Answer in a parag

The underground water is the major reason for the formation of the karst topography. It is formed due to the dissolution of limestone, dolomite and gypsum with the groundwater. It is created because of the gradation, erosion and deposition of these soluble rocks with the groundwater. The Nullarbor in the Great Australian Coast is the world’s largest karst area.

Most of the weathering and erosion occurs through chemical weathering. The solution is the main method of decomposition. Water reacts with the particles and substances found in the rocks, resulting in the breaking down of its particles from within. The reaction between the water molecules and the carbon dioxide in the atmosphere resulting in the formation of carbonic acids. The reaction of the carbonic acid with the carbonate rocks decomposes the rocks and results in its weathering. It basically occurs in the limestone region in the formation of caves.

Some of the erosional features of underground water are:

• Terra Rossa- This majorly occurs in ferrous rocks containing iron. The iron in these rocks reacts with the oxygen in the atmosphere resulting in the formation of iron oxide. This gives a red colour to the clay soil. When the limestone in the rocks dissolves in the water, it results in the deposition and accumulation of red clay in the surface resulting in the formation of clayey to filthy soil known as terra rossas. It is mostly found in the Mediterranean regions.

• Lappies- When the limestone in the rocks dissolves and decomposes in the water, it results in the formation of huge and big troughs and furrows. These channels of furrows are known as lappies.

• Sinkhole- When the limestone in the rocks dissolves and decomposes in the water, it results in the formation of huge and big funnels and shafts in the surface. They can be very deep with depth ranging up to nine meters.

• Caves and caverns- The reaction between the water molecules and the carbon dioxide in the atmosphere resulting in the formation of carbonic acids. When the carbonic acids react with limestone, huge hollows and caves called caves are formed. Caverns are also caves having irregular and asymmetrical floors.