The innermost layer of the Earth is a solid ball made primarily of iron. Which description correctly identifies it?

The innermost layer of the Earth is a solid ball made primarily of iron. Which description correctly identifies it?

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

Answer: (D)

Earth has a solid iron ball at the very center, surrounded by layers with different properties. This central solid sphere is the inner core. It stays solid because the immense pressures at Earth's center keep the iron-nickel alloy rigid, even as the rest of the planet is much hotter. Around the inner core is a liquid layer of iron and nickel—the outer core—which moves in convection currents and generates Earth’s magnetic field. Outside that is the mantle, made of rocky silicate material, and the outermost crust, also rocky. So, a description that points to a solid iron ball at the center correctly identifies the inner core.

Earth has a solid iron ball at the very center, surrounded by layers with different properties. This central solid sphere is the inner core. It stays solid because the immense pressures at Earth's center keep the iron-nickel alloy rigid, even as the rest of the planet is much hotter. Around the inner core is a liquid layer of iron and nickel—the outer core—which moves in convection currents and generates Earth’s magnetic field. Outside that is the mantle, made of rocky silicate material, and the outermost crust, also rocky. So, a description that points to a solid iron ball at the center correctly identifies the inner core.