Unit 4, Set 2 - Plate Tectonics

mid-ocean ridge

chain of underwater mountains at the boundary between two diverging tectonic plates where new ocean floor is produced

seafloor spreading

the formation of new areas of oceanic crust due to magma rising at mid-ocean ridges and moving outward

subduction

process by which one tectonic plate moves under another tectonic plate and sinks into the mantle

tectonic plates

individual sections of the Earth's lithosphere that fit together in a way similar to a jigsaw puzzle, but are always moving very slowly, floating on the asthenosphere

convergent boundary

place where two tectonic plates move toward each other; associated with trenches, island arcs, and folded mountains

divergent boundary

place where two tectonic plates move apart; found primarily on the seafloor; associated with volcanic activity, earthquakes, and high heat flow

rift valley

long, narrow depression that forms when continental crust begins to separate at a divergent boundary

volcanic island arc

chain of volcanoes formed due to subduction of an oceanic plate under another oceanic plate or a continental plate under another continental plate

transform boundary

place where two tectonic plates slide horizontally past each other; characterized by long faults and shallow earthquakes

deep-sea trench

a deep valley along the ocean floor through which oceanic crust slowly sinks toward the mantle