Outdoor Glossary: U

unconformity
A surface that represents a break in the geologic record, with the rock unit immediately above it being considerably younger than the rock beneath. There are three major aspects to consider: (1) Time. An unconformity develops during a period of time in which no sediment is deposited. This concept equates deposition and time, and an unconformity represents unrecorded time. (2) Deposition. Any interruption of deposition, whether large or small in extent, is an unconformity. This aspect of unconformity pre-supposes a standard scale of deposition which is complete. Major breaks in sedimentation can usually be demonstrated easily, but minor breaks may go unrecorded until highly detailed investigations are made. (3) Structure. Structurally, unconformity may be regarded as planar structures separating older rocks below from younger rocks above, representing the break as defined in (1) and (2) above. A plane of unconformity may be a surface of weathering, EROSION or denudation, or a surface of non-deposition, or possibly some combination of these factors. It may be parallel to the upper strata, make an angle with the upper strata, or be irregular. Subsequent Earth movements may have folded or faulted it.

unconsolidated
In referring to sediment grains, loose, separate, or unattached to one another.

underburn
A burn by a surface fire that can consume ground vegetation and "ladder" fuels.

undercutting
erosion of material at the foot of a cliff or bank, e.g., a sea cliff, or river bank on the outside of a meander. Ultimately, the overhang collapses, and the process is repeated.

underparts
Belly, undertail coverts, chest, flanks, and foreneck.

understory
The trees and woody shrubs growing beneath the overstory in a stand of trees.

undertail coverts
Feathers covering underside of base of tail. Synonym(s): crissum.

undertow
(1) A current below water surface flowing seaward; the receding water below the surface from waves breaking on a shelving beach. (2) Actually undertow is largely mythical. As the BACKWASH of each wave flows down the beach, a current is formed which flows seaward. However, it is a periodic phenomenon. The most common phenomena expressed as undertow are actually rip currents.

underwater gradient
The slope of the sea bottom. See slope.

underwing
Underside of wing.

undisturbed water level
Same as still water level.

uneven
aged management - Actions that maintain a forest or stand of trees composed of intermingling trees that differ markedly in age. Cutting methods that develop and maintain uneven-aged stands are single-tree selection and group selection.

universal time (UT)
Same as Greenwich mean time (GMT).

unregulated harvest
Tree harvest that is not part of the allowable sale quantity (ASQ). It can include the removal of cull or dead material or non-commercial species. It also includes volume removed from non-suitable areas for research, to meet objectives other than timber production (such as wildlife habitat improvement), or to improve administrative sites (such as campgrounds.)

unsuitable lands
Forest land that is not managed for timber production. Reasons may be matters of policy, ecology, technology, silviculture, or economics

upbound
from the Atlantic Ocean

updrift
The direction to which the predominant longshore movement of beach material approaches.

upland game birds
nonmigratory birds found on terrestrial habitats. These include prairie chickens, wild turkey, quails, pheasants, grouse, partridges, and ptarmigans. Doves and American woodcock are considered separately for purposes of this publication.

uplands
Land above the mean high water line (shoreline) and subject to private ownership, as distinguished from tidelands, the ownership of which is prima facie in the state but also subject to divestment under state statutes. See tidelands.

upper mandible
Upper part of the bill.

upper mandibular tomia
Cutting edges of upper mandible.

upperparts
Back, rump, hindneck, wings, and crown.

uppertail coverts
Feathers covering upperside of base of tail.

upperwing
Upperside of wing.

upwelling
The process by which water rises from a deeper to a shallower depth, usually as a result of offshore surface water flow. It is most prominent where persistent wind blows parallel to a coastline so that the resultant Ekman transport moves surface water away from the coast.

use, allowable
An estimate of proper range use. Forty to fifty percent of the annual growth is often used as a rule of thumb on ranges in good to excellent condition. It can also mean the amount of forage planned to be used to accelerate range rehabilitation.