Downward motion of the Earth's surface relative to a datum (e.g. the sea level). Subsidence is the motion of the Earth's surface as it shifts downward relative to a datum (e.g. the sea level). Subsidence (dry) can be the result of: geological faulting, isostatic rebound, human impact (e.g. mining, extraction of natural gas) etc. Subsidence (wet) can be the result of: karst, changes in soil water saturation, permafrost degradation (thermokarst) etc