Inside Earth — Revision notes

Inner core

The innermost layer of Earth, made of iron and nickel at around 5,500°C, kept solid by intense pressure

Outer core

A liquid metal layer surrounding the inner core

Mantle

Earth's thickest layer at 2,900 kilometres, composed mostly of solid rock with a tiny fraction that flows slowly over long periods

Crust

The thinnest and coolest outermost layer of Earth ranging from about 5 kilometres thick under the oceans to about 70 kilometres under mountains where continents and oceans are found

Lithosphere

The hard, rigid outer layer of Earth formed by the combination of the upper mantle and the crust

Tectonic plates

Large sections into which the lithosphere is broken

Plate boundary

The region where two tectonic plates meet, associated with earthquakes and volcanic activity

Pacific Ring of Fire

A tectonically active region around the Pacific Ocean containing about three-quarters of the world's volcanoes and nine out of ten earthquakes

Seismic waves

Vibrations from earthquakes that ripple through the planet, used by scientists to work out whether Earth's deep layers are solid or liquid

What this lesson covers

How well do you know each one? Be honest: red means go back over it.

• Name Earth's four layers in order and describe what each one is made ofNot yetSort ofGot it
• Explain why the inner core is solid even though it is hotter than the outer coreNot yetSort ofGot it
• Explain how scientists use seismic waves to work out what is inside the EarthNot yetSort ofGot it
• Define the lithosphere and explain what a tectonic plate isNot yetSort ofGot it
• Explain why most earthquakes and volcanoes happen at plate boundariesNot yetSort ofGot it
• Describe the Pacific Ring of Fire and explain why so much activity is concentrated thereNot yetSort ofGot it

Test yourself

Cover the answer, say it out loud, then check the full quiz on the lesson page.

• What are the four layers of Earth?
• What is the estimated temperature of the inner core?
• Which layer of Earth is liquid?

Topic quiz

13 questions on this topic only — not mixed with anything else, one at a time.

Spelling challenge

Read the definition, then type the correct spelling of the term. Uses the same terms as above.