Sinkholes are formed when a portion of the bedrock below a void has collapsed. A sink can be a narrow, vertical opening leading to a cave or a depression that covers several acres. Natural bridges are voids beneath still-standing rock that are more likely to be filled by air. A polje is a large depression that often has an intermittent stream of water.
A cave may be filled with air by tectonic uplift. The increased surface altitude of the South Island limits the surface altitude change above the caves at Mount Arthur to a few tens of metres. This is due to the caves’ low elevation. But, it is possible to observe air movement in a cave filled with a relatively large amount of air, suggesting that tectonic uplift may help in filling a cave with a sufficient volume of air.
Tectonic uplift, on the other hand, is a result of tectonic plate collisions. It raises buried rocks to the surface. This causes large amounts of earth’s crust to be redistributed. It can also encourage the isostatic reaction, which can lead to local bedrock elevation. Geologists estimate how fast and how high the rates of uplift are based on these processes.
The tectonic uplift of the Alps and the Villefranche gorge in France have both contributed to the formation of the terraced network of epiphreatic cave levels. The limestone gorge’s terraced network of epiphreatic caverns is a result of tectonic uplift. It is also responsible for the existence of the valley floor in Villefranche.