1. the state of balance or equilibrium which sections of the earth's crust are thought ultimately to achieve when the vertical forces upon them remain unchanged.
2. the quality or state of being subjected to equal pressure from every side.
Etymology: Coined in 1889 by geologist Clarence Dutton, from Greek iso (same) + statis (setting, weighing, standing).
This balance is similar to what one might see with a floating iceberg: if more ice is added to the iceberg, it sinks to its new state of equilibrium. Isostasy is a useful tool for explaining height differences on the Earth's surface, although it does not explain everything (for example, mountain ranges that continue to rise due to other pressures).