Plate Tectonics If you look at a map of the world, you may notice that some of the continents could...
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Transcript of Plate Tectonics If you look at a map of the world, you may notice that some of the continents could...
![Page 1: Plate Tectonics If you look at a map of the world, you may notice that some of the continents could fit together like pieces of a puzzle.](https://reader038.fdocuments.us/reader038/viewer/2022110208/56649de65503460f94ade1a9/html5/thumbnails/1.jpg)
Plate Tectonics
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• If you look at a map of the world, you may notice that some of the continents could fit together like pieces of a puzzle.
![Page 4: Plate Tectonics If you look at a map of the world, you may notice that some of the continents could fit together like pieces of a puzzle.](https://reader038.fdocuments.us/reader038/viewer/2022110208/56649de65503460f94ade1a9/html5/thumbnails/4.jpg)
World Plates
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What are tectonic plates made of?
• Plates are made of rigid lithosphere.
The lithosphere is made up of the crust and the upper part of the mantle.
![Page 6: Plate Tectonics If you look at a map of the world, you may notice that some of the continents could fit together like pieces of a puzzle.](https://reader038.fdocuments.us/reader038/viewer/2022110208/56649de65503460f94ade1a9/html5/thumbnails/6.jpg)
What lies beneath the tectonic plates?
• Below the lithosphere is the asthenosphere.
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Plate Movement• “Plates” of lithosphere are moved around by
the underlying hot mantle convection cells
![Page 8: Plate Tectonics If you look at a map of the world, you may notice that some of the continents could fit together like pieces of a puzzle.](https://reader038.fdocuments.us/reader038/viewer/2022110208/56649de65503460f94ade1a9/html5/thumbnails/8.jpg)
What happens at tectonic plate boundaries?
![Page 9: Plate Tectonics If you look at a map of the world, you may notice that some of the continents could fit together like pieces of a puzzle.](https://reader038.fdocuments.us/reader038/viewer/2022110208/56649de65503460f94ade1a9/html5/thumbnails/9.jpg)
• Divergent
• Convergent
• Transform
Three types of plate boundary
![Page 10: Plate Tectonics If you look at a map of the world, you may notice that some of the continents could fit together like pieces of a puzzle.](https://reader038.fdocuments.us/reader038/viewer/2022110208/56649de65503460f94ade1a9/html5/thumbnails/10.jpg)
• Spreading ridges– As plates move apart new material is erupted to
fill the gap (constructive)
Divergent Boundaries
![Page 11: Plate Tectonics If you look at a map of the world, you may notice that some of the continents could fit together like pieces of a puzzle.](https://reader038.fdocuments.us/reader038/viewer/2022110208/56649de65503460f94ade1a9/html5/thumbnails/11.jpg)
Age of Oceanic Crust
Courtesy of www.ngdc.noaa.gov
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• Iceland has a divergent plate boundary running through its middle
Iceland: An example of continental rifting
![Page 13: Plate Tectonics If you look at a map of the world, you may notice that some of the continents could fit together like pieces of a puzzle.](https://reader038.fdocuments.us/reader038/viewer/2022110208/56649de65503460f94ade1a9/html5/thumbnails/13.jpg)
• There are 3 types of convergent plate boundaries (destructive)– Continent-Continent collision– Continent-Oceanic crust collision– Oceanic-Oceanic collision
Convergent Boundaries
![Page 14: Plate Tectonics If you look at a map of the world, you may notice that some of the continents could fit together like pieces of a puzzle.](https://reader038.fdocuments.us/reader038/viewer/2022110208/56649de65503460f94ade1a9/html5/thumbnails/14.jpg)
• Forms mountains, e.g. European Alps, Himalayas
Continent-Continent Collision
![Page 15: Plate Tectonics If you look at a map of the world, you may notice that some of the continents could fit together like pieces of a puzzle.](https://reader038.fdocuments.us/reader038/viewer/2022110208/56649de65503460f94ade1a9/html5/thumbnails/15.jpg)
Himalayas
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• Called SUBDUCTION
Continent-Oceanic Crust Collision
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• Oceanic lithosphere subducts underneath the continental lithosphere
• Oceanic lithosphere heats and dehydrates as it subsides
• The melt rises forming volcanism
• Ex. - The Andes
Subduction
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• When two oceanic plates collide, one runs over the other which causes it to sink into the mantle forming a subduction zone.
• The subducting plate is bent downward to form a very deep depression in the ocean floor called a trench.
• The deepest parts of the oceans are found along trenches. – Ex. -The Mariana Trench is 11 km deep!
