A veil of darkness cloaks the natural beauty of caves. Some are found in cliffs at the edge of the coastline, chipped away by the relentless pounding of waves. Others form where a lava tube's outer surface cools and hardens and the inside of the molten rock drains away. Caves even form in glaciers where meltwater carves tunnels at the beginning of its journey to the sea.
But most caves form in karst, a type of landscape made of limestone, dolomite, and gypsum rocks that slowly dissolve in the presence of water with a slightly acidic tinge. Rain mixes with carbon dioxide in the atmosphere as it falls to the ground and then picks up more of the gas as it seeps into the soil. The combination is a weak acidic solution that dissolves calcite, the main mineral of karst rocks. (Continue reading from National Geographic)
The study of caves and cave systems is called speleology. Here is a list of the different types of caves found in our world.
(Continue reading from World Atlas)