Mine-induced subsidence is not unique to China, but its problems dwarf those of other countries.

A notice board at a deserted Communist Party building in an abandoned village not far from Helin gives an idea of the scale of the disaster.

It lists 19 geological "disaster zones" spread across 23 villages, 55 landslides, 950 cracks in the ground and 808 incidents of mine subsidence - all in an area of just 13.25 sq km.

According to official data, coal mining had already caused as many 26,000 geological disasters by the end of 2014. And according to some estimates, as much as 10,000 sq km of land has been affected, an area the size of Gambia in Africa.

REUTERS