Karst Landforms: Terminology for UPSC Geography Optional

Karst landforms are the surface and underground features produced mainly by the solution of limestone, dolomite and other soluble rocks by carbon-dioxide-charged water. They form a closed vocabulary of Slavic, German and French words, from lapies to polje, that examiners can test in a single line, and speleothems add a second, depositional family found inside caves.

Each entry gives a definition first, then mechanism, features, examples and a sketch line. Terms move from controls, through surface solution forms and tropical residual karst, to caves and their deposits, ending with the karst cycle. UPSC asked speleothems in 2022, conditions for karst development in 2010 and karst landforms in 1988.

Quick Revision Table

Term	Meaning in one line	Example
Karst	Terrain shaped by solution of soluble rock, with underground drainage	Kras plateau, Slovenia
Conditions for karst development	Pure, jointed, massive limestone above the water table, with water and CO2	Meghalaya plateau
Vadose & phreatic zones	Air-and-water zone above the water table; saturated zone below	Belum Caves passages
Karst spring (resurgence)	Point where underground karst water returns to the surface	Aachtopf, Germany
Pseudokarst	Karst-like forms made by processes other than carbonate solution	Krem Puri, Meghalaya
Lapies (karren)	Grooved, fluted, pinnacled limestone surface	Tsingy de Bemaraha, Madagascar
Clints & grykes	Blocks and widened joints of a limestone pavement	The Burren, Ireland
Sinkhole (doline)	Closed funnel-shaped depression formed by solution or collapse	Xiaozhai Tiankeng, China
Swallow hole (ponor)	Opening through which a surface stream sinks underground	Gaping Gill, Yorkshire
Uvala	Large compound depression from merged dolines	Dinaric karst
Polje	Very large flat-floored closed basin, often seasonally flooded	Livno polje, Bosnia
Blind valley & sinking creek	Valley ending at a sink; stream losing water through sinks	Reka at Škocjan, Slovenia
Karst window	Collapse opening that exposes an underground river	Škocjan collapse dolines
Natural bridge	Rock arch left over a stream after cave-roof collapse	Natural Bridge, Virginia
Cockpit karst	Star-shaped hollows between rounded hills	Cockpit Country, Jamaica
Tower karst	Steep isolated limestone towers on a flat plain	Guilin, China
Cone karst	Closely packed conical limestone hills	Chocolate Hills, Bohol
Hum	Isolated residual limestone hill on a karst plain	Dinaric polje floors
Terra rossa	Red clayey residual soil on limestone	Istria, Croatia
Cave (cavern) & theories of cave formation	Underground void enlarged mainly by solution	Mammoth Cave, Kentucky
Speleothem	Any secondary mineral deposit formed in a cave	Borra Caves, Andhra Pradesh
Stalactite	Icicle-shaped deposit hanging from a cave ceiling	Doolin Cave, Ireland
Stalagmite	Blunt deposit growing up from a cave floor	Mawmluh Cave, Meghalaya
Column (pillar) & helictite	Joined stalactite–stalagmite; twisted gravity-defying growth	Borra Caves columns
Flowstone & drapery (curtain)	Sheet deposits on walls and floors; wavy hanging sheets	Belum Caves
Travertine & tufa	Banded spring carbonate; porous plant-encrusted carbonate	Pamukkale; Plitvice
Karst cycle of erosion	Staged evolution from karst plain to hum-studded lowland	Jovan Cvijić, 1918

Karst: Concept and Controls

Karst (karst topography)

Karst is a distinctive terrain developed on soluble rocks, chiefly limestone and dolomite, in which chemical solution by carbonic-acid-charged water dominates erosion, producing closed depressions, bare fluted rock, few surface streams, underground drainage through widened joints and caves, and large karst springs.

