Humans may use their hands or machines, but nature just uses erosion, volcanic explosions, or even tectonic shifts! A couple of examples from a top ten holes list.
Bingham Canyon Mine, Utah. Source: Tim Jarrett
The world’s largest man-made excavation - a copper mine in the USA. It’s 0.75 miles/1.2 km deep and 2.5 miles/4 km wide.
Blue Hole, Lighthouse Reef, Belize. Source: neatorama.com
Once an opening to a cave system during the Ice Age, the Blue Hole, Belize reef is 1,000 feet/305 m across and 400 feet/123 m wide deep.
“For all the practical purposes the over 400-foot depth makes the Blue Hole a bottomless pit. The walls are sheer from the surface until a depth of approximately 110 feet where you will begin to encounter stalactite formtions which actually angle back, allowing you to dive underneath monstrous overhangs.” [Quoted from neatorama.com]
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