PLATE TECTONICS

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PLATE TECTONICS
Plate Tectonic is a theory that unify different
previous geological theories (CONTINENTAL DRIFT
and OCEAN SPREADING) and that can explain the
majority of the solid earth system
observations. Basic concept The outermost
layer (LITHOSPHERE) is divided in a small number
of rigid plates in relative motion one respect
to the other and that are moving on a weak
ASTHENOSPHERE
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PLATE TECTONICS

• Basic concept
• The outermost layer (LITHOSPHERE) is divided in a
  small number of rigid plates in relative motion
  one respect to the other and that are moving on a
  weak ASTHENOSPHERE
• Basic Assumptions
• The astenosphere viscosity is low enough to allow
  on long time scale for viscous flow
• The generation of new plate material occurs by
  sea floor spreading
• The new oceanic lithosphere form part of a rigid
  plate that may or may not include continental
  material
• Earths surface area remains constant this means
  that seafloor spreading must be balanced by
  consumption of plate elsewhere
• Lithospheric plate are capable of transmitting
  stress over great horizontal scale. In other
  words plates are rigid and the deformation is
  concentrated along the boundaries.

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Continental Drift
In 1912 Wegener suggested that the current
position of the continents has evolved and that
the continents were once fit together in a
supercontinent called PANGAEA.
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Evidences for Continental Drift

• The shape of the continent seems to fit
  together.

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Evidences for Continental Drift

• The shape of the continent seems to fit
  together.
• Matching Geological Units

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Evidences for Continental Drift

• The shape of the continent seems to fit
  together.
• Matching Geological Units
• Distribution of Fossils

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Evidences for Continental Drift

• The shape of the continent seems to fit
  together.
• Matching Geological Units
• Distribution of Fossils
• Distribution of Climatic Belts

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Evidences for Continental Drift

• The shape of the continent seems to fit
  together.
• Matching Geological Units
• Distribution of Fossils
• Distribution of Climatic Belts
• Location of past glacial regions.

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Evidences for Continental Drift

• The shape of the continent seems to fit
  together.
• Matching Geological Units
• Distribution of Fossils
• Distribution of Climatic Belts
• Location of past glacial regions.

BIG PROBLEM!!!! HOW CAN THE WEAK CONTINENTS MOVE
TROUGH THE STRONG OCEANS?? WHERE THE FORCES TO
MOVE THE CONTINENTS COME FROM???
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APW Apparent Polar Wander
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A tape recorder An essay of GeoPoetry
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Magnetic Reversal on Sea Floor
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Plate Margins on a flat planet
Transform LL
Constructive
Convergent
Transform RL
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Plate Margins on a flat planet
Transform LL
Constructive
Convergent
Transform RL
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http//www.gasd.k12.pa.us/dpompa/Mini20Lecture.h
tml
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From Lowrie, 2007
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From Lowrie, 2007
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How fast plates move ???
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Hot spot
www.gasd.k12.pa.us/dpompa/Mini20Lecture.html
www.tulane.edu/.../geol204/volclandforms.htm
www.geophysik.uni-frankfurt.de/schmelin/
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Hot spot
www.gasd.k12.pa.us/dpompa/Mini20Lecture.html
www.tulane.edu/.../geol204/volclandforms.htm
www.geophysik.uni-frankfurt.de/schmelin/