• Name and coinage: From the Slovene kras (Italian Carso), the stony limestone plateau behind Trieste on the Slovenia–Italy border, part of the Dinaric karst. Jovan Cvijić (1893) laid the foundations of karst geomorphology and brought the local terms doline, uvala and polje into scientific use.
• Mechanism: CaCO3 + H2O + CO2 ⇌ Ca(HCO3)2. Rainwater picks up far more CO2 from soil air than from the atmosphere, so vegetation and soil boost solution; weathering chemistry is covered under carbonation.
• Landform families: Surface solution forms (karren, dolines, uvalas, poljes, blind valleys), residual hills (cockpits, towers, cones, hums), caves and ponors, and deposits (speleothems, tufa, terra rossa).
• Types: Holokarst (complete, Dinaric) and merokarst (partial, on thin or impure limestones), both Cvijić’s terms; fluviokarst, glaciokarst, tropical karst, covered karst and palaeokarst.
• Distribution: Karstifiable carbonate rocks crop out over about 15.2% of the ice-free land surface, and about 1.18 billion people live on karst (2020 estimate): Dinaric Alps, Causses of France, south China, Yucatán, Florida and Kentucky.
• Indian karst: Meghalaya (Khasi and Jaintia hills: Mawsmai, Krem Liat Prah, Mawmluh), Borra and Belum (Andhra Pradesh), Kotumsar in Kanger Valley National Park, Bastar (Chhattisgarh), Guptadham (Gupteshwar) on the Rohtas plateau (Bihar), karst springs of Kashmir and limestone caves on Baratang Island, Andamans.
• Significance: Easily polluted groundwater, sinkhole hazards, dam leakage and palaeoclimate archives.
• Sketch: Block diagram with lapies, dolines, a sinking stream, cave and resurgence.

Conditions for karst development

Conditions for karst development are the combination of lithological, structural, hydrological and climatic factors that allow solution to dominate a landscape: a thick, pure, massive and well-jointed soluble rock, exposed near the surface, lying above a deep water table, and supplied with abundant water and carbon dioxide over a long time.

• Rock purity: High carbonate content; clay-rich limestones clog joints with residue and give only merokarst.
• Massive bedding: Thick beds support cave roofs and steep walls; thin beds collapse.
• Low primary porosity, dense jointing: Water must move along joints and bedding planes (secondary permeability) and concentrate solution there. Porous chalk soaks water through its whole mass and forms few karst features, which is why England’s chalk downs are largely dry valleys, not true karst.
• Relief and a deep water table: An incised trunk river or uplift gives a strong hydraulic gradient and thick vadose zone, so surface water sinks into conduits.
• Structure: Faults and fractures guide conduits; folding helps but is not essential, and many classic karsts lie on nearly horizontal beds.
• Climate and vegetation: Abundant rain and high soil CO2 from roots and microbes, which is why humid tropical karst is the most spectacular.
• Indian illustration: Meghalaya’s thick limestones, very high rainfall and deep gorges give India’s longest caves; the Rohtas limestones, buried under a thick sandstone cap, show only the single galleried Guptadham cave.
• Sketch: Section showing jointed limestone, soil CO2, vadose zone, water table and incised valley.

Vadose and phreatic zones

The vadose zone is the part of a karst mass above the water table where joints and conduits contain both air and water and flow is downward under gravity; the phreatic zone lies below the water table, where all openings are water-filled and water moves under hydrostatic pressure, even upward, along looping paths.

• Key features: Vadose passages are canyon-shaped, cut downward by free-flowing streams, and carry shafts and waterfalls; phreatic tubes are rounded or elliptical in cross-section, formed by solution on all sides, with scallops showing flow direction.
• Significance: A dry, speleothem-decorated phreatic tube records a fall in the water table, usually because the regional river cut down.
• Examples: “Keyhole” passages, a phreatic tube with a vadose trench in its floor, as in Mammoth Cave.
• Don’t confuse with: the general zone of aeration and zone of saturation used in groundwater hydrology; the karst terms stress conduit flow and passage shape.

Karst spring (resurgence)

A karst spring is a point where water that has travelled through a karst conduit system returns to the surface, usually at the base of a limestone mass where it meets impermeable rock or a valley floor; a resurgence is a spring fed by a stream that sank upstream, while an exsurgence is fed only by percolating rainwater.

