Which layer of the Earth is the most dense?

• A. Crust
• B. Mantle
• C. Outer Core
• D. Inner Core

Answer: (D)

The heaviest, most compact material sits at the center because pressure from overlying rocks squeezes the material more and more as you go inward, and the inner core is composed mainly of iron and nickel in a solid state. This combination makes it the densest part of the Earth, with a density around 12 to 13 g/cm³. The outer core is also iron-nickel but is liquid, so while still very dense, its density is slightly lower than the inner core because the liquid state doesn’t pack atoms as tightly as a solid. Moving outward, the mantle is made of rocky silicate minerals and has densities roughly 3 to 5 g/cm³, and the crust is even less dense, about 2.7 to 3.0 g/cm³ for continental crust (and a bit denser for oceanic crust). Therefore, the center hosts the greatest density among Earth’s layers.