Glossary Starting with the letter: T


Accumulation of fragmented rock debris, usually coarse, angular, and of different sizes, found at the base of valley slopes and walls and produced by falling, rolling, or sliding.


Relating to the forces and the movements of Earth and its lithosphere. Earthquakes, volcanoes, and mountain building are related to tectonic activity.


Relating to land or the planet Earth. Refers to the land above sea level.


A thin region of rapid temperature change separating the warm waters of the upper ocean from the cold waters of the abyssal ocean.

Thermohaline Circulation

Circulation or movement of ocean water masses resulting from density differences caused by variation of temperature and salinity.

Tidal Basin

A body of water, natural or manmade, subject to tidal action.

Tilted Laminations

Thin layers of rock or sediment oriented at an angle from the horizontal.


Surface relief of the land. Topography is usually measured in meters above sea level.

Trade Winds

Part of one of the three major circulation cells in each hemisphere, the trade winds exist from approximately 0° to 30° north or south latitude. Within the regions of the trade winds, prevailing winds blow easterly, or toward the west.

Transition Zone

A region within the mantle that separates the upper and the lower mantle that is characterized by a rapid increase in seismic wave velocities. The depth of the transition zone varies from 410 to 1,000 kilometers beneath the Earth’s surface.


A stream that flows into or joins a larger stream or another body of water.


The lowest layer of Earth’s atmosphere in contact with Earth’s surface. Most weather occurs within the troposphere. The troposphere extends from Earth’s surface to elevations of approximately 10–15 kilometers.


Enormous ocean wave produced by an underwater earthquake, landslide or volcanic eruption.