Definition

Continental drift

• the gradual movement of the continents across the earth's surface through geological time

pangea

• Is a supercontinent that existed during the late paleozoic and early mesozoic eras.

plATE TECTONICS

• a theory explaining the structure of the earth's crust and many associated phenomena as resulting from the interaction of rigid lithospheric plates that move slowly over the underlying mantle.

PLATE

• plate tectonics in Science Expand. plate tectonics. In geology, a theory that the Earth's lithosphere (the crust and upper mantle) is divided into a number of large, platelike sections that move as distinct masses.

divergent boundary

• In plate tectonics, a divergent boundary or divergent plate boundary (also known as a constructive boundary or an extensional boundary) is a linear feature that exists between two tectonic plates that are moving away from each other.

convergent boundary

• in plate tectonics, a convergent boundary, also known as a destructive plate boundary (because of subduction), is an actively deforming region where two (or more) tectonic plates or fragments of the lithosphere move toward one another and collide.

transform fault boundary

• A transform fault or transform boundary, also known as conservative plate boundary since these faults neither create nor destroy lithosphere, is a type of fault whose relative motion is predominantly horizontal in either sinistral or dextral direction.

oceanic ridge

• A mid-ocean ridge is an underwater mountain system formed by plate tectonics. It consists of various mountains linked in chains, typically having a valley known as a rift running along its spine.

rift valley

• A rift valley is a linear-shaped lowland between several highlands or mountain ranges created by the action of a geologic rift or fault.

seafloor spreading

• Seafloor spreading is a process that occurs at mid-ocean ridges, where new oceanic crust is formed through volcanic activity and then gradually moves away from the ridge.

subduction zone

• The subduction zone is the place where two lithospheric plates come together, one riding over the other. Most volcanoes on land occur parallel to and inland from the boundary between the two plates.

trench

• Oceanic trench. The oceanic trenches are hemispheric-scale long but narrow topographic depressions of the sea floor. They also are the deepest parts of the ocean floor. Trenches define one of the most important natural boundaries on the Earth's solid surface, that between two lithospheric plates.

volcanic island arc

• A usually curved chain of volcanic islands bounded on the convex side by a deep oceanic trench. Island arcs form in the overriding tectonic plates of subduction zones as the result of rising melt from the downgoing plate.

paleomagnetism

• the branch of geophysics concerned with the magnetism in rocks that was induced by the earth's magnetic field at the time of their formation.

hot spot

• A place deep within the Earth where hot magma rises to just underneath the surface, creating a bulge and volcanic activity (see volcano). The chain of Hawaiian Islands (see Hawaii) is thought to have been created by the movement of a tectonic plate over a hot spot.

convection

• s the transfer of heat through fluids (gases or liquids) from a warmer spot to a cooler spot. Hawaiian Translation: Paialewa. The particles in fluids (liquids or gases) can move from place to place when heated.

slab-pull

• s the portion of motion of a tectonic plate that can be accounted for by its subduction. Plate motion is partly driven by the weight of cold, dense plates sinking into the mantle at trenches.

ridge-push

• Ridge push or sliding plate force is a proposed mechanism for plate motion in plate tectonics. Because mid-ocean ridges lie at a higher elevation than the rest of the ocean floor, gravity causes the ridge to push on the lithosphere that lies farther from the ridge.

asthenosphere

• layer of the Earth's upper mantle, 1914, from Greek asthenosphere (see asthenia) + sphere. asthenosphere in Science Expand. asthenosphere. The upper part of the Earth's mantle, extending from a depth of about 75 km (46.5 mi) to about 200 km (124 mi).

mantle

• The region of the interior of the Earth between the core (on its inner surface) and the crust (on its outer). Note: The mantle is more than two thousand miles thick and accounts for more than three-quarters of the volume of the Earth.