Tectonics

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Tectonics

• - construction / formation of the features on the
  crust

• 2 kinds of crust
• Oceanic heavier
• (covers the entire
• planet!!!!!)
• Continental lighter
• (not as dense)

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• Lithosphere - shell - rigid (tectonic plate)
• Asthenosphere - gooey rock - acts like plastic
  when under pressure (silly putty)

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Plate Boundaries

• Every plate has an edge boundary
• There are 3 types of boundaries
• 1.Divergent (constructive)
• 2.Convergent (destructive)
• 3.Transform

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Divergent

• Located where 2 plates are separating forming
  new crust
• Creates mountain, volcanoes, earthquakes

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Oceanic Ridge (seafloor is spreading)
New crust is constantly being created about 5
cm/year - Keeps the ocean crust young! Facelift
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This is an example of where ocean crust ridge has
built up so much it is above sea level - island
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Bridge across the Álfagjá rift valley near
Grindavik on the Reykjanes peninsula in southwest
Iceland, the boundary of the Eurasian and North
American continental tectonic plates.
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Continental Rifts(continent is spreading)

• Spreading center develops within a continent
• Landmass may split into 2 or more smaller
  segments.

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East African Rift
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Kilimanjaro Mount Kenya
Volcanoes that formed as land rifts (rips) apart
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road
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Convergent

• located where 2 plates collide, one subducts
  destroys old crust
• There are 3 different scenarios
• ocean//ocean
• ocean//continent
• continent//continent

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Ocean // Ocean

• ?Denser oceanic slab sinks into the asthenosphere
• ?rock heats up and melts into magma
• ?magma rises
• subduction creates volcanoes
• chain of volcanoes island arc
• example Japan, Aleutian Islands
  
• (off of Alaska)

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Ocean // Continent

• ocean crust is subducted
• rememberocean crust is heavier, so it will sink
  down remelt
• creates trenches, mountains, volcanoes
• example Cascade Mountains (Mt. St.Helens, Mt.
  Rainer, etc.), Sierra Nevadas, Andes Mts.

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Continent // Continent

• both plates are uplifted
• creates squished, folded mountains
• example Himalayas

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Transform

• located where 2 plates move past each other - no
  destruction or creation of crust
• creates earthquakes!!!
• example San Andreas Fault

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San Andreas
800 miles long 11 miles deep 6 miles wide
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What causes plates to move?

• Seafloor spreading

What causes sea-floor spreading?

• Convection current

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