• Formation: Conduits converge on a few outlets, so karst springs are large and flashy, rising within hours of rain.
• Key features: High, flashy discharge; tufa at many outlets; a vauclusian spring rises from a flooded shaft under pressure.
• Examples: Fontaine de Vaucluse, France; the Aachtopf, Germany, where Danube water lost near Immendingen reappears and flows to the Rhine; Verinag, Kokernag and Achabal springs, Kashmir.
• Significance: Major water supplies, easily polluted because conduit flow is fast and unfiltered.
• Sketch: Stream sinking at a ponor and re-emerging at the foot of the limestone.

Pseudokarst

Pseudokarst is a landscape of karst-like features, including caves, closed depressions, sinking streams and pinnacles, produced by processes other than the solution of carbonate rocks, such as mechanical piping, lava-tube formation, melting of ground ice or the slow solution of quartz sandstone.

• Types: Lava-tube caves in basalt; suffosion and piping hollows in loess and clay; thermokarst in permafrost; and sandstone or quartzite caves.
• Current debate: Many specialists now class sandstone and quartzite caves formed by slow silica solution as true karst (arenite karst) rather than pseudokarst, because solution is still the controlling process.
• Examples: Krem Puri near Mawsynram, East Khasi Hills, Meghalaya, about 24.5 km long and regarded as the world’s longest sandstone cave; Kazumura lava-tube cave, Hawaii; the quartzite tepuis of Venezuela.
• Don’t confuse with: pseudovolcanic features, which imitate volcanic forms, not karst.

Surface Solution Landforms

Lapies (karren)

Lapies, or karren, are small-scale solution sculptures on bare or soil-covered limestone surfaces, ranging from millimetre-scale grooves to metre-deep clefts and razor-sharp pinnacles, formed as rainwater and soil water charged with carbon dioxide dissolve the rock along its slope lines and joints.

• Formation: Thin films of acidic water dissolve rock fastest where flow concentrates; joints and fractures widen into clefts; the ridges between them are left as sharp crests.
• Types: Rillenkarren (fine parallel flutes on steep bare rock), rinnenkarren (larger runnels), kluftkarren (widened joints, the grykes of Britain) and pinnacle karren.
• Key features: Rough, fretted ground that is hard to cross; lapiés is French, karren German.
• Examples: The giant pinnacle karren (tsingy) of Tsingy de Bemaraha, Madagascar; the Dinaric karst of Croatia.
• Sketch: Limestone block with flutes, runnels and a widened joint.
• Don’t confuse with: clints and grykes, which are the pavement-scale expression of kluftkarren.

Clints and grykes

Clints are the flat-topped, rectangular blocks of a limestone pavement, and grykes are the deep, narrow fissures separating them, formed by solution widening the vertical joints of horizontally bedded limestone once the soil or overlying glacial debris has been stripped from its surface.

• Formation: Pleistocene ice scraped limestone bare; later solution widened the joints into grykes, leaving the blocks between as clints.
• Key features: A chessboard-like pattern following the joint set; grykes may be a metre or more deep and shelter shade-loving plants; clints carry small solution pans and runnels.
• Examples: The Burren, County Clare, Ireland; the pavement above Malham Cove, Yorkshire Dales.
• Sketch: Plan and section of a pavement with rectangular clints separated by joint-controlled grykes.
• Don’t confuse with: lapies in general; clints and grykes are the pavement form of karren, not synonyms for all karren.

Sinkhole (doline: solution and collapse)

A sinkhole, or doline, is a closed, roughly circular depression, from a few metres to over a kilometre across, formed where the karst surface is lowered by concentrated solution around a point of water entry, or where the roof of an underground void collapses; it is the basic diagnostic landform of karst.

• Types: Solution dolines, bowl- or funnel-shaped, formed by faster solution where drainage converges on a joint intersection; collapse dolines, steep-walled and rocky, formed by roof failure over a cave; cover-collapse and subsidence dolines, formed when loose sediments above the limestone slump or are washed down into voids.
• Key features: Clay-plugged dolines hold karst lakes; giant collapse dolines in China are tiankeng.
• Examples: Xiaozhai Tiankeng, Chongqing, China, over 600 m deep; the cover-collapse sinkholes of Florida, a recurring hazard to buildings; the doline fields of the Kras plateau.
• Significance: Collapse is an engineering hazard, often triggered by groundwater pumping.
• Sketch: Paired sections: a funnel-shaped solution doline and a steep collapse doline over a cave.

