Restless Earth

The Structure of the Earth
1. Crust - made from thin layers of tectonic plates
  2. Oceanic Crust
    1. Composed of basaltic rocks
    2. Denser than continental plates
  3. Continental Crust
    1. Composed of granitic rocks
    2. Made of low density minerals
2. Mantle- divided into a solid upper part and a semi-liquid lower part, mainly made of molten rock
  1. Lithosphere - the crust and the top layer of the mantle.
  2. The upper part of the mantle is called the asthenosphere
3. Core - consists of a liquid outer core and a solid iron inner core.
Plate Tectonics
1. Convection Currents
  1. Convection currents form because of the heat rising from the iron core
    1. Created by the pressure of overlying material
    2. The radioactivity of the core creates most of the heat.
  2. The heat from the core rises to the top of the mantle, cools and then falls back down to be heated again.
    1. This puts lots of pressure on the plate tectonics to separate, creating volcanoes and earthquakes
2. Plate boundaries are associated with the characteristics of tectonic events and landforms
  1. Destructive Plate Boundaries
    1. Found where two plates are moving together and oceanic plate material is destroyed.
    2. Nazca Plate and the South American Plate are an example.
    3. Earthquakes, volcanoes and fold mountains.
  2. Constructive Plate Boundaries
    1. Found where new basaltic material rises to the surface, forcing plates apart
    2. Mid- Atlantic ridge between the Eurasian and North American plates
  3. Collision Plate Boundaries
    1. Two continental plates move together, but neither is destroyed because there is no subduction
    2. Indo - Australian plate and the Eurasion plate has lead to the Himalayas being formed.
  4. Conservative Plate Boundaries
    1. Plates are sliding past one another with lots of friction, creating earthquakes and extreme stresses.
    2. North American Plate and the Pacific Plate
Earthquakes and Volcanoes
1. Earthquakes are distributed along the lines of tectonic plate boundaries.
2. Volcanoes are distributed in clusters along coastlines.
  1. Basaltic magma is high in temperature, very low in silica and gas.
    1. Produces fluid lava flow with little explosive activity.
      1. Forms shield volcanoes with sloping shapes
  2. Andesitic magma is low in temperature, has more silica and lots of dissolved gases.
    1. Less fluid and more likely to explode
      1. Composite volcanoes which are steep sided and made up of layers of lava and ash.
  3. Granitic magma has low temperature, high silica content.
    1. Vicious and sticky and get stuck before they reach the surface, so are more likely to cool and become igneous rocks.
The management of tectonic hazards
1. Preparation
  1. Governments, communities and individuals should be ready to respond when disaster strikes
  2. Emergency plans, warning systems and training of personnel
    1. Evacuation plans and rescue teams
2. Mitigation
  1. Reduce the effect of the hazard and the vulnerability to it
  2. Relocating people and strengthening structures
    1. Engineers develop ways to build earthquake resistant structures.
      1. Bolting buildings to their foundations and providing support walls
        Concrete that has steel rods embedded in it, cross bracing and shear core.
      2. Medium sized buildings have bearings made of steel and synthetic rubber to map them shock absorbing.
      3. Flexibility is key

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