The scientists studied how underground mining causes land sinking in China. They measured land movement in an area with coal mining. They found that the ground sinking happens later after the coal is mined. The shape of the land sinking is mainly because of the underground layers. The sinking differs along the length of the coal mining area. The rocks above the coal need to stay solid to keep the land steady. Empty spaces left after coal mining don't help the surface. The land will keep sinking even after coal mining stops. People should be careful when reusing the land above old coal mines to prevent more sinking in the future.