Good Learning Co.
SavannahYear 8
← Geography
GeographyRestless Earth: plates, earthquakes and volcanoes25 min★★★ difficulty

Inside the Earth and the theory of plate tectonics

The ground under your feet is drifting a few centimetres a year, about the speed your fingernails grow. That slow movement is the reason mountains exist, why Iceland is splitting apart, and why Japan practises earthquake drills every year.

Part of your national curriculum
  • Human and physical geography: Understand how geographical processes interact to create distinctive human and physical landscapes that change over time
  • Human and physical geography: Understand tectonic processes and hazards, including earthquakes and volcanic activity

Lesson overview

What you'll learn in this lesson

Describe the structure of the Earth and explain what drives plate movement.

Key learning points

  • • The layers
  • • What makes plates move
  • • Evidence that plates move
  • • The pattern of hazards

This lesson at a glance

  • 25 minutes
  • 17 parts to scroll through
  • 4 quick checks
  • Marked quiz at the end
  • Gentle pace: short sittings with pauses

Words to know

structuredrivesmovementlayersplates

Scroll down — the lesson carries on below

Part 1 of 17 · Discover6%
1

Watch & discover

Part 1 of 17

Watch first

Inside the Earth and the theory of plate tectonics

An English teaching video on this topic from Equatoro. Watch it, then scroll down for the lesson.

In a nutshell

Describe the structure of the Earth and explain what drives plate movement.

2

Learning cycle

Part 2 of 17

Learning cycle 1 of 2

Part 1 · The layers

A short piece of teaching, then a check to make sure it has landed.

3

Explore the idea

Part 3 of 17

Learn

The layers

The Earth has a solid inner core of iron and nickel, a liquid outer core, a thick semi-molten mantle and a thin, brittle crust. Crust comes in two kinds. Continental crust is thick (about 30-70 km), old and low density, so it cannot sink. Oceanic crust is thin (about 5-10 km), young and denser, so it can be forced downwards. That density difference decides what happens whenever two plates meet.

4

Explore the idea

Part 4 of 17

Learn

What makes plates move

Heat from the core sets up convection in the mantle: hotter, less dense rock rises, spreads sideways and cools, then sinks again. Geologists now think the bigger force is slab pull, where a cold, dense plate sinking at a margin drags the rest of the plate along behind it, helped by ridge push as new crust slides off the raised mid-ocean ridge. Convection, slab pull and ridge push work together; you do not have to choose one.

5

Quick check

Part 5 of 17

Quick check

Why can oceanic crust sink beneath continental crust?

6

Quick check

Part 6 of 17

Quick check

Which is the strongest single piece of evidence for sea-floor spreading?

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Learning cycle

Part 7 of 17

Learning cycle 2 of 2

Part 2 · Evidence that plates move

A short piece of teaching, then a check to make sure it has landed.

8

Reset break

Part 8 of 17

Pause

That's sitting 1 of 2 done

Stretch, get a drink, look out of the window. There is no timer and nothing is counting down — your place is saved, so you can come back in five minutes or tomorrow.

Stop here for now
9

Explore the idea

Part 9 of 17

Learn

Evidence that plates move

The coastlines of South America and Africa fit together. Matching rock sequences and mountain belts continue across the Atlantic, and identical fossils such as Mesosaurus, a freshwater reptile that could not swim an ocean, appear on both sides. Magnetic stripes in the sea floor either side of mid-ocean ridges are mirror images, showing new crust forming and spreading outwards. Modern GPS now measures plate movement directly.

10

Explore the idea

Part 10 of 17

Learn

The pattern of hazards

Plot the world's earthquakes and volcanoes on a map and they are not scattered randomly: they form narrow lines. Those lines are plate margins. The Pacific Ring of Fire, the mid-Atlantic ridge and the belt running from the Mediterranean into the Himalayas all trace boundaries. A few volcanoes, such as Hawaii, sit far from any margin over a hot spot, a plume of rising mantle that burns through the plate as it drifts.

