ABSTRACT
Plate tectonics perpetuates the geological distillation and fractionation of planetary raw materials which began as the planets condensed from interstellar gases and led to the formation of Earth's six concentric geospheres. All planetary processes require energy, and Earth has five sources of energy intimately linked with the formation and operation of our solar system. Earth's large mass centred around a dense core provides the primary, endogenetic source of gravity for most geological processes but the gravitational fields of our sun and moon influence astrogeological and some surface (especially tidal) processes. The Earth science revolution after 1960 confirmed that sea-floor spreading is the mechanism driving plate tectonics, through the convection of new crust from the asthenosphere. Earth is of almost unimaginable age and yet its modern character and geological processes can be traced directly to its astronomic origins. Continental lithosphere – a ‘penultimate silicate froth’ containing, additionally, some of Earth's least common elements – is the descendant of Archaean crust.
