Geography Hazardous Environments

• Earthquake


  A violent shaking of the earth's crust

  e.g. Japan 2011
• Volcanic eruption

  An ejection of molten rock, ash or gases from a volcano

  e.g. Monsterrat (1995-1997)
• Tropical cyclone/hurricane/typhoon


  A weather system of very low pressure formed over tropical seas involving strong winds and heavy rainfall
• Distribution and characteristics of earthquakes

  Most earthquakes occur along plate margins especially destructive margins and along the ring of fire (E.g. Japan 2011) Some occur away from main areas due to human processes like fracking or hotspots
• Most occur at place boundaries (destructive and constructive)

  Some occur at hotspots e.g in Hawaii

  75% of historically active volcanoes in Pacific Ring of Fire
• Reasons why people live in hazardous areas

  Social:

  Family and community

  Lack of education

  Densely populated (Honshu, Japan 104 million ppl)

  
  

  Economic:

  Can't afford to move away

  Tourism industry around volcanic scenery/tropical climates creating income. (E.g. 14% of Carrribean GDP)

  
  

  Physical/environmental:

  Fertile soil for farming

  Geothermal energy
• Reasons some countries are more vulnerable than others to impacts of natural hazards

  Physical:

  Global location (near plate boundaries)

  Geology

  
  

  Social:

  Population density

  Education

  
  

  Economic

  Wealth and development of country (healthcare/buildings)

  Insurance (poor ppl cant access with bad homes)
• Volcano short term and long term impacts

  Soufriere Hills Montserrat 1995-1997


  Short term:

  Deaths (19)

  Injuries (7)

  Displacement (2/3 island forced to leave)

  
  

  Long term:

  Political centre destroyed (Plymouth covered in ash)

  Depopulation (12k in 1995 to 1.5k in 2001)
• Tropical cyclone

  Typhoon Haiyan


  Short term:

  Deaths (6.19k)

  Injuries (29k)

  Homelessness (4.1 million people and 1.1 million houses damaged)

  
  

  Long term:

  Lack of education (schools destroyed)

  Increased food prices (12% by 2014)
• Earthquakes


  Japan short term:

  15894 deaths 6152 injuries

  4.4 million households in north east japan left without electricity

  Long term:

  Distruption to transport network (Tohoku expressway)

  Economic cost was 235 billion most expensive natural disaster
• Earthquakes hazard prevention


  Seismometers record time, location, magnitude of vibrations in Earth's crust

  ShakeAlert USA

  
  

  Use damper engineering for seismic resistance (E.g. Taipei 101)

  GIS calculate low and high risk areas based on past info

  Short term- locating and rescuing/treating injured

  Long term- risk assessment, hazard mapping
• Hazard management Japan


  Japan:

  Short term:

  Direct response to identify areas in need e.g 11 military aircraft surveyed the dmg within 30 mins

  Building design- less than 1000 ppl died cuz of building collapse

  Long term:

  Education (e.g 1st September Disaster Prevention Day)

  Insurance (e.g. only 7% have insurance to cover dmg)
• Hazard management Turkey-Syria


  Short term:

  Building deaths due to lack of enforcement of earthquake resistant design

  Ppl allowed to ignore building codes if paying a fee 'construction amnesties'

  Syrian civil war caused divided land with little coordination. Refused to give aid to opposition areas

  
  

  Long term:

  Hazard mapping

  Lack of land use planning
• Focus


  Centre of the earthquake underground
• Epicentre


  Point on the surface directly above the focus
• Hotspots


  Situated above a plume of magma below the crust and becomes extremely hot which rises creating volcanic activity

  Found at plate boundaries (Iceland) or away like (Hawaii)

  Hawaii has chain of volcanic islands
• Destructive boundary


  Plate move together

  Heavier plate (oceanic) subducts under the continental (lighter)

  Volcanic eruptions and earthquakes

  Earthquakes are stronger

  
• Constructive boundary


  Plates move away from each other

  Volcanic eruptions and earthquakes

  Earthquakes are weaker

  e.g. Mid Atlantic Ridge
• Conservative boundary


  Plates slide past each other in opposite directions/same direction in diff speed

  Only earthquakes occur

  e.g. San Andreas Fault
• Tsunamis


  Most tsunamis caused by earthquake only 5% are caused by volcanic eruption e.g. Hunga tonga- hunga ha'apai 2022

  Created by vertical displacement of the sea causing water to push upwards

  Friciton between seabed and tsunami slows the wave down

  Wavelength decresaes but height increases known as shoaling
• Coriolis Force


  Tropical cyclones rotate around their central point because of this force generated by the Earth's rotation.
• wind shear


  A change in wind conditions
• Causes of tropical cyclones

  Low-pressure areas (less than 950mb)

  Tropical Cyclones require specific conditions to form

  Sea surface temperatures over 27°C

  Between 5° and 20° north and south of the equator

  Low wind shear

  A deep layer of humid air
• Storm surges


  a rapid rise in sea level caused by really low-pressure storms