Loess
In some parts of the world the surface topography is mantled with deposits of windblown silt termed loess. Over thousands of years dust storms deposited this material. When loess is breached bystreams or road cuts, it tends to maintain vertical cliffs and lacks any visible layers, as you can see in gradually become concentrated into a tightly packed layer as deflation lowers the surface by removing sand and silt. In this situation, desert pavement is the result of deflation. B. This model shows the formation of desert pavement on a surface initially covered with coarse pebbles and cobbles. Windblown dust accumulates at the surface and gradually sifts downward through spaces between coarse particles. Infiltrating rainwater aids the process This depositional process raises the surface and produces a layer of coarse pebbles and cobbles underlain by a substantial layer at fine sediment.
The distribution of loess worldwide indicates that there are two primary sources for this sediment: deserts and glacial deposits of stratified drift The thickest and most extensive deposits of loess On Earth occur in western and northern China. They were blown there from the extensive desert basins of central Asia. Accumulations of 30 meters are not uncommon, and thicknesses of more than 100 meters have been measured. It is this fine, buff-colored Sediment that gives the Yellow River (Hwang Ho) its name.
In the United States, deposits of loess are significant in many areas, including south Dakota, Nebraska, Iowa, Missouri, and Illinois, as well as portions of the Columbia Plateau in the Pacific Northwest. Unlike the deposits in China, the 10855 in the United States, as well as in Europe, is an indirect product of glaciation. Its source is deposits of stratified drift. During the retreat of the ice sheets, many river valleys were choked with sediment deposited by meltwater. Strong westerly winds sweeping across the barren floodplains picked up the finer sediment and dropped it as a blanket on the eastern sides of the valleys.
LoessIn some parts of the world the surface topography is mantled with deposits of windblown silt termed loess. Over thousands of years dust storms deposited this material. When loess is breached bystreams or road cuts, it tends to maintain vertical cliffs and lacks any visible layers, as you can see in gradually become concentrated into a tightly packed layer as deflation lowers the surface by removing sand and silt. In this situation, desert pavement is the result of deflation. B. This model shows the formation of desert pavement on a surface initially covered with coarse pebbles and cobbles. Windblown dust accumulates at the surface and gradually sifts downward through spaces between coarse particles. Infiltrating rainwater aids the process This depositional process raises the surface and produces a layer of coarse pebbles and cobbles underlain by a substantial layer at fine sediment. The distribution of loess worldwide indicates that there are two primary sources for this sediment: deserts and glacial deposits of stratified drift The thickest and most extensive deposits of loess On Earth occur in western and northern China. They were blown there from the extensive desert basins of central Asia. Accumulations of 30 meters are not uncommon, and thicknesses of more than 100 meters have been measured. It is this fine, buff-colored Sediment that gives the Yellow River (Hwang Ho) its name.In the United States, deposits of loess are significant in many areas, including south Dakota, Nebraska, Iowa, Missouri, and Illinois, as well as portions of the Columbia Plateau in the Pacific Northwest. Unlike the deposits in China, the 10855 in the United States, as well as in Europe, is an indirect product of glaciation. Its source is deposits of stratified drift. During the retreat of the ice sheets, many river valleys were choked with sediment deposited by meltwater. Strong westerly winds sweeping across the barren floodplains picked up the finer sediment and dropped it as a blanket on the eastern sides of the valleys.
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