1. The state of equilibrium of the Earth's crust, in which the weight of continental and oceanic masses is balanced by the buoyancy of the underlying mantle.
Usage: geology; also spelled isostasy

Examples

• The principle of isostacy explains why mountains float on the mantle like icebergs on water.
• Geologists use isostacy to understand how the Earth's crust adjusts after the melting of glaciers.
• Isostacy predicts that regions with thick continental crust will be elevated above sea level.
• The concept of isostacy is fundamental to plate tectonics and crustal dynamics.
• When a heavy ice sheet melts, isostacy causes the underlying land to gradually rise in a process called rebound.