Good Learning Co.
SavannahYear 8
← Geography
GeographyThe restless Earth30 min★★ difficulty

Plates, boundaries and earthquakes

Almost every earthquake on Earth happens in the same narrow lines. In this lesson you learn what those lines are, what the rock is doing along them, and how to explain an earthquake in the order a GCSE answer expects: cause, process, effect.

Part of your national curriculum
  • Human and physical geography: Understand tectonic processes and hazards, including earthquakes and volcanic activity

Lesson overview

What you'll learn in this lesson

Understand tectonic processes and hazards, including earthquakes and volcanic activity

Key learning points

  • • A cracked shell on a hot planet
  • • Three things plates can do
  • • Locked, then released
  • • Measuring and describing effects

This lesson at a glance

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

Words to know

tectonicprocesseshazardsearthquakesvolcanic

Scroll down — the lesson carries on below

Part 1 of 18 · Discover6%
1

Watch & discover

Part 1 of 18

Watch first

Plates, boundaries and earthquakes

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

In a nutshell

Understand tectonic processes and hazards, including earthquakes and volcanic activity

2

What you already know

Part 2 of 18

Before we start

What you already know

You should already know that the Earth has layers, and that maps can show where events happen.

3

Key words

Part 3 of 18

Key words

Words you'll need today

Plate
A huge slab of the Earth's rigid outer shell that moves a few centimetres a year.
Plate boundary
The line where two plates meet; almost all tectonic hazards happen here.
Focus
The point underground where an earthquake starts.
Epicentre
The point on the surface directly above the focus, where shaking is strongest.
Subduction
Where a denser oceanic plate sinks beneath a lighter continental plate.
4

Learning cycle

Part 4 of 18

Learning cycle 1 of 2

Why plates move

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

5

Explore the idea

Part 5 of 18

Learn

A cracked shell on a hot planet

The Earth's outer shell, the lithosphere, is broken into about fifteen large plates and many small ones. Below it the mantle is solid rock that creeps very slowly because it is so hot. Heat escaping from the core sets up slow convection in the mantle, and the plates ride on top, moving between one and ten centimetres a year — roughly the speed your fingernails grow. Over millions of years that is enough to open an ocean or build a mountain range.

6

Explore the idea

Part 6 of 18

Learn

Three things plates can do

At a constructive boundary plates move apart and molten rock rises to fill the gap, as along the Mid-Atlantic Ridge. At a destructive boundary they move towards each other and the denser oceanic plate subducts beneath the continental one, forming a deep trench and a line of volcanoes. At a conservative boundary they slide past each other with no plate made or destroyed. The type of boundary predicts the kind of hazard you get.

7

Quick check

Part 7 of 18

Quick check

What drives plate movement?

8

Reset break

Part 8 of 18

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

Quick check

Part 9 of 18

Quick check

At a destructive boundary, what happens to the oceanic plate?

10

Learning cycle

Part 10 of 18

Learning cycle 2 of 2

Why the ground shakes

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

11

Explore the idea

Part 11 of 18

Learn

Locked, then released

Plates do not slide smoothly. Friction locks them together while the forces keep pushing, so stress builds in the rock. When the rock finally gives way it snaps into a new position and the stored energy travels outwards as seismic waves. That release point is the focus; the spot on the surface above it is the epicentre. Shaking is usually strongest at the epicentre and weakens with distance.

12

Explore the idea

Part 12 of 18

Learn

Measuring and describing effects

Magnitude is measured on the moment magnitude scale, where each whole step means about 32 times more energy released. Magnitude alone does not decide the damage: depth, ground conditions, time of day, building design and how wealthy the country is all matter. Geographers separate primary effects, which happen during the shaking, from secondary effects such as landslides, fires, tsunami and disease that follow it.

13

Quick check

Part 13 of 18

Quick check

An earthquake's focus is 8 km down. What is the epicentre?

14

Quick check

Part 14 of 18

Quick check

Which of these is a secondary effect of an earthquake?

15

Common mix-ups

Part 15 of 18

Common mix-ups

Things people often get wrong

  • Plates float on liquid magma — they do not; the mantle beneath them is solid rock that creeps very slowly.
  • A bigger magnitude always means more deaths — a shallow magnitude 6 under a poorly built city can kill far more people than a deep magnitude 8 offshore.
  • The focus and the epicentre are the same place — the focus is underground, the epicentre is directly above it on the surface.
16

Challenge round

Part 16 of 18

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

17

Mastery quiz

Part 17 of 18

Marked quiz

End of lesson quiz: Plates, boundaries and earthquakes

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

  1. 1. About how fast do plates move?

  2. 2. Which boundary makes new crust?

  3. 3. At a conservative boundary, plates…

  4. 4. Each whole step up the magnitude scale means roughly…

  5. 5. Why can the same magnitude cause very different death tolls?

  6. 6. Where do almost all earthquakes occur?

18

Lesson round-up

Part 18 of 18

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.

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    Understand tectonic processes and hazards, including earthquakes and volcanic activity

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