In the last few years, news of unexpected sinkholes swallowing cars, houses and people have made headlines with disturbingly high frequency. These reports are mainly coming from Florida, the U.S., where almost the entire state is karst terrain (made of limestone), which means it has the potential for sinkholes. Mexico, Belize and parts of Italy and China are also karst area, but the phenomenon of sinkholes suddenly appearing in apparently stable grounds is mostly American. Experts estimate thousands of sinkholes form every year in Florida alone.

Sinkholes form when water flowing underground has dissolved rock, mostly limestone and sometimes clay, below the surface, leading to the formation of underground voids.When the surface layer can no longer take the weight of whatever that’s above, it collapses into the void forming sinkholes. These sinkholes can be dramatic, because the surface land usually stays intact until there is not enough support. Then, a sudden collapse of the land surface can occur.

Here are some incredible sinkholes that made news over the years.

A giant sinkhole caused by the rains of Tropical Storm Agatha is seen in Guatemala City on May 31, 2010. More than 94,000 people were evacuated as the storm buried homes under mud, swept away a highway bridge near Guatemala City and opened up sinkholes in the capital. (Casa Presidencial / Handout / Reuters)