True sinkholes form in karst terrines. But the 2007 sinkhole actually formed in volcanic ash and debris deposits called piping pseudokarst. The "sinkhole" opened up on February 25, 2007 swallowing 3 people along with about a dozen homes. The hole was more than 200 ft. deep.
2007 Guatemala City sinkhole
The 2007 Guatemala City sinkhole is a 100-metre deep sinkhole which formed in Guatemala City in 2007, due to sewage pipe ruptures. Its collapse caused the deaths of five people, and the evacuation of over a thousand.