Layers of the Earth
Earth has a crust, mantle, outer core and inner core.
About this topic
Earth has four main layers. The thin crust (5–70 km) is rock, thinner under oceans; the mantle (about 2900 km thick) is hot, solid rock that flows slowly; the outer core is liquid iron and nickel; and the inner core is solid iron–nickel, kept solid by enormous pressure at about 5400 °C.
Evidence comes from seismic waves: S-waves cannot pass through the liquid outer core, and P-waves bend. Convection in the mantle drives plate movement, and the outer core's motion generates the magnetic field. The lithosphere (crust + upper mantle) is rigid and rides on the softer asthenosphere.
A helpful analogy is an egg or a peach: the crust is the thin shell, the mantle is the thick flesh and the core is the stone. The crust is under 1 percent of Earth's volume, while the mantle is about 84 percent. Temperature rises with depth, reaching about 5400 degrees C in the inner core, similar to the surface of the Sun, but the inner core stays solid because pressure is millions of times higher than at the surface.
The way seismic waves behave gave scientists a picture of the interior without drilling: the deepest borehole, on Russia's Kola Peninsula, reached only about 12 km. A shadow zone where S-waves are missing proved a liquid outer core, and Inge Lehmann discovered the solid inner core in 1936. The magnetic field shields us from the solar wind, and compasses and animal navigation rely on it. A common misconception is that the mantle is liquid magma; it is solid rock that flows over millions of years, like very stiff putty. Magma comes from local melting.
Key ideas
- Crust is thin
- Mantle flows slowly
- Inner core is solid iron and nickel
Quick check
Use cases: where Layers of the Earth helps
- Homework: review the key idea behind Layers of the Earth before you start a problem set.
- Exam revision: use the quick check to test whether you can recall Layers of the Earth without notes.
- Visual learning: play with the interactive lab to see how Layers of the Earth changes when you adjust its inputs.
- Teaching a friend: explain Layers of the Earth in your own words, then compare your version with the key ideas.
Earth science helps with weather forecasts, natural hazards, energy and climate planning.
Frequently asked questions
What is Layers of the Earth?
Earth has a crust, mantle, outer core and inner core.
What will I learn in Layers of the Earth?
Crust is thin. Mantle flows slowly. Inner core is solid iron and nickel.
Is Layers of the Earth part of Earth & Space?
Yes. It is one of 60 Earth & Space topics on LearnViz HighSchoolEdu, with 3 key ideas, a live animation and a quick check.
Does the Layers of the Earth lab work on a phone or tablet?
Yes. The animation resizes to fit your screen and supports touch, so you can drag, tap and slide with your finger.
How should I study Layers of the Earth?
Read the summary and key ideas first, play with the interactive lab to see the idea in motion, then answer the quick check. If you get a question wrong, go back to the key idea it tests.
Do I need an account, and is my progress saved?
No account is needed. Marking a topic as learned is saved in your own browser, so it stays on that device and is not sent to a server.