Tectonic hazards

• an earthquake is a sudden period of ground-shaking, most occur along plate margins where the friction and pressure between the 2 plates is suddenly released.
• there are two types of crust: oceanic and crust
• oceanic crust

  . younger

  . thin

  .denser
• continental crust

  . older

  . thicker

  . less dense
• volcanoes occur along plate margins e.g Pacific Ring of Fire or at hot spots where magma breaks through thin crust e.g Hawaii
• constructive margin

  . plates move away from each other

  . magma forces it way to the surface and as it breaks the crust there are mild earthquakes

  . the magma is very hot so allows lava to flow for along time before cooling

  . this forms volcanoes e.g mid Atlantic ridge
• conservative margin

  . two plates move past each other

  . friction between the plate causes earthquakes

  . no volcanoes as there is no magma

  . for example, San Andreas fault
• destructive margin

  . two plates move towards eachother

  . if its a continental plate and an oceanic plate:

  - oceanic is forced underneath as its more dense creating a subduction zone

  -this allows magma to rise meaning there are earthquakes+ volcanoes

  . if its two continental plates:

  -there is no subduction so no magma rises= no volcanoes

  -crust crumples causing fold mountains e.g Himalayas and powerful earthquakes
• convection currents act as a conveyor belt and move the plate along. this then leads to slab pull as gravity pulls the plate down into the mantle. all of this is ridge push, where the plates meet and move together
• Chile

  . earthquake occurred Feb 2010

  .HIC- GDP is 38th out of 193

  . Nazca plate subduction beneath the South America plate

  . magnitude of 8.8
• Nepal

  . earthquake occurred April 2015

  . LIC- GDP 109th out of 193 countries

  . Indo-austalian plate collided with Eurasia plate

  . magnitude of 7.9
• Chile effects

  primary:

  .500 killed 12000 injured and 800000 effected

  .destruction of infrastructure

  .power,water and communications cut

  . $30 billion in damage

  secondary:

  .landslides

  .coastal towns destroyed by tsunami

  . chemical plant fire meant evacuation
• Nepal effects

  primary:

  . 9000 killed, 20000 injured and 8000000 affected

  . destruction of buildings

  . power, water, communications and sanitations cut off

  . $5 billion in damage

  secondary:

  . landslides and avalanches

  . flooding caused by the landslides as rivers were blocked
• Chile responses

  immediate:

  . emergency services sent out

  . key roads repaired with in 24 hours

  . most power and water restored in 10 days

  . $60 billion national appeal built 30000 emergency wooden shelters

  long-term:

  . foreign aid

  . government reconstruction plan to help 200000 households

  . full recovery in 4 years
• Nepal responses

  immediate:

  .oversees aid and NGOs e.g Oxfam

  . helicopters from aid for search and rescue on Mt Everest

  . 300000 migrated for shelter and support from family

  long-term:

  . roads repaired, landslides cleared and flood lakes drained

  . international conference to seek technical and financial support
• why people live at risk from tectonic hazards

  • poor people have no choice
  • earthquakes and eruptions are rare
  • volcanoes bring fertile soil and geothermal energy
  • they don't know the risks
  • plate margins coincide with favorable locations
  • effective monitoring so they get given evacuation warnings
  • bring tourists, creating job opportunities
• monitoring

  volcanoes- statellites detect heat increase, seismographs record micro shakes, laser beams measure changes in ground shape

  earthquakes- generally occur without warning, bulging of ground, tremors beforehand, raise groundwater levels
• prediction

  volcanoes- monitoring allows accurate predictions and effective evacuations

  earthquakes- impossible due to a lack of clear warning signs, historical records ca help determine probability
• protection

  volcanoes- little can be done to protect property, embankments and explosives used to divert lava flow

  earthquakes- drills keep people alert, resistant construction is best way to reduce risks
• planning

  volcanoes- risk assessments and hazard mapping identify areas to restrict building or practice evacuation

  earthquakes- risk assessments and hazard mapping to identify areas to protect buildings and infrastructure