Magma ocean
Magma oceans exist during periods of Earth's or any planet's accretion when the planet is completely or partly molten. In the early solar system, energy to melt objects came largely from the decay of radioactive aluminum-26. As planets grew larger, the energy was supplied from large or giant impacts. During its formation, the Earth likely suffered a series of magma oceans resulting from giant impacts, the final one being the Moon-forming impact.
Magma oceans are integral parts of planetary formation as they facilitate formation of a core through metal segregation and an atmosphere and hydrosphere through degassing. Magma oceans may survive for millions to tens of millions of years, interspersed by relatively clement conditions.
Magma oceans are widely accepted to have existed on Earth, and the best chemical evidence for them is the abundance of certain siderophile elements in the mantle that record magma ocean depths of approximately 1000 km during accretion. A magma ocean also occurred on the Moon during and following its formation.
