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13 Cards in this Set
- Front
- Back
continental drift |
Wegener's hypothesis that Earth's continents were joined as a single landmass, called Pangaea, that broke apart about 200 MYA and slowly moved to their present positions. |
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Pangaea |
Ancient landmass made up of all the continents that began to break apart about 200 MYA. |
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magnetometer |
Device used to map the ocean floor that detects small changes in magnetic fields. |
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paleomagnetism |
Study of Earth's magnetic record using data gathered from iron-bearing minerals in rocks that have recorded the orientation of Earth's magnetic field at the time of their formation. |
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magnetic reversal |
Changes in Earth's magnetic field over geologic time, recorded in ocean-floor rocks and continental basalt flows. |
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isochron |
Line on a map that connects points of the same age. |
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seafloor spreading |
Hess's theory that new ocean crust is formed at mid-ocean ridges and destroyed at deep-sea trenches; occurs in a continuous cycle of magma intrusion and spreading. |
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theory of plate tectonics |
States that Earth's crust and upper mantle are broken into plates, which are huge rock slabs that move in different directions and at different rates over Earth's surface. |
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divergent boundary |
Place where two of Earth's tectonic plates are moving apart; is associated with volcanism, earthquakes, and high heat flow, and is found primarily on the seafloor. |
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rift valley |
Long, narrow depression that forms when continental crust begins to separate at a divergent boundary. |
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convergent boundary |
Place where two of Earth's tectonic plates are moving toward each other; is associated with trenches, island arcs, and folded mountains. |
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subduction |
Process by which one tectonic plate slips beneath another tectonic plate. |
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transform boundary |
Place where two tectonic plates slide horizontally past each other that is characterized by long faults and shallow earthquakes. |