1 A progressive depression of the Earth's crust, which allows sediment to accumulate and be preserved. Subsidence is caused by mantle convection and by sediment loading. The subsidence rate will control the proportion of deposited sediment which will be preserved in the subsiding area. Subsidence rates in sedimentary basins typically vary from 0.3 to 2.5 mm per year.
2 Sinking or settling of the ground surface due to natural or anthropogenic causes. Surface material with no free side is displaced vertically downwards with little or no horizontal movement.
3 Local sinking, due to underground mine workings.
4 Downward movement of air, characteristically gentle (1–10cm/s) and often in large anticyclones, which is related to the divergence in lower layers near the ground surface. Subsidence results from radiation cooling or from convergence of air horizontally in the upper troposphere. It typically brings settled weather, with evaporation of cloud drops by adiabatic warming in the subsiding air mass, causing cloudless skies above the friction layer near the surface, so that in winter fog and low cloud may prevail when moisture is sufficient.