soil terms - 10/15/02 05:42 PM
Years ago reading Yearbook of Agriculture, there was often
mention of soil type called "loess" but no background of term.
?
As glaciers advanced and retreated during the Pleistocene epoch, four ice ages ocurred. The Nebraskan, which was the first ice age, followed by the Kansan, the Illinoian, and the Wisconsin. During these ice ages, a very fine rock powder was produced by way of scouring the exposed rock as glaciation took place, that powder is known as rock flour or silt (http://www.isgs.uiuc.edu/tours/outliers/geogram5.htm). As the silt accumulated, it could be transported by the wind as the glacier retreated or by glacial outwash as the silt dried during which the climate changed from winter to spring.
As the warmer climate approached, the glacier would begin to melt, saturating the rock flour, which allowed it to be transported as sediment load in streams or rivers. As velocity of the stream decreased, either by the onset of winter or loss of slope angle, the sediment load would drop out and accumulate along the banks which produced a mud of very fine silt.
With the drying of the mud, the wind could now pick up the silt particles and transport them according to their size(http://www.isgs.uiuc.edu/tours/outliers/geogram5.htm). The coarser particles would drop out first, closer to the source and the fine particles would be the last to drop out, which would be farthest from the source.
In the midwest section of theUnited States, the Missouri River Flood Plain is the source of silt that winds transported eastward, into the flood plains. Accumulation of silt over many years produced landforms of various sizes and shapes. The main component of the landforms produced is called loess or as stated previously, the definition of loess is " A blanket deposit of buff-colored calcareous silt, homogeneous, nonstratified, weakly coherent, porous, and friable. A rude vertical parting allows it to stand in steep or vertical faces. Loess covers wide areas in northern Europe, eastern China , and the Mississippi Valley. It is considered to be windblown dust of Pleistocene age."( Bates and Jackson, 1984).
Three types of loess can be found throughout the midwestern states, the Loveland loess, the Pisgah loess, and the Peoria loess (http://pubs.usgs.gov/info-handout/loess/). Each loess having its own characteristics can be found intermixed with glacial till, alluvium, sand, and gravel.
mention of soil type called "loess" but no background of term.
?
As glaciers advanced and retreated during the Pleistocene epoch, four ice ages ocurred. The Nebraskan, which was the first ice age, followed by the Kansan, the Illinoian, and the Wisconsin. During these ice ages, a very fine rock powder was produced by way of scouring the exposed rock as glaciation took place, that powder is known as rock flour or silt (http://www.isgs.uiuc.edu/tours/outliers/geogram5.htm). As the silt accumulated, it could be transported by the wind as the glacier retreated or by glacial outwash as the silt dried during which the climate changed from winter to spring.
As the warmer climate approached, the glacier would begin to melt, saturating the rock flour, which allowed it to be transported as sediment load in streams or rivers. As velocity of the stream decreased, either by the onset of winter or loss of slope angle, the sediment load would drop out and accumulate along the banks which produced a mud of very fine silt.
With the drying of the mud, the wind could now pick up the silt particles and transport them according to their size(http://www.isgs.uiuc.edu/tours/outliers/geogram5.htm). The coarser particles would drop out first, closer to the source and the fine particles would be the last to drop out, which would be farthest from the source.
In the midwest section of theUnited States, the Missouri River Flood Plain is the source of silt that winds transported eastward, into the flood plains. Accumulation of silt over many years produced landforms of various sizes and shapes. The main component of the landforms produced is called loess or as stated previously, the definition of loess is " A blanket deposit of buff-colored calcareous silt, homogeneous, nonstratified, weakly coherent, porous, and friable. A rude vertical parting allows it to stand in steep or vertical faces. Loess covers wide areas in northern Europe, eastern China , and the Mississippi Valley. It is considered to be windblown dust of Pleistocene age."( Bates and Jackson, 1984).
Three types of loess can be found throughout the midwestern states, the Loveland loess, the Pisgah loess, and the Peoria loess (http://pubs.usgs.gov/info-handout/loess/). Each loess having its own characteristics can be found intermixed with glacial till, alluvium, sand, and gravel.