tectonics

• Crust Characteristics


  It is made up of several segments called tectonic plates, There are two kinds of crust. Continental crust, this is 25-90km, made of silica and aluminium for example granite. The other crust is known as oceanic crust, it is only 6km thick, but dense. It is made up of silica and magnesium for example basalt.
• Mantle characteristics


  It is mostly solid and made up of rocks called silicates. It is 3000km thick.
• Outer core characteristics


  It is a liquid.
• Inner core characteristics


  It is a solid which is made up of iron and nickel. It stays solid because the pressure is high it never melts. Its temperature is 3700 degrees celsius.
• Two layers that the mantle is divided into:

  • Lithosphere 
  • The most upper part of the mantle and the crust. 
  • It is 100 km thick 
  • It is thinner under the oceans. 
  • It is broken up into tectonic plates.
  • Asthenosphere
  • Upper mantle
  • Denser than the lithosphere
  • 100-300 km thick
  • 1300℃ 
  • Rocks here flow.
• Two sources of the heat that drives convection currents:


  Radioactive decay - naturally occurring elements such as uranium that release heat

  Residual energy - left behind from when the Earth was formed
• Convergent plate margins - destructive


  The oceanic plate is more dense than the continental plate. This means that is sinks into the asthenosphere. This is known as subduction, forming a deep sea trench (Peru-Chile Trench). As the oceanic plate subducts the increase in temperature and pressure forces water into the asthenosphere. The molten rock is called magma and eventually creates a composite volcano.

  When the plate subducts, friction causes the plates to catch and pressure builds up, when the pressure gets too much they slip and an earthquake occurs.
• Convergent plate margins - collision


  When two continental plates collide subduction does not occur. The plates crumple to create fold mountains. No volcanoes occur as there is no subduction. However, there can be strong earthquakes when the plates slip after pressure builds up.
• Divergent plate margins - constructive


  This is when plates move away from each other. As the plate move apart the rising heat from the asthenosphere creates magma which rises and fills the gap. As it cools it forms new oceanic lithosphere.  It forms shield volcanoes, a chain of volcanoes form creating a mid-ocean ridge. Weak earthquakes occur here as there is little pressure building up.
• Conservative plate margins


  Convection currents cause the plates to move alongside each other. The North American plate and the Pacific plate are moving in the same direction. The differing speeds of the plate movements cause friction. Pressure builds up which eventually is released causing earthquakes. There are no volcanoes here.
• Hotspots

  The parts of the convection currents that move towards the surface are called plumes. The heat here is concentrated and bring heat to the surface.  If these plumes are in the middle of tectonic plates they create hotspots. Creating shield volcanoes far away from plate margins. Hawaii is an example. As the plate moves over the hotspot it creates a chain of volcanoes, which form when they are directly over the hotspot and then become extinct as they move away.
• Where do composite volcanoes occur?

  Destructive plate boundaries
• Where do shield volcanoes occur?

  Constructive plate margins
• What creates shield volcanoes far away from plate margins?

  Plumes in the middle of tectonic plates, creating hotspots.
• What is the Volcanic Explosivity Index?


  The Volcanic Explosivity Index (VEI) measures the destructive power on a scale from 1 to 8. Mount St Helens which erupted in May 1980 measured 4. Modern humans have never experiences an eruption measuring 8.
• Characteristics of a composite volcano

  Andesitic lava erupts, andesitic lava has more silica making it more viscous (thick and sticky) so flows slowly, infrequent eruptions, violent eruption because vent becomes blocked with lava which causes pressure to build, lava bombs, pyroclastic flows, secondary hazard lahars (mudflows).
• Characteristics of a shield volcano

  Basaltic lava erupts, basaltic lava has less silica making it less viscous so flows easily, flows long distances, more frequent eruptions and gentle, primary hazard, property is destroyed from lava
• How do earthquakes form? (PRESA)

  Where two tectonic plates meet they grind against each other building up pressure. This pressure will eventually be released, jolting the rock forward. This shaking movement causes an earthquakes where seismic waves radiate from the focus (the point where the pressure was released). The rocks will settle into new positions often resulting in aftershocks (smaller earthquakes).
• What does PRESA stand for?

  P - Pressure

  R - Released

  E - Earthquake

  S - Seismic waves

  A - Aftershocks
• How are earthquakes measured?

  Earthquakes are measured using seismometers. The amount of energy released is known as the magnitude, which is shown on the Richter scale, An increase of 1 on the scale means shaking is 10 times greater.
• How are tsunamis formed?

