Global Hazards

• Global Atmospheric Circulation (1):

  At the equator:

  • The earth's surface is warmed by the Sun at the equator. The Earth transmits heat to nearby air. This air gets hotter and rises. The rising, hot air forms a low-pressure belt. As the hot air rises, the air will begin to cool, with water vapor condensing, creating rain and clouds.
  • The rising air cools and moves away from the equator towards 30 C north and 30C south.
• Global Atmospheric Circulation (2):

  At 30C North and South:

  • The air is further away from the equator and cold air forms, resulting in a high-pressure belt with minimal rainfall and no clouds
• Global Atmospheric Circulation (3):

  At 60C North and South:

  • Cold air blown from the poles meets warm air surface winds as the warmer air is less dense, it rises and forms a lower pressure belt
• Global Atmospheric Circulation (4):

  At the poles:

  • At the north and south poles, cold air sinks forming a high pressure belt
  • This high pressure belt will move back towards the equator, forming as a surface wind.
• Extreme weather is a weather event that is significantly different from the average/ usual weather pattern
• A drought is a period of time with abnormally dry weather leading to a shortage of water
• El Nino:

  • Sinking air in the western Pacific causes high pressure, leading to unusually dry weather. This can cause droughts and much less rainfall.
  • Rising air in the eastern Pacific causes low pressure leading to unusually wet weather causing serious floods.
• La Nina:

  • Sinking air in the eastern Pacific causes high pressure, leading to unusually dry weather. This can cause droughts and much less rainfall.
  • Rising air in the western Pacific causes low pressure leading to unusually wet weather causing serious floods.
• CASE STUDY: Big Dry(Non-Uk based extreme weather hazard event):

  Causes:

  • El Nino events led to especially low rainfall in South East Australia
  • Climate change
  • Increased temperature than usual in that period
• CASE STUDY: Big Dry(Non-Uk based extreme weather hazard event):

  Consequences:

  Environmental:

  • Less electricity could be produced using water so more coal had to be burned to produce electricity, producing more CO2
  • The drought caused vegetation and soil erosion
• CASE STUDY: Big Dry(Non-Uk based extreme weather hazard event):Consequences:

  Economical:

  • Farmers had to sell their cattle as they couldn't afford to feed them and food prices increased
  • caused rural-urban migration which put greater pressure on cities and rural areas
  • Water bills rose by 20%

  Social:

  • Hundreds of houses were destroyed
  • 8 people were killed
  • suicide rates of farmers increased due to not being able to provide water to their livestock, which caused them to sell their farms
• CASE STUDY: Big Dry(Non-Uk based extreme weather hazard event):

  Responses:

  • The government gave $400 - $600 to farmers per fortnight to compensate farmers for the loss of their livelihood.
  • The government provided more than 23000 rural families and 1500 small businesses with income support for survival.
• A flash flood is a sudden localised flood to heavy rain
• CASE STUDY: Bostcastle floods(UK based extreme weather event):

  Causes:

  Natural:

  • 75mm of rain received in just 2hrs - above average
  • Rain and rising high tide caused the river levels to increase by 2.15m in only 1hr
  • Geology in the area was impermeable, so there was lots of surface runoff

  Human:

  • Pattern of the streets allowed water to run off easily
  • Cars and trees in the flood were trapped under the bridge, which formed a dam, allowing water to go through another route, damaging the buildings and the village more.
• CASE STUDY: Bostcastle floods(UK based extreme weather event):

  Consequences:

  Environmental

  • Trees destroyed due to flood carried downstream
  • 4 bridges were washed away

  Economic:

  • Had to spend £2billion to sort out the flooding
  • 90% of the economy depended on toursim. 20 hotels were forced to shut
  • 25 businesses were destroyed

  Social:

  • 58 properties were destroyed
  • Some residents suffered mental health problems
  • 1000 tourists and residents were destroyed
• CASE STUDY: Bostcastle floods(UK based extreme weather event):

  Responses:

  • 7 helicopters and emergency services were sent to rescue the people
  • Virgin trains had to cancel 20 trains
• Destructive plate boundary(convergent):

  • When two plates are moving towards each other
  • When an oceanic plate meets a continental plate, the denser oceanic plate is forced down into the mantle and destroyed,forming volcanoes and ocean trenches.
• Collision plate boundary(convergent):

  • Both plates are made from continental crust and move towards each other
  • Both plates are folded up and forced upwards, forming fold mountains
• Constructive boundaries(Divergent):

  • When two plates are moving away from each other
  • Magma rises and fills gaps and cools, creating new crust
• Conservative Boundary:

  • Where 2 plates are moving sideways past each other
  • Crust isn't created or destroyed
• The thickness of the oceanic crust is 5 - 10 km thick

  The thickness of the continental crust is 25-100km thick
• Convection is the process of which the mantle is heated by the core and the heated magma rises towards the crust
• An earthquake is a violent shaking in the earth's crust
• Shockwaves are the transfer of energy that radiate out of the focus
• The focus is the point where the ground snaps and moves
• The epicentre is the point on land above the focus
• The hotspot is the place in the middle of a tectonic plate where hot magma rises