Friday 11 November 2016

Seven homes evacuated after sinkhole opens in Ripon, North Yorkshire.

Seven homes have been evacuated after a sinkhole opened in gardens behind them in Ripon in North Yorkshire, England, on Wednesday 9 November 2016. The hole, which measures approximately 20 m by 10 m and is thought to be about 9 m deep was reported to the North Yorkshire Fire Brigade after residents felt the ground moving and investigated. Nobody has been injured due to this incident, but the homes have been evacuated as a precaution, while engineers attempt to make the houses structurally secure.

The scene of the November 2016 Ripon sinkhole. BBC.

Sinkholes are generally caused by water eroding soft limestone or unconsolidated deposits from beneath, causing a hole that works its way upwards and eventually opening spectacularly at the surface. Where there are unconsolidated deposits at the surface they can infill from the sides, apparently swallowing objects at the surface, including people, without trace.

Ripon is prone to sinkholes due to sinkholes due to Permian gypsum deposits which underlie much of the area. It is an evaporate rock, a form of calcium sulphate deposited as mineral-rich water evaporates, often around sulphurous hot springs or volcanic systems. Gypsum is a very soft rock, and soluble in water, so moisture entering gypsum deposits can cause major collapses and subsidence.

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