Estavelle

In karst geology, estavelle or inversac is a ground orifice which, depending on weather conditions and season, can serve either as a sink or as a source of fresh water.

It is a type of ponor or sinkhole.

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Creux-Genat, an intermittent karst estavelle between Chevenez and Porrentruy in the Ajoie , recorded on April 2nd, 2005 and April 17th, 2006.