Sinkholes are closed depressions in areas underlain by soluble rock such as limestone, dolostone, gypsum, or salt. Sinkholes form when surface sediments subside into underground voids created by the dissolving action of groundwater in the underlying bedrock.


A shallow usually funnel-shaped depression of the ground surface formed by solution in limestone regions.


A steep-sided, often conical, depression caused by slumping of ground into a cavity beneath. Shakeholes may or may not contain a cave entrance and/or a stream sink.

Subsidence Incident

Subterranean events other than sinkholes can cause holes, depressions or subsidence of the land surface that may mimic sinkhole activity. these include subsurface expansive clay or organic layers which compress as water is removed, collapsed or broken sewer and drain pipes or broken septic tanks, improperly compacted soil after excavation work, and even buried trash, logs and other debris. Commonly, a reported depression is not verified by a licensed professional geologist to be a true sinkhole, and the cause of subsidence is not known. such an event is called a subsidence incident.


Karst is a landscape formed from the dissolution of soluble rocks including limestone, dolomite and gypsum. It is characterized by sinkholes, caves, and underground drainage systems.

Note about our sinkhole markers

Although our icons are labeled as "Sinkhole", each incident may represent any one of the hole formation types listed above. The majority of the incidents have not been field-checked and the cause of the subsidence may not have been verified by a licensed geologist. Click on a sinkhole icon to bring up the specific details for that event.