Sinkhole may exhibit a visible opening into a cave below. In the case of exceptionally large sinkholes, such as the Minyé sinkhole in Papua New Guinea or Cedar Sink at Mammoth Cave National Park in Kentucky, an underground stream or river may be visible across its bottom flowing from one side to the other. Sinkholes are common where the rock below the land surface is limestone or other carbonate rock, salt beds, or in other soluble rocks, such as gypsum, that can be dissolved naturally by circulating ground water. Sinkholes also occur in sandstone and quartzite terrains. As the rock dissolves,
Dersios sinkhole Dersios sinkhole The Dersios sinkhole (Greek: Σπηλαιοκαταβόθρα "Ο Δέρσιος" "Spilaiokatavothra "O Dhersios"") is a sinkhole in Arcadia, Greece. The sinkhole, which has a depth of , has been known since antiquity and is located towards the north end of the plateau of Palaiochora at a height of 750 m above sea level on mount Parnon. It is about 45 minutes on unsurfaced road from the nearest town of Tyros in the Kynouria region of Arcadia. The sinkhole was first explored in August 1974 to a depth of by a French team (in collaboration with the Hellenic Speleological Society). Since 2003,