Karst topography is a landscape shaped by the dissolution of a layer or layers of soluble bedrock, usually carbonate rock such as limestone or dolomite. Due to subterranean drainage, there may be very limited surface water, even to the absence of all rivers and lakes. Many karst regions display distinctive surface features, with sinkholes or dolines being the most common. However, distinctive karst surface features may be completely absent where the soluble rock is mantled, such as by glacial debris, or confined by a superimposed non-soluble rock strata. Some karst regions include thousands of caves, even though evidence of caves that are big enough for human exploration is not a required characteristic of karst.
Terminology and etymology
Different terms for karst topography exist in other languages - for example, yanrong
in Chinese and tsingy
in Malagasy (Jennings, Ch.1 p.1). The international community has settled on karst
, the German
name for Kras
, a region in Slovenia
partially extending into Italy
where it is called Carso and where the first scientific research of a karst topography was made. The name has a pre-Indo-European
origin (from karra
meaning "stone") and in antiquity it was called Carusardius in Latin. The Slovenian form grast
is attested since 1177, and the Croatian kras
Chemistry of karst landscapes
Karst landforms are generally the result of mildly acidic water acting on soluble bedrock such as limestone or dolostone. The carbonic acid that causes these features is formed as rain passes through the atmosphere picking up CO2, which dissolves in the water. Once the rain reaches the ground, it may pass through soil that may provide further CO2 to form a weak carbonic acid solution: H2O + CO2 → H2CO3. Recent studies of sulfates in karst waters suggests sulfuric and hydrosulfuric acids may also play an important role in karst formation.
This mildly acidic water begins to dissolve the surface and any fractures or bedding planes in the limestone bedrock. Over time these fractures enlarge as the bedrock continues to dissolve. Openings in the rock increase in size, and an underground drainage system begins to develop, allowing more water to pass through and accelerating the formation of underground karst features.
Somewhat less common than this limestone karst is gypsum karst, where the solubility of the mineral gypsum provides many similar structures to the dissolution and redeposition of calcium carbonate.
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 flutes, runnels, 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 blind 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 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.
A karst river 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. Simply named The Sinks and Sinks Canyon State Park, The river flows into a cave in a formation known as the Madison Limestone and then rises again ½ mile down the canyon in a placid pool. When the river was dyed, it took two hours for the dye to reach the rise such a short distance away.
Water drainage and problems
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 is where an underground stream emerges onto the surface between layers of rock, cascades some feet, and then disappears back down, often into a sinkhole.
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 out.
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 itself also poses some difficulties for human inhabitants. Sinkholes can develop gradually as surface openings enlarge, but quite often progressive erosion is unseen and the roof of an underground cavern suddenly collapses. Such events have swallowed homes, cattle, cars, and farm machinery.
The Driftless Area National Wildlife Refuge in Iowa protects Discus macclintocki, a species of ice age snail surviving in air chilled by flowing over buried karst ice formations.
refers to landscape features that 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
), and paleocollapse
List of notable karst areas
- Area around Guilin and Yangshuo in Guangxi Zhuang Autonomous Region, China
- Zhi Jin Dong(Chinese: 织金洞) in Gui Zhou Province, China(The biggest karst cave in the world)
- Zhangjiajie National Forest park, forming part of the Wulingyuan scenic area (a UNESCO World Heritage Site), Zhangjiajie Prefecture, Hunan, China
