Cave

Caves of one sort or another are widely scattered across the planet. Caves are most prevalent in limestone, but can also form in other material, including sandstone, loess, ice, granite, salt, marble, lava, and gypsum.

Cave formation in limestone occurs because limestone dissolves under the action of rainwater and groundwater[?] charged with CO₂ and naturally occurring organic acids. The dissolution process produces a distinctive landform known as karst and characterized by sinkholes, sinking streams[?], and caves. Limestone caves often have spectacular formations produced by calcium carbonate precipitating out of the groundwater that formed them, such as stalactites and stalagmites.

Caves can also form through the abrasive action of the wind or sea. There are also some special cases; ice caves can occur in and under glaciers, and lava tubes[?] can form through volcanic activity.

Caves can range in size from barely enterable to tropical monsters big enough to fly a light aircraft through.

Discovering caves is firstly a matter of finding limestone (or lava, gypsum, etc.). In the United States, most state geological surveys have geological maps[?] where limestone beds are drawn and can be located in the field. Topographic maps, especially the 1:24000 series, are helpful. After the limestone is located, field work to actually find entrances is necessary.

In the United States, since most land in the eastern U.S. is privately held, permission must be obtained from the landowner to look for caves. In the western U.S., a permit for publicly owned lands may be required.

Caving, or spelunking, is a popular activity in several countries.

See also: Quarries, list of caves

Caves[?] is also the name of a commune in the Aude département, in France