A natural depression in a land surface communicating with a subterranean passage, generally occurring in limestone regions and formed by solution or by collapse of a cavern roof.
A saucer-shaped surface depression produced when underlying material, such as limestone or salt, dissolves or when caves, mines, etc. collapse.
A natural depression in a land surface formed by the dissolution and collapse of a cavern roof. Sinkholes are roughly funnel-shaped and on the order of tens of meters in size. They generally occur in limestone regions and are connected to subteranean passages.