The Missouri Sinkhole

Sinkholes are not really too uncommon, but a sudden collapse like this one is not often observed. Most of them probably do start with a relatively quick appearance at the surface, but the real concern is the continuing growth of a hole once it's appeared at the surface - which may continue for years.

In addition to the underground erosion by natural processes, there are a number of "famous" sinkholes that have eaten entire towns in mining regions, where the mineshafts have begun to collapse after mines were abandoned.

John