On March 3, a large sinkhole appeared in a fish pond in Sangzi Town, Loudi City, Hunan Province. The owner of the pond claimed that over 200 catties of carp were raised in the pond, but within minutes, all the water and fish disappeared.
The video released by the media showed a large hole in the nearly dried-up fish pond. Mr. Wu, the pond owner, stated that he originally had over 200 catties of carp in the pond. The collapse occurred on the afternoon of the 3rd, “the water was still full when I was cooking lunch, but within a few minutes, the water dried up.”
According to a report by Red Star News, Mr. Huang, an investigator from the Water Hydrology and Geological Center of the Hunan Provincial Institute of Natural Resources, stated that the incident took place in Dashu Community, Sangzi Town. The hole formed by the collapse has a diameter of about 3 meters and a depth of approximately 1 meter, with water in it. It is initially speculated to be a collapse caused by karst.
Mr. Huang learned from the pond owner that a similar collapse had occurred two to three decades ago about 30 meters away from this fish pond, “at that time, it was a piece of farmland growing rice with water puddles.”
“But there are various factors that trigger collapses,” Mr. Huang said, noting that apart from the weak surface layer, the movement of underground water can also trigger surface collapse. Due to recent rainfall, the loss of underground water leads to the formation of a vacuum underground, resulting in greater pressure on the ground, causing it to collapse, “it’s like sucking a mineral water bottle hard until it shrinks.”
Mr. Huang analyzed that the geological formation of the pond belongs to the Permian Maokou Formation Limestone, which poses a risk of collapse, “but not all areas with this type of formation will necessarily collapse. If there is solid rock underneath the surface and the land itself is thicker, the collapse will not occur.”