Test: Limestone and Chalk Landform - UPSC

Limestone and chalk are sedimentary rocks of organic origin derived from the accumulation of corals and shells in the sea.

Chalk is the pure form of limestone, which is white and soft.

A region with a large stretch of limestone possesses a very distinct type of topography, termed as Karst region.

Volcanic craters are not associated with Karst topography. Karst features include swallow holes, dry surface valleys, and limestone pavement.

The enlarged joints in limestone pavement are called Grikes, and the isolated, rectangular blocks are termed as dints.

Swallow holes are small depressions carved out by solution where rainwater sinks into limestone at the point of weakness, also known as sinkholes.

When a number of swallow holes coalesce, a larger hollow is formed, called a Doline

When a stalactite hanging from the roof eventually joins a stalagmite growing from the floor, a calcite pillar is formed.

The porosity of the rocks and the absence of surface drainage make vegetative growth difficult in Karst regions, hence limestone can usually support only poor grass.

The only mineral found in association with limestone is lead.

Good quality limestone is used as building materials and quarried for the cement industry.

Valleys in chalk landscapes, which once contained rivers but are now dry, are often called Coombes.

Due to the friable nature of chalk rocks, swallow holes and underground cave networks do not generally develop in chalk landscapes.

Chalk is covered with short turf and is used for pasture and sometimes for arable farming.

Volcanic vents are not found in limestone caves. Limestone caves typically contain features such as stalactites, stalagmites, and calcite pillars.