- The Stone Forest called the South China Karst by UNESCO (Yunnan Province, China)
- Ofra region, West Bank
- Bantimurung, Indonesia
- Akiyoshi plateau, Japan
- El Nido, Palawan, Philippines
- Coron, Palawan, Philippines
- Sagada, Mountain Province, Philippines
- Chocolate Hills, Bohol, Philippines
- Negros and Gigante Islands, Negros Oriental, Philippines
- Vang Vieng, Laos
- Gunung Mulu National Park, Malaysia
- Kinta Valley, Perak, Malaysia
- Krabi region, Thailand
- Phangnga Bay Area, Southern Thailand
- Kenting National Park, Taiwan
- Taseli plateau, Turkey
- Halong Bay, Vietnam
- Phong Nha-Ke Bang, Vietnam
- Tam Coc - Bich Dong in Ninh Binh Province, Vietnam
- The Herzegovina region of Bosnia-Herzegovina and Montenegro
- The regions of Dalmatia (including Zagora), Lika, Gorski kotar, Kvarner and the islands in Croatia
- The Moravian Karst
- The Central Rhodope karst in Bulgaria (Trigrad Gorge and caves), the Devnya Valley (karst springs)
- The Apuseni Mountains, Romania
- Slovak Paradise, Slovak Karst and Muránska planina, Slovakia
- The region of Mecsek Mountains in Hungary
- The region of Inner Carniola in Slovenia
- Kras, a plateau in southwestern Slovenia and northeastern Italy
- Murge, in Apulia and Basilicata, southern Italy
- The Cadí mountain range, Catalonia
- The Garraf Natural Park area, Catalonia
- The Picos de Europa and Basque mountains, northern Spain
- The Ciudad Encantada in the Cuenca province (Castilla-La Mancha, Spain)
- El Torcal de Antequera nature preserve, southern Spain
- The White Peak of the Peak District, UK, around Matlock, Castleton, and Thor's Cave
- Yorkshire Dales (including Malham Cove), England
- The Burren (Co. Clare, Ireland)
- Assynt, southeast Skye and near Kentallen in Scotland
- The limestone region of the Southern Brecon Beacons National Park, Wales
- Hönnetal at Balve, Germany
- The Swabian Alb region in the federal state of Baden-Wuerttemberg in southern Germany
- The Ares de l'Anie, in the southernmost part of Barétous valley, southwest France
- The eastern part of the Northern Limestone Alps in the provinces of Salzburg, Upper Austria, Styria and Lower Austria forming huge limestone plateaus such as Steinernes Meer, Hagengebirge, Tennengebirge, Dachstein, Totes Gebirge and Hochschwab
- The area around Graz, Styria, Austria
- The Causses of the southern Massif Central, France.
- The Tuhala karst area, Estonia
- Kosciusko Island, southeast Alaska
- The Mitchell Plain and uplands of southern Indiana
- The Great Valley of Appalachia (Huntsville, Alabama to northeast Pennsylvania)
- The Shenandoah Valley of Virginia
- The Driftless Area of southwest Wisconsin, southeast Minnesota, northeast Iowa and northwest Illinois, left unglaciated by all three phases of the Wisconsin Stage
- The Florida peninsula
- Mammoth Cave area and Bluegrass region of Kentucky
- Illinois Caverns State Natural Area and Illinois Sinkhole Plain in Monroe County, Illinois
- The Ozark Plateau of Missouri and Arkansas
- The Kamas Ranch and Alabaster Cavern area of Oklahoma
- The Cumberland Plateau in Middle Tennessee
- The Grassy Cove Karst Area, Tennessee, a registered National Natural Landmark
- Carlsbad Caverns National Park of New Mexico
- The Hill Country of Texas and its northern extensions, including the Palo Pinto Mountains
- Central Pennsylvania
- Presque Isle County near and around Rogers City in northern Michigan
- The campus of the University of California, Santa Cruz
- The Germany Valley Karst Area, West Virginia, a registered National Natural Landmark
- The Swago Karst Area, West Virginia, a registered National Natural Landmark
- Cutta Cutta Caves National Park & Kintore Caves Conservation Park, Karst limestone landscapes. Katherine, Northern Territory Australia
- Leeuwin-Naturaliste National Park, southwest Western Australia (near Margaret River, Australia
- Northern Swan Coastal Plain, Perth, Western Australia, Australia
- Naracoorte Caves National Park, South Australia, Australia
- Jenolan Caves, New South Wales, Australia
- Wombeyan Caves, New South Wales, Australia
- Mole Creek Karst Conservation Area, Tasmania, Australia
- Waitomo, Oparara regions of New Zealand
- The Nakanai Mountains, East New Britain, Papua New Guinea
List of notable pseudokarst areas
- Jennings, J.N., Karst Geomorphology, 2nd ed., Blackwell, 1985, ISBN 0631140328
- Sweeting, M.M., Karst Landforms, Macmillan, 1973, ISBN 023103623X