PLATE TECTONICS

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PLATE TECTONICS
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Plate Tectonics
Plate - large rigid slab of solid rock Tectonics
- from the Greek root to build

• A relatively new area of study.
• Formed 30 yrs ago, incorporating seismology and
  paleontology
• Seismology - the study of earthquakes
• Paleontology - the study of fossils

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Tectonic Plate Theory

• a solid lithosphere floating on top of the
  asthenosphere gives an idea of how plates can
  float

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Evidence to support Tectonic Theory

• Initial ideas of continental drift
• jig saw puzzle or map fit of continents

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Evidence to support Tectonic Theory

• map fit--already mentioned
• mountain chains formed on continents with
  longitudinal axes perpendicular to movement of
  the continents--examples Himalayan, Rocky
  Mountain and Andes Mountain chains
• same fossils (in rocks),same rocks , mountain
  ranges, and glacial features located on different
  continents in areas representing prejoined
  positions prior to continental drift

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Matching of Fossils from Common Locations on
Separated Continents
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Matching of Mountain Chains from Common
Locations on Separated
Continents
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Matching of Glacial Deposits from Common
Locations on Separated Continents
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Global Ocean Ridge

• presence and shape of global ocean ridge
• a ridge is a raised region on ocean basin which
  is believed to represent prejoined or splitting
  area of separated continents--the shape of the
  ridge contours shape of coast lines of separated
  continents--- this is most evident in the mid
  Atlantic ocean

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HEAT CAUSES PLATES MOVEMENT

• convection cells in Earths interior is the force
  which split the lithosphere and are the driving
  force in continental separation

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Plates of the World

• Seven large and many smaller plates
• 80 km thick
• THREE TYPES OF MOVEMENT.
• CONVERGENT - oceanic and continental plates
  collide forcing the oceanic plate to slide
  beneath.
• DIVERGENT - plates move away from each other,
  where they diverge molten rock rises.
• TRANSFORM - plates move horizontally past each
  other.

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Features Created

• Plates move sideways, apart or together
• Movement produces three tectonic
  processesfolding, faulting (diastrophism),
  volcanism
• These movements create landform and ocean
  features.

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Divergent Plates
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DIVERGENT PLATE BOUNDARY
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Divergent Plates

• kinds of divergent plate boundaries--1)ocean
  basin to ocean basin boundary

example is the mid ocean ridge
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Global Ocean Ridge
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DRIFT AND PLATES

• 2) continental to continental boundary

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Map of East Africa -- a so-called triple junction
(or triple point), - three plates are pulling
away from one another the Arabian Plate, and
the two parts of the African Plate (the Nubian
and the Somalian) splitting along the East
African Rift Zone.
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East Africa may be the site of the Earth's next
major ocean. Plate interactions in the region
provide scientists an opportunity to study first
hand how the Atlantic may have begun to form
about 200 million years ago. Geologists believe
that, if spreading continues, the three plates
that meet at the edge of the present-day African
continent will separate completely, allowing the
Indian Ocean to flood the area and making the
easternmost corner of Africa (the Horn of Africa)
a large island.
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Convergent Plates
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3 types of convergent plate boundaries
1) Ocean basin to continental boundary
(Example is the Cascade Mountain chain)
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Convergent Plate boundary
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2) Ocean basin to ocean basin boundary
(Examples are Aleutian Islands and Japan)
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Aleutian Islands and Japan
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3) Continental to continental plate boundary
(Example is India and Asian continent boundary)
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Transform Plates
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DRIFT AND PLATES

• transformed boundary--plates move parallel to
  boundary

Example are those off the Coast of Western U.S.A.
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