17.3

Rift Valley

Continental crust begins to seperate, the stretched crust forms a long narrow depression.

Tectonic Plates

Huge pieces of crust and rigid upper mantle that fit together at their edges to cover Earth's surface.

Convection Current

In the mantle that helps to drive the movement of the rigid plates making up the Earth's surface.

Slab Pull

Occurs as the weight of the subducting plate pulls the trailing lithosphere into a subduction zone.

Ridge Push

Occurs when the weight of an elevated ridge pushes an oceanic plate toward a subduction zone.

Divergent Boundary

Occurs where tectonic plates move away from each other.

Transform Boundary

Occurs where tectonic plates move horizontally past each other.

Convergent Boundary

Occurs where tectonic plates move toward each other.

Oceanic Crust

Part of Earth's lithosphere that surfaces in the ocean basins. Oceanic crust is primarily composed of mafic rocks, or sima, which is rich in iron and magnesium.

Continental Crust

The layer of igneous, sedimentary, and metamorphic rocks which forms the continents and the areas of shallow seabed close to their shores, known as continental shelves.

Lithosphere

The rigid outer part of Earth. Consisting of the crust and upper mantle.

Asthenosphere

The upper layer of the earth's mantle, below the lithosphere, in which there is relatively low resistance to plastic flow and convection is thought to occur.

Subduction Zone

Two plates collide, the denser plate eventually descends below the other, less dense plate.