doline

A closed depression, often basin-shaped or roughly conical, funnel-shaped depressions, usually formed in the karst land surface of carbonate rock area, as a result of solution or collapse of underlying carbonate rock strata. Dolines have a simple but variable form, e.g. cylindrical, conical, bowl or dish-shaped, and may vary in size dimensions from...
Found on http://www.cancaver.ca/docs/glossary.htm

Doline

A depression or hole in the ground formed by the solution of limestone by chemical weathering.
Found on http://www.bgs.ac.uk/discoveringGeology/glossary.html
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