Guatemala Sinkhole, 2010
In the strictly geologic use of the word, a sinkhole happens when water erodes solid bedrock, carving an underground cavity that can then collapse. Many parts of the United States are at risk for that type of event.
The Guatemala sinkhole fits into a broader use of the term, which refers to any sudden slump of the ground's surface. Instead of solid bedrock, much of Guatemala City rests atop a layer of loose, gravelly volcanic pumice that is hundreds of feet thick. And at least one geologist says leaking pipes—not nature—created the recent sinkhole.
Overall, the risk for repeat sinkholes in Guatemala City is high—but highly unpredictable.