GCSE · Geography · AQA · Spec 8035

Primary and secondary effects of a tectonic hazard

When the ground stops shaking, the disaster isn't over. Some of the damage is still on its way — and sometimes it's the worst of it.

Sort the effects

The instant hit, or the knock-on?

Pick an effect, then choose where it goes. You'll see why straight away — right or wrong.

Did it happen instantly, as the ground shook or the volcano erupted — or in the hours, days and weeks after?

Still to sort

Instantly → primary (0)

Happens as the ground shakes or the volcano erupts.

Hours, days or weeks later → secondary (0)

Follows after the hazard itself.

Where the line is: Timing is a good clue, but it can blur: landslides often come some time after the shaking — and geographers still argue about which box they belong in.

15 of 15 still to sort.

Sorted everything with Test 1? Switch to Test 2 and sort the same effects again. Notice the two tests nearly always agree — and notice the one effect where the line gets blurry.

Exam line: When you write about a secondary effect, name the primary effect it came from: 'fires broke out because ground movement fractured gas pipes'.

Follow the knock-ons

Every secondary effect has a parent

Here are seven effects of an earthquake. Draw the arrows: which effect leads to which? Point each arrow from the cause to the knock-on. Careful — one effect has more than one cause.

Gas pipes fractured
Fires
Homes destroyed
Homelessness
Sanitation destroyed
Roads blocked
Disease spreads (outcome)

Add a link

This factor……made this happen or worse

No links yet.

Exam line: One secondary effect can have several causes. Disease after an earthquake has three roots here — name at least one of them whenever you mention it.

What do you really think?

Does 'secondary' mean 'less serious'?

A classmate says: "Primary effects are the big, deadly ones. Secondary effects are the smaller stuff that happens afterwards."

Which of these is closest to what you think right now?

Secondary effects are always smaller and less serious than the primary ones.If something happens weeks later, it isn't really an effect of the hazard any more.Every effect fits neatly into one box — primary or secondary.A secondary effect can sometimes do more damage than the primary effects that set it off.

How sure are you?

I'm sureI think soI'm guessing

Secondary effects are always smaller and less serious than the primary ones.

This is a common misconception

That's the trap hiding in the word. 'Secondary' means knock-on, not second-rate. Secondary effects sometimes cause more destruction than the primary effects — mudslides following a volcanic eruption are an example. The label tells you how an effect happened, never how bad it was.

If something happens weeks later, it isn't really an effect of the hazard any more.

This is a common misconception

It still is — follow the arrows back. Disease weeks after an earthquake spreads because sanitation was destroyed and roads were blocked. Take away the earthquake and that chain never starts. A secondary effect is still the hazard's effect; it just arrived by a longer route.

Every effect fits neatly into one box — primary or secondary.

This is a common misconception

Most do, but not all. Landslides are the awkward one. They're usually classed as secondary: the shaking destabilises slopes, and soil and rock often slide downhill some time afterwards. But some geographers class them as primary. So if you write about landslides, say they're usually secondary — and that they're hard to categorise.

A secondary effect can sometimes do more damage than the primary effects that set it off.

This matches the evidence

Exactly right. 'Secondary' describes the route, not the size. Secondary effects sometimes cause more destruction than the primary ones — mudslides following a volcanic eruption are an example. So never rank effects by their label.

Primary or secondary tells you how an effect happened — instantly and directly, or as a knock-on. It never tells you how serious it was.

A real earthquake

Haiti, 2010: find the evidence

The 2010 earthquake in Haiti

In 2010, an earthquake struck Haiti. An estimated 220,000 people were killed by collapsed buildings, and about 300,000 homes were damaged or destroyed. Thousands of landslides in the hills around Port-au-Prince destroyed many properties.

Roads were damaged and blocked by rubble, and severe destruction of the harbour delayed emergency supplies entering the country by sea.

600,000 people left Port-au-Prince to stay with friends and relatives, increasing social pressure elsewhere in Haiti. And by July 2011, cholera had killed almost 6,000 people.

Question 1 of 3

Tap the three phrases that describe PRIMARY effects of the earthquake.

Tap the words in the passage that prove your answer.

Exam line: A named example earns its keep through its details: the effect, the figure, and whether it was primary or secondary.

Your turn to write

Describe the effects of a volcanic eruption

Describe the primary and secondary effects of a volcanic eruption. [6 marks]

Your answer

0 words · your answer stays on this page and is not sent anywhere.

The mark scheme

Primary: lava flows, which destroy anything in their path. (1 mark)
Primary: pyroclastic flows — the most deadly effect — which destroy, kill or burn anything in their path. (1 mark)
Primary: ashfall — its weight can collapse roofs, and it can contaminate water sources and cover farmland. (1 mark)
Primary: poisonous gases, which can kill humans, livestock and wild animals. (1 mark)
Secondary: crop failure, because ashfall covers farmland and damages crops. (1 mark)
Secondary: disruption to air travel, because ash in the atmosphere can damage plane engines. (1 mark)
Secondary: climate cooling, because ash in the atmosphere can block incoming solar radiation. (1 mark)

Model answer

The primary effects happen during the eruption itself. Lava flows destroy anything in their path, and pyroclastic flows — the most deadly effect — destroy, kill or burn anything they reach. Ashfall can collapse roofs under its weight, contaminate water sources and cover farmland, and poisonous gases can kill humans, livestock and wild animals. The secondary effects are knock-ons, and most of them come from the ash. Where ash covers farmland, it damages crops and they fail. Ash in the atmosphere can damage plane engines, so air travel is disrupted, and it can block incoming solar radiation, which can cool the climate.

Notice how many secondary effects trace back to one primary effect: ash. That's the knock-on idea doing the work for you.

