Chapter 17 Plate tectonics

Panagea

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

Magnetometer

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

tectonic plates

Huge pieces of earth's crust that covers it's surface and fits together at the edges.

Isochron

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

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 other; 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.

ridge push

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

slab pull

Tectonic process associated with convection currents in earth's mantle that occurs as the weight of the subducting plate pulls the trailing lithosphere into 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 spreading.

continental drift

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

magnet reversal

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