Landforms created by groundwater result from the processes of chemical weathering and erosion, particularly in areas with soluble rock types like limestone, gypsum, and dolomite. These processes lead to the formation of various karst landscapes characterized by unique features such as caves, sinkholes, and springs.
1. Caves and Caverns
Characteristics:
- Formation: Caves and caverns are formed by the dissolution of soluble rocks by acidic groundwater. Rainwater absorbs carbon dioxide from the atmosphere and soil, forming weak carbonic acid, which dissolves limestone and other soluble rocks over time.
- Features: They often contain stalactites (hanging from the ceiling), stalagmites (rising from the floor), and other speleothems formed by the deposition of minerals.
Examples:
- India: The Borra Caves in Andhra Pradesh are limestone caves formed by the action of the Gosthani River.
- World: Mammoth Cave in Kentucky, USA, is the world’s longest cave system, formed in limestone.
2. Sinkholes
Characteristics:
- Formation: Sinkholes are depressions or holes in the ground caused by the collapse of a surface layer into an underground void. They form when groundwater dissolves the underlying soluble rock, creating voids and cavities that eventually collapse.
- Types: They can be solution sinkholes (formed by the gradual dissolution of rock) or collapse sinkholes (formed by the sudden collapse of an underground cavity).
Examples:
- India: The Umpherston Sinkhole in Meghalaya is a natural depression formed by the dissolution of limestone.
- World: The Great Blue Hole in Belize is a large underwater sinkhole formed by the collapse of a limestone cave system.
3. Karst Towers and Karst Landscapes
Characteristics:
- Formation: Karst towers are steep, isolated residual hills formed in tropical karst regions. They result from the dissolution of limestone, leaving behind rugged, tower-like landforms.
- Features: Characterized by a landscape of sharp ridges, towers, and pinnacles formed by differential erosion.
Examples:
- India: The Khasi Hills in Meghalaya have karst features, including isolated limestone hills.
- World: The Guilin Karst in China is famous for its spectacular tower karst landscape, with limestone pinnacles and steep hills.
4. Springs
Characteristics:
- Formation: Springs occur where groundwater naturally flows out of the ground, usually at a point where the water table intersects the Earth’s surface.
- Types: There are various types of springs, including artesian springs (where water is forced to the surface under pressure) and thermal springs (heated by geothermal activity).
Examples:
- India: The Amrit Kund in Rajasthan is a famous natural spring.
- World: Pamukkale in Turkey is renowned for its thermal springs and travertine terraces.
5. Travertine Terraces
Characteristics:
- Formation: Travertine terraces form from the deposition of calcium carbonate precipitated from mineral-rich waters at springs or along riverbanks.
- Features: They often appear as stepped, terraced formations with pools of mineral-rich water.
Examples:
- India: The travertine formations at Manikaran in Himachal Pradesh, known for its hot springs.
- World: Pamukkale in Turkey, where thermal waters have created extensive travertine terraces.
6. Poljes
Characteristics:
- Formation: Poljes are large, flat-floored depressions in karst regions, formed by the dissolution of limestone. They are often surrounded by steep limestone walls and may contain temporary or permanent lakes.
- Features: These depressions can be several kilometers wide and are often used for agriculture due to their fertile soil.
Examples:
- India: While large poljes are not prominent in India, similar features can be found in the limestone regions of the Himalayas.
- World: The Livanjsko Polje in Bosnia and Herzegovina is one of the largest poljes in the world.
Detailed Examination with Examples
1. Caves and Caverns
- Borra Caves, India: These limestone caves in Andhra Pradesh are known for their impressive stalactites and stalagmites, formed by the action of groundwater over millions of years.
- Mammoth Cave, USA: With over 400 miles of explored passageways, this limestone cave system in Kentucky showcases extensive underground formations.
2. Sinkholes
- Umpherston Sinkhole, India: This large sinkhole in Meghalaya is a popular tourist attraction, formed by the dissolution of underlying limestone.
- Great Blue Hole, Belize: A giant marine sinkhole off the coast of Belize, formed by the collapse of a limestone cave system during the last glacial period.
3. Karst Towers and Landscapes
- Khasi Hills, India: These hills in Meghalaya exhibit karst features with limestone formations and caves.
- Guilin Karst, China: Famous for its stunning karst towers and landscape, formed by the extensive dissolution of limestone.
4. Springs
- Amrit Kund, India: This natural spring in Rajasthan is known for its clear waters.
- Pamukkale, Turkey: Notable for its white travertine terraces and thermal springs, attracting tourists from around the world.
5. Travertine Terraces
- Manikaran, India: Known for its hot springs and travertine deposits in Himachal Pradesh.
- Pamukkale, Turkey: The site features spectacular white terraces formed by the deposition of calcium carbonate from thermal spring water.
6. Poljes
- Himalayan Limestone Regions, India: While not large poljes, similar depressions can be found in the karst areas of the Himalayas.
- Livanjsko Polje, Bosnia and Herzegovina: One of the largest poljes in the world, used extensively for agriculture.
Conclusion
Landforms created by groundwater are fascinating and diverse, resulting from the processes of chemical weathering, erosion, and deposition in soluble rock regions. Caves, sinkholes, karst towers, springs, travertine terraces, and poljes each showcase unique characteristics shaped by groundwater activity. Examples from India, such as the Borra Caves and Umpherston Sinkhole, along with global examples like Mammoth Cave and Pamukkale, highlight the remarkable and varied nature of these landforms.
