Early Earth began to heat as the last extraterrestrial collisions subsided 1.Rock is a good insulator – stores heat 2.Collisions produced heat that was stored 3.Radioactivity 4.Gravitational contraction Early in Earth History the Planet Developed a Magma Sea 4.5-4.0 billion years ago What is the physical consequence of melting a homogeneous ball of rock?
Temperature reached melting point of iron: Liquid iron flowed inward Friction raised temperature Liquid Silicon and Oxygen flowed outward (Ca/Na/Al/K) “Iron Catastrophe” Planet became chemically differentiated
Earth’s magnetic field emanates from the core complex and surrounds the planet. Magnetism gained from early nebula is magnified by turbulent iron, nickel fluid of outer core. Magnetic field envelops entire planet Polarity + - tends to reverse and fluctuate with time