An illustration of Earth as it existed during part of its formation billions of years ago, when an ocean of magma covered the surface of the planet and stretched thousands of miles deep into the core.

Shortly after it formed, the Moon was covered in a global ocean of molten rock (magma). As the magma ocean cooled and solidified, dense minerals sank to form the mantle layer, while less-dense ...

Early in the formation of Earth, an ocean of magma covered the planet’s surface and stretched thousands of miles deep into its core. The rate at which that “magma ocean” cooled affected the formation ...