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Hazards

Volcanic Hazards and Eruption Magnitude

  • 4 things to know
  • Component 1

Overview

Recall questions on nuées ardentes, lava flows, lahars, pyroclastic fallout and ash, volcanic gases and acid rain, the size classes of ash, lapilli and bombs, the global distribution of volcanoes, the VEI and why eruption frequency varies.

What you need to know

Answer each one before you reveal it.

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Key term

Define lava flows and state three factors that determine how far they travel.

Key term

What is pyroclastic fallout?

Numbers

What is the size range for lapilli?

Key term

Describe the global spatial distribution of volcanoes.

Questions from this subtopic

Each one with the model answer underneath.

  1. 1

    What are nuées ardentes?

    Model answer

    Fast-moving currents of hot gas and volcanic matter (pyroclastic flows) that travel down volcanic slopes at speeds up to 700 km/h and temperatures exceeding 400°C

  2. 2

    Define lava flows and state three factors that determine how far they travel.

    Model answer

    Streams of molten rock that move downslope from a volcanic vent; their speed and distance are determined by viscosity, temperature and gradient

  3. 3

    What are lahars and how can they be triggered?

    Model answer

    Mixtures of volcanic debris and water that flow rapidly down valleys; triggered when eruptions melt ice or snow, or when heavy rain mobilises loose ash deposits

  4. 4

    What is pyroclastic fallout?

    Model answer

    Fragmented volcanic material ejected into the atmosphere that falls back to the surface, ranging from fine ash to larger bombs and blocks

  5. 5

    State five impacts that ash fallout can have on human populations and infrastructure.

    Model answer

    Collapse of roofs under its weight, contamination of water supplies, damage to crops, disruption to aviation, and respiratory problems over wide areas downwind

  6. 6

    Name the volcanic gas that is most abundant by volume in volcanic emissions.

    Model answer

    Water vapour

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Rapid timed gap-fills on the terms and numbers you need to recall without thinking.

AThe horns have less sand volume, so they move more quickly.
BSand is transported up the gentle windward slope via saltation.
CSand accumulates at the crest.

Build It gets the exam shape right

Assemble a full-mark answer from its marking points, in the order an examiner wants them.

Weathering means breakdown of rock in place.
TrueFalse

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Spot the fault in a statement. The traps are the mistakes students actually make.

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Short focus games to reset attention, so the next set lands better than the last.

Every question in Hazards, on a schedule.

Attempt a question from memory, write the correct version, then attempt it again. Levo records the jump between your first attempt and your last, and brings each question back on the day you are due to forget it.

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