Friday 23 March 2018

Sinkholes swallow car and undermine building in the Centurian area of Gauteng Province, South Africa.

A series of sinkholes have opened up in the Centurian area of Gauteng Province, South Africa (between Pretoria and Midrand), following heavy rains in the area. In Valhala, on Friday 23 March 2017, Mpho Borodi, 30, drove into a sinkhole on an unlit road while on his way to work, while a second driver, had her car trapped as a sinkhole opened up beneath it. In Lyttelton a commercial building was partially undermined by another sinkhole, though the Tshwane Metro Geology Department had apparently previously warned that the building was at risk, while in Makause a number of families have been forced to evacuate their homes due to a nearby sinkhole which has put them at risk.

Car trapped in a sinkhole in Valhala, Gauteng, on 23 March 2018. Centurian Rekord.

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.

 Building undermined by a sinkhole in Lyttleton, Gauteng, on 22 March 2018. Centurian Rekord.

On this occasion the sinkholes have been linked to heavy rains in the area, with over 120 mm of rain recorded in Pretoria in 24 hours, which has caused a series of flash floods in Centurian, Pretoria, Johannesburg and neighbouring parts of Gauteng‚ KwaZulu-Natal and the Free State Provinces. The immediate causes of the sinkholes have not yet been determined, but it is thought that in several cases soft sediment beneath roads has been swept away after storm drains became blocked by vegetation and other debris causing water to escape into the surrounding deposits.

Flash flood in Bryanston, Gauteng, on 23 March 2018. Eyewitness News.

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