[135][136], The extent of Earth's magnetic field in space defines the magnetosphere. The Earth’s Crust; The earth’s crust is the outmost and first layer of the earth. [44] Water vapor from these sources condensed into the oceans, augmented by water and ice from asteroids, protoplanets, and comets. Precipitation patterns vary widely, ranging from several meters of water per year to less than a millimeter. Britannica does not review the converted text. The number of continents is most commonly considered seven but may range as low as four when Afro-Eurasia and the Americas are each considered a single continent. [252] In 2019, 39 million km2 (15 million sq mi) of Earth's land surface consisted of forest and woodlands, 12 million km2 (4.6 million sq mi) was shrub and grassland, 40 million km2 (15 million sq mi) were used for animal feed production and grazing, and 11 million km2 (4.2 million sq mi) were cultivated as croplands. In order from largest to smallest, they are Asia, Africa, North America, South America, Antarctica, Europe, and Australia. [254], Human cultures have developed many views of the planet. The field extends outwards from the core, through the mantle, and up to Earth's surface, where it is, approximately, a dipole. Humans increasingly impact Earth's surface, hydrology, atmospheric processes and other life. [150] This allows total and annular solar eclipses to occur on Earth. Earth has seven continents. [183][184] Most fresh water, about 68.7%, is present as ice in ice caps and glaciers. The Kármán line, defined as 100 km above Earth's surface, is a working definition for the boundary between the atmosphere and outer space. During the summer, the day lasts longer, and the Sun climbs higher in the sky. Ions and electrons of the solar wind are deflected by the magnetosphere; solar wind pressure compresses the dayside of the magnetosphere, to about 10 Earth radii, and extends the nightside magnetosphere into a long tail. [123], The continental crust consists of lower density material such as the igneous rocks granite and andesite. [130][131] Close to 40% of Earth's land surface is used for agriculture, or an estimated 16.7 million km2 (6.4 million sq mi) of cropland and 33.5 million km2 (12.9 million sq mi) of pastureland. ", "What's so special about our Moon, anyway? The most abundant silicate minerals on Earth's surface include quartz, feldspars, amphibole, mica, pyroxene and olivine. For instance, Antarctica is icy and has very little plant and animal life. "[27], Occasionally, the name Terra /ˈtɛrə/ is used in scientific writing and especially in science fiction to distinguish humanity's inhabited planet from others,[28] while in poetry Tellus /ˈtɛləs/ has been used to denote personification of the Earth. The oceans cover an area of 361.8 million km2 (139.7 million sq mi) with a mean depth of 3,682 m (12,080 ft), resulting in an estimated volume of 1.332 billion km3 (320 million cu mi). Earth is the densest planet in the Solar System and the largest and most massive of the four rocky planets. This causes a slow but steady loss of the atmosphere into space. At approximately 750 Ma, one of the earliest known supercontinents, Rodinia, began to break apart. – For millenniums, humans have tried to imagine the world in space. [37] The bodies in the Solar System formed and evolved 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 disk, and then the planets grow out of that disk with the Sun. [175][176] A trojan asteroid companion, 2010 TK7, is librating around the leading Lagrange triangular point, L4, in Earth's orbit around the Sun. [139][140] The ring current is defined by medium-energy particles that drift relative to the geomagnetic field, but with paths that are still dominated by the magnetic field,[141] and the Van Allen radiation belts are formed by high-energy particles whose motion is essentially random, but contained in the magnetosphere. [219] On land, biomes are separated primarily by differences in latitude, height above sea level and humidity. [83] Even if the Sun were stable, a fraction of the water in the modern oceans will descend to the mantle, due to reduced steam venting from mid-ocean ridges. These dates change over time due to precession and other orbital factors, which follow cyclical patterns known as Milankovitch cycles. Earth – Videos – International Space Station: This page was last edited on 12 March 2021, at 00:01. [126] Common carbonate minerals include calcite (found in limestone) and dolomite. [246] Those termed non-renewable resources, such as fossil fuels, only renew over geological timescales. A nebula contains gas, ice grains, and dust (including primordial nuclides). Over the next 1.1 billion years, solar luminosity will increase by 10%, and over the next 3.5 billion years by 40%. Earth is sometimes personified as a deity. [155] Above the Arctic Circle and below the Antarctic Circle there is no daylight at all for part of the year, causing a polar night, and this night extends for several months at the poles themselves. Initial belief in a flat Earth was gradually displaced in Ancient Greece by the idea of a spherical Earth, which was attributed to both the philosophers Pythagoras and Parmenides. [201], The amount of solar energy reaching Earth's surface decreases with increasing latitude. [76][77], Because carbon dioxide (CO2) has a long life time in the atmosphere, moderate human CO2 emissions may postpone the next glacial inception by 100,000 years. As with Roman Terra/TellÅ«s and Greek Gaia, Earth may have been a personified goddess in Germanic paganism: late Norse mythology included Jörð ('Earth'), a giantess often given as the mother of Thor. [196] This last phenomenon is known as the greenhouse effect: trace molecules within the atmosphere serve to capture thermal energy