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P1 The Earth in the Universe • IP1.8




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



 What Earth processes can affect us?




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



 Landslide


 Landslides are triggered
 where:
 • slopes are steep
 • rocks are we...
P1 The Earth in the Universe • IP1.8



 Collapse




 But, even on flat ground:
 • Foundations on weak
   rock can subsid...
P1 The Earth in the Universe • IP1.8



 Flood




 Floods occur:
 • in low-lying areas
 • after a storm upstream
 • after...
P1 The Earth in the Universe • IP1.8



 Flood mayhem




 It’s not just the amount of
 water in a flood:

 • There are th...
P1 The Earth in the Universe • IP1.8



 Eruption afar




 There are no active volcanoes in the UK, but a major eruption
...
P1 The Earth in the Universe • IP1.8



 Eruption on your doorstep




 Catastrophic effects include:
 • blast: 30 km+    ...
P1 The Earth in the Universe • IP1.8



 Earthquakes in the UK




 • They are not big enough to make
   surface waves, so...
P1 The Earth in the Universe • IP1.8



 Earthquake




 In a catastrophic earthquake:
 • The ground rises and falls in wa...
P1 The Earth in the Universe • IP1.8



 Tsunami




 These huge waves produced by
 volcanic eruptions, earthquakes, or
 s...
P1 The Earth in the Universe • IP1.8



 Worry? – Us?




 • Major eruptions and earthquakes       • But – could a geohaza...
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Ip1 8

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Ip1 8

  1. 1. P1 The Earth in the Universe • IP1.8 Geohazards that might affect us
  2. 2. P1 The Earth in the Universe • IP1.8 What Earth processes can affect us? Geohazards that might affect us today are: • landslide • flood • the effects of a volcanic eruption • earthquake • tsunami
  3. 3. P1 The Earth in the Universe • IP1.8 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. 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.
  5. 5. P1 The Earth in the Universe • IP1.8 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
  6. 6. P1 The Earth in the Universe • IP1.8 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. 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
  8. 8. P1 The Earth in the Universe • IP1.8 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
  9. 9. P1 The Earth in the Universe • IP1.8 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
  10. 10. P1 The Earth in the Universe • IP1.8 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
  11. 11. P1 The Earth in the Universe • IP1.8 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. 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.

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