Caves are found in a variety of rock types and in other substances such as ice. There are also a variety of types of caves, but the most common are caves formed by the dissolving of bedrock known as solution caves, as open conduits in cooled fields of lava known as lava caves or tubes, by wave actions along sea and lake coasts known as sea or littoral caves, and as open spaces beneath talus piles known as talus caves.
Karst landscapes are formed usually through the dissolution of carbonate rocks such as limestone, dolomite, marble, and gypsum, though other rock types can display similar karst features. During periods of thaw, ice in glaciers and other thick deposits such as in ice sheets mimic some karst processes.
In a number of parks, entire surface areas are considered a karst landscape while karst can be far less noticeable in other parks. This can range from beds of limestone inter-bedded with other types of less soluble rocks and only exposed on the surface in limited areas to large limestone aquifers buried at depth but covered with non-soluble materials where there is no interaction between the rock types and there is no surface expression of the buried karst.
Poster - Caves and Karst of the National Park System
Caves and Karst in the U.S. National Park System
A poster prepared by the NPS Geological Resources Division showing the location of all park units (c. 2012) on a base map of the karst geology of the United States.
