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Plate Tectonics
Continental drift• – Wegner’s idea that states continents have
moved horizontally along Earth’s surface to their present positions
The drawbacks to continental drift
Pangaea – one supercontinent
Plates are Plates are constantly constantly movingmoving
Plate Boundary Features
Evidence that supports Continental Drift
1. Continents fit together like puzzle pieces.
Going Back in Time!!! 230 mya
Evidence that supports Continental Drift
2. Matching rock layers that were found on Africa and South America.
Evidence that supports Continental Drift
3. Matching fossils of land-based dinosaurs such as Mesosaurus in the southern region of both Africa and South America.
Evidence that supports Continental Drift
4. Ancient Climates – Evidence of ice sheets on continents.• Tropical plant fossils found in the rocks of Antarctica.
Evidence that supports Continental Drift (seafloor spreading) Harry Hess
5. Polarity of ocean crust• Earth’s poles reverse over and over so the iron in the basaltic ocean crust points in different directions.
• (look at animation!!!!)
PPaalleeoommaaggnniittiissmm
20km 20km
http://www.classzone.com/books/earth_science/terc/content/visualizations/es0803/es0803page01.cfm?chapter_no=visualization
Seafloor Spreading and Magnetization
Glomar Challenger
Evidence that supports Continental Drift (seafloor spreading)
Age of ocean rockThe Glomar
Challenger was a drilling ship that found that the youngest ocean rock is near the rift zones and gets older the further away you get from them.
Red – Young Yellow – Average Blue - Old
Convergent Boundaries – Coming together
Subduction – trenches form
Convergent
Divergent
Subduction
Asthenosphere underneath
Divergent Plate Boundary
Mid-Ocean RidgeRift Valley
Young OceanFloor
Old Ocean Floor Old Ocean Floor
Divergent Boundary
• Place on the Earth’s crust where the plates are moving away from each other.
Rift Valley
Mid-Oceanic Ridges
*Tension Forces
New Ocean Floor Creation
Two plates moving against one another
Strike-Slip (Transform)
Transform Fault / Strike Slip (Shearing force)
San Andreas fault (California) Transform Fault/Strike-Slip Boundary
Two Continental Plates
Continental Plates Collide
Continental Plates
Form Mountains (Himalayas, Ural)
Convergent Margins: India-Asia Collision I
Convergent Boundary• Occur in areas where two tectonic plates are colliding
into one another.
Continental Plate
Continental Plate
Oceanic Plate
Subduction
http://www.classzone.com/books/earth_science/terc/content/visualizations/es0808/es0808page01.cfm?chapter_no=visualization
Continental-Continental Convergence
• Two low density granitic plates colliding creates mountains like the Himalayas (Mt. Everest)
Oceanic-Continental Convergent Boundaries (Subduction)
Oceanic plate in water
ContinentOceanic Crust
WET
Subduction!!!!!
Magma Chamber
Oceanic-Continental Convergence
• Pressure eventually melts the oceanic plate creating less dense magma that comes to the surface through continental volcanic arcs (Andes).
More dense oceanic plate
Less dense continental plate
Subduction Zone!!!!
Yummy!
ANDESANDES
Oceanic-Oceanic Convergent• Volcanoes form on the ocean floor
creating volcanic islands arcs. (Philippines, Japan)
Hotspots (like Hawaii)
• The Hawaiian Islands were formed as the Pacific Plate moved in a Northwesterly direction over a hot spot. The hot spot never moves. Magma spurts out of the hot spot creating a volcanic island chain.
Seamounts
Quiz – Part 1Indicate divergent, convergent, transform
Quiz!!!!!
1. What is the name of the ancient super continent.
2. Who proposed the theory of Continental Drift?
3. Name three pieces of evidence that support continental drift.
4. Draw a convergent Oceanic-Continental boundary. Label all features.
5. Name a famous transform fault.