the hypothesis that states that the continents once formed a single landmass, broke up, and drifted to their present locations.
Continental drift
a long, undersea mountain that has a steep, narrow valley at its center, that forms as magma rises from the asthenosphere, and that creates new oceanic lithosphere ( sea floor ) as tectonic plates move apart.
Mid-ocean ridges
the valley at the center of the ridge was a crack in Earth's crust.
the process by which new oceanic lithosphere ( sea floor ) forms as magma rises to Earth's surface and solidifies at a mid-ocean ridge.
Sea-floor spreading
the study of the alignment of magnetic minerals in a rock, specifically as it relates to the reversal of Earth's magnetic poles.
the theory that explains how large pieces of the lithosphere, called plates, move and change shape
Plate tectonics
the solid, outer layer of Earth that consists of the crust and the rigid upper part of the mantle.
the solid, plastic layer of the mantle beneath the lithosphere.
dense and made up of rock that is rich in iron and magnesium.
Oceanic crust
low density and is made up of rock that is rich in silica.
Continental crust
when tectonic plates move, sudder shifts can occur along their boundaries.
form when plate motions generate magma that erupts on Earth's surface.
a major area in the basin of the Pacific Ocean where a large number of earthquakes and volcanic eruptions occur.
Pacific Ring of Fire
move away from each other
Divergent boundary
move towards each other
Convergent boundary
the place where two lithosphere plates come together, one on top of the other
Subduction zone
a curved chain of volcanic islands located at a tectonic plate margin, typically with a deep ocean trench
Island Arc
slide past each other horizontally
Transform boundary
the movement of tectonic plates
the supercontinent that was once a big landmass