The document discusses several types of geohazards that can affect people including landslides, floods, volcanic eruptions, earthquakes, and tsunamis. It provides details on the causes and impacts of each hazard, noting that while the UK does not experience strong earthquakes or volcanoes, other hazards like landslides and flooding can still occur. The effects of geohazards range from property damage to loss of life depending on the scale and location of the event.

1. P1 The Earth in the Universe • IP1.8
Geohazards that might affect
us

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What Earth processes can affect us?
Geohazards that might
affect us today are:
• landslide
• flood
• the effects of a
volcanic eruption
• earthquake
• tsunami

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Landslide
Landslides are triggered
where:
• slopes are steep
• rocks are weak or
fractured
• erosion undermines a
slope
• water builds up in the
ground
• earthquakes strike
• human activities are
poorly planned

4. P1 The Earth in the Universe • IP1.8
Collapse
But, even on flat ground:
• Foundations on weak
rock can subside.
• Old mine workings can
collapse.
• Soluble rocks below
ground can dissolve.

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Flood
Floods occur:
• in low-lying areas
• after a storm upstream
• after many wet days
upstream
• if snow melts quickly
• when rivers overflow
• on stormy coasts at
high tide
• if dams burst

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Flood mayhem
It’s not just the amount of
water in a flood:
• There are thick mud
and silt deposits.
• Sewers overflow.
• Large objects are
swept away:
bridges, houses,
embankments, cars.
• There is electrical
danger.

7. P1 The Earth in the Universe • IP1.8
Eruption afar
There are no active volcanoes in the UK, but a major eruption
elsewhere may cause:
• a volcanic winter – from ash and sulfur dioxide in the atmosphere
• drought over great regions
• widespread crop failure in summer, bitter cold in winter
• the whole Earth cooled
• fantastic sunsets

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Eruption on your doorstep
Catastrophic effects include:
• blast: 30 km+ • tsunami
– everything is destroyed – a great wave in coastal areas
• glowing cloud • lava flow
– a red-hot current of ash – rarely kills because you can get
– travelling with speeds of 100 km/h+ out of the way
• lahar
– waterlogged volcanic ash flooding
down valleys

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Earthquakes in the UK
• They are not big enough to make
surface waves, so little damage
occurs.
• We can feel seismic waves.
• Recent UK earthquakes:
www.quakes.bgs.ac.uk/recent_events/recent_events.html
• Earthquakes are plotted from
eyewitness accounts.
• If you feel an earthquake, send in
your evidence:
www.quakes.bgs.ac.uk/questionnaire/EqQuestIntroB.html

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Earthquake
In a catastrophic earthquake:
• The ground rises and falls in waves. • There may be a tsunami – a huge
• There is total destruction of wave in coastal areas.
non-flexible structures. • Many die afterwards from disease.
• People are killed by falling buildings – • The most recent big earthquake:
outside is safest. earthquake.usgs.gov/eqcenter/
• There is risk from falling glass and fire recenteqsww/index.php?old
storms. =world.html

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Tsunami
These huge waves produced by
volcanic eruptions, earthquakes, or
submarine landslides:
• can form waves over 40 m high
• can reach speeds of 1000 km/h
• can travel 10 000 km across oceans,
killing thousands in coastal areas
• can trick you, because water first
draws back from the coast – and
then thunders back in

12. P1 The Earth in the Universe • IP1.8
Worry? – Us?
• Major eruptions and earthquakes • But – could a geohazard happen
affect only the active zones of the here?
Earth.
• What might its effects be?
• They don’t happen in the UK.