Glossary of terms
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A-B | C-D | E-F | G-H | I-K | L-N | O-Q | R-T | U-Z | [Sources]

ulexite: a mineral, a hydrous sodium and calcium borate, occurring in loose, rounded masses of white, needle-haped crystals that transmit light from one end to the other without being transparent. [AHDOS]

ultrabasic: extremely rich in base-forming elements and poor in silica. [AHDOS]

upheaval: the act of raising, or fact of beign raised, above the original level, expecially by volcanic action. [AHDOS]

Upper: being or relating to a later division of a period, system or the like. [AHDOS]

Upper Carboniferous: the name outside of North America for the Pennsylvanian period. [AHDOS]

upthrow: an upward dislocation of a mass of rock, generally caused by faulting. [AHDOS]

upthrust: an upward movement of part of the earth's crust. [AHDOS]

upwarp: to fold or bend in an anticlinal or upward manner. [AHDOS]

vadose: having to do with or occurring in the unsaturated area between the earth's surface and the water table. [AHDOS]

valley: a broad area of low-lying land situated between hills or mountains and usually having a river or stream flowing along its bottom. [AHDOS]

valley flat: a low, level deposit of sediment in the channel of a stream. [AHDOS]

valley glacier: a glacier that occupies a mountain valley, as in the Alps and the mountains of the western United States. [AHDOS]

valley train: the alluvium deposited by glacial outwash, partially filling the valley below the retreating front of the glacier. [AHDOS]

vitrain: a lithotype of coal having a vitreous luster. [AHDOS]

vivianite: a phosphate of iron, usually occurring in crystals of blue and green color. [AHDOS]

volcanic: of or caused by a vlocano; having to do with volcanoes. [AHDOS]

volcanic ash: finely pulverized pyroclastic material ejected from a volcano in eruption. [AHDOS]

volcanic bomb: a piece of lava, often large and hollow, ejected by a volcano in eruption. [AHDOS]

volcanic cone: a hill around the rim of a volcano, consisting chiefly of matter ejected during eruption. [AHDOS]

volcanic glass: a natural glass produced by the rapid cooling of lava. [AHDOS]

volcaniclastic: consisting of volcanic fragments or sediments. [AHDOS]

volcanic rock: a crystalline or glassy igneous rock formed by volcanic action near the earth's surface. [AHDOS]

volcanism: the phenomena connected with volcanoes and volcanic activity. [AHDOS]

volcano: an opening in the earth's crust through which steam, ashes and lava are expelled in periods of activity. [AHDOS]

volcanogenic: originating in or produced by volcanoes. [AHDOS]

volcanological: of or having to do with volcanology. [AHDOS]

volcanology: the scientific study of volcanoes and volcanic phenomena. [AHDOS]

vulcanism: volcanism [AHDOS]

wacke: a rock similar to sandstone, consisting of unsorted angular fragments of rocks and minerals. [AHDOS]

wadi: a usually dry valley or ravine in Arabia, northern Africa, etc., through which a stream flows during the rainy season. [AHDOS]

water cycle: the cycle by which water evaporates from oceans, lakes, and other bodies of water, forms clouds, and is returned to those bodies of water in the form of rain and snow, the runoff from rain and snow, and ground water. [AHDOS]

waterfall: any sudden descent of a stream or river. A waterfall usually occurs from a great height and is perpendicular or nearly perpendicular. [AHDOS]

water level: the surface level of a stream, lake or other body of water. [AHDOS]

watershed: the ridge between the regions drained by two different river systems. On one side of a watershed, rivers and streams flow in one direction; on the other side, they flow in the opposite direction. [AHDOS]

water table: the level below which the ground is saturated with water. [AHDOS]

wavellite: hydrous phosphate of aluminum, found in globular aggregates with a radiating structure. [AHDOS]

weathering: the chemical and physical processes acting to break down materials at the earth's surface. [AHDOS]

willemite: a mineral, a silicate of zinc, found in masses or hexagonal prisms of various colors from light greenish-yellow to red and black, all of which exhibit bright yellow fluorescence under ultraviolet light. It is a minor zinc ore. [AHDOS]

Wisconsin: of or having to do with the most recent period of glaciation in North America, beginning about 115,000 years ago and lasting about 95,000 years. [AHDOS]

wurtzite: a native sulfide of zinc, a crystalline dimorph of sphalerite. [AHDOS]

xenolith: a fragment of older rock embedded in an igneous mass. [AHDOS]

zincite: native zinc oxide, of a deep-red or orange-yellow color. [AHDOS]

zircon: a native silicate of zirconium that occurs in tetragonal crystals, variously colored. Transparent zircon is used as a gem. Zircon is composed chiefly of silicon, oxygen, and zirconium, but contains small amounts of other elements, such as hafnium, iron and the rare earths. [AHDOS]