Sinkhole

A sinkhole is a depression or hole in the ground produced by the collapse of the surface layer, and the same broad category includes closely related features such as the doline or shakehole, an enclosed depression, the ponor, swallow hole or swallet, an opening through which surface water disappears underground, and the cenote, a sinkhole that exposes groundwater at the surface. Most sinkholes form through karst processes, the chemical dissolution of carbonate rocks such as limestone, together with collapse or suffosion of the ground above a dissolving or draining cavity, and they can appear gradually or very suddenly, ranging from tens to hundreds of meters across and deep. Their shapes vary widely, from soft, soil-lined bowls to sharp, bedrock-edged chasms, though most are roughly circular, and while sinkholes occur naturally worldwide, human activity such as groundwater pumping or construction can trigger a collapse within a few years that would otherwise have taken thousands of years to develop on its own.