The following is a list of sinkholes, blue holes, dolines, crown holes, cenotes, and pit caves. A sinkhole is a depression or hole in the ground caused by some form of collapse of the surface layer. Some are caused by karst processes—for example, the chemical dissolution of carbonate rocks or suffosion processes. Sinkholes can vary in size from 1 to 600 m (3 to 2,000 ft) both in diameter and depth, and vary in form from soil-lined bowls to bedrock-edged chasms. Sinkholes may form gradually or suddenly, and are found worldwide.