The Internal Structure of the Earth

The Earth is layered like an onion, from a thin crust to a hot core.

The Layers

• Crust — thin rocky outer layer, 5–70 km thick; home to all life.
• Mantle — hot, semi-solid rock about 2 900 km thick; convection currents move tectonic plates.
• Outer core — liquid iron and nickel; its movement creates the magnetic field.
• Inner core — solid iron and nickel, extremely hot and under great pressure.

Plate Movement

The crust is broken into tectonic plates that float on the mantle. Where plates collide, mountains form; where they separate, magma rises; where they slide, earthquakes occur.

Hazards

Earthquakes and volcanoes are concentrated along plate boundaries, such as the Ring of Fire around the Pacific.

Practice

1. Name the four main layers of the Earth.
2. Which layer produces the magnetic field, and why?
3. Explain why earthquakes are common along plate boundaries.

Recap

The Earth has a crust, mantle, outer core and inner core. Plate movement causes mountains, earthquakes and volcanoes.