Chapter 8 Vocabulary
In your own words, rewrite each definition and then draw a picture to illustrate the meaning
of the word.
Plate tectonics: The theory that the lithosphere is made of plates that move and interact with
each other at their boundaries.
Continental Drift: A hypothesis that Earth’s continents move on Earth’s surface.
Mid-ocean Ridge: A long chain of mountains with a central rift valley that is located along a
divergent boundary on the ocean floor.
Divergent boundary: A boundary between two lithospheric plates that are moving apart.
Rift valley: A deep valley at a point where lithospheric plates are moving apart, such as a midocean ridge.
Rift: A crack or opening in Earth’s crust.
Convergent boundary: A boundary between two plates that are moving toward each other, or
converging.
Subduction boundary: A convergent boundary where an oceanic plate is plunging beneath
another, overriding plate.
Deep-sea trench: A long, narrow, steep-sided trough that runs parallel to continental margins or
to volcanic island chains.
Collision boundary: A convergent boundary where two continents have come together and are
welded into a single, larger continent.
Transform boundary: A boundary between two plates that are sliding past each other.
Mantle convection: A process by which heat from Earth’s inner and outer cores is transferred
through the mantle.
Ridge push: A force that is exerted by cooling, subsiding rock on the spreading lithospheric
plates at a mid-ocean ridge.
Slab pull: A force at a subduction boundary that the sinking edge of the subducting plate exerts
on the rest of the plate.
Pangea: The name of a hypothetical landmass consisting of all the continents welded together,
which evidence indicates existed about 250 million years ago.
Craton: The ancient core of a continent, which is tectonically stable.
Terrane: A large block of lithospheric plate that has been moved, often over a distance of
thousands of kilometers, and attached to the edge of a continent.