The hypothesis that a single large landmass broke up into smaller landmasses to form the continents, which then drifted to their present locations; the movement of continents.

The theory that Earth's outer layer is made up of large, moving pieces called tectonic plates; the theory explains how plates interact and how those interactions relate to processes such as earthquakes and mountain building.

A system of ideas that explains many related observations and is supported by a large body of evidence acquired through scientific investigation.

The process by which new oceanic lithosphere (sea floor) forms when magma rises to Earth's surface at mid-ocean ridges and solidifies, as older, existing sea floor moves away from the ridge.

The process by which one lithospheric plate moves beneath another plate as a result of tectonic forces.

The process by which Earth's magnetic north pole and magnetic south pole switch positions periodically; a change in the direction in which Earth's magnetic field points.

The solid, outer layer of Earth that consists of the crust and the rigid upper part of the mantle.

The soft layer of the mantle on which the tectonic plates move.

A block of lithosphere that consists of the crust and the rigid, outermost part of the mantle.

The bending, tilting, and breaking of Earth's crust; the change in the shape of rock in response to stress.

The boundary between tectonic plates that are colliding.

The boundary between two tectonic plates that are moving away from each other.

The boundary between tectonic plates that are sliding past each other horizontally.

The natural process by which atmospheric and environmental agents, such as wind, rain, and temperature changes, disintegrate and decompose rocks.

The mechanical breakdown of rocks into smaller pieces that is caused by natural processes and that does not change the chemical composition of the rock material.

The chemical breakdown and decomposition of rocks by natural processes in the environment.

The process by which wind, water, ice, or gravity transports soil and sediment from one location to another.

In geology, the process in which material is laid down.

The size and shape of the land surface features of a region, including its relief.

A map that shows the surface features of Earth.

A line that connects points of equal elevation on a map.

The difference between the highest and lowest elevations in a given area; the variations in elevation of a land surface.

The difference in elevation between one contour line and the next.

On a map, a darker, heavier contour line that is usually every fifth line.

The relationship between the measurements on a model, map, or diagram and the actual measurement or distance.

A measure of the slant of a line; the ratio of rise over run.

The process of gathering and analyzing information about an object without physically being in touch with the object.

A network of satellites that orbit Earth to measure positions on Earth's surface.

A system for capturing, storing, retrieving, analyzing, manipulating, and displaying geographic data.