Plate Tectonics Quizlet

Pangaea

the supercontinent that existed millions of years ago

fossil

any trace of an ancient organism that has been preserved in rock

mid-ocean ridge

an undersea mountain chain where new ocean floor is produced at a divergent boundary

sea-floor spreading

the process by which molten material adds new crust to the ocean floor

deep-ocean trenches

deep valley along the ocean floor beneath which oceanic crust slowly sinks toward the mantle at a convergent boundary

plate-tectonics

the theory that states that pieces of Earth's lithosphere are in constant slow motion

convection currents

currents in the mantle that cause the movement of Earth's plates

tectonic plates

a section of the lithosphere that slowly moves over the asthenosphere, carrying pieces of continental and oceanic crust

transform boundary

a plate boundary where two plates move past each other in opposite directions (for example the San Andreas fault in California)

divergent boundary

a plate boundary where two plates move away from each other (mid-ocean ridge or rift valley can form here)

convergent boundary

a plate boundary where two plates move toward each other (subduction or mountain building)

subduction

the process by which the ocean floor sinks beneath a deep-ocean trench and back into the mantle

rift valley

a deep valley that forms on land at a divergent boundary where two plates move apart

mountain

created by two pieces of continental crust converging or coming together

continental drift

Alfred Wegner's hypothesis that the continents were once joined together in a single landmass and have slowly moved apart

subduction zone

the area where oceanic crust sinks beneath continental crust