Oceanic-Oceanic Plate Collision
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• Where plates slide past each other
Transform Boundaries
Above: View of the San Andreas transform fault
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Continental Transform Boundary - Example: San Andreas
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~800 km
DIVERGENT
CONVERGENT
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Plates move a few cm/year - about the same rate as your fingernails grow!
![Page 25: Plate Tectonics If you look at a map of the world, you may notice that some of the continents could fit together like pieces of a puzzle.](https://reader038.fdocuments.us/reader038/viewer/2022110208/56649de65503460f94ade1a9/html5/thumbnails/25.jpg)
![Page 26: Plate Tectonics If you look at a map of the world, you may notice that some of the continents could fit together like pieces of a puzzle.](https://reader038.fdocuments.us/reader038/viewer/2022110208/56649de65503460f94ade1a9/html5/thumbnails/26.jpg)
…what’s the connection?
Volcanoes and Plate Tectonics…
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Volcanism is mostly focused at plate margins
Pacific Ring of Fire
![Page 28: Plate Tectonics If you look at a map of the world, you may notice that some of the continents could fit together like pieces of a puzzle.](https://reader038.fdocuments.us/reader038/viewer/2022110208/56649de65503460f94ade1a9/html5/thumbnails/28.jpg)
- Subduction - Rifting - Hotspots
Volcanoes are formed by:
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Pacific Ring of Fire
Hotspot volcanoes
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• Hot mantle plumes breach the surface in the middle of a tectonic plate
What are Hotspot Volcanoes?
Photo: Tom Pfeiffer / www.volcanodiscovery.com
The Hawaiian island chain are examples of hotspot volcanoes.
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The tectonic plate moves over a fixed hotspot forming a chain of volcanoes.
The volcanoes get younger from one end to the other.
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…what’s the connection?
Earthquakes and Plate Tectonics…
![Page 33: Plate Tectonics If you look at a map of the world, you may notice that some of the continents could fit together like pieces of a puzzle.](https://reader038.fdocuments.us/reader038/viewer/2022110208/56649de65503460f94ade1a9/html5/thumbnails/33.jpg)
• As with volcanoes, earthquakes are not randomly distributed over the globe
• At the boundaries between plates, friction causes them to stick together. When built up energy causes them to break, earthquakes occur.
Figure showing the distribution of earthquakes around the globe
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Where do earthquakes form?
Figure showing the tectonic setting of earthquakes
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Plate Tectonics Summary• The Earth is made up of 4 main layers
– inner core, outer core mantle, crust
• Tectonic plates are made of crust and upper mantle (lithosphere)
• There are 2 types of plates• There are 3 types of plate boundaries• Volcanoes and Earthquakes are closely linked to
the margins of the tectonic plates
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History of the Theory
• Alfred Wegener • German scientist• “Continental Drift (1905)
– Continents were “drifting” around Earth’s surface
• Did not have a “mechanism” to explain his theory
• Not a generally accepted theory until 1950s
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SO…….
WHAT EVIDENCE DID WEGENER HAVE TO SUPPORT HIS THEORY?
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1. Puzzle-Like Fit of the Landmasses
• The land fit together like a jigsaw puzzle. • He called the land mass “Pangea”.
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2. Similar Rock Types on Separate Continents
• Mountain ranges in North America (Appalachians), Europe (Caledonians), and highlands in England matched or lined up
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3. Similar Fossils on Separate Continents
• Matching reptilian fossils on either side of the Atlantic Ocean, that would tend to indicate the continents were once joined.
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Matching Fossils
![Page 46: Plate Tectonics If you look at a map of the world, you may notice that some of the continents could fit together like pieces of a puzzle.](https://reader038.fdocuments.us/reader038/viewer/2022110208/56649de65503460f94ade1a9/html5/thumbnails/46.jpg)
Fossil Evidence
![Page 47: Plate Tectonics If you look at a map of the world, you may notice that some of the continents could fit together like pieces of a puzzle.](https://reader038.fdocuments.us/reader038/viewer/2022110208/56649de65503460f94ade1a9/html5/thumbnails/47.jpg)
4. Glaciation Patterns on Continents
• Continents that do not have glaciers now, show evidence of past glaciation.
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Fig. 3-4, p. 39
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The following link provides further insight into Wegener’s ideas about “continental drift” and evidence for the modern theory of plate tectonics.
• http://www.ucmp.berkeley.edu/geology/tectonics.html
http://www.ucmp.berkeley.edu/geology/tectonics.html