How are Caves Formed?

Sourabh Gupta Mar 12, 2019
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We love visiting caves as they are exotic places. Being inside a cave gives you a chilling adventure, doesn't it? But, have you ever wondered how they are formed. Know the process of formation of caves by reading this piece of writng.
We see caves as structures of mystery and intrigue. They are a perfect hideout. Animals use them for various reasons; shelter from other carnivorous animals, to protect their young ones, and to be safe during natural phenomena like rain, lightning, etc. Ditto, for prehistoric people.
Pirates used them as a secret hiding to dump their loot. The famous Tora Bora caves in Afghanistan are being used as a hideout by terrorists.
Caves are defined as natural underground voids, which are large enough for human entry. Many speleologists argue that the term 'cave' should only be applied to cavities, which have parts that do not receive sunlight. However, in modern usage, the term includes sea caves and rock shelters too.

Formation

Caves can be classified into many types depending upon their formation, shape, and size. Most of them are formed by dissolution of limestone, which is a chemical reaction. Limestone is a rock that is soluble in water, rich in carbonic acid, and mainly consists of calcite (CaCO3).
However, limestone is quite stable in pure water. The plant material and the soil at the top level of earth's surface decays, releasing carbon dioxide. The rainwater is slightly acidic (pH~6); when it infiltrates through the soil, it reacts with carbon dioxide (CO2 ), and forms carbonic acid (H2CO3).
Carbonic acid is the same acid, that is found in soda pop. It finds its way to the underground water table, and this mixture can be referred to as ground water. The ground water percolates through tiny pores, cavities and openings in the limestone, and dissolves it. The erosion process continues, and cracks form in chambers of the rock.
As the cracks get wider, more ground water enters and erodes the rock. The chambers get bigger with every rainfall. This process is slow, and no one can predict the time required to form a cave. The area from where water enters the cave is called insurgence, and the area from where it leaves, is referred to as spring or resurgence.
Some caves are formed by sulfuric acid, which is found in batteries. It is formed when carbonic acid mixes with hydrogen sulfide.
Over time, they form pointed structures that hang from the ceiling, called stalactites, and those that grow up from the floor are called stalagmites. These structures are the result of slow and steady accumulation of calcium carbonate, which precipitates from the water dripping off the stones.

Types

Solutional caves

As they are formed by soluble rocks, they are called solutional caves. Soluble rocks are chalk, marble, gypsum, and limestone.

Lava caves

These are formed through volcanic activity, and are the most common primary caves.

Sea caves

As the name suggests, they are found along the coasts all over the world. They may be around 5m - 50m in length.

Corrasional caves

Those formed entirely by erosion through flowing streams, that carry rock and other sediments, are called corrasional caves.

Glacier caves

These occur in ice, and are formed under the glaciers by melting. They are also referred to as ice caves.
The chemical composition of air outside the cave and inside is the same. However, there is less amount of carbon dioxide inside. Some fauna or life is found inside the caves, which comprises microscopic organisms and larger species, like bats and salamanders. Crayfish is found in streams inside the caves.
Because of their constant cold conditions and high humidity, caves can be used for preservation or aging of wines and cheese.
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