What is a sinkhole?

After this weeks news that a man was swallowed up by the ground whilst sleeping in his bedroom, there is a lot of questions on how and why this has happened and how dangerous these sinkholes actually are! So here is a short blog on how these form, their occurrences and why they form.

News from Florida where the man is presumed to be dead states that the furniture in the bedroom and the concrete floor had all been swallowed up. The house is currently being demolished as it is too dangerous to go into and it is thought that the sinkhole could swallow up the home. A huge perimeter has been set up around surrounding property in case the hole opened further. The soil around the property was said to be very loose.

A special type of sinkhole, formed by rainwater leaking through the pavement and carrying soil into a ruptured sewer pipe.

 

So a sinkhole is a natural depression on the Earths surface caused by dissolution of carbonate rocks from groundwater or suffusion of sandstone type rocks were loose soil or sediment can slip into fractures and cracks in the rock. They can also be caused by cave collapses and subterranean water pathways. They can vary in size from a metre to 600 metres and can occur slowly or quickly. Erosion and removal of bedrock can result in the soil forming sinkholes and are affected by the position of the water table. Therefore they are more common in areas with a bedrock that is carbonate or sandstone in nature. Human influences can also be a cause, which include collapsing mines, sewers or water main pipes.

They are common in the USA and parts of Italy but can occur in many different places. Some that occur in the UK in areas such as the Yorkshire Dales occur due to glacial till washing into the underlying limestone.

This sinkhole in Guatemala 2010 appeared after a tropical storm, engulfing a house and three story building. This one was 18m and 60m deep, this one caused by a leaking sewer and the very soft volcanic material that the urban areas are on.

 

The strange thing about the recent sinkhole in which a man died is that it has occurred within a building and that there has been a fatality!