Earthquakes

• Earthquakes and volcanic eruptions are caused by the movement of tectonic plates
• Tectonic hazards can destroy buildings, infrastructure, and cause deaths
• The Earth is made up of different layers:

  • The inner core: solid, hottest part of the Earth, made of iron and nickel with temperatures up to 5,500°C
  • The outer core: liquid layer made of iron and nickel
  • The mantle: thickest section of the Earth, made of semi-molten rock called magma
• The Earth's crust is the outer layer, either continental or oceanic, and is broken into tectonic plates
• Mechanisms like slab pull and ridge push are believed to move the tectonic plates
• Slab pull occurs when older, denser tectonic plates sink into the mantle at subduction zones, pulling newer and less dense sections of plate along behind
• Instead of tectonic plates moving because of convection currents, evidence suggests it is the plates that drive the convection
• How many different types of crusts are there?

  2
• What is the continental crust?

  • found under land masses or continents. It is generally older than oceanic crust and is less often destroyed.
• What is the oceanic crust?

  It is found underneath the oceans. It is denser than continental crust and can be subducted.
• What plate margins do earthquakes occur on?

  All 3
• What plate margins do volcanoes occur?

  Constructive and destructive
• Where are most of the world's volcanoes located?

  Around the ring of fire in the pacific
• What is a destructive plate margin?

  A destructive plate margin is a boundary where two tectonic plates collide, resulting in the destruction and subduction of one plate beneath the other.
• Describe how volcanoes and earthquakes occur at destructive plate margins.

  As the plates collide, the oceanic plate is forced beneath the continental plate. This is known as subduction. This happens because the oceanic plate is denser (heavier) than the continental plate.

  When the plate sinks into the mantle it melts to form magma. The pressure of the magma builds up beneath the Earth's surface. The magma escapes through weaknesses in the rock and rises up through a volcano. The volcanic eruptions are often violent, with lots of steam, gas and ash.
• If two continental plates collide what happens?

  If two continental plates collide, neither can sink and so the land buckles upwards to form fold mountains. This is called a collision margin. Earthquakes can occur at collision margins.
• What is a constructive plate margin?

  A constructive plate margin is a boundary where two tectonic plates move away from each other, resulting in the formation of a new crust.
• What is a conservative plate margin?

  A conservative plate margin is a boundary where two tectonic plates slide past each other horizontally without creating or destroying crust.
• What do we use to measure earthquakes?

  Seisometer
• What do we use to categorise earthquakes?

  Richter scale.
• What is slab pull?

  Force exerted on a tectonic plate by the weight of a subducting slab.
• Causes of earthquakes:

  • Earthquakes are caused by the release of built-up pressure at plate margins
• Effects of earthquakes can vary depending on:

  • The size of the earthquake on the Richter scale
  • Level of development of the affected area
  • The depth of the focus
  • Distance from the epicenter
  • Population density
  • The time of day
• Primary effects of earthquakes are immediate, while secondary effects occur in the hours, days, and weeks after the initial earthquake
• Responses to earthquakes are categorized as short-term or immediate responses in the days and weeks after the disaster, mainly involving search and rescue, and long-term responses that involve rebuilding and kick-starting the local economy
• Immediate and long-term strategies after an earthquake:

  • Rescue services and army quickly move into the affected area to clear roads and create access paths
  • Healthcare: field hospitals set up, doctors and nurses flown in, patients flown out for treatment
  • Shelter: army builds temporary shelters quickly for over 300,000 homeless
  • Rebuilding: Reconstruction Design Council with a budget of over 23 trillion Yen to rebuild houses
• Earthquakes are caused by the release of built-up pressure at plate margins, leading to destruction of buildings and infrastructure
• Prediction of earthquakes involves using seismometers to monitor earth tremors, experts can predict where earthquakes are likely to happen but it's difficult to predict when they will occur
• Protection against earthquakes includes constructing buildings with safety measures like rubber shock absorbers in foundations and steel frames that can sway during earth movements
• Preparation for earthquakes in earthquake-prone countries involves drills in public buildings so people know what to do in case of an earthquake, reducing the impact and increasing chances of survival