Exam line: For each secondary effect, name the primary effect it grew from. 'Crop failure' alone is thin; 'crop failure, because ash covers farmland and damages crops' is an explanation.

WHAT YOU'VE LEARNED

A quick recap of today's lesson.

What happens the instant the ground shakes or a volcano erupts — and the knock-on effects that follow for days and weeks.

What you need to know

A primary effect happens instantly, as a direct result of the earthquake or volcanic eruption itself.
A secondary effect is an indirect, knock-on result of a primary effect, following in the hours, days and weeks after the hazard.
Two questions sort any effect: When did it happen? And was it caused by the hazard directly, or by another effect? Timing is a good clue, and a secondary effect is always a knock-on of another effect.
'Secondary' describes how an effect happened, not how bad it was — secondary effects sometimes cause more destruction than the primary ones.
Landslides are usually classed as secondary, but some geographers class them as primary, so they are hard to categorise.

The big picture

The effects of an earthquake or volcanic eruption come in two kinds. Primary effects happen instantly, as a direct result of the hazard itself — buildings collapsing as the ground shakes, lava and pyroclastic flows, ashfall. Secondary effects are knock-ons of those primary effects, following in the hours, days and weeks after — fires from broken gas pipes, disease, homelessness, crop failure. Timing is a good clue; the other question is whether another effect caused it. Secondary never means less serious, and landslides are hard to categorise.

Key points

1Earthquake, primary: buildings and other infrastructure collapse; people are killed or injured by falling debris or trapped under rubble; gas pipelines are fractured by ground movement.

2Earthquake, secondary: fires (leaking gas lit by a spark), homelessness (homes destroyed), disease (sanitation destroyed, clean water blocked, crowded camps) and tsunamis (the seabed moves and displaces the water above).

3Volcano, primary: lava flows, pyroclastic flows (the most deadly effect), ashfall and poisonous gases.

4Volcano, secondary: crop failure, disruption to air travel and climate cooling — each one a knock-on of ash.

5Haiti 2010, primary: roads blocked by rubble, an estimated 220,000 killed by collapsed buildings, about 300,000 homes damaged or destroyed. Secondary: cholera killed almost 6,000 by July 2011, 600,000 people left Port-au-Prince, thousands of landslides, and a wrecked harbour delayed emergency supplies by sea.

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Worked example

Problem

Explain why a tsunami is classed as a secondary effect of an earthquake.

⚠ Watch out

Calling ashfall a secondary effect because the crops fail later. The ash landing is primary — it falls as a direct result of the eruption. It's the crop failure that follows from it that is secondary. Keep the cause and its knock-on in separate boxes.

🧠

Memory hook

Think dominoes. The hazard knocks over the first dominoes directly — those are primary effects. Any domino that falls because another one hit it is secondary. Real knock-ons branch rather than falling in one line, but the question stays the same: what knocked this one over?

✓

Check yourself

Without looking back: name one primary effect of an earthquake and a secondary effect it leads to. Then do the same for a volcanic eruption, and say what links each pair.

Flashcards

(14)

What is a primary effect of a tectonic hazard?

An effect that happens instantly and as a direct result of the earthquake or volcanic eruption itself — for example, buildings collapsing as the ground shakes.

What is a secondary effect of a tectonic hazard?

An indirect, knock-on result of the primary effects, following in the hours, days and weeks after the hazard.

Is timing enough to decide if an effect is primary or secondary?

Timing is a good clue — primary is immediate, secondary comes in the hours, days and weeks after. But check the cause too: a secondary effect is always a knock-on of another effect.

Why can fires break out after an earthquake?

Ground movement fractures gas pipelines (primary). Gas leaking from the broken pipes is ignited by a spark, so the fire is a secondary effect.

Why is homelessness a secondary effect of an earthquake?

People are homeless because the earthquake destroyed their homes — it is a knock-on of that destruction, not of the shaking directly.

Give three reasons disease can spread after an earthquake.

Sanitation is destroyed; blocked roads stop clean water being brought in; and diseases spread quickly among people living on the streets or in camps.

Are landslides a primary or a secondary effect of an earthquake?

Usually secondary: shaking destabilises slopes, and soil and rock slide downhill, often some time later. But some geographers class them as primary, so they are hard to categorise.

Are secondary effects always less serious than primary ones?

No. Secondary effects sometimes cause more destruction than the primary effects — for example, mudslides following a volcanic eruption.

What is the most deadly effect of a volcanic eruption?

Pyroclastic flows. They destroy, kill or burn anything in their path — a primary effect.

Lava flows and poisonous gases: primary or secondary — and what do they do?

Both primary. Lava flows destroy anything in their path; poisonous gases can kill humans, livestock and wild animals.

Name three kinds of damage ashfall can do.

Its weight can collapse roofs; it can contaminate water sources; and it can cover farmland. Ashfall itself is a primary effect.

Which three secondary effects of an eruption are knock-ons of ash?

Crop failure (ash covers farmland and damages crops), disruption to air travel (ash in the atmosphere can damage plane engines) and climate cooling (ash in the atmosphere can block incoming solar radiation).

Haiti earthquake, 2010: what were its primary effects?

Roads were damaged and blocked by rubble; an estimated 220,000 people were killed by collapsed buildings; about 300,000 homes were damaged or destroyed.

Haiti earthquake, 2010: what were its secondary effects?

By July 2011 cholera had killed almost 6,000 people; 600,000 people left Port-au-Prince to stay with friends and relatives; thousands of landslides destroyed many properties; severe destruction of the harbour delayed emergency supplies arriving by sea.

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.

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The instant hit, or the knock-on?

Every secondary effect has a parent

Does 'secondary' mean 'less serious'?

Haiti, 2010: find the evidence

Describe the effects of a volcanic eruption

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