A man was swallowed by a sinkhole in Cẩm Phả City in Quảng Ninh Province, northern Vietnam, on Thursday 5 April 2018. Hoang Quoc Hoan, 31, was standing on a paved area outside his home at about 7.30 pm local time, when a hole opened up beneath him, engulfing him and two motorbikes parked nearby. Prompt action by neighbours enabled him to escape from the hole, which was about ten metres across and four metres deep, with only a small injury to his arm, but neither of the motorbikes was recovered, and an excavator sent to help with the rescue was also swallowed.
The scene of a sinkhole that swallowed a man in Cẩm Phả City, Vietnam, on 5 April 2018, now partially filled in. Minh Cuong/VN Express.
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.
Northern Vietnam is particularly prone to such sinkhole events, as it is covered by a series of karst (limestone) plateaus, from where rivers drain into the lowlands. As the limestone is both soft and porous, much of the water sinks into it, permeating through the rock and excavating caves through which the water flows. If these caves come to close to the surface, then the ground above can collapse into the cave, creating a sinkhole at the surface.
A diagrammatic representation of how sinkholes and caves form in karst landscapes. Wisconsin Geological and Natural History Survey.
Follow Sciency Thoughts on Facebook.