Two homes have been severely damaged and a number of agricultural buildings destroyed after a massive sinkhole opened up in Maoba Village in Qingchuan County in China's Sichuan Province on Friday 13 December 2013. The sinkhole first opened up slightly after midnight, and by about 7.00 pm had reached 60 m in length, 40 m wide and about 30 m deep. The event was preceded by several days of Earth tremors, and though large sinkholes have opened up in the area before, caught local residents largely by surprise. A prompt evacuation when the nature of the sinkhole was realized prevented any loss of human life, though a large number of Chickens are believed to have been swallowed by the hole inside farm buildings.
The Maoba Village sinkhole. Gao Zhinong/Asia News Photo.
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.
The precise cause of this sinkhole has yet to be determined, and it under investigation by the Sichuan Department of Land and Resources. Previous sinkholes in the area have been linked to the erosion of subsurface limestone deposits. Water percolates through the limestone forming extensive cave-systems. When these caves touch the top of the limestone layers unconsolidated sediments above collapse into the resulting voids, creating sinkholes at the surface.
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