Land

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For land on astronomical objects, see Planetary surface. For other uses, see Land (disambiguation).
"Dry land" redirects here. For the song, see Dry Land. For the 2010 film, see The Dry Land.
Land between bodies of water at Point Reyes National Seashore, California

Land or ground is the solid surface of Earth that is not permanently submerged in water.[1] Most but not all land is situated at elevations above sea level (variable over geologic time frames) and consists mainly of crustal components such as rock, sand, soil, and sometimes ice. The vast majority of human activity throughout history has occurred in land areas that support agriculture, habitat, and various natural resources. Some life forms, including terrestrial plants and terrestrial animals, have developed from predecessor species that originated in the bodies of water.

Areas where land meets large bodies of water are called coastal zones. The division between land and water is a fundamental concept to humans. The demarcation line between land and water can vary by local jurisdiction and other factors. A maritime boundary is one example of a political demarcation. A variety of natural boundaries exist to help clearly define where water meets land. Solid rock landforms are easier to demarcate than marshy or swampy boundaries, where there is no clear point at which the land ends and a body of water has begun. Demarcation lines can further vary due to tides and weather.

Land in other planets and astronomical objects are called regolith, and colloquially also called land. In reference to business terminology land is also associated with factor of production, as well as land is the first factor of production and the income or profit earned with help of land is treated as rent.

Etymology[edit]

The word land is derived from the Old English land 'ground, soil', also 'definite portion of the earth's surface, home region of a person or a people, territory marked by political boundaries'. It evolved from the Proto-Germanic *landą and from the Proto-Indo-European *lendʰ- 'land, open land, heath'. The word has many cognates in other languages, such as Old Norse: land, Old Frisian: land, Gothic: land, German: Land, Old Irish: land, Middle Welsh: llan 'an open space', Welsh: llan 'enclosure, church', Breton: lann 'heath', Church Slavonic: ledina 'waste land, heath', and Czech: lada 'fallow land'. Etymological evidence within Gothic usage suggests that the original meaning of land was 'a definite portion of the earth's surface owned by an individual or home of a nation.' The meaning was extended to 'solid surface of the earth'. The original meaning is now associated with country.[2]

A continuous area of land surrounded by ocean is called a landmass. Although it may be most often written as one word to distinguish it from the usage "land mass"—the measure of land area—it is also used as two words. Landmasses include supercontinents, continents, and islands. There are four major continuous landmasses on Earth: Afro-Eurasia, the Americas, Antarctica, and Australia. Land capable of being ploughed and used to grow crops, is called arable land.[3] A country or region may be referred to as the motherland, fatherland, or homeland of its people. Many countries and other places have names incorporating the suffix, -land (e.g. England, Iceland, Greenland, Finland, Swaziland, and New Zealand).

The Indo-Iranian suffix -stan, ultimately descended from Proto-Indo-Iranian *sthāna-,[4] is analogous to the suffix -land, and is present in many country and location names, such as Uzbekistan, Pakistan, and Afghanistan. The suffix is also used more generally, as in Persian rigestân (ریگستان) "place of sand, desert", golestân (گلستان) "place of flowers, garden", gurestân (گورستان) "graveyard, cemetery", Hindustân (هندوستان) "land of the Indo people".

Formation[edit]

See also: History of Earth
Artist's conception of Hadean Eon Earth.

The earliest material found in the Solar System is dated to 4.5672±0.0006 bya (billion years ago);[5] therefore, the Earth itself must have been formed by accretion around this time. The formation and evolution of the Solar System bodies occurred in tandem with the Sun. In theory, a solar nebula partitions a volume out of a molecular cloud by gravitational collapse, which begins to spin and flatten into a circumstellar disc, out of which the planets then grow (in tandem with the star). A nebula contains gas, ice grains and dust (including primordial nuclides). In nebular theory, planetesimals commence forming as particulate matter accrues by cohesive clumping and then by gravity. The assembly of the primordial Earth proceeded for 10–20 myr.[6] By 4.54±0.04 bya,[7][8][9][10] the primordial Earth had formed.

