Volcanic and mass-movement hazards
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Flip to reveal answersDefine a volcanic hazard.
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All 12 Flashcards — Volcanic and mass-movement hazards
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Question
Define a volcanic hazard.
Answer
Any threat from a volcano - **lava flows, pyroclastic flows, lahars, ashfall (tephra)** and toxic gases.
Question
Define a mass movement.
Answer
The **downslope movement of rock, soil or debris under gravity** - rockfalls, landslides, debris flows, slumps.
Question
What is a pyroclastic flow?
Answer
A **fast, super-hot cloud of gas and ash** - the deadliest volcanic hazard, impossible to outrun.
Question
What is a lahar?
Answer
A **volcanic mudflow** of ash and water that races down valleys and buries settlements.
Question
What is tephra / ashfall?
Answer
Fragments thrown out by an eruption that **collapse roofs and ruin farmland**.
Question
What is a trigger for a mass movement?
Answer
The event that sets a slope failing - **heavy rain, an earthquake, undercutting, or an eruption**.
Question
Why is a pyroclastic flow far deadlier than a lava flow?
Answer
It is **fast and super-hot**, so there is no escape; lava is **slow**, destroying property but giving time to leave.
Question
What controls a hazard's severity?
Answer
Its **type and speed**, the **warning time**, **population density**, and the people's **vulnerability** (wealth, housing).
Question
Case study - Nevado del Ruiz (1985)?
Answer
A small eruption melted summit ice; **lahars** buried Armero, killing about **23,000** - warnings were not acted on.
Question
Case study - Eyjafjallajokull (2010)?
Answer
A moderate eruption killed nobody, but its **ash cloud grounded European flights** - a huge economic impact.
Question
Case study - Haiti (2010)?
Answer
The earthquake triggered **landslides** on deforested slopes; over **200,000** died, worsened by poverty and weak housing.
Question
How do you read a hazard distribution diagram?
Answer
**Identify** the modal band, **estimate** by counting events above a threshold, and read coordinates/distance off the **key or scale**.
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Full study notes for Volcanic and mass-movement hazards
Topic 10.2 hub
Geophysical hazard risks
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