EVIDENCE OF PLATE TECTONICS

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EVIDENCE OF PLATE TECTONICS

• By
• Amanda Green

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Plate Tectonics

• Hypothesis
• Large rigid plates interacting
• Seismic belts
• Pangaea
• Earthquakes, Mountains, and Volcanoes

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Pangaea

• Supercontinent
• Continental drift and sea-floor spreading
• Seven continents
• Fit
• Fossils

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Pangaea 200 Ma and Now
Figure 1. (A) Pangaea at 200 Ma and (B) present
position of continents (Keller and Pinter, 1996,
Fig 1.4).
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South America and Africa
Figure2. Bullard et al.s (1965) fit of South
America to Africa (Le Pichon and Others, 1973,
Fig. 8).
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Seismic Activity

• Base Level and Erosion
• Earth is not static
• Continuous elevation
• Seismic activity
• New lithosphere produced
• Older lithosphere consumed

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Stress

• Stress produced
• Stress exceeds the strength of rock
• Rock ruptures
• Energy is released

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Global Seismic Activity
Figure 3. Map of global seismic activity
(1963-1988, Richter magnitude M greater
than 5.0), delineating belts of earthquake
activity that define plate boundaries (Keller and
Pinter, 1996, Fig 1.5).
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Plate Boundaries
Figure 4. Recent volcanoes, earthquake zones, and
plate boundaries (Keller and Pinter, 1996, Fig
1.2).
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Volcanoes

• Consuming plate boundaries
• Lithosphere and asthenosphere
• Lithosphere subducted
• Occur primarily on plate boundaries

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Plate Boundaries
Figure 4. Recent volcanoes, earthquake zones, and
plate boundaries (Keller and Pinter, 1996, Fig
1.2).
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Mountain Building

• Individual and gradual uplift processes
• Convergence
• Partial melting

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Mountains

• Himalayas collision of India with Asia millions
  of years ago
• Still colliding growing today
• Appalachian Mountain North America and Africa
  collided in the Late Paleozoic, around 300 Ma.

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Himalayas
Figure 5. Extrusion of eastern and southeastern
Asia caused by the India-Asia collision (Keller
and Pinter, 1996, Fig 9.7).
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Conclusion

• Evidence
• Importance to society
• Importance to geology