Earth's atmosphere and oceans were formed by volcanic activity and outgassing that included water vapour. The origin of the world's oceans was condensation augmented by water and ice delivered by asteroids, proto-planets, and comets.[11] In this model, atmospheric "greenhouse gases" kept the oceans from freezing while the newly forming Sun was only at 70% luminosity.[12] By 3.5 bya, the Earth's magnetic field was established, which helped prevent the atmosphere from being stripped away by the solar wind.[13] The atmosphere and oceans of the Earth continuously shape the land by eroding and transporting solids on the surface.[14]

The crust, which currently forms the Earth's land, was created when the molten outer layer of the planet Earth cooled to form a solid mass as the accumulated water vapour began to act in the atmosphere. Once land became capable of supporting life, biodiversity evolved over hundreds of million years, expanding continually except when punctuated by mass extinctions.[15]

The two models[16] that explain land mass propose either a steady growth to the present-day forms[17] or, more likely, a rapid growth[18] early in Earth history[19] followed by a long-term steady continental area.[20][21][22] Continents formed by plate tectonics, a process ultimately driven by the continuous loss of heat from the Earth's interior. On time scales lasting hundreds of millions of years, the supercontinents have formed and broken apart three times. Roughly 750 mya (million years ago), one of the earliest known supercontinents, Rodinia, began to break apart. The continents later recombined to form Pannotia, 600–540 mya, then finally Pangaea, which also broke apart 180 mya.[23]

Arrangement[edit]

Main article: Continent

Land is separated by bodies of water. The biggest stretches of land are called continents, which do not have a clear-cut definition.[24] Up to seven geographical regions are commonly regarded as continents. Ordered from largest in area to smallest, these seven regions are: Asia, Africa, North America, South America, Antarctica, Europe, and Australia. [25] North America and South America are sometimes grouped as just America. Europe and Asia are sometimes grouped as Eurasia, and sometimes with Africa to form Afro-Eurasia. Most of the island countries and territories of the Pacific Ocean are frequently grouped with Australia to form a geographical region called Oceania.

Layers[edit]

Land cover[edit]

Main article: Land cover
Land cover as classified by IGBP into 17 classes

Land cover is the physical material at the surface of the earth. Among many things, it includes of grass, asphalt, trees, bare ground, water. Earth cover is the expression used by ecologist Frederick Edward Clements that has its closest modern equivalent being vegetation.[26]: 52  The expression continues to be used by the United States Bureau of Land Management.[27]

There are two primary methods for capturing information on land cover: field survey and analysis of remotely sensed imagery. Land change models can be built from these types of data to assess changes in land cover over time. One of the major land cover issues (as with all natural resource inventories) is that every survey defines similarly named categories in different ways. For instance, there are many definitions of "forest"—sometimes within the same organisation—that may or may not incorporate a number of different forest features (e.g., stand height, canopy cover, strip width, inclusion of grasses, and rates of growth for timber production). Areas without trees may be classified as forest cover "if the intention is to re-plant" (UK and Ireland), while areas with many trees may not be labelled as forest "if the trees are not growing fast enough" (Norway and Finland).

Rock[edit]

Further information: Rock (geology), Continental crust, and Continental shelf

The composition of land is not uniform across the Earth, varying between locations and between strata within the same location. The most prominent components of upper continental crust include silicon dioxide, aluminium oxide, and magnesium. The rock that makes up land is thicker than oceanic crust, and it is far more varied in terms of composition. About 31% of this continental crust is submerged in shallow water, forming continental shelves.[28]

Interactions[edit]

Oceans and seas[edit]

When land is in contact with bodies of water, it is bound to be weathered and eroded.

Climate[edit]

The land of Earth interacts with and influences climate heavily since the surface of the land heats up and cools down faster than air or water.[29] Latitude, elevation, topography, reflectivity, and land use all have varying effects. The latitude of the land will influence how much solar radiation reaches the surface. High latitudes receive less solar radiation than low latitudes.[29] The topography of land is important in creating and transforming airflow and precipitation on Earth. Large landforms, such as mountain ranges, divert wind energy and make air parcels less dense and therefore able to hold less heat.[29] As air rises, this cooling effect causes condensation and precipitation.

