Why are there unknown craters all over the world recently? Thank god, help me.

Why are there so many sinkholes everywhere:/html/html/huazhuangjiqiao/16646.htmlPossible reasons: First, the limestone layer should be relatively thick. Only rocks thick enough can provide enough space for the formation of sinkholes. Second, the water level of the underground river is very deep. Third, the vadose zone (gas-bearing rock) is thick. Fourth, the rainfall should be large, so that the flow and strength of the underground river can be large enough to wash away the fallen stones. Fifth, the rock formation should be flat. From the cliff around the sinkhole, you will find that the rock layer is parallel to the ground, just like layers of stone slabs piled around, and only such rock layers can collapse. Sixth, the earth's crust should protrude. The movement of the earth's crust provides power for the collapse of rock strata. That's probably why.