What is the primary cause of land subsidence?

The primary cause of land subsidence is groundwater withdrawal. When water is extracted from underground aquifers, it reduces the pressure that supports the soil and rock layers above it. This pressure decrease can lead to the collapse of these layers, causing the ground to sink or subside over time. This process is particularly pronounced in areas that rely heavily on groundwater for irrigation, drinking water, and industrial uses.

In contrast, heavy rainfall may lead to temporary flooding or saturated soils but does not typically cause long-term subsidence since it usually replenishes groundwater levels. Soil erosion is related to the removal of soil surface layers, which can impact the landscape but does not directly cause subsidence in the same way that groundwater withdrawal does. Tectonic activity is associated with the movement of the Earth's plates and can cause gradual shifting and subsidence, but it is not the primary cause of subsidence in urban or agricultural areas where groundwater extraction is prevalent.