Learn OC.4a Vocabulary

Learn OC.4a Vocabulary

​A plate boundary where two plates move toward each other.

convergent boundary

​A plate boundary where two plates move away from each other.

divergent boundary

​A plate boundary where two plates move past each other in opposite directions.

transform boundary

​The process by which oceanic crust sinks beneath a deep-ocean trench and back into the mantle at a convergent plate boundary.

subduction

​A chain of volcanic mountains formed at an ocean-continental convergent boundary.

volcanic 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.

volcanic island arc

​The shallow sea floor that is located between the shoreline and the deep ocean bottom.

continental margin

​A gently sloping, shallow area of the ocean floor that extends outward from the edge of a continent.

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continental shelf

The slope between the outer edge of the continental shelf and the deep ocean floor.

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continental slope

​The gently sloping section of the continental margin located between the continental slope and the abyssal plain.

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continental rise

​Usually narrow and consisting of highly deformed sediments. They occur where oceanic lithosphere is being subducted beneath the margin of a continent.

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active
continental
margin

​Margins that consist of a continental shelf, continental slope, and continental rise. They are associated with divergent plate boundaries and therefore experience little volcanism and few earthquakes.

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passive
continental
margin

​A large, flat, almost level area of the deep-ocean basin.

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abyssal plain

​An undersea mountain chain where new ocean floor is produced at a divergent plate boundary; rises are generally shorter, with gentler slopes than ridges.

mid-ocean rise/ridge

​A deep valley that forms where two plates move apart.

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rift valley

​A volcanic mountain rising from the ocean floor that doesn’t reach the surface.

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seamount

​A large, flat-topped seamount resulting from erosion of an island volcano when it was above sea level.

guyot

​A deep, steep-sided canyon in the ocean floor.

trench