Land subsidence occurs when large amounts of ground water have been withdrawn from certain types of rocks, such as fine-grained sediments. The rock compacts because the water is partly responsible for holding the ground up. When the water is withdrawn, the rocks falls in on itself. You may not notice land subsidence too much because it can occur over large areas rather than in a small spot, like a sinkhole. That doesn't mean that subsidence is not a big event

Mostly underground and out of sight, the effects of groundwater over-pumping and declining water tables are difficult for many people to envision, much less conceptualize. The most apparent and tangible manifestation of excessive groundwater pumping seems to be the political and public policy debates the issue provokes.

With the increasing occurrence of land subsidence and resultant earth fissures in certain areas of the state, the consequences of dropping water tables become distinct, physical and sometimes dramatically visible. Land subsidence and fissuring provide tangible evidence that the over withdrawal of groundwater has geological as well as public policy consequences.