doline

(geology) A general term for a closed depression in an area of karst topography that is formed either by solution of the surficial limestone or by collapse of underlying caves.

A closed, steep-sided and flat-floored depression in karst country, such as Dalmatia. The sides are 2-10 m deep and the floor is 10-1000 m in width. Alluvial streamsink dolines form when a stream enters the doline and runs down through the rock to form a trough. Collapsed dolines form when a cave roof falls in. Solution dolines form when solution enlarges a point of weakness in the rock into a hollow. Subsidence dolines form when limestone caves develop below insoluble deposits. These superficial deposits may collapse into the cavern below, but the majority of dolines are corrosion forms.