Term
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Definition
| A portion of the upper mantle that is directly below the lithosphere. A zone of low strength in the upper mantle defines the top of the asthenosphere. This weak zone allows the plates of the lithosphere to slide across the top of the asthenosphere. |
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Term
lithosphere
[image] [image] |
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Definition
| The rigid outer shell of the earth which includes the crust and a portion of the upper mantle. |
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Term
convection currents
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Definition
| This current cools down as it comes closer to the surface of the earth. |
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Term
mantle convection
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Definition
| Mantle convection is the slow creeping motion of Earth's rocky mantle caused by convection currents carrying heat from the interior of the earth to the surface. |
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Term
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Definition
| Ridge-push is a proposed mechanism for plate motion in plate tectonics. |
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Term
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Definition
| As a crustal plate moves further from an oceanic ridge, it cools and becomes increasingly dense. This causes it to sink beneath the continental crust in a subduction zone. |
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Term
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Definition
| A large continental landmass that existed from about 300 million years ago through about 200 million years ago. It included most of the continental lithosphere present at that time. It has since broken up and the fragments have drifted to become the configuration of Earth's present day continents. |
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Term
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Definition
| Plate tectonics is a scientific theory which describes the large scale motions of Earth's lithosphere. |
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Term
collision boundary
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Definition
collision boundary form when two tectonic plates are moving toward each other. These are also known as destructive boundaries because no new crust is being made, and in certain convergent boundaries, the more dense plate is subducted under the less dense plate and eventually becomes part of the mantle.
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Term
convergent boundary
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Definition
| convergent boundary also known as a destructive plate boundary (because of subduction), is an actively deforming region where two (or more) tectonic plates or fragments of lithosphere move toward one another and collide. |
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Term
spreading centers
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Definition
| Spreading centers occur where two plates are moving away from each other, and deep cracks are opened through the crust. |
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Term
divergent boundary
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Definition
| Divergent boundary is a linear feature that exists between two tectonic plates that are moving away from each other. These areas can form on the end of continents but eventually form ocean basins. |
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Term
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Definition
| A craton is an old and stable part of the continental lithosphere. Having often survived cycles of merging and rifting of continents, cratons are generally found in the interiors of tectonic plates. |
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Term
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Definition
| A terrane in geology is a fragment of crustal material formed on, or broken off from, one tectonic plate and accreted — "sutured" — to crust lying on another plate. |
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Term
thin-skinned thrusting
[image] [image] |
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Definition
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Term
subduction boundary
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Definition
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