Chapter 17 Plate Tectonics

Pangaea

Ancient landmass made up of all the continents that began to break apart about 200 mya. Greek word that means "all the earth".

Magnetometer

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

Tectonic plate

Huge pieces of Earth's crust that cover its surface and fit together at their edges.

Isochron

Imaginary line on a map that shows points of the same age; formed at the same time.P

Rift Valley

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

Divergent Boundary

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.

Convergent boundary

Place where two tectonic plates are moving toward each other; is associated with trenches, islands arcs, and folded mountains.

Transform Boundary

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

Subduction

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

Paleomagnetism

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.

Slab Pull

Tectonic process associated with convection currents in Earth's mantle that occurs as the weight of the subjecting plate pulls the trailing lithosphere into a subduction zone.

Ridge Push

Tectonic process associated with convention currents in Earth's mantle that occurs when the weight of an elevated ridge pushes an oceanic plate toward a subduction zone.

Seafloor Spreading

The hypothesis 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 spread.

Contiental Drift

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.

Magnetic reversal

When Earth's magnetic field changes polarity between normal and reversed.