Mount Ararat in the Caucasus, with the Ararat plain in foreground.

In geography, a plain is a flat, sweeping landmass that generally does not change much in elevation. Plains occur as lowlands along the bottoms of valleys or on the doorsteps of mountains, as coastal plains, and as plateaus or uplands.[1]

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 cliffs. Where a geological region contains more than one plain, they may be connected by a pass (sometimes termed a gap). Coastal plains would mostly rise from sea level until they run into elevated features such as mountains or plateaus.[2]

Plains are one of the major landforms on earth, where they are present on all continents, and would cover more than one-third of the world's land area.[3] Plains may have been formed from flowing lava, deposited by water, ice, wind, or formed by erosion by these agents from hills and mountains. Plains would generally be under the grassland (temperate or subtropical), steppe (semi-arid), savannah (tropical) or tundra (polar) biomes. In a few instances, deserts and rainforests can also be plains.[4]

Plains in many areas are important for agriculture because where the soils were deposited as sediments they may be deep and fertile, and the flatness facilitates mechanization of crop production; or because they support grasslands which provide good grazing for livestock.[5]

Types of plain

A small, incised alluvial plain from Red Rock Canyon State Park (California).
A flood plain in the Isle of Wight.

Depositional plains

Depositional plains formed by the deposition of materials brought by various agents of transportation such as glaciers, rivers, waves, and wind. Their fertility and economic relevance depend greatly on the types of sediments that are laid down.[6] The types of depositional plains include:

  • Abyssal plains, flat or very gently sloping areas of the deep ocean basin.[7]
  • Planitia, the Latin word for plain, is used in the naming of plains on extraterrestrial objects (planets and moons), such as Hellas Planitia on Mars or Sedna Planitia on Venus.
  • Alluvial plains, which are formed by rivers and which may be one of these overlapping types:
    • Alluvial plains, formed over a long period of time by a river depositing sediment on their flood plains or beds, which become alluvial soil. The difference between a flood plain and an alluvial plain is: a flood plain represents areas experiencing flooding fairly regularly in the present or recently, whereas an alluvial plain includes areas where a flood plain is now and used to be, or areas which only experience flooding a few times a century.[8]
    • Flood plain, adjacent to a lake, river, stream, or wetland that experiences occasional or periodic flooding.
    • Scroll plain, a plain through which a river meanders with a very low gradient.
  • Glacial plains, formed by the movement of glaciers under the force of gravity:
    • Outwash plain (also known as sandur; plural sandar), a glacial out-wash plain formed of sediments deposited by melt-water at the terminus of a glacier. Sandar consist mainly of stratified (layered and sorted) gravel and sand.[9][10]
    • Till plains, plain of glacial till that form when a sheet of ice becomes detached from the main body of a glacier and melts in place depositing the sediments it carries. Till plains are composed of unsorted material (till) of all sizes.
  • Lacustrine plains, plains that originally formed in a lacustrine environment, that is, as the bed of a lake.[11]
  • Lava plains, formed by sheets of flowing lava.[12]

Erosional plains

Erosional plains have been leveled by various agents of denudation such as running water, rivers, wind and glacier which wear out the rugged surface and smoothens them. Plain resulting from the action of these agents of denudation are called peneplains (almost plain) while plains formed from wind action are called pediplains.[13]

Structural plains

Structural plains are relatively undisturbed horizontal surfaces of the Earth. They are structurally depressed areas of the world that make up some of the most extensive natural lowlands on the Earth's surface.[14]

The Kakanui Range dominates the eastern horizon of the Maniototo Plain
Curry County, eastern New Mexico, on the North American Great Plains
Other Languages
العربية: سهل
aragonés: Plana
asturianu: Llanura
Avañe'ẽ: Ñu
Aymar aru: Pallalla
বাংলা: সমভূমি
Bân-lâm-gú: Pêⁿ-po͘
беларуская: Раўніна
беларуская (тарашкевіца)‎: Раўніна
भोजपुरी: मैदान
bosanski: Ravnica
brezhoneg: Kompezenn
català: Plana
Чӑвашла: Тӳрем
čeština: Planina
chiShona: Mhene
dansk: Slette
eesti: Tasandik
Ελληνικά: Πεδιάδα
español: Llanura
Esperanto: Ebenaĵo
euskara: Ordoki
فارسی: دشت
français: Plaine
Frysk: Flakte
galego: Chaira
한국어: 평야
հայերեն: Հարթավայր
italiano: Pianura
қазақша: Жазық
Kiswahili: Tambarare
latgaļu: Leidzonaine
Latina: Planities
latviešu: Līdzenums
лезги: Кьулувал
lietuvių: Lyguma
lumbaart: Bàsa
magyar: Síkság
മലയാളം: സമതലം
მარგალური: დჷკი (გეოგრაფია)
монгол: Тал газар
Nederlands: Vlakte
日本語: 平野
нохчийн: Аре
norsk: Slette
norsk nynorsk: Slette
олык марий: Тӧрвер
ਪੰਜਾਬੀ: ਮੈਦਾਨ
polski: Równina
português: Planície
română: Câmpie
русский: Равнина
Scots: Plain
sicilianu: Chianu
Simple English: Plain
Soomaaliga: Bannaan
српски / srpski: Равница
srpskohrvatski / српскохрватски: Ravnica
suomi: Tasanko
svenska: Slätt
Tagalog: Kapatagan
தமிழ்: சமவெளி
Taqbaylit: Azaɣar
татарча/tatarça: Тигезлек (геология)
తెలుగు: మైదానం
Türkçe: Ova
українська: Рівнина
Tiếng Việt: Đồng bằng
Winaray: Patag
吴语: 平原
ייִדיש: פלוין
粵語: 平原
žemaitėška: Līgmė
中文: 平原