Layers of the Earth: Interactive Diagram and 3D Globe

What are the layers of the Earth?

If you could slice the Earth in half like a peach, you'd see it is built in layers. NASA describes four main layers, starting with an inner core at the planet's center, wrapped in the outer core, the mantle and the crust. They differ in what they are made of, how hot they are and whether they are solid or liquid.

1. Crust: the thin, rocky shell we live on.
2. Mantle: a very thick layer of hot rock that flows slowly over millions of years.
3. Outer core: liquid iron and nickel.
4. Inner core: a solid ball of iron and nickel at the center.

The diagram above shows a quarter of the Earth cut open, with the center at the lower left. It splits the crust into continental and oceanic crust and the mantle into upper and lower mantle, the six parts you'll find in most middle school diagrams. Tap any pin to learn about that layer, then test yourself with the label and order quizzes.

Earth's layers in order, with depths and temperatures

The Earth's average radius is about 6,371 kilometers (3,959 miles). Here are the layers from the surface down, using the depths and temperatures published by National Geographic and NASA.

Two things change steadily as you go down: it gets hotter, and the pressure gets greater. National Geographic notes that in the mantle the temperature rises about 25 °C for every kilometer of depth near the top.

The crust: Earth's thin outer layer

The crust is where we live, and it is surprisingly thin. National Geographic notes that the crust is just 1 percent of Earth's mass. If the Earth were an apple, the crust would be thinner than its skin.

There are two kinds:

• Continental crust makes up the continents. It is about 30 kilometers (19 miles) thick on average, according to NASA, and as much as 70 kilometers (44 miles) thick under big mountain ranges. It is made mostly of light-colored rocks like granite, and parts of it are more than 4 billion years old.
• Oceanic crust lies under the oceans. It is only about 5 to 10 kilometers (3 to 6 miles) thick and is made mostly of dark, heavy basalt. It is constantly being made at mid-ocean ridges and destroyed where plates collide, so it is young: the oldest, under the Ionian Sea, is about 270 million years old.

Because oceanic crust is denser (almost 3 grams per cubic centimeter, versus about 2.7 for continental crust), it sits lower, which is part of why oceans fill the low places on Earth.

The bottom of the crust is a boundary called the Mohorovičić discontinuity, or Moho, where earthquake waves suddenly speed up. National Geographic puts it about 8 kilometers beneath the ocean and about 32 kilometers beneath the continents.

The mantle: the thickest layer

The mantle is the giant of Earth's layers. National Geographic says it is about 2,900 kilometers (1,802 miles) thick and makes up a whopping 84 percent of Earth's total volume. It is made of rock rich in iron and magnesium.

The mantle is mostly solid, but it isn't rigid everywhere. Here is how scientists divide it:

• Lithosphere (to about 100 km): the crust plus the stiff, brittle top of the mantle. It is broken into the tectonic plates.
• Asthenosphere (about 100 to 410 km): hot enough that rock is soft and partly melted, so it can flow very slowly. The plates slide on top of it. In the diagram it's the dashed line inside the upper mantle.
• Transition zone (about 410 to 660 km): minerals get squeezed into denser forms. National Geographic notes that crystals here may hold as much water as all the oceans on Earth's surface.
• Lower mantle (about 660 to 2,900 km): hotter still, but the pressure is so intense that the rock stays solid.

Heat from the core makes mantle rock rise and sink in huge, slow loops called convection. Those loops help push the tectonic plates, which the USGS says move a few centimeters a year, building mountains and opening oceans over millions of years. That connects the deep Earth to the rock cycle at the surface.

The outer core: a sea of liquid metal

At about 2,900 kilometers down, the rock ends and metal begins. The outer core is about 2,200 kilometers thick and made mostly of liquid iron and nickel, at about 4,500 to 5,500 °C.

It is the outer core that gives Earth its magnetic field. National Geographic explains that the churning metal of the outer core creates and sustains it: a planet needs to rotate, have a fluid inside that can conduct electricity, and have energy to keep that fluid moving. Earth has all three. The result, sometimes called the geodynamo, is why a compass points north.

The inner core: a solid ball at the center

At the very center is the inner core, a ball of mostly iron with some nickel, with a radius of about 1,220 kilometers (758 miles). National Geographic gives its temperature as about 5,200 °C (9,392 °F); NASA says as high as 5,400 °C (9,800 °F). That is about as hot as the surface of the Sun.

So why isn't it liquid like the outer core? Pressure. The weight of the entire planet presses down at nearly 3.6 million times the air pressure at the surface, and that keeps the iron packed into a solid. The inner core is slowly growing as liquid iron from the outer core freezes onto it, which releases heat that helps keep the outer core churning.

How do we know what is inside the Earth?

Nobody has ever been there. The deepest hole ever drilled, on Russia's Kola Peninsula, reached about 12 kilometers, and the USGS points out it never reached the Moho. Instead, scientists use earthquakes as a giant flashlight.

Earthquakes send seismic waves through the planet, and seismometers around the world record when they arrive. Two kinds matter most:

• P waves (primary waves) push and pull, and can travel through solids and liquids.
• S waves (secondary waves) shake side to side, and can't travel through liquid.

The USGS explains that the outer core is considered liquid because it does not transmit S waves, and P waves slow down sharply inside it. The core itself was discovered in 1906 by R.D. Oldham. Then, in 1936, the Danish seismologist Inge Lehmann noticed faint P waves arriving where none were expected and concluded that the core has a solid inner part. The boundary between the inner and outer core is now often called the Lehmann discontinuity.

The work continues. In a 2023 study supported by the U.S. National Science Foundation, seismologists reused data from the global network that listens for nuclear tests and found that the inner core isn't uniform; the lead author described it as more like a tapestry of different fabric. One of the researchers called the inner core "a planet within a planet that has its own rotation."

Layers of the Earth for kids: easy ways to remember

• Peach model. The skin is the crust, the juicy fruit is the mantle, and the pit is the core. (A hard-boiled egg works too: shell, white and yolk.)
• Hot, hotter, hottest. Every layer is hotter than the one above it.
• Solid, squishy, liquid, solid. Crust solid; upper mantle solid but soft enough to flow; outer core liquid; inner core solid again because of pressure.
• Mnemonic. "Cool Mice Often Investigate" for Crust, Mantle, Outer core, Inner core.

Make a layers of the Earth model

A layers of the Earth model is a favorite science project. Two easy versions:

1. Clay ball. Roll a small yellow ball (inner core), wrap it in orange (outer core), then a thick layer of red (mantle), then a thin layer of brown or green and blue (crust). Cut it in half with dental floss, or cut out a wedge like the 3D globe on this page, and label each layer with toothpick flags.
2. Paper plate. Draw four rings on a paper plate, color them, and write the depth and temperature of each layer from the table above.

When it's done, print the labeled layers of the Earth diagram for the science notebook, and use the layers of the Earth worksheet as a quick check.

Explore Earth's layers in 3D

Select Open in 3D to spin a low-poly globe with continents and oceans and a slice cut out of it. Drag the Cutaway slider to open the slice wider or narrower, or choose Open and close to animate it. Tap any layer, or use the guided tour, to read the same explanations as the diagram. The crust and upper mantle are thickened so you can see and tap them; the other layers are to scale. If your device can't show 3D graphics, the page shows the 2D cross-section instead.

Earth science ties together the layers of the Earth, the rock cycle and the water cycle. If you want a full course that builds on them, compare the options in our best homeschool science curriculum guide or browse science programs, many of which families can pay for with a state scholarship or education savings account.