Tuesday 6 November 2018

Flats evacuated after sinkhole opens close to residential block in St Albans, England.

All the residents of a twenty one flat residential block in St Albans, England, have been evacuated after a sinkhole opened up next to an external wall on Tuesday 6 November 2018. Emergency services were called to the building after a member of the public noticed the hole, which is about six metres across and about three metres deep, at about 5.50 GMT, and at 6.45 the decision was taken to evacuate the building. The residents have been warned to expect to be out of the property for at least two weeks.

Sinkhole adjacent to a residential building in St Albans, England, on 6 November 2018. Hertfordshire Fire and Rescue.

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.

he approximate location of the 6 November 2018 St Albans sinkhole. Google Maps.

The precise cause of this particular sinkhole is unclear, but similar holes in the same area in the past have been linked to old old chalk mines. Chalk is a particularly soft form of limestone, and particularly prone to dissolution in water, and the old mineworkings provide both a conduit through which water can flow, and a series of voids into which groundfalls can subside should any further dissolution occur.

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