Squeezing iron into the core after the Earth formed

Cornell

Our planet’s interior is complex and has many layers. There are many unsolved mysteries about the formation and structure of these layers, but new research is providing some clues about how Earth’s internal structure may have evolved.

If you were to take a journey to the center of the Earth, you would find that most material there is made of just three elements, at least until you get to around 3000 km below the surface. These elements—oxygen, silicon, and magnesium (plus a little bit of iron)—make up more than 90% of Earth’s “ceramic” mantle. Electrically and thermally insulating, the minerals of the mantle are the stony part of the planet.

But as you go deeper, things suddenly change. About midway to the center, you cross a boundary from the stony mantle into the metallic core, initially liquid in its upper stretches, and then solid right in the center of the Earth. The chemistry changes, too, with almost all of the core being composed of iron.