The Three Layers of the Earth Quiz

Study Notes

The Earth is made up of multiple layers, including rocky layers and atmospheric layers. This summary focuses on the rocky layers.
The Earth's core consists of a solid inner core and a liquid outer core. Both are primarily composed of iron and nickel.
- Inner core: Extremely hot (over 9000 degrees F) and under immense pressure (up to 3.6 million atmospheres), keeping it in a solid state. Some scientists consider it a solid plasma.
- Outer core: Liquid, made up of iron and nickel, and under less pressure than the inner core, causing it to be in a liquid state. Generates Earth's magnetic field.
The mantle is the largest layer, making up about 84% of the Earth's total volume. It starts about 20 miles below the surface and extends approximately 1800 miles towards the core.
- Asthenosphere: Uppermost layer, about 60 miles below the surface, behaves like a convection oven with molten magma, causes earthquakes and volcanic activity.
- Central mantle/transition zone: Rocks transform into denser forms, extends from 250 to 410 miles below the surface, holds as much water as Earth's oceans.
- Lower mantle: Hottest and densest layer, starts about 410 miles below the surface, more solid than other layers due to increased pressure.
The Earth's crust is the thinnest layer, supporting all life and is solid but brittle. It is about 20 miles thick on average, thinnest at the bottom of the ocean, and thickest at mountain tops.