Land Subsidence

What is land subsidence? 

Subsidence is the motion of a surface (usually the Earth's surface) as it shifts downward relative to a datum such as sea-level. 





Generally land subsidence often occurs when large amount of groundwater/petroleum are pumped out or when an earthquake causes closer repacking of sediment grain. It occurs when ground settles as result of changes in fluid levels underground. 




Subsidence occurs at large regions and its effects are less obvious than sinkholes. Coastal area – subsidence can sink communities closer to the sea level & exposed to flooding. Could caused by human activities; extraction of groundwater, drainage of organic/clay-rich soils and thawing.