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PLATE TECTONICS: PLATE BOUNDARIES PowerPoint Presentation
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PLATE TECTONICS: PLATE BOUNDARIES

PLATE TECTONICS: PLATE BOUNDARIES

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PLATE TECTONICS: PLATE BOUNDARIES

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  1. PLATE TECTONICS:PLATE BOUNDARIES

  2. LAYERS OF THE EARTH • Crust (brown/tan) • Mantle (light & dark orange) • Core (yellow & white)

  3. LAYERS OF THE EARTH Lithosphere{ Crust and upper mantle make up the LITHOSPHERE • rigid plates (OCEANIC & CONTINENTAL plates) • low temperature & pressure Beneath the lithosphere is the ASTHENOSPHERE • plastic” mantle (flows, moves the plates) • higher temperature & pressure

  4. PLATE TECTONICS the surface of the Earth is made of rigid plates • Size and position of plates can change over time • PLATE BOUNDARIES Edges of plates, where two plates “float” side-by-side, is where geologic activity takes place • Plates movement is from convection currents deep in the mantle

  5. EARTH’S MAJOR PLATES: Pacific, N. American, S. American, African, Eurasian, Indian, Antarctic

  6. CONVECTION CURRENTS MOVE THE PLATES

  7. CONVECTION CURRENTS MOVE THE PLATES This continual movement (called convection currents) causes the crust to move in plate tectonics.

  8. CONVECTION CURRENTS MOVE THE PLATES • Material in the mantle is heated by the radioactive core • it floats to the surface next to the crust • as it cools, it moves back down towards the core 7c Movement of matter among reservoirs is driven by Earth’s internal and external sources of energy

  9. PLATE BOUNDARIES • Divergent boundaries plates move apart • Convergent boundaries plates move together • Transformboundariesplates slide past  

  10. DIVERGENT BOUNDARIESMake new crust When two plates move apart and magma surfaces forming NEW crust (usually oceanic) • continental rift zones (landmass splits into two or more segments) • mid-ocean ridges (sea-floor is elevated)

  11. DIVERGENT BOUNDARIESMake new crust Rift valley continent-continent

  12. DIVERGENT BOUNDARIESMake new crust: Sea Floor Spreading • Youngest rocks form at ridge • Older rocks are further from ridge • Oldest rocks are located at subduction zones

  13. DIVERGENT BOUNDARIESMake new crust: Sea Floor Spreading Every ~20,000 years the polarity of the Earth changes. This is change is reflected in the rocks, whose polarity is fixed once the magma is cooled. • As magma rises and cools, iron and magnesium minerals align themselves to the Earth’s magnetic field • “Magnetic Stripes” are formed • The Earth’s magnetic field reverses polarity • Magnetic stripes are mirrored on each side of the mid-ocean ridge

  14. CONVERGENT BOUNDARIESplates colliding • Destroys old crust and forms new mountains • Three types of convergent boundaries

  15. CONVERGENT BOUNDARIESplates colliding Continent-continent convergence: Folded mountains Ex HimalayasEurasian/Indian plates

  16. CONVERGENT BOUNDARIESplates colliding: Subduction Zones • Subduction Zones: where ocean plates slide under another plate • Creates magma which moves upward, pushing up the land above it. • Magma/lava solidifies into intrusive/extrusive igneous rock • Heat from the magma can change the rock around it. Rock that recrystallizes without melting becomes metamorphic rock.. Denser oceanic plates always subduct beneath less dense continental plates

  17. CONVERGENT BOUNDARIESplates colliding Ocean-continent convergence: Trench & Coastal Volcanoes Andes MountainsNazca & S.American plates

  18. CONVERGENT BOUNDARIESplates colliding Ocean-ocean convergence: Trench & Island arc

  19. TRANSFORM BOUNDARIES When two plates slide past each other • no tearing or crushing - no damage occurs to the lithosphere • Faults –San Andreas Fault • Cause most earthquake damage

  20. Summary of Plate Movements Convection currents