Over time, Earth's interior—which is made mostly of silicate rocks and metals—differentiated into four layers. At the planet's heart lies the inner core, a solid sphere of iron and nickel that ...

By the time of the moon-forming impact, the Earth was already separated into these rock and metal layers. However, the intense force and heat of the impact re-melted the proto-Earth, re-mixing the ...

The Earth's interior is composed of four layers, three solid and one liquid—not magma but molten metal, nearly as hot as the surface of the sun. The deepest layer is a solid iron ball ...