Tectonics

• Four types of tectonics plate boundaries

  Convergent

  Divergent

  Conservative

  Collision
• What are convergent plate Boundaries

  Oceanic plate subducts under the continental plate. This happens because the oceanic plate is more dense
• What are divergent plate boundaries

  Plates move away from each other
• What are collision plate boundaries

  Two continental plates move towards each other
• What are Conservative plate boundaries

  Two plate boundaries move side by side
• What is an intra plate processes

  Processes that occur in the middle of the plate and not on the boundary
• Example of divergent plate

  Iceland
• Example of convergent plate

  Pacific and Australian plate
• Example of Conservative plate

  San Andreas fault
• Example of collision plate

  Himalayas
• Hazards at divergent plate boundaries

  Low magnitude earthquakes usually between 5 and 6. Low scale volcanic eruptions
• Hazards at Conservative plate boundaries

  Earthquakes of moderate magnitude between 6 and 8.
• Hazards at collision plate

  Earthquakes magnitude between 7 and 9
• Hazards at convergent plates

  High magnitude earthquakes. Explosive volcanoes
• Hot spot

  Localised source of high heat energy that sustains volcanism that is in the middle of a plate
• Lithosphere 


  Layer compromising of the uppermost part of the mantle and all of the crust. It forms the tectonic plates. And makes up the oceanic and continental crust
• Asthenosphere 


  The layer in the earth's upper mantle below the lithosphere. The high temperatures cause the rocks to soften and become viscous meaning they can easily deform. Convection takes place here
• Convection currents


  Hot mantle rock begins to rise because its less dense and Spreads out across the surface, cools and becomes denser so it sinks back down to be reheated and made to rise again. This can cause plate movement
• MOHO


  The boundary between the crust and the mantle. It lies 35km below the continents and 10-15km beneath the ocean floor
• Plate drag


  Convection currents in the asthenosphere drag the overlying plate with it
• Trench pull


  Weight of oceanic crust subduction at an oceanic trench pulls down rest of the plate
• Ridge push


  Upwelling of magma causes sea floor spreading causing plates to push apart
• Paleo magnetism


  When the cooling magma locks into earth's polarity
• Wegener's theory 


  Alfred Wegener's Continental Drift hypothesis in 1912 that postulated that now-separate continents had once been joined in a super continent known as pangea
• How did paleomagnetism help forward plate tectonic theory 


  The discovery in the 1960s of magnetic strips in the oceanic crust of the sea bed; these are palaemagnetic signals from past reversals of the Earth's magnetic field and prove that new ocean crust is created by the process of sea-floor spreading at mid-ocean ridges.
• Earth's crust 


  Divided into continental and oceanic. Oceanic is more dense.
• How does depth of focus affect magnitude of earthquake

  Shallower the focus the more energy is released because it has less area to dissipate the energy
• How does type of plate boundaries affect earthquake magnitude 


  Conservative plate boundaries have lots of energy due to tension between the faults
• How does gas content affect magnitude of volcano

  The greater the gas content the more explosive the volcano
• How does the water content affect the magnitude of the volcano


  The more water the less viscous lava means less gas built up so less explosive
• How does silica content affect magnitude of volcano


  Greater silica means more viscous lava so more gas trapped so more explosive
• Epicentre 


  The point directly above the focus on the surface
• Focus


  Point of energy release under the ground. Where the earthquake begins
• Primary waves


  Compressional longitudinal waves. They push and pull the ground
• Secondary waves 


  Slower than P waves. Transverse waves. Shake the ground back and forth perpendicularly
• Love waves


  Move back and forth horizontally
• Rayleigh waves


  Elliptical movement
• Liquefaction 


  Extreme shaking caused by an earthquake causes soil to act like a liquid so the ground is like quicksand and causes buildings to sink
• Primary effects of volcanoes


  Lava flow

  Pyroclastic flows

  Tehran

  Volcanic gases
• Pyroclastic flows


  Fast moving clouds of fragmented material