Plate Tectonics Chapter 17

Front 1

continental drift

Back 1

Wegener's hypothesis that Earth's continents were joined as a single landmass, called Pangaea, that broke apart about 200 MYA and slowly moved to their present positions.

Front 2

Pangaea

Back 2

Ancient landmass made up of all the continents that began to break apart about 200 MYA.

Front 3

magnetometer

Back 3

Device used to map the ocean floor that detects small changes in magnetic fields.

Front 4

paleomagnetism

Back 4

Study of Earth's magnetic record using data gathered from iron-bearing minerals in rocks that have recorded the orientation of Earth's magnetic field at the time of their formation.

Front 5

magnetic reversal

Back 5

Changes in Earth's magnetic field over geologic time, recorded in ocean-floor rocks and continental basalt flows.

Front 6

isochron

Back 6

Line on a map that connects points of the same age.

Front 7

seafloor spreading

Back 7

Hess's theory that new ocean crust is formed at mid-ocean ridges and destroyed at deep-sea trenches; occurs in a continuous cycle of magma intrusion and spreading.

Front 8

theory of plate tectonics

Back 8

States that Earth's crust and upper mantle are broken into plates, which are huge rock slabs that move in different directions and at different rates over Earth's surface.

Front 9

divergent boundary

Back 9

Place where two of Earth's tectonic plates are moving apart; is associated with volcanism, earthquakes, and high heat flow, and is found primarily on the seafloor.

Front 10

rift valley

Back 10

Long, narrow depression that forms when continental crust begins to separate at a divergent boundary.

Front 11

convergent boundary

Back 11

Place where two of Earth's tectonic plates are moving toward each other; is associated with trenches, island arcs, and folded mountains.

Front 12

subduction

Back 12

Process by which one tectonic plate slips beneath another tectonic plate.

Front 13

transform boundary

Back 13

Place where two tectonic plates slide horizontally past each other that is characterized by long faults and shallow earthquakes.