Geology Chapter 2 Vocab.

Front 1

plate tectonics

Back 1

the theory proposing that the lithosphere is broken into about a dozen large plates that move over earth's surface. Each plate acts as a distinct rigid nit that rides on the asthenosphere, which also is in motion. the theory attempts to explain seismicity, volcanism, mountain building, and evidence of paleomagnetism in terms of plate motions.

Front 2

continental drift

Back 2

the large scale motion of continents across earth's surface driven by plate tectonics.

Front 3

pangea

Back 3

a supercontinent that coalesced in the latest paleozoic era and comprised all present continents. The break up of this began in mesozoic time, as inferred from paleomagnetic and other data.

Front 4

seafloor spreading

Back 4

mechanism which new seafloor is created along the rift as the crest of a mid-ocean ridge as adjacent plates move apart. the crust separates along the rift, and new seafloor forms as hot new crust upwells into these cracks. The new seafloor spreads laterallyaway from the rift and is replaced by even newer crust in a continuous process of plate creation.

Front 5

spreading centers

Back 5

the region at the crest of a mid-ocean ridge, where new crust is being formed by seafloor spreading.

Front 6

subduction

Back 6

sinking of an oceanic plate beneath an over-riding oceanic or continental plate at a convergent plate boundary.

Front 7

island arc

Back 7

linear or arc-shaped chain of volcanic islands formed on the seafloor at a convergent plate boundary. The islands are formed in the overriding plate from rising melt derived from fluid-induced melting of the mantle wedge above the downgoing lithosphere slab.

Front 8

transform faults

Back 8

a plate margin at which the plates slide past each other and lithosphere is neither created nor destroyed. Relative displacement occurs along the fault as horizontal slip between the adjacent plates.

Front 9

magnetic anomaly

Back 9

pattern of long, narrow bands of high and low magnetic fields on the seafloor that are parallel to and almost perfectly symmetrical with respect to the crest of a mid-ocean ridge. The detection of such patterns was one of the great discoveries that confirmed seafloor spreading and led to plate tectonics theory.

Front 10

magnetic time scale

Back 10

detailed history of earth's magnetic field reversals going back into geologic time, as determined by measuring the thermoremanent magnetization or rock samples.

Front 11

relative plate velocities

Back 11

velocity at which one plate moves relative to another plate.

Front 12

geodesy

Back 12

ancient science of measuring the shape of the earth and locating points on its surface.

Front 13

isochrons

Back 13

a contour that connects points of equal age on the world's ocean floors are determined by magnetic reversal data and fossils from deep-sea drilling.

Front 14

rodinia

Back 14

supercontinent that formed about 1.1 ga and began to break up about 750 ma.