A sinkhole, also known as a swallow hole, shake hole, swallet, or doline, is a depression or hole caused by a collapse of the surface layer of the earth. Sinkholes can range from just one meter (swallowing up a single person walking by on the street) up to hundreds of kilometers, taking out entire cities. They can happen naturally by wind or water erosion, or artificially due to people mining and drilling in unsafe areas.