Long-Term Eustasy and Epeirogeny

Abstract

The major cause of change in the Earth’s crust is the radiogenic heat engine, which drives mantle convection and generates the geomagnetic field. Convection distributes heat and drives plate tectonics. Oceanic and continental crust are subject to heating close to sea-floor spreading centres where new, hot, oceanic crust is generated (causing “ridge push”), and to cooling overlying subduction zones, where cold oceanic crust descends to the mantle (generating “subduction pull”). Widespread cooling and subsidence occur over the downwelling zones where continental fragments converge. The same cooling and subsidence occur above old, cold, downgoing oceanic slabs in subduction zones, and partial melting of the water-saturated rocks as they descend in the subduction zone is what generates arc magmatism. The differential heat distribution and consequent heating and cooling of different parts of the overlying Earth’s surface results in broad regional uplifts, downwarps and tilts, because of the effects on crustal densities.