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Earth Science Chapter 17 PLATE TECTONICS

Continental Drift, Plate Tectonics, and Volcanoes.
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Convection (As it relates to plate tectonics)
Transfer of energy by the flow if a heated material. Convection currents in the asthenosphere (soft, plastic-like part of mantle) are thought to cause plate movement. Convection cycle rises at the mid-ocean ridges of divergent boundaries and sinks at the deep-sea trenches of convergent bondaries.
Continental Drift
The theory that states that all Earth's continents were once a single landmass called Pangaea.
Pangea
The one single landmass scientists believe existed before the continents broke apart.
Plate Tectonics
The theory that says Earth's crust and rigid upper mantle are broken into enormous slabs called plates.
Divergent Boundaries
Places where tectonic plates are moving apart from one another.
Convergent Boundaries
Places where tectonic plates are moving towards one another.
Ocean Ridge
Divergent boundary in ocean where seafloor spreading occurs as magma rises, cools, forms new rock, forcing the 2 plates apart.
Rift Valleys
Divergent boundaries that occur on land
Subduction
When plates meet and 1 of the 2 plates is is forced benath the other.
Deep Sea Trench
Formed at convergent boundaries when subduction occurs and the more dense oceanic plate slips under another plate. The deepest one is by the Mariana Islands.
Folded (Very High) Mountains
Extremely high mountains formed when 2 continental plates converge (collide). Because the continental plates have similar density there is no subduction and plates are crumpled & forced up instead.
Paleomagnetism
Study of Earth's magnetic field, based on magnetic iron of basalt on the ocean floor. The iron lines up and "points" in the direction of the Earth's magnetic field when the magma cooled and formed rock.
Magnetic Reversal
Change in Earth's magnetic field. The iron in the basalt on the ocean floor indicate the Earth's magnetic field has reversed several times.
Seafloor Spreading
The theory that new ocean crust is formed at ocean ridges and destroyed at deep-sea trenches.