Swallow hole (ponor)

A swallow hole, or ponor, is an opening in the floor of a doline, valley or polje through which a surface stream or runoff sinks directly into the underground conduit system; it may be a vertical shaft, an inclined passage or a choke of boulders, and in France a vertical shaft is called an aven.

• Formation: Solution and abrasion enlarge a joint intersection that captures surface flow.
• Key features: The point where a stream disappears; some ponors reverse in floods and act as springs (estavelles), especially in poljes.
• Examples: Gaping Gill, Yorkshire, where Fell Beck plunges down a shaft of about 100 m; the swallow holes of the Danube near Immendingen, Germany, which in dry seasons take the whole river underground towards the Aachtopf spring.
• Sketch: Section of a stream entering a shaft that joins a cave passage.
• Don’t confuse with: a doline, the depression itself; the ponor is the opening through which water leaves it.

Uvala

An uvala is a large, irregular or elongated closed depression in karst, from a few hundred metres to a kilometre or more across, formed by the coalescence of several neighbouring dolines as solution enlarges them and removes the ridges between them; it is also called a compound doline.

• Formation: Growth of adjacent dolines along a joint set or fault; roof collapse over a large cave can also produce uvala-like forms.
• Key features: Scalloped rims marking the original dolines; an uneven floor; drainage through ponors.
• Examples: Common in the Dinaric karst of Slovenia, Croatia and Bosnia–Herzegovina, where the term originates; the Kras plateau.
• Significance: A marker of maturity in the karst cycle.
• Sketch: Three merging dolines forming one lobed depression.
• Don’t confuse with: a polje, which is far larger, has a flat alluviated floor and is usually structurally controlled.

Polje

A polje is a very large, flat-floored closed basin in karst, several to tens of kilometres long, bounded by steep walls and floored by alluvium, which drains underground through ponors and is often flooded seasonally when springs and estavelles deliver more water than the ponors can swallow.

• Formation: Most large poljes are tectonic depressions, grabens or downfolds, later modified by solution, a view now generally accepted; others are border poljes, where water from impermeable rocks floods onto the limestone, or base-level poljes, cut down to the water table.
• Key features: Flat alluvial floor, surface streams that rise from springs and vanish into ponors, seasonal lakes, and isolated residual hills (hums).
• Examples: Livno polje, Bosnia–Herzegovina, one of the largest; Cerknica polje, Slovenia, with an intermittent lake that appears and vanishes each year; Popovo polje, Herzegovina.
• Significance: The main farmland of the Dinaric karst, despite seasonal floods.
• Sketch: Section of a flat-floored basin with steep limestone walls, spring on one side, ponor on the other and seasonal lake level.

Blind valley and sinking creek

A blind valley is a river valley that ends abruptly against a steep limestone wall or in a closed depression, where its stream disappears through a swallow hole; a sinking creek is a stream that loses its water progressively through a line of sinks in its bed, leaving a dry channel downstream.

• Formation: A stream flowing from impermeable rocks sinks on reaching limestone; the valley upstream keeps deepening while the limestone downstream, lacking surface flow, is not lowered, so a wall forms at the valley end.
• Key features: Open upstream, closed downstream; dry valleys beyond.
• Examples: The Reka, which sinks into the Škocjan Caves, Slovenia, and re-emerges near Trieste as the Timavo; Lost River, Indiana, a sinking creek.
• Sketch: Long section of a stream crossing shale onto limestone, sinking at a ponor at the foot of a cliff.

Karst window

A karst window is an opening, usually a collapse doline, through which an underground karst river can be seen flowing briefly in daylight before disappearing again, formed where the roof of a cave passage has fallen in along the course of a subterranean stream.

