Cavers love them, as do divers when they fill with water. Many occur naturally where Limestone is present, and are caused by underground water erosion. They also occur when we pump too much water from the water table, if there is leakage from man made water supply and sewage pipes, or as a result of deep mining.
They are a threat to homes and cities and also become a threat to water supplies if they fill up with water from rain. We sometimes use them as landfill, so worsening the effects of them filling with rainwater which then seeps into the water table we rely on so much for fresh supplies.
Sink holes vary in size, and can increase in size, a particularly bad trait if they occur in a city. This little beauty recently appeared in Guatemala City. It is said to be some 330 feet deep, twice as deep as the Statue of Liberty is tall. One has to wonder how the City authorities will deal with it. Worse still, will it increase in size? More could appear.
It is said that one hears rumbling before a sink hole creation. I would imagine that it is difficult to tell exactly where a sink hole will appear. One thing is sure, the people of Guatemala City will have to be very careful.