Karst (Groundwater) Topography: Sinkholes, Dolines, Uvalas
Geography › Geomorphic Processes and Landform Evolution · Topic 3.21
Karst topography is the landscape formed by the dissolving of soluble rocks, mainly limestone, dolomite and gypsum, by groundwater. Rainwater, made weakly acidic by dissolved carbon dioxide, widens cracks and drains underground, so the surface has few streams. Typical surface features are sinkholes (swallow holes and collapse sinkholes), dolines, uvalas (merged dolines), poljes (large flat-floored basins), karren (grooved rock), and blind and dry valleys. The name comes from the Kras plateau in Slovenia.
5 min read · UPSC Prelims · Geography · Geomorphic Processes and Landform Evolution
At a Glance
- Rocks Limestone, dolomite, gypsum
- Process Solution by carbonic acid
- Sinkhole Depression where rock dissolves or collapses
- Doline and uvala Small bowl and merged bowls
- Polje Large flat-floored basin
- Exam link UPSC Prelims, Geography: Geomorphic Processes and Landform Evolution
Where Does It Fit?
This topic follows the two on running water and takes up the work of groundwater, which is important only in soluble rocks. It is paired with the next topic on the depositional features of caves. Previous topic: Running Water Depositional Landforms: Alluvial Fans, Deltas, Floodplains, Natural Levees, Meanders, Oxbow Lakes, Braided Channels. Next topic: Karst Depositional Landforms: Stalactites, Stalagmites, Pillars.
What Is Karst Topography?
In short: karst is a landscape where soluble rock has been dissolved by water into sinkholes, caves and underground streams.
The term karst comes from the Kras plateau in Slovenia and Italy. Karst landscapes develop in regions of thick, well-jointed limestone, dolomite or gypsum, with enough rain. Rainwater absorbs carbon dioxide from the air and soil and becomes weak carbonic acid, which dissolves calcium carbonate, a process called carbonation, as described in Exogenic Processes: Denudation, Weathering, Mass Movements, Erosion, Transportation, Deposition. The water enlarges joints and bedding planes, and most drainage goes underground, so there are few surface streams. The characteristic features are a pitted surface and a network of caves below. The rock itself is explained in Sedimentary Rocks.
What Are the Surface Karst Landforms?
| Landform | Description |
|---|---|
| Karren or lapies | Small grooves and ridges cut in bare limestone by dissolving rainwater; a surface of ridges and furrows is called a limestone pavement |
| Sinkhole (doline) | A funnel-shaped depression from a few metres to hundreds of metres across, formed by solution or by the collapse of a cave roof |
| Swallow hole | A sinkhole where a stream disappears underground |
| Uvala | A large basin made by the merging of several sinkholes |
| Polje | A very large flat-floored depression, kilometres in size, in karst |
| Karst window and natural bridge | Collapse exposes an underground stream, and a surviving arch forms a natural bridge |
| Tower karst | Isolated steep limestone hills in humid tropical karst, as in Guilin in China |
How Do Sinkholes, Dolines, Uvalas and Poljes Differ?
| Landform | Size and shape | Formation |
|---|---|---|
| Karren (lapies) | Small grooves and ridges on bare limestone | Rain and runoff dissolve the rock along joints |
| Sinkhole (swallow hole) | Funnel-shaped or cylindrical hole through which surface water drains underground | Solution along a joint; collapse of the roof of a cave gives collapse sinkholes |
| Doline | Bowl-shaped depression, tens to hundreds of metres across | Solution or sinking of the surface; the commonest karst feature |
| Uvala | A larger, irregular depression from the merging of several dolines | Joining of neighbouring dolines |
| Polje | Large, flat-floored basin, several to hundreds of sq km, with steep sides | Solution and collapse, sometimes along faults; may flood in the wet season |
| Blind valley and dry valley | Valley where a stream disappears underground; abandoned valley with no stream | Surface stream goes underground into a swallow hole |
| Cenote | Water-filled collapse sinkhole | Yucatan peninsula, Mexico |
What Conditions Are Needed for Karst?
- Soluble rock: thick, pure limestone, well jointed, close to the surface.
- Water and acid: abundant rainfall and carbon dioxide from the air and soil, so carbonation, as in Weathering: Chemical, Physical/Mechanical and Biological Processes, can work.
- Relief: enough height between the surface and the water table for water to sink and flow.
- Vegetation and soil: organic soil makes the water more acidic.
Karst is best developed in humid regions. The surface of a karst area is dry and bare in many places, while all the drainage runs below, so people often find water scarce, and farming is poor.
