Geog 2.1

• Crust


  The outer layer of the Earth, broken into sections called tectonic plates. It is the thinnest layer and the one which we live on.
• Mantle


  The thickest layer of the Earth and consists of molten rock.
• Outer core


  Molten and about 3000 degrees C.
• Inner core


  Solid due to the immense pressure and is about 5000 degrees C. Both the inner & outer core consist of iron & nickel.
• Structure of the Earth


  1. Crust

  2. Mantle

  3. Outer core

  4. Inner core
• The Earth's crust is broken into different sections which are slowly moving about.
• Convection currents


  In the mantle, distribute the heat from the core and drag the plates in different directions, responsible for earthquakes and volcanoes.
• Over millions of years the land masses have moved around the planet as the tectonic plates shifted about.
• Where the different sections of tectonic plate meet, the movement causes geographical features such as mountains, volcanoes and earthquakes.
• Constructive boundaries


  1. Convection currents in the mantle drag the plates apart

  2. Magma rises to fill the gap and solidifies to form new crust

  3. As the process repeats a ridge is formed and this slowly gets wider as the plates continue to separate
• Fissure volcanoes


  Long cracks, less explosive
• Destructive boundaries


  1. Oceanic & continental plates collide

  2. The oceanic plate is denser and so sinks under the continental plate

  3. As the oceanic plate sinks it takes some sand, water and other material from the sea bed with it. This melts and is gaseous which causes it to force its way up to the surface as a volcano

  4. The continental plate crumples at the edge creating fold mountains in addition to the volcanoes
• Collision boundaries


  1. Convection currents in the mantle pull two plates of continental crust together

  2. Since both crusts are made of the same material and have equal density neither subducts. They crumple up

  3. This process creates fold mountains. There are no volcanoes at these boundaries but earthquakes occur
• Shield volcanoes


  Gentle sloping, created by basic lava (travels along way before solidifying). Found at constructive boundaries.
• Composite volcanoes


  Alternating layers of acid lava & rock/ash create the classic conical shape. Found at destructive boundaries.
• Ash & cinder volcanoes

  Alternating layers of ash & cinder compacted.
• Fissure volcanoes


  Volcanoes running along a crack in the crust, usually a constructive boundary.
• Caldera


  Crater volcano created after volcano collapses in on itself having emptied the magma chamber.
• Dome volcanoes


  Steep sided volcano created by acid lava which cools before it has travelled far.
• Destructive boundary volcanoes are often cone shaped and explosive.
• Constructive boundary volcanoes are often more gently sloped and have less violent eruptions.
• Volcanic features


  • Secondary vents (fumaroles) occur when magma and gases force their way through weaknesses in the main volcanic structure
  • Lava, ash, cinders and smoke may be ejected from the vent
• The Pacific Ring of Fire is an area with a high concentration of volcanoes and earthquake activity.
• Focus


  The exact point at which the earthquake occurred- often deep in the ground.
• Epicentre


  The point on the surface of the earth directly above the focus (so it can be located easily on maps).
• Seismic waves


  The shockwaves that move outwards from the focus. Their energy dissipates the further they travel.
• Seismometer


  Instrument that measures the magnitude of earthquakes.
• Older buildings tend to suffer more damage in earthquakes than newer ones.
• Buildings built on soft land suffer more than those with foundations on rock.
• Seismograph


  The print out/graph produced by the seismometer.
• Richter scale


  The scale traditionally used to record the magnitude of an earthquake.
• Moment Magnitude Scale


  The scale often used currently to record the magnitude of earthquakes (it is more accurate for large earthquakes than the Richter scale).
• The Haiti earthquake was caused by the collision of the North American and Caribbean tectonic plates.
• Collision boundary


  2 continental crusts crashing into each other
• Transform boundary


  2 sections of crust sliding past each other
• Tsunami


  Large wave often triggered by earthquakes under the sea
• Vent


  The passage in a volcano through which the magma travels up
• Continental crust


  Least dense crust made from granite
• Oceanic crust


  • Outer layer of the earth
  • Heavier, denser crust made of basalt
  • Least dense crust made from granite
• Pyroclastic flow


  Very hot fast moving cloud of ash and steam and that races down the slopes of volcanoes