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Ch. 12 Vocabulary
Term | Definition |
---|---|
mid-ocean ridge | underwater mountain range, formed by plate tectonics. |
rift valley | a large elongated depression with steep walls formed by downward displacement of a block of the Earth's surface between nearly parallel faults or fault systems. |
divergent boundary | linear feature that exists between two tectonic plates that are moving away from each other. |
convergent boundary | actively deforming region where 2 or more tectonic plates of the lithosphere move toward one another and collide. |
subduction | the sideways and downward movement of the edge of a plate of the Earth's crust into the mantle beneath another plate. |
transform boundary | plate tectonic boundary that exists as a large fault, or crack, along which lithospheric plates move in a horizontal direction. |
fault | a crack along which movement has taken place. |
elastic rebound | the sudden energy release that goes with fault movement. |
focus | point of origin |
epicenter | the point on Earth's surface directly above the focus |
discontinuity | a boundary that marks a density change between layers |
shadow zone | "dead zone" between 105 and 140 degrees from an Earth's epicenter, where nothing is recorded on a seismogram |
asthenosphere | a weaker, plastic like layer upon which Earth's lithospheric plates move. |
viscosity | a measure of the resistance of a fluid to flow |
cinder cone volcano | small, violently erupting volcano formed by accumulation of large pyroclastic materials around a vent |
shield volcano | broad, flat volcano formed by layers of free-flowing, high temperature, basaltic lava. |
composite volcano | large volcano formed by alternating lava flows and violently erupting pyroclastic materials. |