Science // Volcanoes & Earthquakes

Why Earthquakes Happen

Understand that earthquakes happen when rocks underground suddenly move or break, releasing energy that shakes the ground

Ages
7 to 9
Type
Concept
Builds on
1 topic
Leads to
4 topics

Quick check

If the learner felt a small tremor or saw footage of an earthquake, could they explain that it happens because rocks deep underground suddenly shift or crack?

Ask this to see whether the topic is secure.

Topic // Mastery

What mastery looks like

What a learner can do once this topic is secure.
  • Explain that earthquakes are caused by rocks underground suddenly moving
  • Describe how this movement sends shaking through the surrounding ground
  • Distinguish between the underground cause and the surface effects of an earthquake

Topic // Map

Where this fits

What to learn first and what this topic opens up, with the reason for each link. Required links come first.
  • RequiredMust come first
  • HelpfulHelps, but not essential

Before this

1 topic
  • What Is an EarthquakeRequired

    Volcanoes & Earthquakes // Ages 5 to 7

    Understanding earthquake causes builds on knowing what an earthquake is

You are here

Why Earthquakes Happen

Ages 7 to 9 // Concept

Leads to

4 topics
  • Plate BoundariesRequired

    Volcanoes & Earthquakes // Ages 9 to 11

    Plate boundaries as earthquake cause builds on simpler causal model

  • Measuring Earthquake StrengthRequired

    Volcanoes & Earthquakes // Ages 9 to 11

    Measuring earthquakes requires understanding what causes them

  • Ring of FireHelpful

    Volcanoes & Earthquakes // Ages 7 to 9

    Mapping patterns benefits from understanding earthquake causes

  • TsunamisHelpful

    Volcanoes & Earthquakes // Ages 7 to 9

    Tsunamis also caused by earthquakes, so understanding earthquake causes helps

Topic // Research-informed

Teaching notes

From the Marble Skill Taxonomy. These notes have not been validated in classrooms, so treat them as a starting point for your own judgement.

The approach

For ages 7–9, teach that earthquakes are caused by rocks underground being pushed until they suddenly slip or break along a crack (a fault), releasing energy that spreads outward as shaking. The central insight is the slow build-up then SUDDEN release, and the separation of the underground CAUSE from the surface EFFECT (felt shaking and cracks). Keep it pre-plate-tectonics: rocks move/break underground. A hands-on or simulated stick-slip model makes the build-then-snap tangible; a labelled cross-section supports the cause/effect distinction; targeted questioning and myth-busting address the 'ground swallows people' and 'earthquake weather' ideas.

Common misconceptions

  • Earthquakes happen because the ground simply 'opens up' and swallows things (the cause is rock slipping/breaking; large open chasms are rare).
  • The shaking starts everywhere at once (energy spreads OUT from the slip point, arriving and fading with distance).
  • Rocks move smoothly and slowly, so shaking should be gentle (rocks stick then release suddenly — the sudden slip causes strong shaking).
  • Earthquakes are caused by the weather, or by volcanoes only (most are caused by rock movement underground along faults).
  • The cause and the shaking are the same thing (the underground slip is the cause; the felt shaking is its effect).

Useful representations

  • Two rough blocks pushed until they suddenly jerk (stick-slip friction model) — the canonical analogy for fault movement
  • Snapping a bent stick or dry spaghetti to model slow bending then sudden break + release
  • Cross-section showing the underground slip (focus) with shaking rippling up to the surface
  • Ripples spreading on water / a shaken tabletop as an image of energy travelling outward from one spot

Teaching practices

  • Make the cause a build-then-release story: push slowly, resistance grows, then a SUDDEN slip — the suddenness is why shaking is violent even though plates creep slowly.
  • Use a hands-on stick-slip analogy (push two rough blocks/bricks past each other until they jerk; snap a dry stick/spaghetti) so the release is felt, then map it to rock underground.
  • Explicitly separate the underground cause from the surface effect: draw the slip at depth (the focus) and the shaking spreading up and out to where people feel it.
  • Correct the 'ground opens and swallows people' image directly and reassuringly — the ground shakes and can crack, but the main hazard is shaking, and most earthquakes are small.
  • Introduce 'energy travels out as shaking (waves)' informally as ripples spreading from the slip point, seeding the later idea of seismic waves without formal wave vocabulary.

Activities to try

  1. 1

    Feel the stick-then-slip: a build-up-then-release model

    Why it works: Force can build up while nothing visibly moves, then release all at once; this sudden slip of underground rock is why the ground shakes, sometimes strongly, even though the pushing is slow and invisible.

    1. Loop an elastic band around a small block or brick sitting on rough sandpaper. Before pulling, PREDICT: as the far end of the band is pulled slowly and steadily, will the block slide smoothly and evenly, or do something else — and WHY?
    2. Pull the band slowly and watch: usually the block stays STUCK while the band stretches (tension builds), then suddenly JERKS forward — stick, then slip. Repeat several times and notice whether it happens the same way each time.
    3. As an alternative release model, slowly bend a dry stick or piece of dry spaghetti and feel the slow bend end in a sudden snap.
    4. Map the model to the ground: the stuck block is like rocks underground being pushed; the sudden jerk is the slip that causes an earthquake.
    5. Optionally work a simulated side-view fault rig: slowly crank a push on two rough rock blocks, watch a stress meter climb while the blocks stay stuck, then see them snap and ripples race up to houses that wobble harder near the slip and gently far away; reset and repeat.
  2. 2

    Cross-section: where the cause is and how shaking spreads

    Why it works: The underground slip is the cause; the felt surface shaking is its effect, and the energy spreads out from one spot rather than starting everywhere at once.

    1. Study (or draw) a side-view cutaway of the ground showing two rough rock blocks meeting along a fault line, the slip point deep underground, and arrows of shaking rising up to houses on the surface.
    2. Tap or point to reveal/label: the fault, the underground slip point (the cause), and the shaking spreading up and outward to the surface (the effect).
    3. Mark where the shaking would be strongest (near the slip) and where it would be gentler (far away).
    4. Say in your own words which part is the CAUSE (underground slip) and which is the EFFECT (surface shaking and cracks).
  3. 3

    Myth-buster: does the ground swallow people?

    Why it works: Earthquakes are caused by rock slipping/breaking underground along faults, not by the ground opening to swallow things and not by the weather; shaking (not swallowing) is the primary hazard.

    1. Consider the question 'Does the ground open up and swallow people in an earthquake?' and predict the answer.
    2. Reveal/discuss the answer: no — the ground shakes and can crack, but the main hazard is the shaking; huge open chasms are rare, and most earthquakes are small.
    3. Discuss a second myth: 'Can a hot, still, sunny day cause an earthquake?' Explain why not — earthquakes come from rock moving underground, not from weather.
    4. State what actually causes an earthquake in your own words, rejecting the 'ground opens up' and 'earthquake weather' explanations.

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