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Ch 4 Plate Tectonics

Terms in this set (20)

Divergent Plate Boundary
a boundary at which two lithosphere plates move apart from each other by sea floor spreading; they are marked by mid-ocean ridges

High heat flow, active volcanism, shallow focus earthquakes
Seismic Belts
the relatively narrow strips of crust on Earth under which most earthquakes occur.
Pillow Basalts
cooled lava blobs on the ocean floor
Black Smokers
the cloud of suspended minerals formed where hot water spews out of a vent along a mid-ocean ridge; the dissolved sulfide components of the hot water instantly precipitate when the water mixes with seawater and cools.
Convergent Plate Boundary
boundary at which two plates move toward each other so that one (oceanic) plate sinks (subducts) beneath the other
Marked by deep ocean trench
Back-Arc Basin
an area of of extension behind an area of intense compression that can develop if a volcanic arc is built on oceanic crust

dependent on the angle of subduction
Subduction
process by which one oceanic plate bends and sinks down into the asthenosphere beneath another plate

Only oceanic lithosphere can subduct
Wadati-Benioff Zone
a sloping band of seismicity defined by earthquakes that occur in the down going slab of a convergent plate boundary
Accretionary Prism
piling up of sediment scraped off the downgoing plate
Transform Plate Boundary
boundary at which one plate slips laterally past another. No new plate forms and no old plate is consumed
Triple Junction
boundary of 3 plates
Hot Spot
location at the base of the lithosphere, at the top of a mantle plume, where temperatures can cause melting. As a plate moves over this the volcano moves off and dies, and a new volcano forms over the (blank)
Mantle Plumes
a column of very hot rock rising up from deep in the mantle
When hot rock reaches base of lithosphere, it starts to melt and produces magma that seeps up through lithosphere—some of this magma reaches Earth's surface and erupts to produce a hot-spot volcano
Subducted material ponding at the U-L mantle boundary
or the Core-Mantle boundary can promote these
Continental Rift
a linear belt along which continental lithosphere stretches horizontally and thins vertically
Upwelling
a place where deep water rises in the ocean, or where hot magma rises in the asthenosphere.
Downwelling
a place where near-surface water sinks.
Ridge-push Force
process in which gravity causes the elevated lithosphere at a mid-ocean ridge axis to push on the lithosphere that lies farther from the axis, making it move away.
Slab-pull Force
once an oceanic plate starts to sink, it gradually pulls the rest of the plate along behind it
Relative Plate Velocity
the movement of one lithosphere plate with respect to another
Absolute Plate Velocity
the movement of a plate relative to a fixed point in the mantle.
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