cave

A cave is a natural underground space large enough for a human to enter. Caves form in various rock types, most commonly in soluble rocks such as limestone, dolomite, or gypsum, but also in lava, ice, and other materials. They occur worldwide and range from small chambers to vast systems that extend for many kilometers.

Cave formation occurs through several processes. Speleogenesis refers to the chemical dissolution of rocks by mildly acidic groundwater, especially in karst regions, gradually enlarging joints into passageways. Lava tubes form when flowing lava creates hollow conduits as temperatures fall and the lava drains away. Wave action can carve sea caves along coastlines, and persistent freezing and thawing can produce ice caves.

Common cave features include speleothems such as stalactites, stalagmites, and columns formed by mineral deposition from dripping water. Flowstones, draperies, and crystal formations add variety. Many caves contain passages that interconnect into networks, sometimes hosting underground rivers or lakes.

Biological communities in caves adapt to darkness and limited nutrients. Troglobitic species live exclusively underground, while troglophiles use caves regularly. Bats roost in many caves, and microbial and invertebrate life often thrives on mineral substrates and organic inputs from outside environments.

Human interaction with caves spans shelter, ritual use, and scientific study, to recreation and tourism. Safety considerations include unstable rock, flooding, hypothermia, and poor ventilation. Conservation aims to protect delicate formations and organisms from damage and contamination, preserve archaeological or cultural artifacts, and regulate access through guided tours and legal protections.