Tableland: A large elevated region with a relatively low relief surface.

Tar sand: A sandstone containing the densest asphaltic components of petroleum - the end-product of evaporation of volatile components or of some thickening process.

Talus: A deposit of large angular fragments of physically weathered bedrock, usually at the base of a cliff or steep slope.

TECHNOLOGY:refer to material objects of use to humanity, such as machines,hardware or utensils but can also encompass broader themes, including systems, methods of organitation and techniques. The term can either be applied generally or to specific areas

Tectonics: The study of the movements and deformation of the crust on a large scale, including epeirogeny, metamorphism, folding, faulting, and plate tectonics.

Terminal moraine: A sinuous ridge of unsorted glacial till deposited by a glacier at the line of its farthest advance.

Terrestrial planet: A planet similar in size and composition to the Earth; especially Mars, Earth, Venus, and Mercury.

Terrestrial sediment: A deposit of sediment that accumulated above sea level in lakes, alluvial fans, floodplains, moraines, etc., regardless of its present elevation.

Texture (rock): The rock characteristics of grain or crystal size, size variability, rounding or angularity, and preferred orientation.

Thermonuclear reaction: A reaction in which atomic nuclei fuse into new elements with a large release of heat; especially a reaction that is self-sustaining. Occasionally used to include fission reactions as well.

Thrust fault: A dip-slip fault in which the upper block above the fault plane moves up and over the lower block, so that older strata are placed over younger.

Tidal current: A horizontal displacement of ocean water under the gravitational influence of Sun and Moon, causing the water to pile up against the coast at high tide and move outward at low tide.

Tidal flat: A broad, flat region of muddy or sandy sediment, covered and uncovered in each tidal cycle.

Till: An unconsolidated sediment containing all sizes of fragments from clay to boulders deposited by glacial action, usually unbedded.

Time scale: The division of geologic history into eras, periods, and epochs accomplished through stratigraphy and paleontology.

Topographic map: See Contour map; also a schematic drawing of prominent landforms indicated by conventionalized symbols, such as hachures or contours.

Topography: The shape of the Earth's surface, above and below sea level; the set of landforms in a region; the distribution of elevations.

Transgression: A rise in sea level relative to the land which causes areas to be submerged and marine deposition to begin in that region.

Transition element: Elements of atomic number 21 to 29, 38 to 46, and 71 to 78, whose second outermost electron shell is only partially filled.

Transpiration: The removal of water from the ground into plants, ultimately to be evaporated into the atmosphere by them.

Transverse dune: A dune that has its axis transverse to the prevailing winds or to a current. The upwind or upcurrent side has a gentle slope, and the downwind side lies at the angle of repose.

Trap (oil): A sedimentary or tectonic structure that impedes the upward movement of oil and gas and allows it to collect beneath the barrier.

Travertine: A terrestrial deposit of limestone formed in caves and around hot springs where cooling, carbonate-saturated groundwater is exposed to the air.

Trellis drainage: A system of streams in which tributaries tend to lie in parallel valleys formed in steeply dipping beds in folded belts.

Trench: A long and narrow deep trough in the sea floor; interpreted as marking the line along which a plate bends down into a subduction zone.

Triple junction: A point that is common to three plates and which must also be the meeting place of three boundary features, such as divergence zones, convergence zones, or transform faults.

Tsunami: A large destructive wave caused by sea-floor movements in an earthquake.

Tuff: A consolidated rock composed of pyroclastic fragments and fine ash. If particles are melted slightly together from their own heat, it is a "welded tuff."

Turbulent flow: A high-velocity flow in which streamlines are neither parallel nor straight but curled into small tight eddies (compare Laminar flow).