem" in most publications, specifically excludes secondary mineral deposits in mines, tunnels and on man-made structures. Hill and Forti more concisely defined "secondary minerals" which create speleothems in caves as;
A "secondary" mineral is one which is derived by a physicochemical reaction from a primary mineral in bedrock or detritus, and/or deposited because of a unique set of conditions in a cave; i.e., the cave environment has influenced the mineral's deposition.Subterranean river
A subterranean river is a river that runs wholly or partly beneath the ground surface – one where the riverbed does not represent the surface of the Earth (rivers flowing in gorges are not classed as subterranean). It should also not be confused with an aquifer which may flow like a river but is contained within a permeable layer of rock or other unconsolidated materials.
Subterranean rivers may be entirely natural, flowing through cave systems. In karst topography, rivers may disappear through sinkholes, continuing underground. In some cases, they may emerge into daylight further downstream. Some fish (popularly known as cavefish) and other troglobite organisms are adapted to life in subterranean rivers and lakes. The longest subterranean river in the world is located in Mexico.Subterranean rivers can also be the result of covering over a river and/or diverting its flow into culverts, usually as part of urban development. Reversing this process is known as daylighting a stream and is a visible form of river restoration. One successful example is the Cheonggyecheon in the centre of Seoul.Examples of subterranean rivers also occur in mythology and literature.Yucatán Peninsula
The Yucatán Peninsula (; Spanish: Península de Yucatán), in southeastern Mexico, separates the Caribbean Sea from the Gulf of Mexico, with the northern coastline on the Yucatán Channel. The peninsula lies east of the Isthmus of Tehuantepec, a northwestern geographic partition separating the region of Central America from the rest of North America. It is approximately 181,000 km2 (70,000 sq mi) in area, and is almost entirely composed of limestone.
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