Solutional cave

A cave formed as water dissolves soluble rock, commonly limestone, gypsum, or salt. Its passages develop through chemical weathering and may extend into extensive underground drainage systems.

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Carbonic acid: A weak acid formed when carbon dioxide dissolves in water. Rain and soil water gain acidity from carbon dioxide, enabling them to dissolve limestone.
Limestone: A sedimentary rock composed chiefly of calcium carbonate, often formed from accumulated marine material. Its calcite dissolves in mildly acidic water, making limestone the most familiar cave-forming rock.
Karst aquifer: An aquifer in soluble rock where groundwater flows through fractures, enlarged conduits, and cavities. Solutional caves can become major conduits within aquifers that supply springs and wells.
Mammoth Cave: A large cave system in Kentucky, developed mainly in Mississippian-age limestone. Its extensive passages illustrate the scale possible in a mature limestone cave system.
Lava tube: A tunnel formed when the surface of a lava flow solidifies while molten lava continues to drain beneath it. Unlike solutional caves, lava tubes form through volcanic cooling and drainage rather than rock dissolution.
Karst: A landscape shaped by dissolution of soluble rock, often marked by sinkholes, caves, and underground drainage. Solutional caves are the underground features of this broader dissolution-shaped landscape.
Gypsum: A soft evaporite mineral composed of hydrated calcium sulfate. Gypsum dissolves more readily than limestone, allowing caves to form rapidly in suitable settings.
Sinkhole: A depression or hole at the land surface formed by collapse or by gradual removal of underlying material. Cave-roof collapse or dissolution can create sinkholes above solutional cave systems.
Carlsbad Caverns: A cave system in New Mexico, famous for its large chambers and speleothems. Its formation involved sulfuric acid dissolving limestone, offering a distinct chemical pathway.
Talus cave: A cavity among fallen blocks of rock, commonly formed on steep slopes. Its openings lie between collapsed blocks rather than being dissolved into bedrock.