What layer of the Earth is primarily composed of iron and nickel?

The layer of the Earth primarily composed of iron and nickel is the outer core. This layer lies beneath the mantle and surrounds the inner core. The outer core is in a liquid state, and its movement generates Earth’s magnetic field through the geodynamo process. The composition of the outer core consists mainly of molten iron and nickel, which contributes to its distinctive properties.

The crust is the outermost layer, made primarily of lighter silicate materials. The mantle, located beneath the crust, is composed mainly of silicate rocks that include minerals rich in magnesium and iron, but it is not predominantly made up of iron and nickel like the outer core. The inner core, while also composed mainly of iron and nickel, is solid due to the immense pressures at that depth, distinguishing it from the liquid nature of the outer core. Therefore, the outer core is correctly identified as primarily consisting of iron and nickel.