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Unit Z: Plate Tec
Plate Tectonics Vocab 8th Gr.
| Term | Definition |
|---|---|
| Plate Tectonic Theory | Theory that the lithosphere is divided into tectonic plates that slowly move on top of the asthenosphere |
| lithosphere | Cool, rigid, outermost layer of Earth that is divided into enormous pieces called tectonic plates; consists of the crust and the uppermost part of the mantle |
| asthenosphere | the upper part of the mantle below the lithosphere. It is made of partially molten rock. |
| convection currents | a circular or cyclical motion that occurs because of heat causing density differences in the mantle; the engine for plate movement. |
| Continental Drift | Theory that the continents were once all connected but have moved apart in the last 250 million years |
| fossils | impressions of organisms left in rock layers that indicate the organisms once lived in the area |
| sea floor spreading evidence | a parallel pattern of rock material found at identical locations on each side of the Mid-Atlantic Ridge reveals rock of the same geologic age and magnetic polarity |
| divergent boundary | the boundary between two tectonic plates moving away from each other; on land it creates rift valleys, on the sea floor it creates new ocean crust and mountainous ridges |
| subduction | the process in which a denser plate is pushed downward beneath a less dense plate when plates converge; occurs at continental to oceanic boundaries and oceanic to oceanic boundaries |
| convergent boundary | the boundary between two tectonic plates moving toward each other; results in volcanic activity when an ocean plate subducts, or moves below, a continental plate or another oceanic plate |
| transform boundary | the boundary between two plates that slide sideways past one another; creates sudden shifts that result in earthquakes and the release of stored energy |
| convergent boundary, continental to continental | continental plates of equal density converge; creates tall mountains |
| ocean trench | deep and narrow depressions in the seafloor where the subducted plate moves down into the asthenosphere |
| atmosphere | the layer of air all around Earth |
| hydrosphere | the water all around Earth |
| biosphere | the living things all around Earth |
| volcanic eruptions | events in which molten rock spews out from the mantle to the surface of Earth as ash, lava, and gases |
| mountain building | major geological even that occurs when continental plates of equal density converge and are pushed up |
| spreading ridges | ridges formed from magma creating new crustal material at diverging oceanic plate boundaries |
| earthquakes | major geological events that occur at ALL types of plate boundaries when the plates shift suddenly and release stored energy |
| oceanic | the type of crustal material that is thinner and denser |
| continental | the type of crustal material that is thicker and less dense |
| density | the amount of matter (mass) packed into a given volume |
| tectonic plates | huge pieces of Earth's lithosphere that move slowly on the asthenosphere. They meet at "boundaries." |
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LMS 8 Sci
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