What caused a massive 656-foot sinkhole to open up in Chile?

Chile’s National Geology and Mining Service have begun an exhaustive investigation into a massive sinkhole which appeared in the Tierra Amarilla region of the country last Saturday. The round sinkhole is 100 metres wide and has been getting bigger over the past few days. Authorities are not exactly sure how deep the hole is but estimate it could be as much as 64 metres deep or more - approximately the size of as 25-storey block of flats.

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The cavity was discovered near a copper mine in the Atacama desert. The terrain is operated by a Canadian mining company Lundin Mining Corporation, who have run the open-pit Candelaria copper mining complex since 2014. Lundin Mining own 80% of the property while the remaining 20% is in the hands of Japanese firm Sumitomo Corporation.

Tierra Amarilla mayor Cristóbal Zúñiga explained, “It is an enormous sinkhole, of dimensions never seen before. It is close to a housing estate and health centre. It appeared overnight. Tierra Amarilla is a mining community, with many deposits which serve the rest of the country. We have always feared that something like this could happen”.

Why do sinkholes appear?

Authorities believe that the sinkhole is related to the Candelaria copper mining complex. Numerous factors can cause a sinkhole to appear - a sudden decline in water levels through droughts or groundwater pumping (wells, quarries and mines); when large qualitities of earth are disturbed by digging through soil layers, soil removal or drilling; water leaks or pressure from heavy loads on the surface of the ground - buildings or heavy industrial equipment. A lot of the time, it is a combination of factors. A sinkhole left open to take more water may continue to grow and can contribute to the appearance of more sinkholes nearby.

Another theory is that the sinkhole could have been caused by blasting agents such as dynamite, which is in daily use in the Tierra Amarilla area.