Definition of: isostasy

(ī·sos′tə·sē) noun
1. Geol. The theoretical condition of equilibrium which the earth's surface tends to assume under the action of terrestrial gravitation, as affected by the transference of material from regions of denudation to those of deposition, and by differences in density in various portions of the earth's mass near the surface.
2. Equilibrium resulting from equal pressure on all sides. [<ISO- + Gk. stasis a standing still]
—i·so·stat·ic (ī′sə·stat′ik) adjective