ES CH.7 'Plate Tectonics' vocab

Plate Tectonics:

The theory of global tectonics stating that the lithosphere is segmented into several plates and move relative to one another by floating on and sliding over the plastic asthenosphere.

Continental Drift:.

The hypothesis proposed by Alfred Wegener that Earth’s continents were once joined together and later split and drifted apart

Asthenosphere:

The portion of the upper mantle just beneath the lithosphere, extending from a depth of 100-350 kilometers below the surface of Earth and consisting of weak, plastic rock where magma may form.

Mid-Ocean Ridge:

The undersea mountain chain that forms at the boundary between divergent tectonic plates within oceanic crust; it circles the planet like the seam on a baseball, forming Earth’s longest mountain chain.

Normal Magnetic Polarity:

A magnetic orientation the same as that of Earth’s current magnetic field.

Magnetic Reversal:

A change in Earth’s magnetic field in which the north magnetic pole becomes the south magnetic pole and vice versa; has occurred on average every 500,000 years over the past 65 million years.

Seafloor Spreading:

The hypothesis that segments of oceanic crust are separating at the mid-ocean ridge.

Plate Boundary:

A fracture or edge that separates two tectonic plates.

A plate boundary where tectonic plates move apart from each other and new lithosphere is continuously forming; also called a spreading center or rift zone.

Divergent Boundary:

Convergent Boundary:

A plate boundary where two tectonic plates move toward each other and collide.

Transform Boundary:

A plate boundary where two tectonic plates slide horizontally past one another.

Continental Rifting:

The process by which a continent is pulled apart at a divergent plate boundary.

Subduction:

The process in which two lithospheric plates of different densities converge and the denser one sinks into the mantle beneath the other.

Convection:

The upward and downward flow of fluid material in response to density changes produced by heating and cooling.

:A rising column of hot, plastic rock within the mantle.

Mantle Plume

Hot Spot:

The hot upper mantle rock located within a plume and associated with a volcanic center that forms on the overlying lithosphere.

Supercontinent:

A continent, such as Pangaea, consisting of all or most of Earth’s continental crust joined together in a single, large landmass.

Isostasy:

The concept of balance between gravity and buoyancy that causes the lithosphere to float on the mantle at different elevations.