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EPS 122: Lecture 2 - Plate tectonics: A historical review
Plate tectonics: A historical review
Reading: Tectonics: Fowler Ch 2 p5-10
For those unfamiliar with plate tectonics: Press & Siever “Understanding Earth” Ch 20
EPS 122: Lecture 2 - Plate tectonics: A historical review
A continental jigsaw
1620: Francis Bacon
Africa and South America
fit together
1655: Antonio Snider
Published a sketch
Mid 1800’s:
First proposed that
continents did fit
together
Toward plate tectonics:
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EPS 122: Lecture 2 - Plate tectonics: A historical review
1912: Alfred Wegener – Continental Drift
1. Similar fossils: N America and Europe S America and Africa
2. Similar rock formations across boundaries
Conclusion: There used to be a supercontinent - Pangaea
Flora and fauna Toward plate tectonics:
Mesosaurus Glossopteris
EPS 122: Lecture 2 - Plate tectonics: A historical review
Skeptics Toward plate tectonics:
Wegener’s ideas were only discussed for a decade and then dropped.
• The coastlines don’t match perfectly
• Were the rock formations really the same?
Alternatives:
1. Land masses sank as the Earth cooled and contracted
2. Land bridges between the continents could explain the fossil record
3
EPS 122: Lecture 2 - Plate tectonics: A historical review
Bathymetry The plate tectonic revolution
After World War II …no evidence of land bridges!
EPS 122: Lecture 2 - Plate tectonics: A historical review
Vine and Matthews - 1963
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EPS 122: Lecture 2 - Plate tectonics: A historical review
Vine and Matthews - 1963
EPS 122: Lecture 2 - Plate tectonics: A historical review
Vine and Matthews - 1963
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EPS 122: Lecture 2 - Plate tectonics: A historical review
Magnetic stripes
Atlantic Pacific
Plate tectonics
EPS 122: Lecture 2 - Plate tectonics: A historical review
Seafloor age Plate tectonics
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EPS 122: Lecture 2 - Plate tectonics: A historical review
Euler poles Plate tectonics
EPS 122: Lecture 2 - Plate tectonics: A historical review
Morgan 1968 1968
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EPS 122: Lecture 2 - Plate tectonics: A historical review
Morgan 1968
EPS 122: Lecture 2 - Plate tectonics: A historical review
Morgan 1968
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EPS 122: Lecture 2 - Plate tectonics: A historical review
Morgan 1968
EPS 122: Lecture 2 - Plate tectonics: A historical review
Isacks, Oliver, Sykes 1968
1968
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EPS 122: Lecture 2 - Plate tectonics: A historical review
Isacks, Oliver, Sykes 1968 thanks to the WWSSN
EPS 122: Lecture 2 - Plate tectonics: A historical review
Identifying the plates
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EPS 122: Lecture 2 - Plate tectonics: A historical review
Isacks, Oliver, Sykes 1968
Plate motion directions, from what?
Relative motions
EPS 122: Lecture 2 - Plate tectonics: A historical review
Categories of plate boundaries
Divergent • Established mid-ocean ridge • New rift zone, new ocean
Transform • Along mid-ocean ridges • Across continents
Convergent • Ocean – continent • Ocean – ocean
• Continent – continent
Plate tectonics:
What kinds of beach balls?
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EPS 122: Lecture 2 - Plate tectonics: A historical review
Categories of plate boundaries
Divergent • Established mid-ocean ridge Mid-Atlantic Ridge • New rift zone, new ocean East African Rift
Transform • Along mid-ocean ridges Fracture Zones e.g. south Pacific
• Across continents San Andreas Fault
Convergent • Ocean – continent Off west coast of South America • Ocean – ocean Japan Trench, western Pacific • Continent – continent Himalaya
Plate tectonics:
EPS 122: Lecture 2 - Plate tectonics: A historical review
Mid-Atlantic Ridge Divergent boundaries:
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EPS 122: Lecture 2 - Plate tectonics: A historical review
Ocean transforms Transform plate boundaries:
Mid-ocean ridges are
offset by
ocean transforms:
Fracture Zones
Ocean bathymetry map
EPS 122: Lecture 2 - Plate tectonics: A historical review
Ocean transforms Transform plate boundaries:
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EPS 122: Lecture 2 - Plate tectonics: A historical review
San Andreas Fault Transform plate boundaries:
EPS 122: Lecture 2 - Plate tectonics: A historical review
Different types Convergent plate boundaries:
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EPS 122: Lecture 2 - Plate tectonics: A historical review
Hotspot tracks 1963: Wilson’s
Hawaii
Easter
MacDonald
Galapagos
EPS 122: Lecture 2 - Plate tectonics: A historical review
Morgan 1971
…so hotspot tracks provide absolute plate motion
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EPS 122: Lecture 2 - Plate tectonics: A historical review
Plate velocities Plate tectonics
relative and absolute
EPS 122: Lecture 2 - Plate tectonics: A historical review
Diffuse regions of seismicity …and deformation
plate tectonics is not a perfect model