Editing Plain (section)

== Description ==
[[File:Marmilla las plassas.jpg|thumb|Plain of [[Campidano]], [[Italy]]]]
A plain or flatland is a flat expanse of land with a layer of grass that generally does not change much in [[elevation]], and is primarily treeless. Plains occur as [[lowland]]s along [[valley]]s or at the base of [[mountain]]s, as [[coastal plain]]s, and as [[plateau]]s or [[Highland|uplands]].<ref>{{Cite journal|last=Rood|first=Stewart B.|last2=Pan|first2=Jason|last3=Gill|first3=Karen M.|last4=Franks|first4=Carmen G.|last5=Samuelson|first5=Glenda M.|last6=Shepherd|first6=Anita|date=2008-02-01|title=Declining summer flows of Rocky Mountain rivers: Changing seasonal hydrology and probable impacts on floodplain forests|journal=Journal of Hydrology|volume=349|issue=3–4|pages=397–410|doi=10.1016/j.jhydrol.2007.11.012|bibcode=2008JHyd..349..397R}}</ref> Plains are one of the major [[landform]]s on earth, where they are present on all continents, and cover more than one-third of the world's land area.<ref name="Wilson">{{Cite book |author1=Geoff C. Brown |url=https://books.google.com/books?id=Kgk4AAAAIAAJ&pg=PA93 |title=Understanding the Earth |author2=C. J. Hawkesworth |author3=R. C. L. Wilson |publisher=Cambridge University Press |year=1992 |isbn=978-0-521-42740-1 |edition=2nd |page=93 |archive-url=https://web.archive.org/web/20160603090000/https://books.google.com/books?id=Kgk4AAAAIAAJ&pg=PA93 |archive-date=2016-06-03 |url-status=live}}</ref>

In a valley, a plain is enclosed on two sides, but in other cases a plain may be delineated by a complete or partial ring of hills, by mountains, or by [[cliff]]s. Where a geological region contains more than one plain, they may be connected by a [[Mountain pass|pass]] (sometimes termed a [[Gap (landform)|gap]]). Coastal plains mostly rise from [[sea level]] until they run into elevated features such as mountains or plateaus.<ref>{{cite book|author=Whittow, John |date=1984|title=Dictionary of Physical Geography|location=London|publisher=Penguin|page= 467|isbn=978-0-14-051094-2}}</ref> Plains can be formed from flowing [[lava]]; from [[Deposition (geology)|deposition]] of sediment by water, ice, or wind; or formed by [[erosion]] by the agents from hills or mountains.

[[Biome]]s on plains include [[grassland]] ([[temperate]] or [[subtropical]]), [[steppe]] ([[semi-arid]]), [[savannah]] ([[tropical climate|tropical]]) or [[tundra]] ([[polar climate|polar]]). In a few instances, [[desert]]s and [[rainforest]]s may also be considered plains.<ref>{{cite book | editor-last = Gornitz | editor-first = Vivien | date = 2009 | title = Encyclopedia of Paleoclimatology And Ancient Environments | publisher = Springer | location = Dordrecht | page = 665 | ISBN = 9781402045516}}</ref>

Plains in many areas are important for [[agriculture]] because where the soils were deposited as [[sediment]]s they may be deep and [[Fertility (soil)|fertile]], and the flatness facilitates mechanization of crop production; or because they support grasslands which provide good grazing for [[livestock]].<ref>Powell, W. Gabe. 2009. Identifying Land Use/Land Cover (LULC) Using [[National Agriculture Imagery Program]] (NAIP) Data as a Hydrologic Model Input for Local Flood Plain Management.  Applied Research Project, Texas State University.</ref>