Glossary Database

Select a Letter to view the associated terms.

 Glossary Term: 


 Taiga  a region of boreal forest, the largely evergreen forest vegetation of northern areas of the Northern Hemisphere, below the arctic and subarctic tundra regions (Morris 1992).
 Tail (caterpillar)  A loose term used to describe any noticeable extension at the rear of the caterpillar.
 Tail(butterfly)  A thin, relatively short extension of the rear of the hindwing. In some species, such as the Hairstreaks, it is thought to mimic insect antennae and thus mislead bird predators into biting at the wrong end and only getting a mouthful of wing while the butterfly escapes in the opposite direction.
 Talc  An extremely soft, light green or gray mineral. It feels soapy and has a hardness of 1 on the Moh's scale.
 Talus  1.) Rock fragments that accumulate in a pile at the base of a ridge or cliff. 2.)a steep, concave, downward sloping formation, formed by the accumulation of coarse, angular rock debris at the base of the cliff or slope (Morris 1992).
 Tawny  1. of a dark yellowish or dull yellowish-brown color. 2. a shade of brown tinged with yellow; dull yellowish brown (Stein 1966).
 Tectonic creep  Slow, apparently continuous movement along a fault (as opposed to the sudden rupture that occurs during an earthquake).
 Tectonics  The branch of geology that deals with regional or global structures and deformational features of Earth.
 Temperate  Refers to the geographical region or zone located between the arctic and the tropics. It is characterized by warm summers and cold winters.
 Temperate climate  A moderate climate found at mid-latitudes on Earth, with adequate precipitation for plant growth and no extreme temperatures.
 Temperature  The degree of hotness or coldness of anything.
 Tension  Stress that tends to pull materials apart.
 Tephra  A general term for pyroclastic material ejected from a volcano. It includes ash, dust, bombs, and other types of fragments.
 terete  Round or oval in cross section.
 Terminal moraine  A ridge of material deposited by a glacier at the line of maximum advance of the glacier.
 Terra (pl. terrae)  A densely cratered highland on the Moon.
 Terrace  A nearly level surface bordering a steeper slope, such as a stream terrace or wave-cut terrace.
 Territorial  To defend a defined area from intruders. Territories are usually established and defended by the males of a given species.
 Tertiary  The first period of the Cenozoic era covering from 65 to 2 million years ago. It is divided into five epochs. View timeline of geologic events.
 Tetrahedra (tetrahedron)  A figure with four triangular faces.
 Texture  The size, shape, and arrangement of the particles that make up a rock.
 Theory  An explanation for some natural phenomenon that has a large body of supporting evidence; to be considered scientific, a theory must be testable.
 Thermal  Caused by heat. A heat event or warm air, etc.
 Thermal doming  Doming of the earth's crust probably from some form of volcanic event.
 Thermohaline circulation  The convection of the ocean caused by differences in temperature and salinity.
 Thermosphere  Belt of atmosphere above the mesosphere where the temperature increases as you move upwards.
 Thin section  A slice of rock mounted on a glass slide and ground to a thickness of about 0.03 mm, thin enough for light to pass through many kinds of minerals.
 thoracic  Located in, or pertaining to, the chest region.
 Thorax  One of the three main regions comprising an insect. It is located between the head and the abdomen and is where the legs and/or wings are attached.
 Thrust fault  A low-angle fault (45 degrees or less) in which the hanging wall has moved upward in relation to the footwall. Thrust faults are caused by horizontal compression.
 Thrust sheet  Sheetlike mass of rock moving forward over a low-angle overthrust fault.
 Tibial tuft  A group of specialized hairs on the tibia (fourth segment up) of the hind leg of some male butterflies, especially Skippers. The hairs are used to help direct pheromone towards a female during courtship.
 Tidal flat  A large, nearly horizontal area of land covered with water at high tide and exposed to the air at low fide. Tidal flats consist of fine-grained sediment (mostly mud, silt, and sand).
 Tide  See ocean tide.
 Till  Sediment deposited directly by glacial ice and than has not been resorted by a stream.
 Tillite  A rock formed by lithification of glacial till (unsorted, unstratified glacial sediment).
 Tombolo  A beach or bar connecting an island to the mainland.
