Question

How can water erosion by groundwater form a cave?

Answer 1

Hint: The ground is not a homogenous material. Rather, it is a heterogeneous mixture of all kinds of materials. Rocks in the ground may be of various degrees of solubility, some more and some less.

Complete answer: The ground is formed by various processes. It can be formed by volcanic activity, or by deposition in water bodies, etc. Thus, they can have many different rock constituents.

When water peeps into the ground, it is encountered by underground rocks. Some of them are soft rocks, easily breakable by the action of flowing water. While some of them are harder rocks. The water easily makes its way through the soft and soluble rocks, forming underground water channels. The surrounding rocks may also get eroded over time, leading to the formation of underground rivers. Such rivers further intensify the process of removal of soluble rock components.

Over years, such rivers may settle deeper, or diverge channels. The empty spaces left are what form caves or series of caves.

Note: One of the main reasons for erosion by groundwater is its chemical composition. Rainwater, wehen falling, absorbs Carbon dioxide, which makes the water acidic. This acidic character reacts with certain underground rocks (for example, limestone) and dissolves them.