Tectonic hazards

• Atmospheric hazards are driven by processes at work in the atmosphere eg: air
• Inner core

  • mostly solid
  • made of iron and nickel
  • slowly growing
• Continental crust

  • granite rocks
  • known as sial layer as well
  • over 1500 million years old
  • subducts the oceanic crust
• Primoridial is the heat left over from the Earth’s formation
• Radiogenic is the heat produced from radioactive decay of isotopes
• Ridge push is when new crust is formed due to tension forces.

  • mantle rock rises and experiences a reduction in pressure
• Father of plate tectonic theory is Alfred Wegner
• Harry Hess updated the plate tectonic theory in 1962
• Constructive plate boundary

  • plates moving away from each other
  • both plates are either oceanic or continental
  • magma rises - filling the void and creating new crust
  • basaltic lava fills the gap
  • oceanic ridges made
• Oceanic ridges:

  • formed from the basaltic lava that comes up
  • ridges can have breaks in them called transform faults
  • these ridges and faults wider at different rates meaning there will be frictional stress causing earthquakes
  • higher than other area - it is buoyant
• Collision plate boundary

  • usually continental and continental
  • crusts need to be the same density
  • two plates collide and crumple upwards
  • forms fold mountains eg: Himalayas
• A magma plume is extremely hot magma that breaks through the oceanic crust and and cools to form a small volcano

  • the volcano gets bigger over time
  • it later becomes extinct as the plates moves
  • the volcano moves off the plate boundary and the hot spot
• Extinct volcanoes sink as they become heavy and they also become smaller due to erosion
• Tephra

  • fragments of volcanic rock and lava thrown into the air
• Crater

  • main opening of the volcano
• Pyroclastic flow (speeds of 50mph)

  • rock fragments, gases and ash which destroys everything in its path
• Andesitic lava:

  • viscous
  • high silica content
  • cooler
  • loses gas quickly
• Caldera volcanoes: (shield)

  • large circular/oval depressions
  • some filled with lakes
  • often surrounded by steep cliffs
  • formed by the inward collapse of a volcano
• Vulcanian volcanoes: (composite)

  • thick lava, basaltic/andesitic/rhyolitic
  • less frequent, violent eruptions of gases
• Vesuvian volcanoes: (composite)

  • thick lava, basaltic/andesitic/rhyolitic
  • long periods of inactivity
  • very violet has explosions
• Peléan volanoes: (composite)

  • andesiitic and rhyolitic
  • violent eruptions
• Plinian volcanoes: (composite)

  • rhyolitic - viscous, tend to form thick blocky lava flows
  • violent
  • erupt gas, ash and pumice
  • rainstorms cause lahars
• Evidence for continetal drift:

  • if the continents were pieced together, they would fit almost perfectly
  • fossil remains - identically evolved repitle fossils found in both South America and Africa
  • coal found in Antartica - coal needs tropical climates and dense vegetation
• Hawaiian volcanoes: (shield)

  • non-explosive eruptions
  • generate red hot lava rivers - basaltic lava
  • sloping mountains