• Formation: Solution and stream erosion thin the roof of a large conduit until it collapses; the river is then exposed between an upstream resurgence and a downstream sink.
• Key features: Steep walls; a stream rising at one end and sinking at the other.
• Examples: The great collapse dolines of Škocjan, Slovenia (a UNESCO World Heritage Site), which expose the Reka; windows along the Lost River, Indiana.
• Sketch: Long section of an underground river with a roof collapse revealing it.
• Don’t confuse with: an uvala; some older writing used “karst window” for large dry uvalas, but the modern meaning is an opening onto an active underground stream.

Natural bridge

A natural bridge in karst is a rock span left standing over a valley or stream when most of the roof of a cave passage or underground stream course has collapsed or been removed by solution and erosion, leaving a short surviving remnant of the roof as an arch.

• Formation: A cave roof collapses along most of its length, forming a gorge, but a short, stronger section stays intact; or a surface stream captures a shorter underground route through a meander neck.
• Key features: An arch over a stream in a steep-sided valley; often associated with karst windows and collapse gorges.
• Examples: Natural Bridge, Virginia, carved by Cedar Creek through limestone; the Veliki naravni most of Rakov Škocjan, Slovenia; the Pont d’Arc over the Ardèche, France.
• Significance: Evidence that many karst gorges are unroofed caves.
• Sketch: Cave passage with collapsed roof segments and a surviving arch.
• Don’t confuse with: a sea arch, cut by waves through a headland.

Tropical Residual Karst and Soils

Cockpit karst

Cockpit karst is a humid tropical karst landscape of closely packed, steep-sided, star-shaped closed depressions (cockpits) separated by rounded or conical residual hills, forming a polygonal, egg-box pattern in which the depressions, not the hills, are the primary solution features.

• Formation: Intense rain and high biogenic CO2 concentrate solution at joint intersections; depressions expand until only residual hills remain.
• Key features: Depressions tens to hundreds of metres deep; drainage entirely underground; very difficult terrain for movement.
• Examples: Cockpit Country, Jamaica, which gave its name to the landform and sheltered escaped slaves (Maroons); parts of Guangxi, south China (fengcong or peak-cluster karst).
• Sketch: Plan of polygonal depressions with star-shaped outlines, and a section of alternating cones and cockpits.
• Don’t confuse with: cone karst, which describes the same terrain from the hills’ point of view; tower karst has isolated towers standing on a flat plain.

Tower karst

Tower karst is a tropical karst landscape of steep-sided, often vertical-walled limestone towers rising abruptly from a flat alluvial or corrosion plain, formed where lateral solution and river undercutting at the plain level attack the base of residual hills and keep their sides steep.

• Formation: Residual hills of cockpit or cone karst are isolated as the plain between them is lowered to the water table and alluviated; swamp water and rivers dissolve the tower bases, producing notches and foot caves.
• Types: Fenglin (peak forest, isolated towers on a plain) and fengcong (peak cluster, towers joined at their base).
• Examples: Guilin–Yangshuo along the Li river, Guangxi, part of the South China Karst World Heritage Site; the drowned towers of Ha Long Bay, Vietnam; the mogotes of the Viñales valley, Cuba.
• Sketch: Vertical-walled towers with basal notches on a flat plain.

Cone karst

Cone karst, or kegelkarst, is a humid tropical karst landscape of numerous closely spaced, symmetrical conical or hemispherical limestone hills that are separated by closed, star-shaped depressions, the hills being residuals left as intense solution deepens and widens the intervening hollows.

• Formation: Depressions grow along a regular joint network; solution of the flanks makes the hills conical.
• Key features: Hills of similar height, typically tens of metres; smooth rounded summits; depressions draining underground.
• Examples: The Chocolate Hills of Bohol, Philippines, more than a thousand grass-covered cones; Gunung Sewu (“thousand hills”), southern Java, Indonesia; the haystack hills of northern Puerto Rico.
• Significance: With continued lowering of the plain, cone karst grades into tower karst.
• Sketch: A row of cones separated by closed depressions.
• Don’t confuse with: tower karst, where hills are steep-walled and stand on a flat plain rather than rising from depressions.

Hum

A hum is an isolated, low residual hill of limestone standing above the floor of a polje or karst plain, the last remnant of a limestone mass in the old stage of the karst cycle, after most of the rock has been dissolved down to the water table or the impermeable rock beneath.

