The layer of Earth between the crust and the core, composed of silicates of iron and magnesium. The mantle has an average density of about 4.5 g/cm^3 and accounts for about 68% of Earth's mass.

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

Answer: (B)

The layer between the crust and the core is the mantle. It’s made mainly of silicate minerals rich in magnesium and iron, such as peridotite, giving it a mid-range density around 4.5 g/cm^3. That density sits between the lighter crust and the much denser core, and the mantle accounts for a large portion of Earth’s mass—about 68%—because it has a huge volume and is composed of these moderately dense rocks. The crust is the outer, less-dense shell, while the core is metal-rich and much denser overall; the outer core specifically is the liquid portion of the core, not the mantle.