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water table

The upper surface of groundwater, that is, the underground level at which groundwater is accessible.


An area of land from which all water under or on it drains to the same location.


A spinning, funnel-shaped cloud over a body of water. “Tornadic” waterspouts are simply tornados that originated on land during severe thunderstorms and and moved over water. “Fair weather” waterspouts develop near the surface of the water and grow upward; they form in low wind conditions and may move little, but do become tornados if they move to land.


A unit of power measuring the rate of energy conversion or transfer designated by the International System of Units as one joule per second.


The measure of short-term conditions of the atmosphere such as temperature, wind speed, and humidity. These conditions vary with the time of day, the season, and yearly or multi-year cycles.


The breakdown of rocks by physical or chemical means. Rocks are constantly being worn down and broken apart into finer and finer grains by wind, rivers, wave action, freezing and thawing, and chemical breakdown.
Over millions of years, weathering and erosion can reduce a mighty mountain range to low rolling hills. Some rocks wear down relatively quickly, while others can withstand the power of erosion for much longer. Softer, weaker rocks such as shale and poorly cemented sandstone and limestone are much more easily worn away than hard, crystalline igneous and metamorphic rocks, or well-cemented sandstone and limestone. Harder rocks are often left standing alone as ridges because surrounding softer, less resistant rocks were more quickly worn away.


With relatively uniform grain size.


The movement of air from areas of high pressure to areas of low pressure. The greater the temperature difference, the greater the air pressure difference and, consequently, the greater the speed at which the air will move.

wind shear

When wind speed and/or direction changes with increasing height in the atmosphere. Wind shear can happen when a cold front moves rapidly into an area with very warm air. There, the condensing water droplets mix with the cooler, drier air in the upper atmosphere to cause a downdraft.


Upwind; facing into the prevailing winds, and thus subject to orographic precipitation.

Wisconsinian glaciation

The most recent interval of glaciation, which occurred during the Pleistocene, 85,000 to 11,000 years ago.


A calcium inosilicate mineral (CaSiO3) that can contain small amounts of iron, magnesium, or manganese substituting for calcium; it forms when impure limestone or dolostone is subjected to high temperature and pressure sometimes in the presence of silica-bearing fluids as in skarns or contact metamorphic rocks.


See also limestone, metamorphism.


Wollastonite is primarily mined for use in ceramic tiles, porcelain, and paints. It is also used as a replacement for asbestos in brake linings.