Diagramium
🌍 Narrated diagram

Layers of the Earth

From the thin rock under your feet to a ball of solid iron as hot as the Sun's surface — every layer of the planet, with real depths, temperatures and how anyone found out.

15 steps3 min readNarrated with a studio voice
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Layers of the Earthoutermost layerthin, under the seathick, under the landends atwhere it beginsjoins the upper mantle asslides overincludesincludesstirred bydragssits abovegeneratessurroundskept warm byrevealed byA key idea or topic — the main building block of the mapPlanet EarthA key idea or topic — the main building block of the mapThe crustA narrower idea branching off a conceptOceanic crustA narrower idea branching off a conceptContinental crustA concrete example of a concept — drawn as an ovalThe Moho boundaryA key idea or topic — the main building block of the mapThe mantleA narrower idea branching off a conceptThe lithosphereA narrower idea branching off a conceptThe asthenosphereA narrower idea branching off a conceptThe lower mantleA concrete example of a concept — drawn as an ovalConvection currentsA key idea or topic — the main building block of the mapThe outer coreA concrete example of a concept — drawn as an ovalThe magnetic fieldA key idea or topic — the main building block of the mapThe inner coreA concrete example of a concept — drawn as an ovalWhere the heat comes fromA concrete example of a concept — drawn as an ovalHow anyone knows
Layers of the Earth — the complete diagram. Press Present to watch it build itself.
Layers of the Earth — Planet Earth
Step 1 of 15

Planet Earth

You are standing on the thin skin of a very hot ball. It is six thousand three hundred and seventy one kilometres from your shoes to the centre of the Earth, and every layer on the way down gets hotter, denser and stranger.

Layers of the Earth — The crust
Step 2 of 15

The crust

The crust is the only layer anyone has ever touched. It runs from about five to seventy kilometres thick, which sounds enormous until you scale it: in proportion, the crust is thinner than the skin on an apple.

Layers of the Earth — Oceanic crust
Step 3 of 15

Oceanic crust

Oceanic crust is young, dark basalt, only around seven kilometres thick, and almost none of it is older than two hundred million years. It is constantly made fresh at mid ocean ridges and swallowed back down at deep trenches.

Layers of the Earth — Continental crust
Step 4 of 15

Continental crust

Continental crust is granite. It is lighter and far thicker, reaching seventy kilometres under the Himalayas. Because it floats high and refuses to sink, some of it has survived four billion years, nearly as long as the planet itself.

Layers of the Earth — The Moho boundary
Step 5 of 15

The Moho boundary

In nineteen hundred and nine a Croatian scientist noticed that earthquake waves suddenly sped up at a particular depth. That jump marks the Mohorovicic discontinuity, the sharp floor where crust stops and mantle starts, and nobody has ever drilled through it.

Layers of the Earth — The mantle
Step 6 of 15

The mantle

The mantle is the main event: nearly two thousand nine hundred kilometres of hot silicate rock making up about eighty four percent of the planet's volume. It is genuinely solid, yet over millions of years it flows like extremely thick treacle.

Layers of the Earth — The lithosphere
Step 7 of 15

The lithosphere

The crust and the cold top of the mantle are welded into one rigid shell called the lithosphere. That shell is cracked into the tectonic plates that carry the continents around at roughly the speed your fingernails grow.

Layers of the Earth — The asthenosphere
Step 8 of 15

The asthenosphere

Below it sits the asthenosphere, weak, partly molten rock about a hundred kilometres down. It is soft enough for the plates above to slide over, and that softness is the whole reason Earth has drifting continents when other rocky planets do not.

Layers of the Earth — The lower mantle
Step 9 of 15

The lower mantle

Deeper still, crushing pressure repacks the minerals into denser forms and the lower mantle becomes stiff again. It is already past two thousand degrees where this layer begins, and it reaches about three thousand seven hundred degrees where the mantle finally meets the core.

Layers of the Earth — Convection currents
Step 10 of 15

Convection currents

Heat leaking out of the core drives slow convection. Hot rock rises, cools, and sinks again in loops that take hundreds of millions of years to turn once. Those loops are the engine behind every earthquake, every volcano and every mountain range.

Layers of the Earth — The outer core
Step 11 of 15

The outer core

At two thousand nine hundred kilometres down, rock gives way to a real ocean of liquid iron and nickel, over two thousand kilometres deep and around four thousand degrees. We know it is liquid because one type of earthquake wave stops dead at its edge.

Layers of the Earth — The magnetic field
Step 12 of 15

The magnetic field

That swirling metal conducts electricity, and as the planet spins it works like a colossal dynamo, generating our magnetic field. The field deflects the solar wind, and it is the reason our air was not stripped away like the air of Mars.

Layers of the Earth — The inner core
Step 13 of 15

The inner core

Right at the middle sits a solid iron ball about two thousand four hundred kilometres across, very nearly the size of Pluto, and as hot as the surface of the Sun at around five thousand four hundred degrees. It stays solid only because the pressure there is over three million times the pressure at sea level.

Layers of the Earth — Where the heat comes from
Step 14 of 15

Where the heat comes from

So where does all that heat come from? About half is left over from the planet's violent birth four and a half billion years ago, and the rest comes from uranium, thorium and potassium quietly decaying inside the rock right now.

Layers of the Earth — How anyone knows
Step 15 of 15

How anyone knows

Nobody has ever seen any of this. The deepest hole ever drilled stopped at twelve kilometres, barely a scratch, so everything we know about the inside comes from earthquake waves bending as they pass through, like an ultrasound of the whole planet.

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