• Formation: Lateral solution at the level of the water table and the alluvial plain wears back the edges of limestone blocks until only scattered knobs remain.
• Key features: Small, steep-sided knolls rising abruptly from a flat floor; often caves at their base.
• Examples: The hums on the floors of Dinaric poljes in Bosnia–Herzegovina and Croatia, where the term originates; low mogotes on the karst plains of western Cuba.
• Significance: In the karst cycle, hums are equivalent to monadnocks on a fluvial peneplain.
• Sketch: Polje floor with isolated limestone knobs rising from alluvium.

Terra rossa

Terra rossa is a reddish, clay-rich soil formed on limestone and dolomite, mainly under a Mediterranean climate, in which iron oxides such as haematite give the red colour; it was classically regarded as the insoluble residue left after carbonate rock is dissolved away.

• Formation: Solution removes the calcium carbonate; the small percentage of clay, quartz and iron minerals in the limestone accumulates; dry summers oxidise the iron, reddening the soil.
• Current view: Because pure limestone contains very little residue, recent studies show that many terra rossa soils also contain wind-blown dust, such as Saharan dust, and other external material; they are therefore polygenetic rather than purely residual.
• Key features: Thin, patchy red soils in joints and dolines, used for vines and olives.
• Examples: Istria (Croatia), Apulia (Italy), southern Spain, and the Kras plateau.

Caves and Cave Deposits

Cave (cavern) and theories of cave formation

A cave in karst is a natural underground void large enough for a person to enter, formed chiefly by the solution of limestone by groundwater flowing along joints and bedding planes, later enlarged by stream erosion and breakdown; a cavern is a large cave or chamber.

• Theories: Deep-phreatic origin (William Morris Davis, 1930; J Harlen Bretz, 1942): caves dissolve well below the water table and are drained later. Water-table theory (A. C. Swinnerton, 1932): the most active solution is at the water table. Vadose theory: free-flowing streams above the water table cut caves. The four-state model (Derek Clifford Ford and R. O. Ewers, 1978) reconciled them: cave depth below the water table depends on fracture density, deep phreatic loops in poorly jointed rock and water-table caves in densely fractured rock.
• Hypogene caves: Some are dissolved from below by rising acidic water; Carlsbad Cavern, New Mexico, was formed by sulphuric acid.
• Examples: Mammoth Cave, Kentucky, with more than 680 km surveyed, the world’s longest; Son Doong, Vietnam, the largest cave passage; Krem Liat Prah system, East Jaintia Hills, Meghalaya, about 34 km, India’s longest; Belum Caves, Nandyal district, about 3.2 km; Borra Caves, Ananthagiri hills, about 80 m deep.
• Don’t confuse with: sea caves, cut by waves.

Speleothem

A speleothem is any secondary mineral deposit formed inside a cave from water, most commonly calcite precipitated from dripping, flowing or standing water that has lost carbon dioxide on entering the cave air; the term, from Greek spelaion (cave) and thema (deposit), was introduced by George W. Moore (1952).

Mechanism

• CO2 degassing: Percolating water dissolves limestone under the high CO2 pressure of soil air. On entering a cave, where CO2 is much lower, the water releases CO2, becomes supersaturated with calcite and precipitates it: Ca(HCO3)2 → CaCO3 + H2O + CO2.
• Evaporation: Secondary, near entrances and in dry caves; it concentrates solutions and produces gypsum and aragonite forms.
• Growth: Usually fractions of a millimetre a year.

Forms by the behaviour of water

• Dripstones: Stalactites and soda straws hang from ceilings; stalagmites rise from floors; columns join the two.
• Flowstones: Flowstone sheets on walls and floors; draperies or curtains under sloping ceilings.
• Pool deposits: Rimstone dams (gours) terracing cave streams, and cave pearls, spheres coated layer by layer in agitated splash cups.
• Erratic forms: Helictites, twisting in any direction under capillary forces, and needle-like anthodites.

