tectonic plates

• Tectonic plates are pieces of earths crust uppermost mantle, together refer to as the lithosphere
• Tectonic plates are 100km thick and move at 10cm per year
• Oceanic crust - also called sima from silicon and magnesium.
• Earthquakes and volcanoes are caused by the movement of tectonic plates.
• Plate margin is the boundary between two tectonic plates.
• Ridge push - at mid-ocean ridges, the oceanic lithosphere is higher than it is where it sinks onto the asthenosphere. Because of the ridge push, the oceanic lithosphere slides downhill under the force of gravity.
• Convection - hot rock from deep within the earth rises but cooler rock near the surface sinks. Convection causes, the oceanic lithosphere to move sideways and away from the mid-ocean ridge
• Slab pull - because oceanic lithosphere is denser than the asthenosphere, the edge of the tectonic plate that contains oceanic lithosphere sinks and pulls the rest of the tectonic plates with a process of slab pull
• Shield volcanoes

  • gently sloping sides
  • Formed by frequent, gentle eruptions of thin, runny lava
  • 4100+ metres in height
  • Usually found at constructive boundaries or over hotspots
  • Nice to live near
• Rift valley - a magma chamber below land fills with upwelling magma. This causes pressure on the land above. The pressure releases and drops, causing the land to stretch and drop, the land will collapse once its elasticity has strained. This creates a landform: a rift valley.
• Iceland -

  • 400km magma superploom serves it
  • Volcanoes are vicious
  • Sits on a constructive boundary
  • Ends up with super explosive volcanoes
• subduction - a process that takes place at a destructive boundaries, where one plate moves under another, due to being denser, into the asthenosphere (lower mantle)
• Destructive collision

  • earthquake busy
  • When two continental plates meet at a destructive boundary, the continents themselves collide
  • Usually, there has been an earlier phase of subduction of intervening oceanic lithosphere that has resulted in the closure of an ocean
  • The best known and most spectacular example is the collision between India and Asia, which began 50 million years ago, following the closure of an intervening ocean and produced the Himalayas and Tibetan Plateau
• destructive subduction -> 2 plates collide and one is forced under the other
• conservative boundary and earthquake theory:

  •oceanic + oceanic -> gap, upwelling magma -> fissure / shield volcanoes

  • continental + continental -> magma rises and falls -> pressure on overlying rock -> drop -> rift valley

  •continental + oceanic -> oceanic subducts because it is lighter -> fold mountains are formed from continental plate and accretionary wedge
• seismic waves -> vibrations released on surface
• focus -> tension being released underground (source of the epicentre)
• epicentre -> where the vibrations from the focus have travelled to the earths surface. this is also the location of the earthquake
• response to earthquakes

  •listening for survivors

  •rescue dogs

  •rubble lifting machines
• you can predict an earthquake by analysing:

  •cracks in surface

  •ground movement change

  •radon gas escaping from the gaps of the earth
• you can predict a volcanic eruption by analysing:

  • changes in volcanoes surface

  •heat change

  •river water temperature change
• earthquake proof buildings:

  •rolling weights on roof

  •dampers

  •triangle shape

  •rubber bearings

  •planning and safety checks

  •automatic shutters

  •fire resistant
• monitoring for earthquakes:

  •animals act strange

  •smart phones detect ground movement

  •sensitive seisometers are used to measure tremors
• advantages of living in tectonically active areas:

  •fertile soils

  •tourism

  •houses may be more affordable

  •geothermal energy

  •springs

  •cultural attachment
• fault lines -> a fracture line in the rocks of earths surface, where one side moves in relation to the other
• seismometer -> an instrument that responds to the grounds motions
• remote sensing ->scientific analysis of the earths surface using satillite imagery