Hazardous earth theory

• what is a constructive plate margin?

  When two plates move away from each other
• what is a destructive plate margin?

  where two plates are moving towards each other
• what is a conservative plate margin?


  plates slide past each other
• what is the structure of the earth?


  inner core, outer core, mantle, crust
• what is a composite volcano?

  tall, cone-shaped mountains in which layers of lava alternate with layers of ash
• what is a shield volcano?


  a wide, gently sloping mountain made of layers of lava and formed by quiet eruptions
• what is the distance between the core and the mantle?

  2900km
• what is the Mohorovicic discontinuity?

  boundary between crust and mantle
• what is the depth of the Moho?

  35km under continents and 10-15km under surface
• what is the width of the asthenosphere?

  100km to 300km
• What is the asthenosphere?


  upper layer of mantle; semi-molten
• what is the lithosphere?

  crust and upper mantle
• what is the chemical composition of the crust?

  least dense material; thin outer layer; made up of tectonic plates
• what is the chemical composition of the mantle?

  thickest layer; less dense; silicate rock - rich in iron and magnesium
• what is the chemical composition of the core?

  densest material - iron and nickel; temperature of 5500 degrees
• Is the inner core solid or liquid?

  solid
• is the outer core solid or liquid?

  liquid
• what is the mesosphere?

  lower mantle
• What is the Gutenberg Discontinuity?

  boundary between mantle and outer core; 2900km depth
• What is the Lehmann discontinuity?


  boundary between inner and outer core; depth of 5100km
• what are S waves?

  ONLY travels through solids; stronger; high frequency; vibrate at right angles to travel
• what are P waves?

  can travel through both solids & liquids, moves by a pushing/pulsing motion, fast; low frequency (primary)
• What are convection currents?


  the flow that transfers heat within a fluid; occurs in asthenosphere; generated by heat
• What is Pangaea?


  the name of the supercontinent that existed millions of years ago
• what is the continental drift theory?

  the belief that continents have moved slowly apart to their current locations on Earth
• what are the three types of evidence for continental drift according to Wegner?

  geological, biological, climatological
• what is the geological evidence for continental drift - shelf fit?

  continental shelf fit - continents fit together through there coastline - suggests may have been joined together
• what is the geological evidence for continental drift - geological sequences?

  rock types and geological structures are the same from two sides of two sides of the world - eg Appalachian mountains in North America and Caledonian mountains in Scotland have the same igneous sequence and sedimentary rocks
• what is the geological evidence for continental drift - mountain chains?

  fold mountain chains - eg Precambrian fold mountain chain across Africa and South Africa
• what is the biological evidence for continental drift

  fossils - some fossils found (such as Marsupials) in other parts of the world which suggests world used to be joined - marsupials alive in Australia but fossils found in other parts of world
• what is the climatological evidence for continental drift

  evidence of glaciation from carboniferous period and matching glacial sediment deposits imply used to be joined together
• what did Harry Hess do in 1962?

  create the plate tectonic theory
• what is the Plate tectonic theory?

  The theory that the Earth's crust is divided into plates that move around on the top of the mantle - seas are like conveyor belts
• what is the evidence for plate tectonic theory - sea floor spreading?


  magma from mantle rises to create new ocean floor at mid-ocean ridges
• what is the evidence for plate tectonic theory - sea floor mapping?

  you can see the movement in continents
• what is the evidence for plate tectonic theory - age of rocks?

  you can see where the new ocean floor is building through the youngest rocks being the middle of the trench and the newest floor
• what is the evidence for plate tectonic theory - paleomagnetism?


  as magma cools and solidifies the metallic elements within it are magnetised in direction of earth's magnetic field
• what is the evidence for plate tectonic theory - GPS (global positioning system)?

  satellites used to measure exact location of series of receivers on earth's surface
• what tectonic hazards occur at constructive margins?


  shield volcanoes and shallow earthquakes
• what tectonic hazards occur at destructive margins?

  composite volcanoes and earthquakes