The reflectivity of the earth is called planetary albedo, and the type of land cover that receives energy from the Sun affects the amount of energy that is reflected or transferred to Earth.[30] Vegetation has a relatively low albedo meaning that vegetated surfaces are good absorbers of the sun's energy. Forests have an albedo of 10–15% while grasslands have an albedo of 15–20%. In comparison, sandy deserts have an albedo of 25–40%.[30]

Land use by humans also plays a role in the regional and global climate. Densely populated cities are warmer and create urban heat islands that have effects on the precipitation, cloud cover, and temperature of the region.[29]

Relationship with humans[edit]

Usage[edit]

Main article: Land use

Land use involves the management and modification of the natural environment or wilderness into built environment such as settlements and of semi-natural habitats such as arable fields, pastures, and managed woods. Land use by humans has a long history, first emerging more than 10,000 years ago.[31][32] It has been defined as "the purposes and activities through which people interact with land and terrestrial ecosystems"[33] and as "the total of arrangements, activities, and inputs that people undertake in a certain land type."[34] Land use and land management practices have a major impact on natural resources including water, soil, nutrients, plants, and animals.[35] Human tribes since prehistory have segregated land into territories to control the use of land.

Cultural[edit]

Main article: Earth in culture
Imago Mundi Babylonian map, the oldest known world map, 6th century BC Babylonia.

Creation myths in many religions recall a story involving the creation of the world by a supernatural deity or deities, including accounts wherein the land is separated from the oceans and the air. The Earth itself has often been personified as a deity, in particular a goddess. In many cultures, the mother goddess is also portrayed as a fertility deity. To the Aztecs, Earth was called Tonantzin—"our mother"; to the Incas, Earth was called Pachamama—"mother earth". The Chinese Earth goddess Hou Tu[36] is similar to Gaia, the Greek goddess personifying the Earth. Bhuma Devi is the goddess of Earth in Hinduism, influenced by Graha. In Norse mythology, the Earth giantess Jörð was the mother of Thor and the daughter of Annar. Ancient Egyptian mythology is different from that of other cultures because Earth (Geb) is male and sky (Nut) is female.

In early Egyptian[37] and Mesopotamian thought, the world was portrayed as a flat disk floating in the ocean. The Egyptian universe was pictured as a rectangular box with a north–south orientation and with a slightly concave surface, with Egypt in the center. A similar model is found in the Homeric account of the 8th century BC in which "Okeanos, the personified body of water surrounding the circular surface of the Earth, is the begetter of all life and possibly of all gods."[38] The biblical earth is a flat disc floating on water.[39]

The Pyramid Texts and Coffin Texts reveal that the ancient Egyptians believed Nun (the ocean) was a circular body surrounding nbwt (a term meaning "dry lands" or "islands"), and therefore believed in a similar Ancient Near Eastern circular Earth cosmography surrounded by water.[40]

The spherical form of the Earth was suggested by early Greek philosophers, a belief espoused by Pythagoras. Contrary to popular belief, most educated people in the Middle Ages did not believe the Earth was flat: this misconception is often called the "Myth of the Flat Earth". As evidenced by thinkers such as Thomas Aquinas, the European belief in a spherical Earth was widespread by this point in time.[41] Prior to circumnavigation of the planet and the introduction of space flight, belief in a spherical Earth was based on observations of the secondary effects of the Earth's shape and parallels drawn with the shape of other planets.[42]

See also[edit]

References[edit]

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  2. ^ Harper, Douglas. "land". Online Etymology Dictionary. Retrieved July 18, 2021.
  3. ^ Oxford English Dictionary, 3rd ed. "arable, adj. and n." Oxford University Press (Oxford), 2013.
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External links[edit]

Look up land in Wiktionary, the free dictionary.
Wikiquote has quotations related to Land.
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