Are you feeling depressed by sinkholes?

When a large sinkhole appeared without warning in the parking lot at the Burlington Mall in Massachusetts earlier this year, it served as a timely reminder that sinkholes can represent a significant hazard to both people and property. In this case, the sinkhole almost swallowed a car.  Thankfully catastrophic sinkholes are rare.

A sinkhole can be defined as any sudden depression in the earth caused when surface sediment subsides into an underground cavern. Natural sinkholes are caused by the erosion of soluble rock formations such as limestone, gypsum, or salt. They can form after a period of prolonged heavy rain or flooding, or following a drought which has lowered the local water table. However, sinkholes can also be caused by abandoned septic tanks, the decay of buried organic material (such as trash), collapsed mines, and by large-scale suburban housing construction.