 Topographic map  A map which depicts topography as well as locations.
 Topography  The shape and form of Earth's surface as expressed in elevations above or below sea level.
 Topsoil  Dark-colored upper portion of a soil.
 Torpid  Characterized by a dormant, inactive condition or state (Morris 1992).
 Torpor  A stress reaction resulting in lethargy (Morris 1992)
 total length  The greatest length from the tip of the nose (with the mouth closed) to the tip end of the tail (with the tail lobes pressed together).
 Trachea  the air tube supported by cartilaginous rings that stretches from the pharynx into the the thorax, where it divides into the bronchial tubes (Morris 1992).
 Tragus  the cartilaginous projection in front of the external auditory meatus (Morris 1992).
 Transform fault  A special type of strike-slip fault forming the boundary between two moving lithospheric plates, usually along an offset segment of the oceanic ridge. See also: passive plate margin.
 Transpiration  The process by which water vapor is released into the atmosphere by plants.
 Transport  The shifting of material from one place to another on the earth's surface by moving water, ice or air.
 Transverse dune  An asymmetrical dune ridge that forms at right angles to the direction of prevailing winds.
 Travertine terrace  A terrace formed from calcium carbonate deposited by water on a cave floor.
 Treaty  An agreement between two or more parties - typically involving issues of peace or trade.
 Trellis drainage pattern  A drainage pattern in which tributaries are arranged in a pattern similar to that of a garden trellis.
 Trench  A narrow, elongate depression of the deep-ocean floor oriented parallel to the trend of a continent or an island arc.
 Tributary  A stream flowing into or joining a larger stream.
 Trichoptera  the caddis flies, and order of insects with two pairs of hairy, scaled wings and long antennae and legs; the wormlike aquatic larvae build cases of sand and other particles glued with secretions (Morris 1992).
 Triclinic system  One of six crystal systems characterized by a one-fold axis of symmetry and having three axes that are unequal.
 Trophy  A management program which limits, by regulation, the size and numbers of fish which may be harvested in order to provide increased catch rates for larger fish which are considered trophy size by most anglers. May be applied to water areas or to specific species within a water area.
 Tropical climate  A climate that is frost-free with temperatures high enough to support year-round plant growth and abundant precipitation.This climate prevails near the equator.
 Troposphere  Lowermost layer of the atmosphere in which air temperature falls steadily with increasing altitude. 0 - 6 miles above the earth's surface. Rain clouds form in this layer of atmosphere.
 truncate  Having a square or broad end.
 Trunk stream  The main stream in a system of streams.
 Tsunami  A seismic sea wave; a long, low wave in the ocean caused by an earthquake, faulting, or a landslide on the seafloor. Its velocity can reach 800 km per hour. Tsunamis are commonly and incorrectly called tidal waves.
 Tubercle  1.) A small, raised bump on a caterpillar that often bears a spine. 2.)A small, rounded, discrete hump or bump in skin (Peters 1964).
 Tuff  A fine-grained rock composed of volcanic ash.
 Tularemia  a disease of rodents, lagomorphs, certain birds and sometimes humans, due to infection caused by the microorganism Pasteurella tularensis and transmitted by fleas and ticks; characterized by fever, headache, muscle pain, and nodule formations in the liver, spleen, and lymph nodes (Morris 1992).
 Tundra  a vast , nearly level, barren, treeless region located in the Arctic; characterized by very low winter temperatures, short, cool summers, and vegetation consisting of various grasses, rushes, perennial herbs, lichens, and dwarf woody plants (Morris 1992).
 Turbidite  A sedimentary rock deposited by a turbidity current. Graded bedding is characteristic.
 Turbidity current  A current in air, water, or any other fluid caused by differences in the amount of suspended matter (such as mud, silt, or volcanic dust). Marine turbidity currents, laden with suspended sediment, move rapidly down continental slopes and spread out over the abyssal floor.
 Turbulent flow  A type of flow in which the path of motion is very irregular, with eddies and swirls. Contrast with laminar flow.
 Tympanum  The membrane covering the external ear opening of the middle ear chamber or vestibule (Peters 1964).