How do we know?
↻ One of the pages with a moving picture
Quake waves bend and bounce at each layer.
- Crust: the rocky skin we live on. About 3 miles thick under oceans, 19 under land.
- Mantle: hot rock that can very slowly flow. About 1,800 miles thick!
- Outer core: liquid metal, mostly iron and nickel, about 1,400 miles thick.
- Inner core: a solid metal ball right in the middle.
Quake waves bend and bounce at each layer. In 1936, a Danish scientist named Inge Lehmann used them to find the solid inner core.
No one can dig that far. The deepest hole ever dug, the Kola Superdeep Borehole in Russia, is 7.5 miles deep. It took almost 20 years and never reached the mantle.
From the outside in: the crust is about 3 miles thick under oceans and 19 under land. The mantle is about 1,800 miles thick. The liquid outer core, mostly iron and nickel, is about 1,400 miles thick.
Wow number
4,000 miles to Earth’s center. Driving there at highway speed (60 mph) would take about 66 hours, nearly 3 days and nights!
Myth or fact?
Earth is hollow inside, like a ball. Myth. It is packed with rock and metal layers.
The spinning liquid outer core makes Earth’s magnetic field. Fact. Moving liquid metal creates it.
Think about it
If an elevator could go to Earth’s center, what would it need to survive?
Where in the world?
Kola Superdeep Borehole, Russia the deepest hole ever dug. In New Zealand, a quake in 1929 led to a discovery about Earth’s insides — 69.3967° N, 30.6097° E.
Where these facts come from
Every number on page 21, and who measured it
This page tells us about Earth's layers and how thick each one is.
Inside the Earth [This Dynamic Earth, USGS] — The U.S. Geological Survey, the government's Earth scientists
pubs.usgs.gov/gip/dynamic/inside.html
We checked it on 31 October 2026
This page tells us about the deepest hole ever dug.
Ask Smithsonian: What's the Deepest Hole Ever Dug? — Smithsonian magazine, from the Smithsonian museums
smithsonianmag.com/smithsonian-institution/ask-smithsonian-whats-deepest-hole-ever-dug-180954349
We checked it on 31 October 2026
This page tells us how Inge Lehmann discovered Earth's solid inner core.
Inge Lehmann — Oxford University's Museum of Natural History in England
oumnh.ox.ac.uk/learn-inge-lehmann
We checked it on 31 October 2026
This page tells Inge Lehmann's story too.
The American Museum of Natural History in New York
amnh.org/learn-teach/curriculum-collections/earth-inside-and-out/inge-lehmann-discoverer-of-the-earth-s-inner-core
We checked it on 31 October 2026
This page tells us Earth is made of three shells — a thin crust, the mantle and the core — so there is no hollow space inside.
The Interior of the Earth — The U.S. Geological Survey, the government's Earth scientists
pubs.usgs.gov/gip/interior
We checked it on 5 November 2026
This page tells us Earth's liquid outer core makes its magnetic field.
How does the Earth's core generate a magnetic field? — The U.S. Geological Survey, the government's Earth scientists
usgs.gov/faqs/how-does-earths-core-generate-a-magnetic-field
We checked it on 5 November 2026
Has this changed?
Earth’s layers are not changing in any way we can see, so this answer is not going to change.
What changes is how well we can see them. Scientists keep learning more from quake waves.
Words from this page
- crust
- Earth’s thin rocky outer skin, where we live.
- mantle
- The thick layer of hot rock under the crust that can very slowly flow.
- core
- The metal middle of Earth, with a liquid outer part and a solid inner part.
Try it!
Build Earth’s layers out of clay.
1. Roll a clay ball: the inner core. 2. Wrap on a thick outer core, a thicker mantle, then a thin crust, each a new color. 3. Have a grown-up slice it in half with floss.
Look: like a boiled egg, there is a thin shell, a thick middle and a center.
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