Land subsidence is the lowering of the land-surface elevation from changes that take place underground. Common causes of land subsidence from human activity are pumping water, oil, and gas from underground reservoirs; dissolution of limestone aquifers (sinkholes); collapse of underground mines; drainage of organic soils; and initial wetting of dry soils.

Tips:

 ·Refill the cave-ins produced by subsidence to protect surrounding buildings.
 ·Block the cave-ins to prevent water from flooding in. 
 ·Buildings with fissures resulting from subsidence should be sealed off. Proper measurements should be determined only after the safety of the buildings is evaluated.
 ·The shepherds and herb collectors should not risk entering areas affected by subsidence. 

Suggestions:

 ·During flood seasons, residents in mining areas should watch out for any deformation or fissure of the earth around the house. 
 ·If there are massive rainwater sinking rapidly down into the ground, evacuate immediately and report to the relevant government agencies.