And we have no way to detect them.

Read More:

Sinkhole Swallows Sleeping Man In Florida
m.npr.org/news/front/173225027?start=25
-There's a terrifying story from Florida this morning.

Sinkhole, Landslides Wreak Havoc in Guatemala: Big Pics
news.discovery.com/earth/weather-extreme-events/guatemala-sinkhole.htm
-In downtown Guatemala City, the rains opened an enormous sinkhole 66 feet across and 100 feet deep on Saturday that swallowed a clothing factory and a city intersection.

Brother Tries to Save Man After Massive Sinkhole Swallows Florida Bedroom
foxnews.com/us/2013/03/01/florida-man-swallowed-by-massive-sinkhole-in-bedroom/?test=latestnews#ixzz2MK6lZ99F
-A Florida man screamed for help and disappeared as a large sinkhole opened under the bedroom of a house, his brother said Friday.