Plate Tectonics

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Plate Tectonics

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Theory of Plate Tectonics

• Meaning plate structure
• Developed 1960s
• Explains the movement of Earths plates, causes
  of volcanoes, earthquakes, ocean trenches,
  mountain formation, and other geological
  phenomena.

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Plate Tectonics Theory The Earths lithosphere
is divided into sections (plates) that move
(float) on the asthenosphere due to convection
currents in the mantle.
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Earths Major Plates
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Seven Major Plates Seven Minor Plates
African PlateAntarctic PlateEurasian PlateIndian-Australian PlateNorth American PlatePacific PlateSouth American Plate Arabian PlateCaribbean PlateCocos PlateJuan de Fuca PlateNazca PlatePhilippines PlateScotia Plate
 
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• Plates move about 1-10 cm per year!!!
• Seismic activity (volcanoes and earthquakes)
  occur as plate boundaries interact.

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• http//www2.wwnorton.com/college/geo/egeo/animatio
  ns/ch2.htm

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Stress Tension Compression Shearing
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Deformation
lthttp//www.unitedstreaming.com/gt
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Earthquake
lthttp//www.unitedstreaming.com/gt
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Anticline
lthttp//www.unitedstreaming.com/gt
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Syncline
lthttp//www.unitedstreaming.com/gt
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Normal Fault
http//www.tinynet.com/faults.html
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Reverse Fault
http//www.tinynet.com/faults.html
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Strike-slip Fault
http//www.tinynet.com/faults.html
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Ring of Fire
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Plate Boundaries

• There are 3 types of plate boundaries
• Divergent
• Convergent
• Transform

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Divergent movement of 2 plates away from each
other (tension)
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Quiet (non catastrophic) eruptions
lthttp//www.unitedstreaming.com/gt
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Types of lava
aa lava
lthttp//www.unitedstreaming.com/gt
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pahoehoe lava
lthttp//www.unitedstreaming.com/gt
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mid ocean ridge fissure
lthttp//www.unitedstreaming.com/gt
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Shield Volcano
lthttp//www.unitedstreaming.com/gt
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Mid-ocean ridge
lthttp//www.unitedstreaming.com/gt
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Surtsey
lthttp//www.unitedstreaming.com/gt
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Stages in basin history are Embryonic - rift
valley forms as continent begins to
split. Juvenile (young) - sea floor basalts begin
forming as continental sections diverge. Mature -
broad ocean basin widens, trenches develop and
subduction begins. Declining - subduction
eliminates much of sea floor and oceanic
ridge. Terminal - last of the sea floor is
eliminated and continents collide forming a
continental mountain chain. Geosuture (relic
scar) folded mountains with evidence of former
ocean basin.
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New crust forming in axial trough via sea-floor
spreading
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Basalt injections in narrow trough resulting is
separation from Africa
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3-3
Because Earths size is constant, expansion of
the crust in one area requires destruction of the
crust elsewhere.

• Currently, the Pacific Ocean basin is shrinking
  as other ocean basins expand.
• Destruction of sea floor occurs in subduction
  zones.

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• Major Ocean Basins
• Pacific Ocean
• largest (180,000,000 km2) and deepest (averaging
  3,940 m) basin
• extensive marginal seas and volcanic island
  systems and trenches 
• considerable mountain building and earthquake
  activity along boundaries
• little freshwater input
• Atlantic Ocean
• second largest basin (107,000,000 km2)
• average depth 3,310 m
• large freshwater input (Amazon, Congo,
  Mississippi, Niger, Orinoco Rivers)
• small number of marginal seas (Gulf of Mexico,
  Caribbean, Mediterranean)
• Indian Ocean
• smallest basin (74,000,000 km2)
• average depth 3,840 m
• large sediment input (Indus and Ganges River
  deltas)
• small number of marginal seas (Arabian Sea,
  Persian Gulf, and Red Sea)

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• Chronology of Modern Ocean Basin Development
• 200 million years ago
• formation of the supercontinent Pangaea
• presence of the Panthalassan 'super ocean'
• Atlantic and Indian Oceans not present
•  180 million years ago
• initial break up of Pangaea and formation of
  Laurasia and Gondwanaland
• presence of an east-west trending basin (the
  Tethys Sea)
• 140 million years ago
• separation of Eurasian and North American plates
• onset of mid-Atlantic ridge development
• early formation of the North Atlantic
• South Atlantic still closed
• 80 million years ago
• separation of the African and South American
  plates
• early formation of the South Atlantic
• 60 million years ago
• Indian plate reaches equator after separation
  from Australia and Antarctica
• North and South Atlantic continue to widen 40
  million years ago

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Hot SpotsHawaii Mauna Loa (shield volcano)
lthttp//www.unitedstreaming.com/gt
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Kilauea Eruptions
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Yellowstone
lthttp//www.unitedstreaming.com/gt
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Transform plates sliding horizontally past each
other.
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San Andreas fault 100 miles north of L.A
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Convergent colliding of 2 plates
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Convergent collision continental plate vs.
continental plate - forms folded mountains -
shallow earthquakes
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Convergent subduction ocean plate vs.
continental plate - forms trenches, volcanic
mountains - deep earthquakes
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How does the ocean floor keep getting wider

• The ocean floor plunges into deep under water
  trenches.
• A deep ocean trench forms where the oceanic crust
  collides with continental crust.
• Subduction is the process by which the ocean
  floor sinks beneath a deep-ocean trench and back
  into the mantle.

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Convergent subduction ocean plate vs. ocean
plate - forms trenches, volcanic island arc -
deep earthquakes
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FYI

• Most ocean trenches are found in the Pacific
  Ocean.
• The deepest part of the ocean is the Mariannas
  Deep. It is located in the Pacific Ocean
• The Pacific Ocean is shrinking, but it is still
  the Largest ocean

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Vulcanean eruption
http//www.nationalgeographic.com/forcesofnature
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Paricutincinder cone volcano
http//www.nationalgeographic.com/forcesofnature
http//www.nationalgeographic.com/forcesofnature
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Mt. St. Helenscomposite cone volcano
http//www.nationalgeographic.com/forcesofnature
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Mt. Mazama
http//www.nationalgeographic.com/forcesofnature
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Mt. Tambora Indonesiathe year without a summer
http//www.nationalgeographic.com/forcesofnature
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Vesuvian eruption
http//www.nationalgeographic.com/forcesofnature
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Vesuvius Pompei
http//www.nationalgeographic.com/forcesofnature
http//www.nationalgeographic.com/forcesofnature
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Strombolian eruption
http//www.nationalgeographic.com/forcesofnature
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Krakatoa
http//www.nationalgeographic.com/forcesofnature
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Peléan eruptionNueés Ardente - a super hot
cloud of ash and gas that flows very fast like a
liquid.
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Mt. Pelee
http//www.nationalgeographic.com/forcesofnature
http//www.nationalgeographic.com/forcesofnature