PLATE MOTIONS AND PLANETARY EVOLUTION

PLATE MOTIONS RESULT FROM THE EARTH'S CONTINUING EVOLUTION OR DIFFERENTIATION FROM AN INITALLY UNIFORM PLANET TO A LAYERED PLANET

THIS PROCESS INVOLVES THE VERTICAL MOVEMENT OF HEAT AND MATERIAL THROUGH TIME

THE PLATES - OR LITHOSPHERE - ARE THE COLD, STRONG OUTER BOUNDARY LAYER ("thin scum": 100 / 6371 km)

PLATE TECTONICS CAUSES VOLCANISM, WHICH PRODUCES

GASSES (carbon dioxide CO2 ; water H2O) IN ATMOSPHERE NEEED TO SUPPORT LIFE AND KEEP PLANET WARM ("GREENHOUSE" )