2.4 tectonic plate boundaries
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2.4 tectonic plate boundaries

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2.4 tectonic plate boundaries 2.4 tectonic plate boundaries Presentation Transcript

  • Tectonic Plate Boundaries Ag Earth Science Mr. Silva
  • Three Plate Boundaries• Divergent Plate Boundaries • aka. Spreading Centers• Convergent Plate Boundaries • aka. Subduction Zones• Transform Boundaries • aka. Transform Faults
  • Divergent Plate Boundaries
  • hotSpreading center
  • tension Rift valley basalt basaltOceanic Oceanic crust magma crust Hot mantleSpreading center
  • Divergent Plate Boundaries• Pull Apart• Tension• Create new rock (Lithosphere) • Occur under water (Oceanic Crust) • Occur on land (Continental Crust)
  • Mid Atlantic Ridge Mid-Atlantic Ridge
  • Continental RiftingContinental rifting: spreading center opensunder a continent
  • African Rift Valley Example of Continental Rifting
  • Convergent Plate Boundaries
  • coldSubduction zone
  • CompressionOceanic volcanoes crust Continental crust Melting and magmaMantle Mantle Subduction zone
  • Convergent Plate Boundaries• Push together “plates collide”• Compression• Destroy/Recycle rock (lithosphere)
  • Deep Accretionary Forearc VolcanicOcean Wedge Basin ArcTrench (1) (2) (3) (4) 1 2 3 4
  • Subduction zones have several geomorphic features:1. A deep ocean trench, where the descending slab drags down the upper plate2. An accretionary wedge of material scraped off of the descending slab3. A forearc basin between the accretionary wedge and the volcanic arc4. A volcanic arc produced by the eruption of andesitic magmas 1 2 3 4
  • Convergent Plate Boundaries• Three Possible Collisions • Oceanic-Continental Collision • Oceanic-Oceanic Collision • Continental-Continental Collision
  • Oceanic-Continental Collision• Denser oceanic crust dives under continental crust• Oceanic crust is then recycled by melting back into the mantle• This massive collision creates deep ocean Subduction zones have several geomorphic features: 1. A deep ocean trench, where the descending slab drags down the upper plate 2. An accretionary wedge of material scraped off of the descending slab trenches, an accretionary wedge, a forearc basin, 3. A forearc basin between the accretionary wedge and the volcanic arc 4. A volcanic arc produced by the eruption of andesitic magmas and a volcanic arc.• Exactly like the 1 2 3 4 California landscape.
  • California’s ProfileAccretionary Forearc Volcanic Wedge Basin ArcCoast Ranges Central Valley Sierra Nevada
  • Oceanic-Oceanic Collision• One oceanic plate will subduct under another• Creates deep ocean trenches arc, separate from a A volcanic island continent is created by the subduction of• Creates volcanic island arcs oceanic crust under oceanic crust• Japan Example: the Aleutian Islands in Alaska or Eurasian Plate Pacific Plate Japan
  • Aleutian Islands are a Volcanic Island Arc
  • Continental-Continental Collision• ThisIndo-Australiancontinental crust is riding occurs when on a subducting plate and then smashes Eurasian into another continent Plate Plate India Tibet Continental Continental crust crust
  • Indo-Australia Eurasia Plate Plate Himalayas India Tibetan plateau Suture
  • Transform Fault Boundaries
  • Transform fault boundaryIn the simplest form, plates slide past each other
  • Transform Faults connectother plate boundaries.They frequently offsetmid-oceanic ridges (whichcan be thought of asjagged tears); in this casethe transform faultsconnect two portions ofa spreading center. Onlybetween the offsetportions of the spreadingcenter are rocks moving inopposite directions (theactive region of thetransform fault; beyondthe ridge segments, rockis moving in the samedirection and there is nofault (inactive region), onlya fracture zone.
  • Transform faults and fracture zones
  • San Andreas Fault North American PlatePacific Plate
  • In Review Three plate boundaries1. Spreading Center: two plates created and diverge; oceanic crust forms2. Subduction Zone: two plates converge and one is recycled; continental crust forms3. Transform Fault: two plates slide past one another