continental drift
the hypothesis that states that the continents once formed a single landmass, broke up, and drifted to their present locations
Pangea
(plate tectonics) a hypothetical continent including all the landmass of the earth prior to the Triassic period when it split into Laurasia and Gondwanaland
plate tectonics
the theory that proposes that earth's outer shell consists of individual plates that interact in various ways and thereby produce earthquakes, volcanoes, mountains, and the crust itself
plate
a rigid layer of the Earth's crust that is believed to drift slowly
divergent boundary
a plate boundary where two plates move away from each other
convergent boundary
a plate boundary where two plates move toward each other
transform fault boundary
a boundary in which two plates slide past each other without creating or destroying lithosphere
oceanic ridge
a continuous elevated zone on the floor of all the major ocean basins and varying in width from 1000-4000km; the rifts at the crests represent divergent plate boundaries
rift valley
a deep valley that forms where two plates move apart
seafloor spreading
The process that creates new sea floor as plates move away from each other at the mid-ocean ridges
subduction zone
a destructive plate margin where oceanic crust is being pushed down into the mantle beneath a second plate
continental volcanic arc
mountains formed in part by igneous activity associated with the subduction of oceanic lithosphere beneath a continent
volcanic island arc
a chain of volcanic islands generally located a few hundred kilometers from a trench where there is active subduction of one oceanic plate beneath another
paleomagnetism
the natural remnant magnetism in rock bodies. the permanent magnetization acquired by rock that can be used to determine the location of the magnetic poles and the latitude of the rock at the time it became magnetized.
normal polarity
a magnetic field that is the same as that which exists at present
reverse polarity
a magnetic field opposite to that which exists at present
hot spot
a concentration of heat in the mantle capable of producing magma, which rises to Earth's surface; The Pacific Plate moves over a hot spot, producing the Hawaiian Islands
Albert Wegener
radical scientist who proposed the continental drift hypothesis