crust
the thin and solid outermost layer of Earth above the mantle
mantle
the layer of rock between the Earth's crust and core
core
the central part of Earth below the mantle
lithosphere
the solid, outer layer of 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 a single large landmass broke up into smaller landmasses to form the continents, which then drifted to their present locations; the movement of continents
sea-floor spreding
the process by which new oceanic lithosphere (sea floor) forms as magma rises to Earth's surface and solidifies at a mid-ocean ridge
plate tectonics
the theory that explains how large pieces of Earth's outermost layer, called tectonic plates, move and change shape
converent boundary
the boundary between tectonic plates that are colliding
divergent boundary
the boundary between tectonic plates that are colliding
transform boundary
the boundary between tectonic plates that are sliding past each other horizontally
compression
stress that occurs when forces act to squeeze an object
tension
stress that occurs when forces act to 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 regions of the Earth's crust to higher elevations
subsidence
the sinking of regions of the Earth's crust to lower elevations
compound
a substance composed of two or more elements
seismic wave
vibration created when an earthquake happens
seismograph
machines which measure the times at which seismic waves arrive at different distances from an earthquake
Pangaea
greek for "all earth
mid-ocean ridges
places where sea-floor spreading takes place
magnetic reversal
when Earth's magnetic poles switch places
global positioning system
measures the rate of tectonic plate movement
deformation
the process by which the shape of a rock changes because of stress
anticline
upward-arching folds
syncline
downward, troughlike folds
monocline
step-like folds
fault block
the block of crust on each side of the fault
normal fault
when hanging wall moves down relative to the footwall
reverse fault
when hanging walll moves up relative to the footwall
strike-slip fault
when hanging wall and foot wall move horizontally past each other
folded mountains
form when rock layers are squeezed together and pushed upward
fault-block mountains
form when this tension causes large blocks of the Earth's crust to drop down relative to other blocks
rebound
crust slowly springs back to its previous elevation
rift zone
a set of deep cracks that forms between two tectonic plates that are pulling away from each other