n.
Naturally formed underground cavity.
A cave often consists of a number of underground chambers, constituting a series of caverns. An assemblage of such caverns interconnected by smaller passageways makes up a cave system. Primary caves, such as lava tubes and coral caves, develop during the time when the host matrix is solidifying or being deposited. Secondary caves, such as marine grottoes, originate after the host matrix has been deposited or consolidated. Most caves are of the latter type, including solution caves formed by the chemical dissolution of a soluble host rock that has been weakened by fracturing and mechanical erosion; Mammoth Cave and Carlsbad Caverns are examples of solution caves.