iron catastrophe

The iron catastrophe was an event early in the History of Earth when dense iron sank towards the core during the formation of the Earth. The sinking of large amounts of iron towards the core released large amounts of energy in the form of heat. The sinking of denser materials, such as iron, results in the layered Earth we have today with a hot core and mantle and a cold crust.
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The sequence of events resulting in the separation of the Earth's matter into concentric zones of differing densities. This sequence began when the temperature of the Earth at depths of 400 to 800 kilometers below the surface rose to the melting point of iron. Molten iron then gravitated toward the Earth's center, and its movement raised the Earth's temperature to approximately 20,000 C. This led other substances to start melting. The densest matter then sank toward the Earth's center, while lighter matter rose toward the surface. The iron catastrophe took place between a few hundred million and one billion years after the Earth formed.