AFOQT Practice Test

Which layer of the Earth is primarily liquid?

1. Inner core

2. Outer core

3. Asthenosphere

4. Lithosphere

The correct answer is: Outer core

The outer core is primarily liquid and is composed mainly of molten iron and nickel. This layer lies beneath the mantle and surrounds the solid inner core. The movement of the liquid outer core is responsible for generating Earth’s magnetic field through the dynamo effect. In contrast, the inner core is solid due to the immense pressure at that depth, which forces the iron to remain in a solid state despite the high temperatures. The asthenosphere, while it has some partially molten properties, is primarily solid and allows for the movement of tectonic plates. The lithosphere encompasses both the crust and the upper mantle and is also solid. Thus, the outer core stands out as the only primarily liquid layer of the Earth.