Which layer is composed primarily of liquid nickel and iron?

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

Answer: (C)

The outer core is the layer that is liquid and composed primarily of iron with nickel. In Earth’s interior, temperatures are hot enough to melt iron-nickel, but the pressures are not so extreme as to keep it solid at that depth. That combination creates a molten metal shell surrounding the solid inner core. The crust and mantle are rocky silicates, not metals, and the inner core remains solid because the pressures there are immense enough to keep the metal crystalline despite the high temperature. The liquid iron-nickel in the outer core also drives the magnetic field through convective currents.