  An earthquake occurs which has its epicentre on the sea bed. The sea bed drops and water falls into the space created by the earthquake. As the water drops or is forced upwards a wave froms and spreads out over the ocean. As the wave approaches the shore it gets slowed down by friction with the sea bed. The wave is squeezed upwards. This makes it taller. As the wave approaches the shore the water close to land is sucked back out to sea. The tsunami hits the coast.
• Primary impacts of the Japan Earthquake

  15,845 killed, 3,375 missing, 5,894 injured.

  Short term, local.

  Social - people were affected and the deaths would have caused trauma for the family.

  Economic - Many people who were dead or injured would be unable to work and contribute to the recovery.
• Primary impacts of the Japan Earthquake

  128,479 properties totally destroyed.

  Short term - Japan is a developed country, has the money to rebuild fairly quickly

  Local

  Social - People would have been left homeless, lead to long term impacts of children missing school, affecting future earning potential. Also leaves people vulnerable to diseases and sickness.

  Economic - Cost to rebuilding all the houses. Also many insurance claims.

  Environmental - Rubble in the streets that needs clearing
• Secondary impacts of Japan earthquake

  The Fukushima nuclear power plant was damaged which exposed people to radiation. 200,000 had to be evacuated. From the 20km evacuation zone.

  Long term, local.
• Social repercussions of damaged Fukushima nuclear power plant


  People may have been exposed to radiation poisoning, higher rates of cancer in the future. People lost their homes, may never be able to return.
• Economic repercussions of damaged Fukushima nuclear power plant


  Disrupted energy supply, businesses wouldn't be able to function. Wider impacts on country's GDP.
• Environmental repercussions of damaged Fukushima nuclear power plant


  Radiation impacts the plants and animals in the area, led to pollution - will take a long time to recover
• Secondary impacts of the Japan earthquake

  Agriculture devastated affecting rice production, the region impacted accounts for 3-4% of rice production.

  Long term, global.
• Social repercussions of devastated rice production

  Food shortages, potentially led to starvation and famine.
• Economic repercussions of devastated rice production

  Farmers would have lost income, Japan usually trades rice, affects country's GDP.
• Environmental repercussions of devastated rice production

  Land will have been covered in salt water, unable to grow crops on for many years.
• Short term responses to the Japan earthquake

  Earthquake measurement equipment was upgraded costing £500 million. This has reduced the time between early earthquake detection and electricity cut-off to the lines and trains, from 3 to 2 seconds.

  Short term - prevents death

  Preparation - made sure the sensors cut off the electricity when the earthquake hit
• Short term responses to the Japan earthquake

  452,000 people put into evacuation shelters

  Short term - Japan is a developed country and can rebuild quickly, people won't need to be in shelters for long

  Preparation - part of Japan's preparation for the earthquake.
• Short term responses to Japan earthquake

  Japan Self-Defence Forces (JSDF) moved debris within 2 days so goods could be delivered twice a day.

  Short term - debris is moved quickly, supports long term recovery

  Preparation - JSDF are ready to support after the earthquake
• Long term responses to the Japan Earthquake

  Michinoku ALERT 2008. JSDF carried out a massive emergency training drill. It involved 18,000 participants in 22 towns throughout the Tohoku region.

  Long term - Ensuring they are prepared for any future disaster

  Preparation - conducting drills to ensure they are ready
• Long term responses to Japan earthquake

  New Growth Strategy. Created to improve the economic growth of Japan back to what it was before the earthquake. The Japanese government approved a budget of 23 trillion yen (£190 billion).

  Long term - attempting to help Japan's economy grow in the future.
• Primary impacts of Nepal earthquake

  Villages destroyed in the Gorkha region.

  Long term - Nepal is developing, long time to recover.

  Local

  Social - homelessness, Himalayas are clod, risk of hypothermia

  Economic - already poor country, additional cost of repairing villages
• Primary impacts of Nepal earthquake

  Ancient monuments and temples destroyed in Kathmandu valley

  Long term - ancient monuments

  Global - tourist attractions people want to visit

  Social - historical importance to the locals

  Economic - damage to tourist industry
• Primary impacts of Nepal earthquake

  Over half a million homes were destroyed.

  Long term - Nepal is an LIC

  Global - may migrate to neighbouring countires

  Social - homelessness, lack of water and food, risk fo diseases, children miss school

  Economic - $$$ to rebuild, LIC

  Environmental - rubble + debris to be cleared
• Primary impacts of Nepal earthquake

  Hundreads of buildings (including businesses) were damaged or destroyed in Kathmandu.

  Long term - Nepal is an LIC, no one working because business are destroyed, makes recovery harder.

  Local

  Economic - businesses closed impacts GDP, makes recovery harder.