Unit 6 - Plate Tectonics

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crust
the thin and solid outermost layer of the Earth above the mantle
mantle
the layer of rock between the Earth's crust and core
outer core
A layer of molten liquid iron and nickel that surrounds the inner core of Earth
inner core
A dense sphere of solid iron and nickel at the center of Earth
lithosphere
the solid, outer layer of the Earth that consists of the crust and the rigid upper part of the mantle
asthenosphere
the soft layer of the mantle on which the tectonic plates move
mesosphere
the strong, lower part of the mantle between the asthenosphere and the outer core
tectonic plate
a block of lithosphere that consists of the crust and the rigid, outermost part of the mantle
continental drift
the hypothesis that states that the continents once formed a single landmass, broke up, and drifted to their present locations
sea-floor spreading
the process by which new oceanic lithosphere forms as magma, rises toward the surface, and solidifies
plate tectonics
the theory that explains how large pieces of the Earth's outermost layer move and change shape
convergent boundary
the boundary formed by the collision of two lithospheric plates
divergent boundary
the boundary between two tectonic plates that are moving away from each other
transform boundary
the boundary between tectonic plates that are sliding past each other horizontally
mid-ocean ridge
an underwater mountain range made at divergent plate boundaries where new ocean floor is formed
compression
stress that occurs when forces act to squeeze an object
tension
stress that occurs when forces stretch an object
folding
the bending of rock layers due to stress
fault
a break in a body of rock along which one block slides relative to another
uplift
the rising of region's of the Earth's crust to higher elevations
subsidence
the sinking of regions of the Earth's crust to lower elevations
seismology
the study of earthquakes
deformation
the bending, tilting, and breaking of the Earth's crust; the change of the shape of rock in response to stress
elastic rebound
the sudden return of elastically deformed rock to its undeformed shape
seismic wave
a wave of energy that travels through the Earth, away from an earthquake in all directions
P wave
a seismic wave that causes particles of rock to move in a back-and-forth direction
S wave
a seismic wave that causes particles of rock to move in a side-to-side direction
seismograph
an instrument that records vibrations in the ground and determines the location and strength of an earthquake
epicenter
the point on Earth's surface directly above an earthquake's starting point, or focus
focus
the point along a fault at which the first motion of an earthquake occurs
gap hypothesis
the idea that a major earthquake is more likely to occur along the part of an active fault where no earthquakes have occurred for a certain period of time
seismic gap
an area along a fault where relatively few earthquakes have occurred recently but where strong earthquakes have occurred in the past
volcano
a vent of fissure in the Earth's surface through which magma and gases are expelled
magma chamber
the body of molten rock that feeds a volcano
vent
an opening at the surface of the Earth through which volcanic material passes
crater
a funnel-shaped pit near the top of the central vent of a volcano
caldera
a large, semicircular depression that forms when the magma chamber below a volcano partially empties and causes the ground above to sink
lava plateau
a wide, flat landform that results from repeated nonexplosive eruptions of lava that spread over a large area
rift zone
an area of deep cracks that forms between two tectonic plates that are pulling away from each other
hot spot
a volcanically active area of Earth's surface far from a tectonic plate boundary
trench
extremely deep areas in the ocean that are created by a subducting plate

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