Paper 1 ~ ALevel Geo

• Conservative plate boundary


  where two tectonic plates slide past each other
• convergent plate boundary


  plates move towards each other and collide
• Divergent plate boundary


  Plates move away from each other
• Alfred Wegener 1912

  All continents were once joined in a super continent called Pangea. Continental drift caused Pangea to move apart
• Holmes 1929


  Convection in the mantle is the force behind continental drift
• oceanographic vessels 1950s


  submarines that mapped the topographic features of the ocean basin. Discovered mid-ocean ridges
• Harry H Hess


  sea floor spreading
• Vine & Mathew


  Plates seperate at mid ocean ridges
• Nuclear Test Ban Treaty


  Detected earthquake activity leading to the evidence that EQ's and Volcanoes almost always occur at the edges of tectonic plates
• vessel Glomar Challenger 1968


  Rocks closer to mid-ocean ridges are younger
• What is a Volcanic Hotspot?

  An area in the mantle from which heat rises as a hot thermal plume from deep in the earth
• What is the lithosphere?

  the rigid outer part of the earth, consisting of the crust and upper mantle.
• What is the asthenosphere?


  the upper layer of the earth's mantle, below the lithosphere.
• P waves (Primary waves)


  travel through liquids and solids, push and pull, faster, arrive first
• S waves (secondary waves)


  Vibrate at right angles to the direction of travel. Can cause damage due to shearing effect
• L-waves (love waves)


  Move side to side
• Factors affecting earthquake intensity

  •Duration of locked fault

  •Depth of hypo-centre

  •Timing & intensity of seismic waves
• basaltic magma


  magma that has low viscosity and low silica and gas content; eruption is non-explosive
• andestic magma


  Medium eruption temp and viscosity
• Rhyolitic Magma


  magma that has a high viscosity and high silica and gas content; eruption tends to be very explosive
• Composite volcanoes


  large, steep-sided volcanoes that result from explosive eruptions of andesitic and rhyolitic lava and ash along convergent plate boundaries. Poses most danger to Hunan life.
• Shield Volcanoes


  Gently sloping mountains formed by thin, runny lava. Frequently eruptive
• What is the "Benoiff zone"


  A dipping flat zone where earthquakes are produced by the interaction of a submerging oceanic crustal plate with a continental plate
• What is a fault

  A fracture in the rocks that make up the earth's crust
• What is an epicentre?

  The point on the Earth's surface straight above the focus.
• What is a Hypocentre?


  The point within the Earth where an earthquake rupture starts (the focus)
• Secondary Hazards of Earthquakes

  •liquefaction

  •landslides

  •tsunamis
• What is soil liquefaction?

  When an earthquake causes the ground to shake to the point of making it liquid
• What is a landslide?

  the sliding down of a mass of earth or rock from a mountain or cliff.
• What is a tsunami?

  Convection currents in the mantle move plates towards each-other. Pressure builds up as the denser plate is forced beneath the overriding plate. An EQ occurs. Water is displaced creating a wave which spreads out. As wave approaches shore, height increases and wave length shortens
• Global distribution of tsunamis

  90% occur in the Pacific Basin. Most are generated at subduction zones (convergent PB)
• What are the Primary Hazards of a Volcano?

  •pyroclastic flow

  •tephra

  •volcanic gases

  •lava flows
• What is a pyroclastic flow?


  The result of magma and hot gas frothing and exploding, ejecting glass shards, pumice and ash in clouds up to 100 degrees.
• What is tephra?


  rock fragments and particles ejected by a volcanic eruption.
• What is a lava flow?

  a mass of flowing or solidified lava, determined by silicon dioxide
• What are volcanic gases?

  Water, sulphur dioxide, hydrogen and CO2
• What are the secondary impacts of a volcano?

  •Jokulhlaups

  •Lahars
• What are Jokulhlaups?


  Sudden, violent and short-lived increase in discharge of glacial meltwater
• What are lahars?


  volcanic mudflows composed of a slurry of pyroclastic material, rocky debris and water
• What is Degg's model?

  Shows us how different hazardous events, and existing vulnerabilities, can lead to disasters