Give typical speeds and temperatures for a pyroclastic flow.

They commonly travel at well over 100 km h⁻¹ and can reach several hundred degrees Celsius, in some cases around 700°C.

Why is a pyroclastic flow so lethal?

It moves far faster than anyone can run, it is hot enough to kill instantly, and it fills the lungs with ash, so almost nobody caught in one survives.

Give an exception in which a lava flow did kill people.

The 2002 eruption of Nyiragongo in the Democratic Republic of Congo, whose unusually fluid lava reached the city of Goma quickly, killing about 150 people and leaving around 120,000 homeless.

WJEC A-Level Geography 601-8455-3

Coastal Landscapes

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Tectonic Hazards

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Development in an African ContextContemporary theme

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Tectonic Hazards

Primary volcanic hazards

3 things to know
AS Unit 1 and A2 Unit 4

Overview

Pyroclastic flow, three hazards created by a heavy fall of ash and main gases released by a volcano.

What you need to know

Answer each one before you reveal it.

Your recallNot started

Key term

What is a pyroclastic flow?

Numbers

Name an eruption in which a pyroclastic flow destroyed a whole town.

Key term

Why do lava flows rarely kill people?

Questions from this subtopic

Each one with the model answer underneath.

1
What is a pyroclastic flow?
Model answer
A pyroclastic flow is a ground-hugging avalanche of hot gas, ash and rock fragments that rushes down the flanks of a volcano.
2
Give typical speeds and temperatures for a pyroclastic flow.
Model answer
They commonly travel at well over 100 km h⁻¹ and can reach several hundred degrees Celsius, in some cases around 700°C.
3
Why is a pyroclastic flow so lethal?
Model answer
It moves far faster than anyone can run, it is hot enough to kill instantly, and it fills the lungs with ash, so almost nobody caught in one survives.
4
Name an eruption in which a pyroclastic flow destroyed a whole town.
Model answer
The 1902 eruption of Mont Pelée on Martinique, whose pyroclastic flow destroyed St Pierre and killed around 28,000 people in a matter of minutes.
5
Why do lava flows rarely kill people?
Model answer
Most lava advances slowly enough for people to walk clear of it, so it destroys property rather than life.
6
Give an exception in which a lava flow did kill people.
Model answer
The 2002 eruption of Nyiragongo in the Democratic Republic of Congo, whose unusually fluid lava reached the city of Goma quickly, killing about 150 people and leaving around 120,000 homeless.

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