Physical GEOG: Chapter 3 - Plate Tectonics


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Physical GEOG: Chapter 3 - Plate Tectonics

  1. 1. Layer Thickness (km) Temperature (°C) Composition Inner 1 370 Mostly Fe, Ni, Core 3 000 to 5 000 forming an alloy Outer 2 100 Mixture of solid Mantle 2 900 1 400 to 3 000 and molten rocks (magma) Less dense Continental 10 to 70 minerals (eg. Al) Crust -14 to 1 200 Denser minerals Oceanic 5 to 10 (eg. Mg) Tectonic plates Continental plate Oceanic plate Major plate Minor plate1. North American 1. Nazca 1. North American 1. Nazca2. South American 2. Pacific 2. South American 2. Philippine3. African 3. Philippine 3. African 3. Cocos4. Eurasian 4. Cocos 4. Eurasian 4. Caribbean5. Indo-Australian 5. Caribbean 5. Indo-Australian 5. Scotia6. Antarctic 6. Scotia 6. Antarctic 7. PacificDivergent Convergent TransformOceanic – Oceanic Oceanic – Oceanic Transform faultForms a mid-oceanic ridge Forms undersea volcanoes, (eg. San Andreas Fault)(eg. Mid-Atlantic Ridge) oceanic trench and volcanic islands (eg. Mariana Trench, When plates slide past eachFormation: Islands) other, a transform boundary isRising and spreading convection formed. This often results incurrents in the mantle cause the Formation: earthquakes.(Plate name) and (Plate name) to Cooling and sinking convectionmove away from each other. As currents in the mantle cause thethe plates move apart, tensional (Plate name) and (Plate name) tostresses cause fractures in the move towards each other andlithosphere. New basaltic converge. The denser oceanicmagma wells up at the spreading plate is subducted under thecentre where it cools and less dense continental plate.solidifies to form new sea floor. The sinking crust is melted in the magma due to immense pressure and heat. Less dense silica-rich magma then rises thru fractures in the crust to pour onto the ocean floor, forming undersea volcanoes. When they are built up and appear above the sea, they form volcanic islands.
  2. 2. Continental – Continental Continental – ContinentalForms rift valleys Forms fold mountains -Formation: Formation:REFER TO CHAPTER 4. REFER TO CHAPTER 4. Oceanic – Continental* Forms subduction volcanoes, oceanic trench, fold mountains Formation: Cooling and sinking convection currents in the mantle cause the (oceanic plate name) to converge and collide with the (continental plate name). The denser (oceanic plate name) subducts under the lighter (continental plate name), forming a narrow, linear depress- ion parallel to the boundary - called an oceanic trench. The subducted part of the (oceanic plate name) melts due to immense friction and heat in the mantle. The less dense silica-rich magma then rises thru fractures on the surface where it cools and solidifies to form subduction volcanoes. Due to compression of the rock strata of the (contin- ental plate name), the rock strata are bent, uplifted and contorted to form fold mountains.Formation of subduction volcanoes, fold mountains and oceanic trench