isostasy

noun

1. (uncountable, usually)The state of balance or pressure equilibrium thought to exist within the Earth's crust, whereby the upper lithosphere floats on denser magma beneath.

   “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.”