Gamache-Chapter 8

Fracture Zones

prominent linear breaks in the oceanic crust which include both the active transform faults as well as their inactive extensions into the plate interior

Paleomagnetism

remnant magnetism in rock bodies

Seafloor Spreading

the mechanism responsible for producing new seafloor between two diverging plates

Partial Melting

the process by which most igneous rocks melt

Lithosphere

the rigid outer layer of Earth, including the crust and upper mantle

Curie Point

the temperature above which a material loses its magnetization

Transform Boundary

the type of plate boundary where plates grind past each other without creating or destroying lithosphere

Divergent Boundary

the type of plate boundary where plates move apart, resulting in an upwelling of material from the mantle to create new seafloor

Slab Pull

a mechanism that contributes to plate motion in which cool, dense oceanic crust sinks into the mantle and "pulls" the trailing lithosphere along

Ridge Push

a mechanism that may contribute to plate motion involving the oceanic lithosphere sliding down the oceanic ridge under the pull of gravity

Plate

a rigid slab of earth's lithosphere

Asthenosphere-

a subdivision of the mantle situated below the lithosphere

Plate Tectonics

a theory in which the Earth's outer shell consists of about 20 rigid slabs

Continental Drift

a theory that originally proposed that the continents are rafted about, proposed by Wegener in his 1915 book

Island Arc

alternate name for Volcanic Island Arc

Fossil Magnetism

alternate name for paleomagnetism

Oceanic Ridge System

an elevated portion of the seafloor that forms along well-developed divergent plate boundaries

Deep Ocean Trench

as an oceanic plate slides beneath an overriding plate, this deep, linear fracture often forms on the ocean floor adjacent to the zone of subduction

Continental Volcanic Arc-

mountains formed in part by igneous activity associated with the subduction of oceanic lithosphere beneath a continent

Pangaea

supercontinent that Wegener hypothesized existed about 200 million years ago that broke into smaller continents that drifted to their present day positions

Convergent Boundary

the type of plate boundary where plates move together, causing one of the slabs to be consumed into the mantle as it descends beneath an overriding plate

Hot Spot

this is caused by a rising plume of mantle, one of these is responsible for the intraplate volcanism that produced the Hawaiian Islands

Reverse Polarity

when rocks exhibit magnetism opposite of the present magnetic field, they are said to possess this

Normal Polarity

when rocks exhibit the same magnetism as the present magnetic field, they are said to possess this

Volcanic Island Arc

a chain of small volcanic islands that forms when two oceanic slabs converge, one descending beneath the other

Magnetic Reversals

a change in Earth's magnetic field resulting with opposite magnetic directions being aligned with one another

Rift Valley

a downfaulted valley created by material displaced downward along spreading centers on continents

Subduction Zone

a long, narrow zone where one lithospheric plate descends beneath another

Slab Suction

a mantle circulation that pulls both the subducting and overriding plates toward the trench

Mantle Plume

a mass of hotter-than-normal mantle material that ascends toward the surface, where it may lead to igneous activity