The Earth is like an Apple! CRUST (where we live) MANTLE CORE The Structure of the Earth CRUST MANTLE CORE <ul><li>Inner </li></ul><ul><li>Outer </li></ul>
The 2 different types of plate - 5-10KM thick - Dense - Constantly being renewed and destroyed <ul><li>25-100km thick </li></ul><ul><li>Light (and so does not sink) </li></ul><ul><li>Not destroyed as easily as oceanic crust </li></ul>OCEANIC CONTINENTAL
Plates move due to convection currents <ul><li>The hot magma rises from above the core </li></ul><ul><li>As it cools, it sinks and then moves downwards towards the core again. </li></ul><ul><li>This causes the plates to move apart </li></ul>Convection Currents Mantle Crust
Plate Names African Plate Indo Australian Plate North American South American Eurasian Pacific Nazca Antarctic
Evidence for plate tectonics 1. Study of fossils – similar fossils are found on different continents. This is evidence that these regions were once very close or joined together. 3. Shape of continents fit together like a jigsaw. Africa South America 2. Pattern of rocks – similar pattern of rock layers on different continents is evidence that the rocks were once close together or joined.
What are plate margins? <ul><li>This is where 2 or more plates meet. </li></ul><ul><li>There are 3 different types of plate movement; </li></ul><ul><ul><li>Away from each other (Constructive – as new crust is constructed) </li></ul></ul><ul><ul><li>Towards each other (Destructive – as crust is being destroyed). This category can be sub divided into subduction and destructive </li></ul></ul><ul><ul><li>Sliding past each other (Conservative) </li></ul></ul>
A destructive plate boundary is found where a continental plate meets an oceanic plate. The oceanic plate descends under the continental plate because it is denser. As the plate descends it starts to melt due to the friction caused by the movement between the plates. This melted plate is now hot, liquid rock (magma). The magma rises through the gaps in the continental plate. If it reaches the surface, the liquid rock forms a volcano. 1) Destructive Plate Boundary a) Subduction
Collision boundaries occur when 2 plates of similar densities move together (i.e. a continental plate and a continental plate). This causes the material between them to buckle and rise up, forming fold mountains. The Himalayas are an example of a chain of fold mountains. They have been formed by the African plate colliding into the Eurasian plate. 1) Destructive cont. b) Collision Boundary
Conservative plate boundaries exist where two plates do not directly collide but slide past each other along a fault (weakness). No volcanoes are found along these plate boundaries, but earthquakes do occur. An example of such a boundary is the San Andreas Fault in California. 2) Conservative Boundary
3) Constructive Plate Boundary At a constructive plate boundary, two plates move apart. As the two plates move apart, magma rises up to fill the gap. This causes volcanoes at this type of boundary. However, since the magma can escape easily at the surface the volcano does not erupt with much force. Earthquakes are also found at constructive boundaries. An example of a constructive boundary is the Mid-Atlantic Ridge.
Sea Floor Spreading! Did you know that the ocean floor in the Atlantic is growing by 3cm per year? <ul><li>Which of the following pairs of continents are moving further away from each other? </li></ul><ul><li>Europe and Africa </li></ul><ul><li>Europe and North America </li></ul><ul><li>South America and North America </li></ul>Mid-Atlantic ridge
Name this plate boundary Continental crust Mantle The oceanic crust melts and rises Explosive volcanoes Oceanic plate The oceanic crust sinks under the less dense continental crust Earthquakes occur due to friction Match the labels to the letters A B C D E F G
Constructive plate boundaries Ocean Oceanic Crust Mantle MID OCEAN RIDGE Where would you find older rocks – at A or at B? A B