... convergent margin therefore a subduction site. Pacific coast of No-West American What drives Plate Tectonics? Geothermal heat flux - heat escapes to the surface mostly through mantle convection Origin of heat in Earth's interior: 1. Radioactive decay 2. Residual heat from Earth's formation - Radioactive decay: unstable isotopes that spontaneously disintegrate (decay) to a more stable form of a different element. Heat is released - Carbon-14 - half-life is 5730 years. - Potassium, uranium and thorium. E.g. 40K has half-life of 1.24 billion year - Residual heat: associated with heating events during Earth's formation. - Accretion of planetesimals that collided and merged forming large, primitive planet. - Larger collisions probably caused widespread melting of Earth's upper mantle - One collision, with a Mars-sized object is believed to have melted the whole surface of Earth and sent bits and pieces out into orbit which then coalesced into the moon. - Segregation of Earth into less dense mantle and crust and denser core released ...

See this essay or coursework document in full right now