Significance

• Uranium–thorium-dated stalagmite layers record past rainfall and temperature through oxygen isotopes, one of the palaeoclimate proxies; a stalagmite from Mawmluh Cave, Meghalaya, defines the base of the Meghalayan Age.
• Examples: Borra Caves, with stalactites and columns several metres long; Belum Caves; Mawsmai Cave, Sohra (Cherrapunji).
• Sketch: Cave section with stalactite, stalagmite, column, flowstone, drapery and rimstone pools labelled, showing CO2 escaping from a drip.

Stalactite

A stalactite is an icicle-shaped speleothem hanging from the roof of a cave, formed as drops of carbonate-rich water hang at the ceiling, lose carbon dioxide to the cave air and deposit a ring of calcite before falling, the rings building downward into a hollow tube that thickens into a cone.

• Formation: Growth begins as a soda straw, a thin tube about the diameter of a water drop (about 5 mm) with a central canal; when the canal clogs, water flows down the outside and the straw thickens into a tapering cone.
• Key features: A central canal; concentric growth bands; a tip pointing straight down.
• Examples: The Great Stalactite of Doolin Cave, County Clare, Ireland, about 7 m long and one of the longest free-hanging stalactites; stalactites of the Borra and Belum caves, Andhra Pradesh.
• Sketch: Section of a stalactite with central canal and growth rings, with the drop and CO2 release at the tip.
• Don’t confuse with: a stalagmite, which grows upward from the floor; stalactites hold tight to the ceiling.

Stalagmite

A stalagmite is a speleothem that grows upward from the floor of a cave where water dripping from the ceiling, or from a stalactite above, splashes and loses more carbon dioxide, depositing calcite layer upon layer; stalagmites are blunter and broader than stalactites and have no central canal.

• Formation: Each drop spreads over the stalagmite top, degasses and leaves a thin calcite film; the stalagmite rises and widens with time.
• Key features: A rounded top; layers stacked like inverted cups; compound stalagmites grow from several neighbouring drips.
• Examples: The stalagmites of Mawmluh Cave, Meghalaya, one of which was chosen to define the Meghalayan Age; the stalagmite revered as a Shivling at the end of Kotumsar Cave, Bastar.
• Significance: Their time-ordered, precisely datable layers make stalagmites the most valuable speleothems for reconstructing past monsoons.
• Sketch: Section of a stalagmite with stacked cup-shaped layers beneath a dripping stalactite.

Column (pillar) and helictite

A column, or pillar, is a speleothem formed when a stalactite growing downward and a stalagmite growing upward beneath it meet and fuse into a continuous floor-to-ceiling pillar; a helictite is a small, twisting speleothem that grows in any direction, apparently defying gravity, because water moves through its tiny central canal by capillary action.

• Column formation: Continued dripping thickens the join; flowstone may coat the column until it looks like fluted masonry.
• Helictite formation: Seepage too slow to form drops creeps through a capillary canal; crystal orientation and air currents send growth sideways or in spirals.
• Key features: Columns are thick and fluted; helictites are thin, curved and a few centimetres long.
• Examples: Columns about 6 m tall in the Borra Caves, Andhra Pradesh; helictite-rich chambers of Carlsbad Cavern and Jenolan Caves, Australia.
• Sketch: Stages from stalactite and stalagmite to a joined column; a sideways-curling helictite from a wall.
• Don’t confuse with: anthodites, needle-like aragonite clusters that radiate rather than twist.

Flowstone and drapery (curtain)

Flowstone is a sheet-like speleothem deposited by thin films of water flowing over cave walls and floors, building smooth, layered coatings that resemble frozen waterfalls; a drapery, or curtain, is a thin, wavy sheet of calcite hanging from an inclined ceiling, formed where water trickles along a line beneath it.

• Formation: Flowstone forms where water spreads rather than drips; each film degasses and deposits a thin lamina. A drapery starts as a line of drips running down a sloping ceiling, each drop depositing calcite along the same path, so the deposit grows as a folded sheet.
• Key features: Flowstone is laminated and may bury older deposits; draperies are translucent when lit from behind and often banded red and white by iron-stained layers, called “cave bacon”.
• Examples: Flowstone and draperies of the Belum Caves and of Mawsmai Cave, Meghalaya.
• Sketch: Sloping ceiling with a folded drapery and flowstone on the wall.

