isostasy

1. (geology) The state of balance or pressure equilibrium thought to exist within the Earth's crust, whereby the upper lithosphere floats on denser magma beneath.Examples: "The process of vertical movement, known as isostasy, was a foundation of geological belief for generations, though no-one had any really good theories as to how or why it happened."; "A great thickness of comparatively light sedimentary rocks accumulating in a geosyncline would ultimately ‘rebound’ because of isostasy – like a depressed rubber duck bouncing back upwards in a bath."; "When a continent carries an ice sheet, the weight of that sheet distorts the equilibrium, the isostasy that causes the crust to float as it does."uncountableusually