Sinkholes: The Hidden, Deadly Physics of Cave-Ins

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CBS News via YouTube

Mention the word “sinkhole,” and most people probably start thinking of potholes. But the video footage coming in from St. Jude, Quebec, where a farmhouse was swallowed by the Earth on Tuesday, suggests something far larger in scale.

The ground gave way, and four family members – who were reportedly in the basement – went down with the house. Toronto’s CP24 reported fatalities.

Here’s a quick word on the how of it all: Sinkholes typically occur where the surface rock is comprised of limestone, salt beds, carbonate rock or other material that can naturally be dissolved by the ground water coursing underground. It’s this water that slowly chips away at the underground foundation, slowly eroding and destabilizing the bedrock, creating new hidden caves that eventually give way in violent episodes.

Sinkholes occur both naturally and as a result of human behavior. The building of streets and highways can often cause changes to water run-off. With new residential developments – where ground water is being pumped up from below – or with new industrial developments, where run-off changes course and water patterns are altered, erosion can ensue. That said, sinkholes will always vary in size and location – and in the case of the Canadian farmhouse, it would appear that this was simply a house built at just the wrong spot, and that the family was home at just the wrong time.

The world’s biggest sinkhole is believed to be the Great Blue Hole off the coast of Belize. In this instance, a limsetone cave system collapsed as the oceans rose, leaving a 300-meter wide, 125-meter deep feature some 60 miles from the coast of Belize.

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