GEOS 112 Lecture Topics 13003

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GEOS 112 Lecture Topics 1/30/03

• Plate Tectonic Theory (1968)
• Plate Boundary Types and Processes
• Plate Dynamics - how do plates move?
• Mantle Plumes, Hotspots, Plate Velocity

Read Chapter 19 (Plate Tectonics) USGS Plate
Tectonic Book (link from GEOS112 Homepage) Quiz
1 on Thursday 1/30
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Development of Plate Tectonic Theory

• Continental Drift Hypothesis (A. Wegener, late
  1920s)

• Rock Magnetism (1940 - 1950s)

• Seafloor Topography Global Distribution of EQs
  and volcanoes (late 1940s - 1950s)
• Seafloor Spreading Hypothesis (H. Hess, 1962)

• Marine Magnetic Anomalies (mid 1960s)

• Ocean Drilling Project (late 1960s)

• Plate Tectonic Theory (1968)

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Plate Tectonic Theory
Figure 1.9

• 6 large plates (e.g., Pacific Plate)

• 7-10 small plates (e.g., Arabian Plate)

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Mantle Convection Drives Plate Motion
internal heat engine
Heat Sources

• Original accetionary from formation of the Earth

• Radioactive decay of U, Th, and K in the core and
  mantle

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Types of Plate Boundaries

• Divergent

• Transform

3. Convergent
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Divergent Boundaries
Seafloor Spreading
Important Process Production of New Oceanic
Lithosphere
Continental Plate Separation
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Divergent Boundaries
Seafloor Spreading
Continental Plate Separation
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Volcanism, but of non-explosive type! Small
Earthquakes
Figure 19.22
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Figure 19.21
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Types of Plate Boundaries

• Divergent

• Transform

3. Convergent
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Transform Boundary
Figure 19.19
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Transform Boundary
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Transform Boundary
(San Andreas Fault, CA)
Pacific Plate
North American Plate
No volcanism Moderate to large earthquakes
Figure 19.27
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Types of Plate Boundaries

• Divergent

• Transform

3. Convergent

• ocean-ocean

• ocean-continent

• continent-continent

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Convergent Boundaries
ocean-continent subduction zone (Andes Mtns)
ocean-ocean subduction zone (Japan, Aleutians)
continent-continent collision zone (Himalayas,
Alps)
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Important Process SUBDUCTION ? destruction of
old oceanic lithosphere at subduction zones
Volcanic island arc
Trench
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Ocean-Ocean Convergence
Aleutian Islands, N Pacific
Pacific Plate (oceanic)
Phillipine Plate (oceanic)
Marianas Islands, SW Pacific
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Ocean-Ocean Convergence
Largest earthquakes on Earth!!
Figure 19.28
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Oceanic Island Arc System
Explosive volcanoes!
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Convergent Boundaries
ocean-continent subduction zone (Andes Mtns)
ocean-ocean subduction zone (Japan, Aleutians)
continent-continent collision zone (Himalayas,
Alps)
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Ocean-Continent Convergence
South American Plate (continental)
West Coast of South America Andes Mountains
Nazca Plate (oceanic)
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Ocean-Continent Convergence
Largest earthquakes on Earth!!
Figure 19.32
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Ocean-Continent Convergence
Continental Volcanic Arc System (explosive
volcanism)
Crustal Deformation- Mountain Building
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Continental Volcanic Arc
Cascade Range, NW USA
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Convergent Boundaries
ocean-continent subduction zone (Andes Mtns)
ocean-ocean subduction zone (Japan, Aleutians)
continent-continent collision zone (Himalayas,
Alps)
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Continent-Continent Convergence
SE Asia
India
60 million years ago
30 million years ago
Himalaya
Tibetan Plateau
Today
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Continent-Continent Convergence
Tibetan Plateau, Himalaya Mts SE Asia
Eurasian Plate (continental)
Crustal Deformation- Mountain Building No
volcanism! Moderate to large earthquakes
Indian Plate (continental)
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