Sinkholes

thumb|The Red Lake (Croatia)|Red Lake sinkhole in [[Croatia]] A sinkhole is a depression or hole in the ground caused by some form of collapse of the surface layer. The term is sometimes used to refer to doline, enclosed depressions that are also known as shakeholes, and to openings where surface water enters into underground passages known as ponor, swallow hole or swallet. A cenote is a type of sinkhole that exposes groundwater underneath. Sink and stream sink are more general terms for sites which drain surface water, possibly by infiltration into sediment or crumbled rock.

thumb|Cenote at Hubiku, Yucatan

thumb|The river Dobra (Kupa)|Dobra enters a 17 km long cave system at in [[Ogulin, Croatia.|276x276px]] A ponor is a natural opening where surface water enters into underground passages; they may be found in karst landscapes where the geology and the geomorphology is typically dominated by porous limestone rock. Ponors can drain stream or lake water continuously or can at times work as springs, similar to estavelles. Morphologically, ponors come in forms of large pits and caves, large fissures and caverns, networks of smaller cracks, and sedimentary, alluvial drains.

marine sinkhole or cavern

Suffosion is one of the two geological processes by which subsidence sinkholes or dolines are formed, the other being due to collapse of an underlying cave or void, with most sinkholes formed by the suffosion process. Suffosion sinkholes are normally associated with karst topography although they may form in other types of rock including chalk, gypsum and basalt. In the karst of the UK's Yorkshire Dales, numerous surface depressions known locally as "shakeholes" are the result of glacial till washing into fissures in the underlying limestone.

American drama television series

thumb|Grotta Plutone is a foiba close to Basovizza, Trieste ([[Italy)]]

2021 South Korean film

marine sinkhole

thumb|Medieval Pinge and ring-shaped bank at a mineshaft on the Ochsenhügel near Suhl in Germany's [[Thuringian Forest]] thumb|The Pinge of an iron ore pit near Warstein A Pinge ([ˈpɪŋə], plural: Pingen) or Binge ("binger") is the name given in German-speaking Europe to a wedge-, ditch- or funnel-shaped depression in the terrain caused by mining activity. This depression or sink-hole is frequently caused by the collapse of old underground mine workings that are close to the Earth's surface. Unlike natural landforms, a Pinge is a direct result of human activity. The term has no direct equivalen