Plate Boundaries and Crustal Features

Tectonic plates

"Broken" pieces of Earth's lithosphere, composed of two types of material: oceanic crust and continental crust

Island arc

A curved chain of volcanic islands located at convergent boundaries; usually parallel to a trench along subduction zones

Trench

Deep, narrow depression in the ocean floor where one tectonic plate subducts under another

Lithosphere

Earth's crust and uppermost mantle; broken into tectonic plates

Folded mountains

Feature created at convergent boundaries between two continental plates

Mid ocean ridge

Long, underwater mountain ranges along divergent boundaries where new oceanic crust forms

Rift valley

Low region that forms where Earth's tectonic plates separate at continental divergent boundaries

Transform boundary

Places where tectonic plates slide sideways past each other; process called shearing

Subduction

Process that destroys/recycles oceanic crust; an oceanic plate pushes under another plate at a convergent boundary

Convergent boundary

Tectonic plates collide; can be destructive if one or both plates are oceanic crust

Divergent boundary

Tectonic plates separate; constructive boundary (builds new crust) where tectonic plates move away from each other

Continental crust

The thick part of Earth's crust that forms the large landmasses; can not subduct because it is too thick and crumbly

Oceanic crust

The thin and dense part of Earth's crust that underlies the ocean basins; can subduct at convergent boundaries

Seafloor spreading

This process forms new oceanic crust, as of magma at mid ocean ridges at divergent boundaries

Asthenosphere

Zone of Earth's upper mantle, below the lithosphere, where convection occurs