During its formation, the Earth likely suffered a series of magma oceans resulting from giant impacts, the final one being the Moon-forming impact. The best chemical evidence for the existence of magma oceans on Earth is the abundance of certain siderophile elements in the mantle that record magma ocean depths of approximately 1000 km during accretion. The scientific evidence to support the existence of magma oceans on early Earth is not as developed as the evidence for the Moon because of the recycling of the Earth's crust and mixing of the mantle. Unlike Earth, indications of a magma ocean on the Moon such as the flotation crust, elemental components in rocks, and KREEP have been preserved throughout its lifetime.
Today Earths outer core is a liquid layer about  thick, composed mostly of molten iron and molten nickel that lies above Earths solid inner core and below its mantle. This layer may be considered as an ocean of molten iron and nickel inside Earth.