Main Cave Areas of the Continental U.S.A.

This map shows the continental United States. Karst areas are the main topic and are shown in blue for limestone and dolomite and in green for gypsum and salt. Additionally, the pink areas are volcanic areas which contain lava tubes. Sinkholes or dolines are marked in red if there are many. In volcanic areas only collapse dolines exist, in soluble rocks there are also solutional dolines.

Source: USGS. Public Domain. DOI