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Plate Tectonics
Chapter 2
Interactions at plate boundaries
depend on the direction of relative
plate motion and the type of crust.
Which kind of plate boundary is associated with Earthquake activity? A. Divergent Boundary B. Convergent Boundary C. Transform-fault Boundary D. All of the above
Interactions at plate boundaries
depend on the direction of relative
plate motion and the type of crust.
Which kind of plate boundary is associated with Earthquake activity?
A. Divergent Boundary B. Convergent Boundary C. Transform-fault Boundary D. All of the above
At which kind of plate boundary is new oceanic lithosphere formed?
A. Oceanic transform boundary B. Oceanic divergent boundary C. Ocean-ocean convergent boundary D. Ocean-continent convergent boundary
Interactions at plate boundaries
depend on the direction of relative
plate motion and the type of crust.
At which kind of plate boundary is new oceanic lithosphere formed?
A. Oceanic transform boundary B. Oceanic divergent boundary C. Ocean-ocean convergent boundary D. Ocean-continent convergent boundary
Interactions at plate boundaries
depend on the direction of relative
plate motion and the type of crust.
Plate Tectonics: Learning Goals
- Scientific Method
- Development of Plate Tectonics Theory
- Lithosphere vs Asthenosphere
- Crust vs Mantle
- Plates contain continent and ocean
- Plate boundaries (where the action is)
- Convergent Boundaries
- Divergent Boundaries
- Transform Boundaries
Divergent, Convergent and Transform plate boundaries
Crust and Mantle vs Lithosphere and Asthenosphere
Plates are lithosphere:
Both continent and ocean
crust
Scientific Method
- Observation (fact)
- This is a repeatable measurement or experiment
- Hypothesis
- One or more possible explanations to link observations
- Testing
- Further experiment or observation to test hypothesis
- Non-testable hypotheses also rejected
- Theory
- A grand or unifying hypothesis that has survived tests
- Relativity, Evolution, Plate tectonics
- Observation: Early Evidence (Wegener)
- The geometric fit of the continents.
- The similarity in rock age groups between adjoining regions.
- The similarity in Paleozoic fossils between adjoining areas.
- The distribution of Paleozoic glaciation in S.America, S.Africa, Australia, and India.
The geometric fit of the continents.
- Test the Hypothesis
- The hypothesis makes several predictions that allow it to be tested by further observation.
- Rocks in adjoining parts of Africa and South America should be similar in age and type.
- Rocks on Atlantic floor should get younger toward the mid-ocean ridge.
- New bathymetric measurements define the continental crust boundary. Do South America and Africa still fit together?
- If crust is being created at mid-ocean ridges, it should also be consumed. Where is the crust consumed?
- There needs to be a driving force.
- Test the Hypothesis
- Rocks in adjoining parts of Africa and South America were age-dated using new radio- isotopic methods: they matched perfectly.
- Rocks were dredged from the sea floor: they showed ages symmetrically increasing away from the ridge. There were no old rocks (>250MY).
- The fit of continents was revised using the edge of the continental slope rather than the coastline: the match was nearly perfect.
Rocks were dredged from the sea floor: They showed ages symmetrically increasing away from the ridge.
There were no old rocks (>250MY).
- Test the Hypothesis
- Theory of Plate Tectonics
- There appear to be 13 major plates that cover the globe.
- The plates can contain oceanic, or continental crust or both.
- New oceanic crust is created at the mid-ocean ridge (divergent boundary).
- Old oceanic crust is consumed (subducted) at convergent plate boundaries.
Continental Margins: Passive and Active
Divergent, Convergent and Transform plate boundaries
Transform, Divergent, and Convergent plate boundaries
Crust and Mantle vs
Lithosphere and Asthenosphere
Crust and Mantle vs Lithosphere and Asthenosphere
Interactions at plate boundaries
depend on the direction of relative
plate motion and the type of crust.
Key Figure 2.6 (pages 26-27) Go to next slide to begin
Divergent Boundaries Oceanic Plate Separation
Mid- Atlantic Ridge
Divergent, Convergent and Transform plate boundaries
Convergent Boundaries Ocean-Ocean Convergence
Mariana Islands Marianas Trench
Convergent Boundaries Ocean-Ocean Convergence
Mariana Islands Marianas Trench
Deep-sea trench; volcanic island arc.
Convergent Boundaries Ocean-Continent Convergence
Andes Mountains
South American Plate
South American Plate
Peru-Chile Trench
Convergent Boundaries Ocean-Continent Convergence
Andes Mountains
South American Plate
South American Plate
Peru-Chile Trench
A volcanic belt of mountains forms.
Convergent Boundaries Continent-Continent Convergence
(No Volcanoes)
Main thrust fault
Tibetan Plateau
Eurasian Plate
Eurasian Plate
Himalaya
Convergent Boundaries Continent-Continent Convergence
Himalaya
Main thrust fault
Tibetan Plateau
Eurasian Plate
Eurasian Plate
Crust crumbles, creating high mountains and a wide plateau.
Convergent Boundaries
- Ocean – Ocean
- Tonga trench
- Marianas Trench
- Ocean - Continent
- West coast South America
- Japan Trench
- Aleutians
- Continent – Continent
Divergent, Convergent and Transform plate boundaries
Transform-Fault Boundaries Mid-Ocean Ridge Transform Fault
Transform-Fault Boundaries Mid-Ocean Ridge Transform Fault
Spreading centers offset.
As plates move past each other...
Pacific Plate N. American plate
The San Andreas fault Looking SW from Joshua Tree
Transform Boundaries
- San Andreas Fault
- Cuba
- North coast South America
Divergent, Convergent and Transform plate boundaries
There appear to be 13 major plates that cover the globe.
Theory of Plate Tectonics
- Continental crust resists subduction.
- Continent-continent convergent boundaries form major mountains.
- Ocean-ocean and ocean-continent convergent boundaries form subduction zones marked by deep ocean trenches and Benioff Zones (deep earthquake zones extending to 670km).
There appear to be 13 major plates that cover the globe.
Read Grotzinger Chapter 3
Earth Materials
Assignment^ Divergent Boundaries
- Mid-Atlantic Ridge
- East Pacific Rise
- Red Sea-East Africa rift
Transform Boundaries
- San Andreas Fault
- Cuba
- North coast South America
Convergent Boundaries
- Ocean – Ocean
- Tonga trench
- Marianas Trench
- Ocean - Continent
- West coast South America
- Japan Trench
- Aleutians
- Continent – Continent
