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Definition
first proposed hypothesis in 1915
published The Origin of Continents and Oceans |
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Term
| Wegener's continental drift theory |
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Definition
Believed in a supercontinent called Pangea and that it began breaking apart about 200 million years ago
Believed that the contients drifted to present positions
Believed that the continents broke the ocean crust |
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Term
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Definition
1. Fit of South America and Africa
2. Fossil matches across the seas
3. Rock type and Structure matches
4. Ancient climates
5. Main objection: The inability to provide a mechanism |
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Term
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Definition
More encompassing than conti nental drift
Associated with Earth's rigid outer shell |
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Term
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Definition
Consists of several plates
1.Plates are moving slowly
2.Largest plate is the Pacific Ocean
3.Plates are mainly beneath the ocean |
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Term
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Definition
1.Exists beneath the lithosphere
2.Hotter and weaker than lithosphere
3.Allows for movement of lithosphere |
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Term
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Definition
| All major interactions occur along their boundaries |
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Term
| Divergent Plate Boundaries |
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Definition
constructive margins
two plates move apart
mantle material upwells to create new seafloor |
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Term
| Ocean ridges and Seafloor spreading |
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Definition
A. Oceanic ridges develop along well developed boundaries
1. represents 20% of Earth's surface
2. Rift valleymay develop along the axis
B.Along ridges, seafloor soreading createss new seafloor
1.Topographic differences are controlled by spreading rates.
2.A spreading rate of 5-9 centimeters per year is the norm.
3.Continental rifts form at spreading centers within a continent. |
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Term
| Convergent Plate Boundaries |
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Definition
Destructive margins
1. Plates collide, an ocean trench is formed, and lithosphere is subducted into the mantle. |
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Term
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Definition
A. Oceanic-Continental Convergence
1. Denser oceanic slab sinks into the asthenosphere
2.Pockets of magma develop and rise
3.Continental volcanic arcs form
a. Andes
b. Cascades
c. Sierra Nevada |
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Term
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Definition
Oceanic- oceanic convergence
!. Two oceanic slabs converge and one descends beneath others
2. Often forms volcanos on the ocean floor
3.Volcanic island arcs form as volcanos emerge from the sea
A. Aleutian Islands
B. Mariana Islands
C. Tonga Islands |
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Definition
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