Download Unit 3:Tectonic Processes

November 14, 2011
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I will return your exams tomorrow. (Grades
Look Good)
Pick up a textbook from the library
We will start Unit 3 today( Tectonic Processes)
This unit has a lot of vocabulary words.
Please download the vocabulary pdf from my
website.
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Let's look at Tectonic Processes. These are
the forces that are trying to build the earth.
Physical evidence of this happening includes
volcanoes, earthquakes, folds, and faults.
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Knowledge has come from studying seismic
waves which are generated by
earthquakes and are registered on
seismographs
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1) Body Waves: travel through the interior of
the earth
a) primary (P) or compression waves: travel
fastest through any material
b) secondary (S) or shearing-deformation
waves: travel only through solid materials
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Surface Waves: travel only through the crust
(i.e. L or long waves)
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Crust or Lithosphere
5 to 64 km thick
brittle shell of solid rock that cracks, warps,
and bends
thinnest on the ocean floors
Sial (i.e. light granitic rock): major component
of the continents
Sima (i.e. dense basaltic rock): major
component of the ocean basins
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approx. 2900 km thick
upper part is known as
the asthenosphere very hot, approx. 1650
deg. C in upper part
driving force for volcanoes, mountain
building, and continental drift
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approx. 2900 km thick
Outer core: likely made of liquid iron
Inner core: believed to be solid iron, 4000 to
6000 deg. C, inner heat believed to be caused
by the decay of radioactive rock
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located in the upper mantle
- partially molten (i.e. approx. 10%)
- lithosphere "floats" on top of the
asthenosphere
- zones that have become molten, or partially
molten, can develop convection currents
- convection currents in the asthenosphere
are responsible for plate movement
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Convection currents in the outer core are
partially responsible for the earth's magnetic
field but do not drive the tectonic plates
convection: transmission of heat within a
liquid or gas by movement of heated
particles.
molten: liquefied by heat