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43 Cards in this Set
- Front
- Back
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Modern Definition of Plate Tectonics |
A theory that explains the global distribution of geological phenomena in terms of the formation, destruction, movement, and interaction of earth's lithospheric plates |
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Alfred Wegner |
Idea that continents move based off observations of fossil distribution (and others) |
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Evidence of Continental Drift |
Fossil distribution, Jigsaw puzzle fit of the continents, fossil evidence, evidence from ice flow, mountain ranges, seafloor topography |
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Glossopteris, mososaurus fossil significance |
Provided evidence based on geological separation that continents must have once been together - because it could have not existed in isolated conditions |
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Continents Shape |
Had a "jigsaw puzzle fit" - continents fit together if you arranged them in a certain way |
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Ice Flow |
Unless water can flow up mountains, there had to be one super continent so that the glaciers ridge marks made sense - flowed down mountains into the middle Radial patterns of glacial melting observed in a non-circular place on earth |
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Appalachian Mountain Range |
Continued on in Europe when continents brought together |
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Seafloor Topography |
Mountain belt-like features found, along with trenches and volcanic patterns |
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Formation of Ocean Floor (Q) |
Little-weathered pillow basalt along axes of mid-ocean ridges and there was basalt farther away from ridges covered with more sediment |
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Magnetic Stripes (Q) |
Geophysical surveys found magnetic "stripes" of reversing polarity on ocean floor |
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Age of Ocean Floor (Q) |
Dating of ocean floor revealed youngest areas to be in the middle and oldest near edges of continents |
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Thickness of Ocean Sediment (Q) |
Ocean sediment increased AWAY from mid ocean ridges |
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Sea Floor Spreading (Hess's Hypothesis) |
FOUNDATION OF PLATE TECTONICS Magma is ejected into central rift of mid-ocean floor, forming new sea ridges, therefore old sea floor gets moved away |
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Magnetic Stripes (A) |
Magma cools rapidly in ocean, and ions arrange themselves to polarity of Earth's field at the time - "recording" it |
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Sediment Thickness (A) |
With Seafloor spreading, sediment pile would get pushed away as oceanic lithosphere grows |
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Trenches (A) |
If seafloor is made at mid-ocean ridges, it must be destroyed somewhere Submerged back into mantle at trenches (is subducted under other plates)q |
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Notion of Mantle Convection |
Cycling in the mantle due to seafloor spreading Hot material -> less dense = comes up and cools -> becomes more dense = sinks back down and gets subducted This convection drags the plates along |
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Transform Faults |
Compensate for Earth's curvature Plates move alongside each other Oceanic ridges result in a zig-zag pattern |
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Three Types of Plate Boundaries |
Divergent, Convergent, Transform |
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Divergent Plate Boundaries |
Two plates move away -> makes oceans |
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Convergent Plate Boundaries |
Two plates approach each other -> one is forced under the other |
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Transform Plate Boundaries |
Two plates move alongside each other |
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The continental lithosphere is much ______er than the oceanic lithosphere |
Older |
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Effect of Density |
Oceanic lithosphere floats low on asthenosphere Continental lithosphere floats higher on the asthenosphere |
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Effect of Lithospheric Thickness |
In a material of the same density, a thick block stands higher than a thin one Called "isostacy" = equal standing Continental lithosphere stands higher on the asthenosphere than oceanic lithosphere |
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Continents are like ________ ____________ |
Floating Rafts, cannot be subducted back into the mantle |
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Divergent Plate Boundaries |
Creates new oceanic crust - "constructive" "runny" "mafic" magma extruded |
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Convergent Plate Boundaries |
Oceanic Lithosphere consumed - "destructive" Pyroclastic deposits at the surface |
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Types of Convergent Plate Boundaries |
Oceanic-Oceanic Oceanic-Continental Continental-Continental |
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Oceanic-Oceanic Convergent Plate Boundaries |
Molten material rises to form an island |
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Oceanic-Continental Convergent Plate Boundaries |
Rises to form a continental arc |
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Continental-Continental Convergent Plate Boundaries |
Continental lithosphere cannot be subducted -> therefore it shortens -> creates mountains |
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Evidence of Subduction |
Areas with severe earthquakes get more severe the deeper into the trench you get because the plate keeps getting subducted more and more into the mantle |
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How do earthquakes occur? |
Two plates converging, pressure builds up until it overcomes friction holding them apart, and then is released all at once |
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Subduction Leading to Collision |
Rocks/fossils of oceanic origin found high on mountains because when the two plates converge, the one scrapes the other as it forms a mountain and brings up ocean material onto it |
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Transform Plate Boundaries |
Oceanic lithosphere is not created or destroyed Sometimes called "strike-slip" No magma is created |
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Consequences of plate Tectonics |
"Clastic Wedge" forming progressively smoother and smaller sediment towards sea Compression created by converging plates and heating of rock produced regional metamorphism |
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Hotspot Volcanoes |
"Tracks" produced by plate movement Plates move over a source of stationary magma and consistently form volcanoes as magma escapes Creates a chain of volcanoes Can even see a kink in the chain where the plate switched directions |
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Possible Mechanisms of Plate Movement |
Convection, Ridge Push, Slab Pull |
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Ridge Push |
Plates forced apart by creation of new lithosphere material |
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Slab Pull |
Oceanic plates dragged down at convergent boundaries due to increasing density as they cool - density driven movement |
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Implications for History of Life |
Climate change - Ontario was once on the equator |
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Implications for Evolution |
Plate tectonics can create/destroy geographical isolation to produce new species |
