Anticline: a rock fold which is closed at the top; an upwarp in folded rock srata

Bermuda High: A cell of high atmospheric pressure that exists over the Atlantic Ocean in the subtropical latitudes of the northern hemisphere in the general vicinity of Bermuda. This region, where air is descending from the upper atmosphere, serves as the major source area for moist air masses reaching Virginia.

Carbonate Rock: rock composed primarily of calcium carbonate; e.g, limestone

Climate: The average annual pattern of weather in a given region. Includes both precipitation patterns and temperature patterns

Cold Air Drainage: The downslope flow of cold air from mountain tops to the valleys below. This usually occurs during clear, windless nights when the colder, denser air of higher elevations slips down and under the warmer air at the lower elevations. The result is a temperature inversion by morning with the possibility of fog and frost in the valley bottoms and warmer temperatures and lower humidity on the mountain slopes.

Condensation: the process in which water changes state from a vapor to a liquid

Convectional precipitation: Rain or hail that is generated when a heated surface causes the air above it to warm, expand, and rise. Accounts for much of the summer precipitation in Virginia.

Continental Divide: a ridge or other elevated area that determines the direction of flow of waters running off adjacent drainage basins and the region of the world ocean into which they empty. The Eastern Continental Divide separates land draining to the Atlantic from that draining to the Gulf of Mexico.

Continentality: Refers to the wide ranges in temperatures experienced annually by places located away from the moderating influence of the sea.

Crust: outermost shell or layer of planet Earth

Divide: A ridge or elevated area that determines the direction of runoff flowing from adjacent slopes or basins. The boundary line between adjacent drainage basins.

Drainage basin: The land drained by a particular stream or stream system. Also referred to as river basin or watershed.

Drainage system: a network of streams that collect runoff from the land and carry it to a larger stream, lake, or the ocean.

Erosion: the transport (removal) of weathered particles

Estuary: A bay or drowned valley where a river meets the sea. It is a zone where fresh and salt water mix and in which nutrients washed from the land can collect. Often highly productive areas in biological terms, frequently serving as nursery areas for a variety of marine lifeforms.

Evaporation: The change in state of water from a liquid to a vapor (gas)

Faulting: the breaking and displacement (movement) of rock layers

Fog: a cloud in contact with the ground

Frontal precipitation: Rain, sleet, or snow that is produced when warm, moist air is forced to rise over a colder, denser air mass. Accounts for much of Virginia's winter precipitation.

Growing season: the time between the last killing frost of Spring and the first killing frost of Autumn. (Note: this concept has nothing to do with moisture or soil conditions.)

Headwaters: The smallest, uppermost tributaries of a drainage system

Igneous Rock: rock formed by the crystallization (cooling and hardening) of molten material either when magma cools slowly within the earth's crust (forming coarse-grained granitic rock) or when lava cools rapidly on the earth's surface in contact with either the atmosphere or the sea (forming fine-grained volcanic rock such as basalt or rhyolite)

Karst: a set of landforms or a landscape formed by the solution of carbonate rocks. Depressions or pits (sinkholes) and disappearing streams are characteristic of karst areas in temperate regions; below the surface, caves and caverns are common. Karst is well developed in the Valley and Ridge physiographic province of Virginia.

Lithology: type of bedrock; the kinds of rock comprising the substrate

Lithospheric or Tectonic Plate: segment of the earth's crust that moves as a unit.

Maritime influence: the moderating effect of the sea on air temperatures. Results in coastal areas and islands experiencing a relatively low range of temperatures on an annual basis

Metamorphic Rock: rock, initially either sedimentary or igneous, in which minerals and texture have been significantly altered by heat or pressure (e.g., slate, marble, gneiss, schist, greenstone)

Monadnock: a mountain that is the result of removal of surrounding rocks; an erosional remnant. Buffalo Mountain in Floyd County is nearby example of this type of mountain.

Orogeny: a major mountain-building episode in geologic history

Orographic precipitation: Rain or snow that is generated when a moisture-bearing air mass is forced to rise over a land surface, especially evident on the windward side of mountains

Physiography: the natural configuration of the land surface

Physiographic Province: a contiguous area (i.e., region) characterized by similar elevations, relief, lithology, geologic structure and geologic history.

Pleistocene relict: a relict is a species whose present distribution area may be explained as the remnant of wider range that existed in some previous climatic or geologic time period. Pleistocene relict refers to a species that persists today in isolated mountaintop habitats in Virginia but 18,000 years ago--at the height of the last ice age--may have occurred throughout state. Today most members of the species are found far to the north of Virginia. Examples include red spruce and the northern flying squirrel.

Rainshadow: that area on the leeward side of mountains that receives markedly less precipitation than slopes on the windward side.Rainshadow effect: the creation of relative dryness on the leeward slope of a mountain, where descending air masses warm and increase their ability to hold water vapor.

Relief: the difference in elevation between the highest and lowest points on a given land surface

Rifting: the splitting apart of the earth's crust when it is stretched by tectonic activity. Results in the downfaulting of blocks of crust and creation of flat-floored valleys or troughs known as rift valleys (e.g., Virginia's Triassic lowlands)

Sedimentary Rock: rock formed from particles generally weathered and eroded from pre-existing rock material but also from the deposition of shells and other organic detritus (e.g., carbonate rocks) or the precipitation of salts from solution.

Stream piracy: the capture of the headwater streams of one drainage system by a stream of another system. Occurs when headward erosion breaks through a drainage divide into the adjacent drainage basin

Structure (geologic): the arrangement of bedrock; e.g., horizontal, tilted, folded or faulted

Subtropical high: a zone of descending air that occurs between 25 and 35 degrees latitude in both hemispheres. This air, which is forced downward from the upper atmosphere due to the Earth's rotation, is compressed and exerts high atmospheric pressure at the Earth's surface.

Syncline: a rock fold which is open at the top; a downwarp.

Tectonic: pertaining to crustal movements of the Earth

Temperature inversion: a reversal of the usual pattern in which temperature decreases with increasing altitude. During a temperature inversion the lowest temperatures are closest to the ground; warmer temperatures at found at higher altitudes

Topography: all surface features, both physical and cultural

Tributary: any stream that feeds into another, larger stream

Weathering: the in situ decomposition of bedrock through mechanical (such as freeze-thaw) and/or chemical (such as solution or hydrolysis) processes. Breaking solid rock into small particles.