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Abrasion, under its strictest definition, is commonly confused with attrition and sometimes hydraulic action however, the latter less commonly so. Both abrasion and attrition refers to the wearing down of an object. Abrasion occurs as a result of two surfaces rubbing against each other, resulting in the wearing down of one or both of the surfaces.
Deflation and abrasion are specific means of sediment transport than can also be attributed to aeolian processes. Deflation, which is named for the Latin word "deflare" meaning "to blow away", refers to the scattering and removal of rock particles by wind. Deflation occurs in deserts where diverse particles dominate the surface.
A continued supply of abrading fragments is required to uphold a similar level of abrasion. The fragments must be harder than the bedrock. Quartz fragments will abrade shale but shale fragments will not abrade a quartz rich bedrock. A constant flow of meltwater between the basal surface and the bedrock speeds abrasion.
The federal standard for LA abrasion testing was formally adopted by the ASTM in 1937. [10] Decades later, field studies found that the LA test results do not always correlate with reality, thus engineers outside of the United States developed different national standards like the French wet micro-Deval procedure or the British Standard 812. [1]
Also amphidrome and tidal node. A geographical location where there is little or no tide, i.e. where the tidal amplitude is zero or nearly zero because the height of sea level does not change appreciably over time (meaning there is no high tide or low tide), and around which a tidal crest circulates once per tidal period (approximately every 12 hours). Tidal amplitude increases, though not ...
Near the glacier the outwash plain is composed of long bars of coarse gravel with very variable grain size, with a few large channels between the bars. Further away there are transverse bars and a web of many braided channels. The sediment now includes gravel and sand, and the grains are rounder due to sorting and abrasion.
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A raised beach, coastal terrace, [1] or perched coastline is a relatively flat, horizontal or gently inclined surface of marine origin, [2] mostly an old abrasion platform which has been lifted out of the sphere of wave activity (sometimes called "tread"). Thus, it lies above or under the current sea level, depending on the time of its formation.