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{{Short description|Plain of glacial till}}
{{Redirect|Glacial till plains|the landform of Ohio|Glacial till plains (Ohio)}}
'''Till plains''' are an extensive flat [[plain]] of [[glacial till]] that forms when a sheet of [[ice]] becomes detached from the main body of a [[glacier]] and melts in place, depositing the [[sediment]]s it carried. [[Moraine#Ground moraines|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.<ref>{{Cite web|date=2019-01-15|title=The Importance of Glaciers to Wisconsin|url=https://www.schlitzaudubon.org/2019/01/15/the-importance-of-glaciers-to-wisconsin/|access-date=2020-11-26|website=Schlitz Audubon|language=en}}</ref> 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)]]).<ref>{{Cite web|title=The retreat chronology of the Laurentide Ice Sheet during the last 10,000 years and implications for deglacial sea-level rise|url=https://serc.carleton.edu/vignettes/collection/58451.html|access-date=2020-12-18|website=Vignette Collection|language=en}}</ref>
[[File:Ground moraine 9004.jpg|thumb|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 [[till]] has been deposited from a melted glacier. In some areas, these depositions can be up to hundreds of feet thick. The morphology of the till plain is generally reflective of the topography of the bedrock below the glacier. Another term for till plain is [[ground moraine]]. Not to be confused with [[outwash plain|outwash plains]], till plains differ due to their sorting mechanisms and resulting deposit characteristics.<ref>{{cite journal |last1=Janowski |first1=Lukasz |last2=Tylmann |first2=Karol |last3=Trzcinska |first3=Karolina |last4=Rudowski |first4=Stanislaw |last5=Tegowski |first5=Jaroslaw |title=Exploration of Glacial Landforms by Object-Based Image Analysis and Spectral Parameters of Digital Elevation Model |journal=IEEE Transactions on Geoscience and Remote Sensing |date=2021 |volume=60 |pages=1–17 |doi=10.1109/TGRS.2021.3091771|doi-access=free }}</ref> Till plains are deposited as unsorted material picked up by ice as glaciers advance and retreat, or if a body of ice becomes detached from the main glacier and melts in place. Glacial till contain various sizes of material from clay to large glacial erratics, and form a [[loam]] texture due to variance in deposited material. Till plains are also the location in which [[drumlins]], drumlin fields, [[Flute (glacial)|flutes]], and additional [[moraines]] form, all composed of glacial till.<ref>{{Cite web|title=Geotechnical Engineering Manual - MnDOT|url=http://www.dot.state.mn.us/materials/geotmanual.html|access-date=2020-11-25|website=www.dot.state.mn.us}}</ref> 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.<ref>{{cite journal|doi=10.1111/j.1502-3885.2011.00208.x|title=Provenance of des Moines lobe till records ice-stream catchment evolution during Laurentide deglaciation|year=2011|last1=Lusardi|first1=Barbara A.|last2=Jennings|first2=Carrie E.|last3=Harris|first3=Kenneth L.|journal=Boreas|volume=40|issue=4|pages=585–597|bibcode=2011Borea..40..585L |s2cid=129303587 }}</ref>

== Hydrogeologic importance ==
Subglacial meltwater is the main product of glacial [[Ablation till|ablation]]. This meltwater acts as the force that causes subglacial tills to deform, and also plays a significant role in shaping the morphology and distribution of the till on the till plain. The composition of till plains is economically important due to their hydraulic properties. This property typically makes them confining units, or [[Aquitard|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 [[Darcy's law|darcian]] or [[Advection|advective]] flows, although the precise method is often speculated and debated.<ref name=":0">{{Cite book|last=Bennett|first=Matthew|title=Glacial Geology: Ice Sheets and Landforms|publisher=Wiley-Blackwell|year=2009|isbn=978-0-470-51690-4|pages=81–107}}</ref>

== 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 [[Loam|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.<ref name=":0" />

==See also==
*[[Glacial till plains (Ohio)]]
*[[Southeastern Wisconsin Till Plains (ecoregion)]]
*See ''[[plain]]'' article for other types of plains.

==References==
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{{glaciers}}{{Continental glaciations}}{{DEFAULTSORT:Till Plain}}
[[Category:Glaciology]]
[[Category:Geomorphology]]

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