Till plain

Source: Wikipedia, the free encyclopedia.
"Glacial till plains" redirects here. For the landform of Ohio, see Glacial till plains (Ohio).

Till plains are an extensive flat

glacial till that forms when a sheet of ice becomes detached from the main body of a glacier and melts in place, depositing the sediments it carried. Ground moraines are formed with melts out of the glacier in irregular heaps, forming rolling hills. Till plains are common in areas such as the Midwestern United States, due to multiple glaciation events that occurred in the Holocene epoch. During this period, the Laurentide Ice Sheet advanced and retreated during the Pleistocene epoch.[1] Till plains formed by the Wisconsin glaciation cover much of the Midwest, including North Dakota, South Dakota, Indiana, Minnesota, Wisconsin, Iowa, Illinois, and northern Ohio (see Glacial till plains (Ohio)).[2]

Image of ground moraine in New York. Note flat/rolling topography.

Characteristics

Till plains are large flat or gently sloping areas of land on which glacial

moraines form, all composed of glacial till.[4] The material composition of till plains vary greatly, and is dependent on the travel path of the transporting glacier, indicated by the provenance of the deposited material. Till plains may be deposited as a single sheet of till, but often a single plain may contain multiple sheets of till. This occurs where changing climate and/or ice dynamics led to multiple phases of glacier advance and retreat.[5]

Hydrogeologic importance

Subglacial meltwater is the main product of glacial

aquitards, which inhibit groundwater flow. Meltwater, as well as groundwater, tends to preferentially flow through subglacial sediment deposits, given that they are sufficiently porous, soft, and deformable. The flow regime is assumed to be either darcian or advective flows, although the precise method is often speculated and debated.[6]

Soil formation and fertility

During the last glaciation, much of the Midwestern and Central United States were covered by glaciers. As the glaciers retreated and melted, much of the land was covered in till plains. These till plains were the basis from which the present day soil formed from. The parent material which these soils formed from varies greatly from one area to another, and is dependent on the path of the glacier which deposited the initial glacial till. This has caused different soils to form over time, but most generally share similar properties such as a loamy texture and poor drainage if derived from glacial till. The soils developed from till plains have become some of the most productive agricultural regions in the United States, due to the combination of thick till deposits forming rich fertile soils, and the gently rolling to flat topography being very suitable for farming practices.[6]

See also

References

  1. ^ "The Importance of Glaciers to Wisconsin". Schlitz Audubon. 2019-01-15. Retrieved 2020-11-26.
  2. ^ "The retreat chronology of the Laurentide Ice Sheet during the last 10,000 years and implications for deglacial sea-level rise". Vignette Collection. Retrieved 2020-12-18.
  3. doi:10.1109/TGRS.2021.3091771
    .
  4. ^ "Geotechnical Engineering Manual - MnDOT". www.dot.state.mn.us. Retrieved 2020-11-25.
  5. S2CID 129303587
    .
  6. ^
    ISBN 978-0-470-51690-4
    .
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