1. ITV Report

Ripon sinkhole: Expert explains what caused the 50ft hole

The sink hole "with an unknown depth" which appeared in gardens in Ripon, North Yorkshire. Photo: PA

Investigations are continuing after a 50-foot sinkhole opened up in North Yorkshire. It happened in the back gardens of a row of terraced houses on Magdelen's Road, in Ripon.

Residents have now been moved out of 12 properties after the giant sinkhole, measuring more than 20 metres wide and 10 metres deep, appeared there on Wednesday 9th.

Surveyors spent the morning at Magdalen's Road deciding whether it's safe for any of the householders to return home. A further five homes were evacuated today.

Experts say it's down to a type of rock in the area called Gypsum:

It's quite a soft rock called Gypsum and that is susceptible to dissolution or the creation of caves or voids within it as a result of ground water flow.

– Dr Jean Hall, Newcastle University

What is Gypsum?

Gypsum is a soft white or grey mineral consisting of hydrated calcium sulphate. It's highly soluble and dissolves very quickly.

It is found in layers that were formed under salt water millions of years ago. The water evaporated and left the mineral.

Are sinkholes common in Ripon?

They are relatively common in Ripon and are usually caused by the dissolution of thick gypsum deposits beneath the area.

After the 2014 partial house collapse, the British Geological Survey (BGS) said gypsum under the town had dissolved to form a maze-like cave system.

It said in a report that sinkholes appeared in Ripon every two or three years in the 1980s and 1990s but there had not been any reported in the seven years before the 2014 event.

The BGS said there were a number of possible triggering mechanisms, relating to action of water underground.

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