Travertine and tufa

Travertine is a dense, banded, often crystalline calcium carbonate deposit precipitated from springs, especially warm or hot springs rich in carbon dioxide, and tufa is a soft, porous, spongy carbonate deposited from cool springs and streams, typically encrusting mosses, algae and plant stems, both forming where water degasses at the surface.

• Formation: Emerging groundwater loses CO2 by turbulence, warming or plant photosynthesis and deposits carbonate.
• Key features: Travertine forms terraces, mounds and fissure ridges; tufa forms barrages and cascades full of plant moulds. Some writers use “calc-tufa” for the soft material and “travertine” for the hard, banded variety.
• Examples: The white travertine terraces of Pamukkale, Turkey, and Mammoth Hot Springs, Yellowstone; the tufa barriers that hold up the Plitvice Lakes, Croatia.
• Don’t confuse with: volcanic tuff, a consolidated ash deposit with a similar-sounding name.

Evolution of Karst Landscapes

Karst cycle of erosion

The karst cycle of erosion is the idea that a limestone landscape passes through ordered stages, from the initiation of surface drainage, through the loss of streams underground and the growth of dolines, uvalas and caves, to roof collapse and a lowland of hums, applied to karst by Joshua William Beede (1911) and Jovan Cvijić (1918).

1. Youth: Surface streams on the limestone begin to sink; lapies, dolines and swallow holes multiply; caves start to form; ends when surface drainage has largely disappeared.
2. Maturity: All drainage is underground; dolines merge into uvalas; caves reach their largest size; roofs thin and collapse, forming karst windows, natural bridges and poljes.
3. Late maturity: Cave roofs have collapsed and the pitted ridges between uvalas narrow and fall in height.
4. Old age: The limestone is lowered to the water table or removed, surface drainage reappears on the impermeable rock below, and scattered hums remain, the karst equivalent of a peneplain.

• Views: Beede gave three stages, Cvijić four; William Morris Davis (1930) treated karst as a special case of the normal cycle.
• Critique: Base level is uncertain because water tables fluctuate; uplift and climatic change interrupt the sequence; tropical cockpits and towers do not fit the European model.
• Sketch: Four block diagrams from karst plain to hum-studded lowland.

PYQs Built on These Terms

• Define Speleothem. Discuss the various forms and features of speleothem. (2022)
• Write short note on Essential conditions for the development of Karst topography. (2010)
• Analyse the sequential development of landforms in either Karst or Coastal region. (1991)
• Write short note on Karst landforms in about 200 words. (1988)

Frequently Asked Questions

What is the difference between a stalactite and a stalagmite?

A stalactite hangs from the cave ceiling and grows downward from dripping water, while a stalagmite rises from the floor where the drips land. Stalactites are thinner, often with a hollow central canal; stalagmites are blunter and layered. When the two meet they form a column.

How are speleothems formed?

Most speleothems form when water carrying dissolved limestone enters a cave, whose air holds less carbon dioxide than the soil it passed through. The water releases carbon dioxide, becomes supersaturated with calcite and deposits it, drop by drop or film by film, as stalactites, stalagmites, flowstone and other forms.

What is the difference between a doline, an uvala and a polje?

They differ in size and origin. A doline is a single sinkhole formed by solution or collapse; an uvala is a larger compound depression formed where several dolines merge; a polje is a very large, flat-floored and usually tectonic basin, several kilometres long, drained by ponors and often seasonally flooded.

What is the difference between travertine and tufa?

Both are calcium carbonate deposited where spring or stream water loses carbon dioxide at the surface. Travertine is dense, banded and often forms at warm springs, as at Pamukkale; tufa is soft and porous, forming in cool water around mosses and plants, as in the Plitvice Lakes barriers.

Where are karst landforms found in India?

India’s best karst lies in Meghalaya, with Krem Liat Prah, Mawsmai and Mawmluh caves; in Andhra Pradesh, at Borra and Belum; in Bastar, Chhattisgarh, at Kotumsar; and on the Rohtas plateau of Bihar, at Guptadham. Karst springs occur in Kashmir, and limestone caves on Baratang Island in the Andamans.