emitted from the ground, thereby raising the average temperature. Improved homework resources designed to support a variety of curriculum subjects and standards. At higher latitudes, the sunlight reaches the surface at lower angles, and it must pass through thicker columns of the atmosphere. The combination of these processes recycles the oceanic crust back into the mantle. [192], The atmospheric pressure at Earth's sea level averages 101.325 kPa (14.696 psi),[193] with a scale height of about 8.5 km (5.3 mi). [174], Earth's co-orbital asteroids population consists of quasi-satellites, objects with a horseshoe orbit and trojans. Another convention capitalizes "Earth" when appearing as a name (for example, "Earth's atmosphere") but writes it in lowercase when preceded by the (for example, "the atmosphere of the earth"). Sometimes people think of Europe and Asia as a single continent called Eurasia. As the plates slide over the melted rock, the continents also move. These nutrients are constantly recycled between different species. [193] Water vapor content varies between 0.01% and 4%[193] but averages about 1%. [243] The farthest that humans have traveled from Earth is 400,171 km (248,655 mi), achieved during the Apollo 13 mission in 1970. Africa, though, tends to be very warm and has a great variety of plants and animals. [168] Due to their tidal interaction, the Moon recedes from Earth at the rate of approximately 38 mm/a (1.5 in/year). In the Northern Hemisphere, winter solstice currently occurs around 21 December; summer solstice is near 21 June, spring equinox is around 20 March and autumnal equinox is about 22 or 23 September. A continent is a large solid area of land. [199], The primary atmospheric circulation bands consist of the trade winds in the equatorial region below 30° latitude and the westerlies in the mid-latitudes between 30° and 60°. [206] Finally, temperatures decrease with height causing mountainous areas to be colder than low-lying areas. The result is atmospheric circulation that drives the weather and climate through redistribution of thermal energy. [99][98], Earth's interior, like that of the other terrestrial planets, is divided into layers by their chemical or physical (rheological) properties. As of 4 January 2018, the United States Strategic Command tracked a total of 18,835 artificial objects, mostly debris. The crust is separated from the mantle by the Mohorovičić discontinuity. [200] The Köppen system rates regions based on observed temperature and precipitation. Fifty years ago, we finally saw it", "Apollo 8's Earthrise: The Shot Seen Round the World – Half a century ago today, a photograph from the moon helped humans rediscover Earth", "We Are All Riders on the Same Planet – Seen from space 50 years ago, Earth appeared as a gift to preserve and cherish. [248] These deposits are used by humans both for energy production and as feedstock for chemical production. At the same time, the upwelling of mantle material at divergent boundaries creates mid-ocean ridges. There is a small flattening at the poles and bulging around the equator due to Earth's rotation. [43], Earth's atmosphere and oceans were formed by volcanic activity and outgassing. [171] Some theorists think that without this stabilization against the torques applied by the Sun and planets to Earth's equatorial bulge, the rotational axis might be chaotically unstable, exhibiting large changes over millions of years, as is the case for Mars, though this is disputed. This accumulated snow and ice eventually forms into glaciers, bodies of ice that flow under the influence of their own gravity. [83][84], The Sun will evolve to become a red giant in about 5 billion years. [46] In this model, atmospheric greenhouse gases kept the oceans from freezing when the newly forming Sun had only 70% of its current luminosity. On a globe , continents are the easiest things to spot. [244], Earth has resources that have been exploited by humans. The oldest oceanic crust is located in the Western Pacific and is estimated to be 200 Ma old. [49], The seven major plates are the Pacific, North American, Eurasian, African, Antarctic, Indo-Australian, and South American. [196] Each layer has a different lapse rate, defining the rate of change in temperature with height. [n 3] Earth's largest artificial satellite is the International Space Station. They now believe that the continents sit on a number of large plates. Viewed from a vantage point above the north poles of both the Sun and Earth, Earth orbits in a counterclockwise direction about the Sun. Earth's axis of rotation is tilted with respect to its orbital plane, producing seasons on Earth. [57] High- and middle-latitude regions have since undergone repeated cycles of glaciation and thaw, repeating about every 21,000, 41,000 and 100,000 years. Model of a flat Earth, with the continents modeled in a disk-shape and Antarctica as an ice wall. Sometimes people think of Europe and Asia as a single continent called Eurasia. As a red giant, the Sun will lose roughly 30% of its mass, so, without tidal effects, Earth will move to an orbit 1.7 AU (250 million km; 160 million mi) from the Sun when the star reaches its maximum radius. 3.48 Billion-Year-Old Dresser Formation, Pilbara, Western Australia", "Hints of life on what was thought to be desolate early Earth", "Potentially biogenic carbon preserved in a 4.1 billion-year-old zircon", "Oldest fossils ever found show life on Earth began before 3.5 billion years ago", "SIMS analyses of the oldest known assemblage of microfossils document their taxon-correlated carbon isotope compositions", "Estimates of the magnitudes of major marine mass extinctions in earth history", "Freeze, Fry or Dry: How Long Has the Earth Got?

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