Of all cave types, solution caves have the most complex developmental histories. They are formed by the dissolving action of underground water as it flows through fractures, partings, and pores in bedrock. Such caves must grow rapidly enough to reach traversable size before the rock material that contains them is destroyed by surface erosion. Because of their sensitivity to local landscapes and patterns of water flow, solution caves contain clues to the entire geomorphic, hydrologic, and climatic history of the region in which they are located. At the land surface most of this evidence is rapidly lost to weathering and erosion; but in caves these clues can remain intact for millions of years.