Download Plate Tectonics Lithosphere broken into plates 3 Types of plate

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Plate Tectonics
Def.: A theory that explains the behavior of the Earth’s lithosphere in terms of several moving plates.
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Lithosphere broken into plates
Seven (or more) major plates
In motion and continually changing in shape and size
Largest is the Pacific plate
Several include an entire continent plus a large area of seafloor
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Fig. 19.17, p. 532-533
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3 Types of plate boundaries:
Diagram of plates showing movement direction and velocity
Divergent
Convergent
Transform
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Divergent plate boundaries
Seafloor spreading occurs along the oceanic ridge system
Fig. 19.18
p. 534
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Divergent plate boundaries
Continental rifts
Split landmasses
East African rift
& Rhine Valley
Not all develop into full-fledged spreading centers
Fig. 19.20, p. 538
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Bouger gravity anomaly map of the Midcontinent of North America
http://csd.unl.edu/csd/resource/vol-13/oldrocks.htm
Shows the extent of the 1.1 billion year old Midcontinent Rift, across Minnesota, Wisconsin, Iowa,
Nebraska and Kansas.
Manifested in outcrop by basalt flows and associated gabbro intrusions, plus flanking sediment basins
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Convergent plate boundaries
Fig. 19.22, p. 540
Oceanic plates return to the mantle in these
destructive plate margins
Surface expression an ocean trench
Called “subduction zones”
Average angle of descent is about 45°
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Types of convergent boundaries
Oceanic - Continental
Oceanic - Oceanic
Continental - Continental
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Types of boundaries
Transform Faults
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WHY Plate Tectonics? Fig. 19.A, p. 535
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Driving Mechanisms for Plate Tectonics
Plate movements are result of Earth dissipating interior heat
Ridge Push
Slab Pull
Ch. 17, pp. 489-491
Ch. 19, pp. 550-553
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Mantle Convection
Double-layer
Whole Mantle
Deep Layer
Fig. 19.32, p. 552
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Mantle Convection
Investigations using:
Seismic Tomography
(CAT scans using seismic energy)
Numerical Modeling
Fig. 17.D, p. 491
http://www.cacr.caltech.edu/Publications/annreps/annrep94/earth-01.html
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