Mantle thickness and composition?

• A. A rock layer around 2850 km thick that reaches half the distance to the centre
• B. A molten iron core surrounding the mantle
• C. A hollow layer with air
• D. A thick layer of ice

Answer: (A)

Think of Earth's interior as concentric shells. The mantle is the thick, rocky middle layer between the crust above and the core below, about 2,850 km thick, reaching roughly halfway to the center of the planet. Its composition is silicate rocks rich in magnesium and iron, not molten metal or ice. The idea that a molten iron core surrounds the mantle is reversed—the core lies beneath the mantle. A hollow layer with air or a thick layer of ice would not describe Earth's internal structure.