What happens when the plates meet

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  • Then use GE to show Pacific Ring of fire
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  • What happens when the plates meet

    1. 1. http://www.newscientist.com/articleimages/dn14422/1-mud-springs-reveal-true-extent-of-san-andreas-fault.html
    2. 2. The link?
    3. 3. What happens at the battleground at plate boundaries?
    4. 4. Key Terms <ul><li>Fault: </li></ul><ul><li>Continental drift: </li></ul><ul><li>Subduction Zone: </li></ul><ul><li>Convergent: </li></ul><ul><li>Divergent: </li></ul><ul><li>Transform: </li></ul><ul><li>Continental Crust: </li></ul><ul><li>Oceanic Crust: </li></ul>
    5. 5. What happens when the plates meet? Type of Margin Description of Changes Earthquake / Volcanic activity Examples Convergent (oceanic and continental) Convergent (two continental) Divergent on Land Divergent under the Ocean Transform
    6. 6. Convergent (Oceanic & Continental) <ul><li>Oceanic crust is denser than continental crust and so subducts (is forced to sink into the mantle) </li></ul><ul><li>This is a subduction zone </li></ul><ul><li>The sinking crust melts under friction & pressure…forms magma which creates volcanoes in the continental crust surface </li></ul><ul><li>E.g. The Nazca plate in South America – forms the Andes & a line of volcanoes </li></ul>
    7. 7. Convergent: Oceanic & Continental
    8. 8. Convergent (Two Continental)
    9. 9. Convergent (Two continental) <ul><li>If both plates are continental, then they are both too light to really subduct </li></ul><ul><li>So, a collision occurs </li></ul><ul><li>Forms large </li></ul><ul><li>mountain chains </li></ul><ul><li>e.g. the Himalaya </li></ul>
    10. 10. Divergent on land
    11. 15. Divergent (on land) <ul><li>A.K.A. ‘constructive’ boundary </li></ul><ul><li>As plates diverge, this allows magma to the surface </li></ul><ul><li>When crusts diverge on land, it forms a rift valley </li></ul><ul><li>e.g. Mid-Atlantic rift in Iceland, </li></ul><ul><li>East African Rift </li></ul>
    12. 16. Divergent under the ocean <ul><li>When plates diverge under the ocean, magma rises to the surface to create new land </li></ul><ul><li>The Mid-Atlantic Ridge is the biggest area of divergence </li></ul><ul><li>As magma rises it cools, forming ridges of mountains / volcanoes and new land </li></ul><ul><li>This is part of the recycling of oceanic crust </li></ul>
    13. 17. Divergent under the ocean <ul><li>In Iceland, the Mid-Atlantic ridge is diverging and splitting the country apart </li></ul><ul><ul><ul><ul><ul><li>Iceland is growing every year! </li></ul></ul></ul></ul></ul>
    14. 18. Transform <ul><li>Where plates slide past each other </li></ul><ul><li>No real surface features </li></ul><ul><li>Creates a lot of earthquakes as friction builds up then one plate jumps forward </li></ul><ul><li>E.g. San Andreas Fault, California, USA </li></ul>
    15. 19. Transform fault
    16. 20. Hotspots <ul><li>Weak areas in the earth’s crust that are far from plate boundaries that allow magma to punch through to the surface </li></ul><ul><li>E.g. Hawaii </li></ul>

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