Unit 6 - Plate Tectonics

the thin and solid outermost layer of the Earth above the 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
the solid, outer layer of the Earth that consists of the crust and the rigid upper part of the mantle
the soft layer of the mantle on which the tectonic plates move
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
stress that occurs when forces act to squeeze an object
stress that occurs when forces stretch an object
the bending of rock layers due to stress
a break in a body of rock along which one block slides relative to another
the rising of region's of the Earth's crust to higher elevations
the sinking of regions of the Earth's crust to lower elevations
the study of earthquakes
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
surface waves
seismic waves that travel through and produce motion in the upper few kilometers of the Earth's crust; these waves travel more slower than body waves and are more destructive
body waves
seismic waves that travel through the interior of Earth
P wave
pressure or primary seismic body waves; these are the fastest seismic waves and the first detected in an earthquake; these waves move the rock parallel to the wave; these waves can travel through both solid and liquid layers of the Earth
S wave
shear or secondary seismic body waves; these are the second-fastest seismic waves and they stretch rock in a side to side motion moving the rock perpendicular to the direction of the wave; these waves can only travel through layers of the Earth that are solid
an instrument that records vibrations in the ground and determines the location and strength of an earthquake
the point on Earth's surface directly above an earthquake's starting point, or 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
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
an opening at the surface of the Earth through which volcanic material passes
a funnel-shaped pit near the top of the central vent of a volcano
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
extremely deep areas in the ocean that are created by a subducting plate

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