Question

Why do geologists think Earth's core contains mostly iron?

A. The crust also contains mostly iron.
B. The entire core is a solid mass.
C. Iron is the lightest element.
D. Comets contain more iron than Earth's crust does.

Answer 1

Geologists believe Earth's core contains mostly iron because the density differences between Earth's layers and the overall planet suggest a denser core. Metallic meteorites and the generation of Earth's magnetic field also support this composition.

Step-by-step explanation:

Geologists think Earth's core contains mostly iron because the density of Earth's surface layers is much less than the overall density of the planet. The calculations made from the planet's rotation suggest that if the surface layers are less dense, the core must be denser to account for the average density of Earth. This leads to the conclusion that the core is about 85% iron metal, with nickel making up much of the remaining 15%.

Supporting this, metallic meteorites, which are thought to represent the core's composition, also have an iron to nickel ratio similar to what is expected in the core. Furthermore, Earth's generation of a global magnetic field suggests a metallic core since such a magnetic field is created by the movement of molten iron in the outer core. The sinking of denser materials like iron to the center during the planet's molten phase due to gravity further emphasizes the presence of iron in the core.