11

Quick check

Part 11 of 17

Quick check

What does slab pull describe?

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Quick check

Part 12 of 17

Quick check

Why is Hawaii volcanic despite sitting far from a plate margin?

13

Explore the idea

Part 13 of 17

Worked example

Worked answer: explain why plate movement occurs (4 marks)

Heat released in the core makes mantle rock rise, spread and sink in convection cells, which drags the plates above (1). Where a dense oceanic plate sinks at a margin, its cold weight pulls the rest of the plate down with it, called slab pull (1), and new crust at the raised ridge slides away under gravity as ridge push (1). Together these forces move plates a few centimetres each year, which is fast enough over millions of years to open oceans and build mountains (1). Notice that each mark is a linked step, not a separate fact.

14

Challenge round

Part 14 of 17

Game · Sort it

Which of these are true?

Drag each card into the right column. Tap a card first if dragging is fiddly.

True

Not true

15

Challenge round

Part 15 of 17

Game · Fill the gaps

Finish the sentences

Choose the word that belongs in each gap.

That density difference decides what happens whenever two ____ meet.

Modern GPS now measures plate ____ directly.

16

Mastery quiz

Part 16 of 17

Marked quiz

End of lesson quiz: Inside the Earth and the theory of plate tectonics

4 questions, marked with the reasoning shown. No timer.

  1. 1. Why can oceanic crust sink beneath continental crust?

  2. 2. Which is the strongest single piece of evidence for sea-floor spreading?

  3. 3. What does slab pull describe?

  4. 4. Why is Hawaii volcanic despite sitting far from a plate margin?

17

Lesson round-up

Part 17 of 17

Lesson round-up

Ready when you are

Quiz score

Not sat

Games

Not played

Points this lesson

0

Best run

0 in a row

Luna: 0 out of 4 on the practice checks. Only if you feel up to it — one more?

Ask Luna

Do the work

Your written work for this lesson

This is the part you'd do in your book at school. Pick the pieces below, write here or on paper, and photograph anything you draw or work out.

Case study

Flooding on the River Calder

The town of Harbrook sits where a steep valley opens onto a flat floodplain. In December 2015, 120 mm of rain fell in 36 hours onto ground that was already saturated. The river rose 2.4 m in five hours, and 380 homes and 54 businesses flooded. Two roads and the railway closed for eleven days.

Geographers pointed to physical causes — steep slopes, impermeable rock, heavy rainfall — and human causes: moorland drained upstream, new housing built on the floodplain, and drains designed for smaller storms.

Since then the town has planted 40 hectares of woodland upstream, built leaky dams in small streams, and raised flood walls to 1.8 m. In the storm of 2020 the peak river level was 0.3 m lower and 40 homes flooded, not 380.

Written for Good Learning Co.

Reading questions

  1. List two physical and two human causes of the 2015 flood.
  2. Explain how planting woodland upstream lowers the river's peak level.
  3. Using the figures, judge how successful the scheme has been. Quote data in your answer.

  • Case study notes

    Writing

    Write the place, the facts and the figures from this lesson so you can revise them later.

    Half a page

  • Explain answer

    Writing

    Answer in full sentences, giving causes and effects. Use one figure or place name as evidence.

    8–10 sentences

  • Map or sketch

    Diagram

    Draw the map, cross-section or field sketch with a key, title and labels, then photograph it.

    1 map with a key

  • Data work

    Working out

    Plot your figures as a graph on paper and write one sentence about the pattern.

    1 graph + 1 sentence

Saved as you type.

Part 1 of 17 · Watch & discover

How this is going

  • Not looked at yet

    Understand how geographical processes interact to create distinctive human and physical landscapes that change over time

  • Not looked at yet

    Understand tectonic processes and hazards, including earthquakes and volcanic activity

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