May 16. Two large dip in the ground appeared on the back yards of local homes in the province of Ha Tinh. At least one family was evacuated from the area. Sinkhole in Huong Vinh commune has about 7 m deep and 6 m in diameter with small cracks appearing on the surface around the area.
"The failure could be caused by a collapse of underground limestone caves," — said the deputy head of the Department of Environmental Protection, Pan Van Binh. Karst topography — this landscape formed by the layers breaks the basic rocks, usually saturated with carbon dioxide, such as limestone or dolomite, due to the movement of water through the void.
"When wet limestone, the rock formation moves that quickly crumble when torrential rains" — said Binh.
Local resident Le Van Thuong said the night of 3 May, at a time when his family was watching TV, they heard a strange noise coming from their garden.
"To our surprise, we found a deep hole just 4 meters from our kitchen and immediately saw another failure, because of which formed the second hole with a yellow water bubbling out."
Tuong family moved into temporary housing, where they remain to this day because of the threat of yet another failure.
"Limestone — this geological formation with a soft structure, and depletion of groundwater can cause subsidence in the rain," — said Minh.
He added that the dips in the ground have also been found in other areas, such as Lam Dong province in the Central Highlands and Ho Chi Minh City.
The incident was reported to the Ministry of Natural Resources and Environment for the study.