hazardous earth

• lithosphere-rigid outer layer of earth composed of the upper mantle and crust
• Asthenosphere- a solid layer of the mantle with a plastic like quality. The high temperature and pressure causes the rock to be viscous and liquid like (ductile)
• Mesosphere- has a 'solid' like rock from the high temperatures and higher pressure
• The mantle- crust boundary is marked by the moho discontinuity

  continental crust depth= 35km

  oceanic crust depth= 10km
• convection currents

  Radioactive decay within the core heats up the layers. Warm plumes of magma are less dense than their surroundings so they rise. When reaching the lithosphere, the magma is forced sideways dragging the lithosphere with it (friction). Once the magma plume cools it descends and the process restarts.
• Ridge push

  newly formed pates at mid ocean ridges are warm, and so they have a higher elevation than the colder denser material further away, gravity causes the other plate at the ridge to push the lithosphere that lies further from the ridge.
• Slab pull

  as the rock gets older it cools and gets denser causing it to lie lower. As they sink in subduction zones they pull the lithosphere with them
• One evidence for continental drift are fossils.

  Fossils of the same fauna/flora have been found on multiple continents despite being separated by ocean, suggesting the continents must of been connected. E.g. Mesosaurus was a fresh water reptile in Africa and Brazil. Tropical fossils have been found in Antarctica (near same tropics)
• Ancient glaciations

  Glacial striations and till deposits have been found South America, Africa from the same time period (unless an ice sheet extended all the way from the south pole to the equator) the continents must have once been connected. Striations show glacial movement away from the equator towards the pole based on current continent locations, suggesting the continents must have been in different locations
• Sea floor spreading and Palaeomagnetism

  Minerals in rocks of different ages align north south or south north. We know the magnetic north and south reverse every 450,000 years.

  when these ocean floor magnetic patterns were mapped they show a zebra like pattern with stripes of reversing polarity. The stripes directly either side of the ridge have modern day polarity.

  This symmetry of polarity suggests the land was created at the same time and they are a similar distance away from the ridge.
• Age of sea floor rocks

  Core drilling has shown that the thickest and oldest sediments are found nearest to the continents away from the ridges, and the youngest are closer to oceanic ridges, plus no older core is older than 200 million years. This suggests land moves from ridges towards continents
• The 'Jigsaw' theory

  At a depth of 1000m below sea level the coasts of south america and africa match exceptionally well. Gaps can be explained by more recent erosion/deposition and isostatic/eustatic change. This suggests that land masses were once connected. Also the mid atlantic ridge follows the shape of the two continents shape.
• Mountain chains and geology

  Eastern South America and West Africa have a continuous ancient rock craton over 2000 million years old stretching between them. Fragments of old fold mountains belt around ~400 million years old are found on widely separated continents today. The uk contains lots of coal deposits however, coal only forms near tropics which suggests the uk must have moved away from the tropics.
• Stratovolcanoes

  They are composed with layers of ash and acid lava. The acidic magma is highly viscous therefore, it moves slowly and it doesnt travel far before cooling. This gives it its steep cone like shape. They are mainly on convergent plate boundaries and have explosive eruptions which often create chains of stratovolcanoes. Indonesia is the worlds most volcanic country with 130 active along the archipelago.
• earthquakes are sudden release of pressure that has built up within the lithosphere sending seismic waves radiating from the focus
• In shallow focus earthquakes the seismic waves dont have to travel too far before reaching the surface therefore they retain more energy
• deep focus earthquakes the seismic waves travel further and therefore the energy dissipates before reaching the surface. Also the deeper the focus the more viscous rock and less energy is released
• escarpments is a cliff that separates two level pieces of ground. Faulting creates escarpments by shifting large pieces of land. They also form either side of rift valleys. Weathering and erosion alter escarpments after creating by reducing the slope angle. Height ranges greatly from a few meters to several
• rift valleys

  Most rift valleys are the result of sea floor spreading but some are formed when fault lines slip. If two escarpments form parallel to each other following an earthquake a rift valley is created in-between.
• park model

  The impact of a tectonic disaster on quality of life usually follows a sequence of events. This can create a disaster response curve known as the park impact/response model which defers per event based on

  • speed of onset events
  • magnitude
  • duration
  • level of monitoring
  • quality/quantity of relief
• Pre-disaster

  Quality of life is normal

  Locals try to prevent any events and preparations should happen and education.
• Relief

  quality of life suddenly drops and people take immediate action to preserve life and if possible the built environment. Medical attention, rescue services are delivered. Can last from a few hours to several days. slowly quality of life increases.
• rehabilitation

  This follows the immediate response of relief. Food, shelter, water are distributed and can last from a few days to weeks.
• reconstruction

  Infrastructure and property are reconstructed and crops regrown. The experience of the event is used to improve future responses.
• 7 major plates with minor plates as well
• Divergent plate boundaries

  plates moving apart and magma rises through the aesthenosphere.

  Consist of long mountain chains
• Mid ocean ridges

  They have frequent intervals, broken into segments by transform faults. They vary in shape which is dependent on amount of magma brought to surface.
• Formation of pillow lavas

  Underwater magma erupts directly on sea bed cooling it rapidl along divergent plate boundaries.
• black smokers are superheated jets of water sometimes re emerge o the ocean floor, contains metal sulphides. They support ecosystems
• Convergent plate boundary

  occurs when there is a difference in densities which forces the denser plate to subduct. This can form trenches