click below
click below
Normal Size Small Size show me how
Plate Tectonics
Term | Definition |
---|---|
Lithosphere | Rigid outer part of the Earth, consisting of the crust and upper mantle. |
Plates | Each of the several rigid pieces of the Earth's lithosphere that together make up the Earth's surface. |
Asthenosphere | Upper layer of Earth's mantle, below the lithosphere, in which there is relatively low resistance to plastic flow and convection is thought to occur. |
Continental Drift | The gradual movement of the continents across the Earth's surface thought geological time. |
Pangea | Supercontinent that existed during the late Paleozoic and early Mesozoic eras. |
Oceanic Ridge System | A long, seismically active submarine ridge system situated in the middle of an ocean basin and marking site of the upwelling of magma associated wi sea floor spreading. |
Sea Floor Spreading | The formation of new areas of oceanic crust, which occurs through the upwelling of magma at mid-ocean ridges and its subsequent outward movement on either side. |
Subduction | The sideways and downward movement of the edges of a plate of the Earth's crust into the mantle beneath another plate. |
Convergent Boundaries | Tectonic plates or fragments of the lithosphere move toward one another and collide. |
Divergent Boundaries | Two tectonic plates that move away from each other. |
Transform Fault Boundaries | Two plates that slide past each other. |
Mid-Ocean Ridge | Ridge in the middle of the ocean |
Trenches | A long, narrow, deep depression in the ocean floor. Typically one running parallel to a plate boundary and marking a subduction zone. |
Spreading Center | A linear zone in the sea floor along which magma rises and from which adjacent crustal plates are moving apart. |
Rift Valley | A large elongated depression with steep walls formed by the downward displacement of a block of the Earth's surface between nearly parallel faults or fault systems. |
Deep Ocean Trench | Deep trench in the ocean. |
Volcanic Island Arc | Result from the subduction of an oceanic tectonic plate and often parallel to an oceanic trench. |
Constructive Forces | Processes that help build up the Earth, either by depositing soil or silt in a river, or by volcanoes and lave flows that generated new land. |
Destructive Forces | Processes that break down the Earth, either thought the violent actions of volcanoes and earthquakes or by the steady flow of a river. |