Plate Tectonics Vocabulary Terms
Terms in this set (34)
the thin, rocky outermost layer of the Earth. The ocean's crust can be as thin as 10 km (6 miles) and where there are mountains the crust can be as thick as 65 km (40 miles).
Earth's thickest layer that comprises more than 80% of earth's volume and is located between the crust and the core.
a layer of molten iron and nickel that surrounds the inner core
of the Earth.
a dense sphere of solid iron and nickel at the center of the earth.
the rigid, brittle layer made up of the crust and the uppermost part of the mantle. It is broken up into pieces called tectonic plates.
the upper layer of the mantle with a plastic-like consistency on which the tectonic plates move.
the single huge super continent that existed about 200 million years ago, when all of Earth's continents were joined together.
a German meteorologist and geophysicist who originated the theory of continental drift.
a hypothesis that the continents were a single landmass at one time in the past and have moved across the ocean's floor over time to their present locations. The theory of continental drift was first suggested by Alfred Wegener.
an American geologist who studied mid-ocean ridges using echo-sounding surveys of the Pacific and ultimately developed the theory of sea-floor spreading.
a device that determines the distance of an object under water by recording echoes of sound waves.
the process by which new oceanic crust is formed when magma rises up through fissures and solidifies at the mid-ocean ridges and thus pushing the older, adjacent seafloor towards trenches. This is why the age of the sea floor increases with distance away from the mid-ocean ridges.
a deep valley along the ocean floor beneath which oceanic crust slowly sinks toward the mantle.
the switching or changing of Earth's magnetic poles such that the north magnetic pole becomes located at the south magnetic pole's position and vice-versa. Scientists have found evidence of magnetic reversals in layers of rock along the ocean floor.
Isochron Map of Ocean-Floor Crust
a map that shows the points that have the same age, that is, they were formed at the same time. The relatively young ocean-floor crust is near ocean ridges, while older ocean crust is found along deep-sea trenches.
a section of the lithosphere that slowly moves over the asthenosphere, carrying pieces of continental and oceanic crust.
the large pieces of the lithosphere that slowly move on top of the asthenosphere.
theory of plate tectonics
the theory that Earth's lithosphere is broken into enormous slabs, or plates, that are in motion. Scientists use the theory of plate tectonics to explain how Earth's continents drift.
the amount of mass in a given volume of matter.
the convection currents in the mantle that occur because hot rock in the lower part of the mantle is less dense and rises, and cooler rock in the upper part of the mantle cools, becomes more dense, and sinks. Mantle convection is thought to be the mechanism driving the movement of tectonic plates.
a chain of mountains on the ocean floor. New ocean floor forms at the mid-ocean ridge where the seafloor is spreading and ridge push is initiated.
a tectonic process associated with convection currents in Earth's mantle that occurs when the weight of an elevated ridge pushes an oceanic plate towards a subduction zone
the process by which one tectonic plate sinks below another, returning to the mantle, where the rock is re-melted. Subduction takes place at convergent plate boundaries. Oceanic crust, which is denser, will always subduct under the less dense continental crust. It is also the process in which slab pull occurs.
a convection current process that occurs at subduction zones when a denser tectonic plate sinks into the asthenosphere and "pulls" the trailing lithosphere along.
where two tectonic plates move toward each other.
where two tectonic plates move away from each other.
a deep valley caused by the rifting (splitting) of a continental tectonic plate. The East African Rift Valley is an example of continental rifting in progress.
where two tectonic plates slip past each other, moving in opposite directions.
a break or crack in Earth's lithosphere along which the rocks move.
a stationary area below the Earth's crust where a column of magma rises from deep within the Earth's mantle and heats the lithosphere above it, often causing volcanic activity at the surface that can result in island formation.
a trace of an ancient organism that has been preserved in rock.
less dense and thus able to float
an extinct Triassic land reptile found as fossils in South America and South Africa, and from the Lower Triassic.
Ring of Fire
an area around the Pacific Ocean where 75% of active and dormant volcanoes are located and 90% of earthquakes occur