GCSE · Geography · AQA · Spec 8035

Plate tectonics theory

Nothing under your feet is standing still. The ground is being carried by rock moving deep inside the Earth — and that is where earthquakes come from.

The engine inside the Earth

1Heated at depth2Rises3Carries theplate4Cools and sinks5Returns tothe heat

Stage 1 of 5: Heated at depth. paused

Heated at depth · 1/5scrub the loop →

Heat from the Earth's core warms the mantle rock lying just above it. Nothing has moved yet — this is the loop being wound up.

Scrub the loop. The rock never stops turning over — and neither does the plate riding on top of it.

Watch out: The mantle is not an underground ocean of lava. It is solid rock that can creep and flow, but only extremely slowly. The plates riding on it stay rigid, which is why they can be carried along in one piece instead of stirring into it.

The two kinds of plate

Oceanic platevsContinental plate

Read the first row first. It is the one the theory actually rests on.

Focus

Density

Oceanic plate

Denser — the heavier of the two for its size.

Continental plate

Less dense — the lighter of the two for its size.

The insight

This is the difference that matters, and it belongs to the plate itself. Naming the two kinds is naming a difference in density, not a difference in address.

Thickness

Oceanic plate

Thin — only a few kilometres from top to bottom.

Continental plate

Thick — tens of kilometres from top to bottom.

Rock it is made of

Oceanic plate

Mostly basalt — a dark, dense volcanic rock.

Continental plate

Mostly granite — a paler, less dense rock.

Where you find it

Oceanic plate

It forms the floor beneath the oceans.

Continental plate

It forms the continents — the land masses.

From movement to hazard

?

Reason it through

If the Earth's surface is solid rock, why does the ground shake and why do volcanoes erupt?

Link 1 of 4

First link · your turn

The mantle beneath a plate keeps turning over. What does that do to the plate sitting on top of it?

2
Locked — reveal the link above first
3
Locked — reveal the link above first
4
Locked — reveal the link above first

Predict, then check

Commit to an answer before you reveal it.

Right now, with no earthquake happening anywhere near you, is the plate you are standing on moving?

WHAT YOU'VE LEARNED

A quick recap of today's lesson.

Why the ground moves, and why earthquakes and eruptions are results rather than accidents.

What you need to know

  • The Earth's outer shell is broken into large pieces called tectonic plates.
  • Heat inside the Earth drives slow movement in the mantle, and the plates resting on that moving rock are carried along with it.
  • The mantle is solid rock that can flow extremely slowly; the plates riding on it stay rigid.
  • The movement is continuous — the loop that drives it does not switch off.
  • Plates meet along their edges, and earthquakes and volcanic eruptions are the result of physical processes that take place there.
  • An earthquake is stress stored in the rock at a plate edge, released suddenly when the rock gives way.
  • A volcanic eruption is molten rock reaching the surface, brought up by a physical process at a plate edge.
  • Oceanic plate is denser and thinner; continental plate is less dense and thicker.

The big picture

The Earth's outer shell is broken into large plates, and those plates are being moved all the time by heat-driven movement in the mantle below. Earthquakes and volcanic eruptions are what that movement produces where plates meet: results of a physical process, not random disasters.

Key points

1Plate tectonics theory describes the Earth's surface as moving plates, not fixed ground.
2The movement is driven by heat inside the Earth, and it is continuous rather than occasional.
3Earthquakes and volcanic eruptions are the result of physical processes, so each one has a mechanism and a place.
4The two kinds of plate differ first of all in density: oceanic is denser, continental is less dense.
5Movement is the normal state of the ground; a hazard is what happens when that movement is resisted at an edge.

Worked example

Problem

A news report describes an earthquake near the edge of a plate as 'a natural disaster that struck without warning'. Using plate tectonics theory, write an explanation of why the earthquake happened where it did.

⚠ Watch out

Answering 'where' when the question asks 'why'. Saying earthquakes happen at plate edges describes where they occur; it does not explain them. The explanation is that the plates are being moved all the time, and at their edges that movement is resisted until the rock gives way.

🧠

Memory hook

Heat turns the mantle, the mantle turns the plates, and the plates take it out on each other at the edges.

✓

Check yourself

Without looking back: name the thing that keeps the plates moving, say what happens to that movement where a plate meets its neighbour, and finish this sentence — an earthquake is what happens when ______.

Flashcards

(6)
What does plate tectonics theory say the Earth's surface is like?
It is broken into large plates that are being moved continuously by processes going on inside the Earth, rather than being one fixed, solid shell.
What drives the movement of the plates?
Heat inside the Earth drives slow movement in the mantle. The plates rest on that moving rock and are carried along with it.
Is the mantle liquid?
No. It is solid rock that can creep and flow, but extremely slowly. The plates sitting on top of it stay rigid.
What is an earthquake, described in terms of plate movement?
Movement that has been resisted at a plate edge and stored as stress in the rock, then released suddenly when the rock gives way.
What does plate tectonics theory say about a volcanic eruption at a plate edge?
It is the result of a physical process at that edge bringing molten rock up to the surface — not a random event.
How does oceanic plate differ from continental plate?
Oceanic plate is denser and thinner, and is made mostly of basalt. Continental plate is less dense and thicker, and is made mostly of granite.

Tap any card to flip it, or use Study as deck to go through them one at a time. In the full lesson these run as a spaced-repetition deck — you rate each card Hard, Good or Easy and the tricky ones keep coming back until they stick.

Learning with Lightbulb is opening soon

You can use this lesson now. Join the waitlist and we'll let you know when the full Lightbulb experience is ready.

Keep me posted

More AQA GCSE Geography topics

See the full AQA Geography curriculum →

How this lesson was checked. This AQA GCSE Geography (specification 8035)lesson was published through Lightbulb Learning's human-designed editorial process — the educational standards, accuracy rules and publication checks it must pass were authored and approved by Philip Halpin. It passed subject-specific assessment, automated educational checks and technical publication verification before going live (publication checks completed 29 September 2026). Published pages are monitored, human spot-checking is ongoing across the lesson library, and anything found wrong is corrected or withdrawn. How our lessons are made and checked. Spotted a mistake? Email hello@lightbulblearning.co and we'll review it.