- 行业: Government
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The United States Army Corps of Engineers is a federal agency with a mission to provide vital public engineering services in peace and war to strengthen the nation's security, energize the economy, and reduce risks from disasters. It is also a major U.S. Army organization employing some 38,000 ...
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:
# 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.
# 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.
# 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.
Industry:Engineering
(1) The flowing of water, or other liquid or gas. (2) That portion of a stream of water which is moving with a velocity much greater than the average or in which the progress of the water is principally concentrated. (3) Ocean currents can be classified in a number of different ways. Some important types include the following:
# Periodic - due to the effect of the tides; such Currents may be rotating rather than having a simple back and forth motion. The currents accompanying tides are known as tidal currents;
# Temporary - due to seasonal winds;
# Permanent or ocean - constitute a part of the general ocean circulation. The term drift current is often applied to a slow broad movement of the oceanic water;
# Nearshore - caused principally by waves breaking along a shore.
Industry:Engineering
Quotient of the wetted cross-sectional area and the wetted perimeter.
Industry:Engineering
Line connecting points on the seabed with an equal depth of sediment.
Industry:Engineering
A model probability distribution, commonly used in analysis of waves.
Industry:Engineering
That part of a river where the water level is influenced by the tide.
Industry:Engineering
An instrument that determines its distance above a particular surface.
Industry:Engineering
Function specifying the joint distribution of two (or more) variables.
Industry:Engineering