Where Are the Main Karst Regions?
- World: the Kras plateau of Slovenia and Italy (the original karst), the Dinaric Alps, the Guilin tower karst in China, the Yucatan peninsula in Mexico, Florida, Kentucky (Mammoth Cave, the longest known cave system), and the Causses in France.
- India: Meghalaya (the Jaintia, Khasi and Garo hills have some of the longest caves in the subcontinent, including Krem Liat Prah), Chhattisgarh (Kutumsar and Kailash caves, and Chitrakoot), Andhra Pradesh (Borra and Belum caves), Uttarakhand (Dehradun-Mussoorie hills and Pithoragarh), Madhya Pradesh and Jammu and Kashmir.
The depositional features inside the caves are in Karst Depositional Landforms: Stalactites, Stalagmites, Pillars. As an analytical point, karst regions are fragile: groundwater is easily polluted because water passes quickly through the rock with little filtration, and mining of limestone damages the landscape.
Why Is This Topic Important?
- Terms Karst landforms are asked
- India Cave regions
- Water Groundwater pollution
What Came Next?
The next topic describes the depositional landforms of karst: stalactites, stalagmites and pillars. Next topic: Karst Depositional Landforms: Stalactites, Stalagmites, Pillars.
Key People and Terms
- Karst Landscape of dissolved limestone
- Doline Bowl-shaped depression
- Uvala Merged dolines
- Polje Large flat-floored basin
- Karren Grooved limestone surface
- Cenote Water-filled sinkhole
Exam Corner
Points to Remember
- Karst is made by solution of limestone.
- Dolines merge into uvalas.
- The name karst is from Slovenia.
- Mammoth Cave is the longest known cave system.
- Borra Caves are in Andhra Pradesh.
Do Not Confuse With
- Doline and uvala Single bowl versus compound depression
- Sinkhole and doline Often used loosely; a sinkhole is a drain hole or collapse
- Karst and glacial landscape Solution versus ice erosion
Memory Hook
Lime dissolves, holes appear; doline small, uvala more, polje floor.
Mains Angle
Questions ask for karst forms and their regions. These points add depth.
- Process Carbonation
- Forms Surface and underground
- Issues Water scarcity and pollution
A Question You May Face
An original practice question, not a past paper question.
“What is karst topography? Describe its surface landforms and their occurrence in India.”
How to Answer
- Define Karst.
- Conditions Rock, water, acid.
- Forms Sinkholes to poljes.
- India Meghalaya, Chhattisgarh, Andhra.
GS Relevance
Frequently Asked Questions
What is karst topography?
Karst topography is the landscape formed in regions of soluble rock, mainly limestone, by the dissolving action of slightly acidic water. It has sinkholes, caves, underground streams and few surface streams, and is named after the Kras plateau of Slovenia.
What is a sinkhole?
A sinkhole or doline is a funnel-shaped or circular depression in karst land, formed by the solution of limestone at the surface or by the collapse of the roof of an underground cave. Several sinkholes may merge into a larger basin called an uvala.
Where are the famous limestone caves of India?
Famous limestone caves of India include the Borra Caves in the Araku Valley, Andhra Pradesh, the Belum Caves in Kurnool, Mawsmai and Krem Liat Prah in Meghalaya, Gupt Godavari in Chitrakoot, and the Sahastradhara and Robber's Cave near Dehradun.
What is a doline?
A doline is a bowl-shaped depression in a limestone region, formed by the solution of rock at the surface or by the slow sinking of the ground above a dissolved cavity. It is the commonest karst feature, usually tens to hundreds of metres across, and several dolines can merge to form a larger uvala.
What is a polje?
A polje is a large, flat-floored closed basin in a karst region, with steep sides, ranging from several to hundreds of square kilometres. It is formed by solution and collapse, sometimes along faults, and may be flooded in the wet season when underground streams back up.
PYQ Practice — Statement Analysis
1 Karst topography is characteristic of limestone regions.
The rock is dissolved by weak acid.
2 Uvalas are formed by the merging of dolines.
They are larger depressions.
3 Karst topography is typical of granite regions.
It forms in soluble rocks such as limestone.
4 The Borra Caves lie in Andhra Pradesh.
They are limestone caves.
Past Mains Questions on This Topic
This topic comes under Geomorphic Processes and Landform Evolution. UPSC Mains questions asked on the matching syllabus topic, year-wise with marks:
Related Topics
Browse the full Geography index