Figure 15.12

Collapse sinkhole formation. (A) The process of limestone weathering that leads to a collapse sinkhole can take thousands of years or more, but the collapse event happens in a matter of minutes after the ceiling of a subterranean cavern gives way. (B) The world’s largest collapse sinkhole, China’s Xiaozhai Tiankeng, located in Chongqing municipality, is a double collapse sinkhole 662 m (2,172 ft) deep. The larger depression formed first. The interior sinkhole formed later.

(B. Courtesy of John Gunn, University of Birmingham)