198-500: An aurora ( pl. aurorae or auroras ), also commonly known as the northern lights ( aurora borealis ) or southern lights ( aurora australis ), is a natural light display in Earth 's sky, predominantly seen in high-latitude regions (around the Arctic and Antarctic ). Auroras display dynamic patterns of brilliant lights that appear as curtains, rays, spirals, or dynamic flickers covering
396-533: A circumstellar disk , and then the planets grow out of that disk with the Sun. A nebula contains gas, ice grains, and dust (including primordial nuclides ). According to nebular theory , planetesimals formed by accretion , with the primordial Earth being estimated as likely taking anywhere from 70 to 100 million years to form. Estimates of the age of the Moon range from 4.5 Ga to significantly younger. A leading hypothesis
594-557: A longhouse in Stöðvarfjörður that may date to as early as 800. Swedish Viking explorer Garðar Svavarsson was the first to circumnavigate Iceland in 870 and establish that it was an island. He stayed during the winter and built a house in Húsavík . Garðar departed the following summer, but one of his men, Náttfari , decided to stay behind with two slaves. Náttfari settled in what is now known as Náttfaravík, and he and his slaves became
792-464: A shield volcano with a magma chamber underneath). Several classifications of the systems exist, for example there is one of 30 systems, and one of 34 systems, with the later currently being used in Iceland itself. The climate of Iceland's coast is subarctic . The warm North Atlantic Current ensures generally higher annual temperatures than in most places of similar latitude in the world. Regions in
990-528: A summit in Reykjavík in 1986 between United States President Ronald Reagan and Soviet Premier Mikhail Gorbachev , during which they took significant steps towards nuclear disarmament . A few years later, Iceland became the first country to recognise the independence of Estonia , Latvia , and Lithuania as they broke away from the USSR. Throughout the 1990s, the country expanded its international role and developed
1188-536: A volcanic plateau with sand and lava fields , mountains and glaciers , and many glacial rivers flow to the sea through the lowlands . Iceland is warmed by the Gulf Stream and has a temperate climate , despite a latitude just south of the Arctic Circle . Its latitude and marine influence keep summers chilly, and most of its islands have a polar climate . According to the ancient manuscript Landnámabók ,
1386-444: A 32 percent increase in Iceland's gross national income between 2002 and 2007. In 2003–2007, following the privatisation of the banking sector under the government of Davíð Oddsson , Iceland moved towards having an economy based on international investment banking and financial services. It was quickly becoming one of the most prosperous countries in the world, but was hit hard by a major financial crisis . The crisis resulted in
1584-492: A common barycenter every 27.32 days relative to the background stars. When combined with the Earth–Moon system's common orbit around the Sun, the period of the synodic month , from new moon to new moon, is 29.53 days. Viewed from the celestial north pole , the motion of Earth, the Moon, and their axial rotations are all counterclockwise . Viewed from a vantage point above the Sun and Earth's north poles, Earth orbits in
1782-634: A convicted child sex offender. Snap elections in October 2017 brought to power a new coalition consisting of the Independence Party, the Progressive Party, and the Left-Green Movement , headed by Katrín Jakobsdóttir . After the 2021 parliamentary election , the new government was, just like the previous government, a tri-party coalition of the Independence Party, the Progressive Party, and
1980-542: A counterclockwise direction about the Sun. The orbital and axial planes are not precisely aligned: Earth's axis is tilted some 23.44 degrees from the perpendicular to the Earth–Sun plane (the ecliptic ), and the Earth-Moon plane is tilted up to ±5.1 degrees against the Earth–Sun plane. Without this tilt, there would be an eclipse every two weeks, alternating between lunar eclipses and solar eclipses . The Hill sphere , or
2178-636: A defence agreement was signed with the United States. American troops returned to Iceland as the Iceland Defence Force and remained throughout the Cold War . The US withdrew the last of its forces on 30 September 2006. Iceland prospered during the Second World War. The immediate post-war period was followed by substantial economic growth , driven by the industrialisation of the fishing industry and
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#17328524927282376-460: A famine that killed nearly a quarter of the island's population. In addition, the eruption caused dust clouds and haze to appear over most of Europe and parts of Asia and Africa for several months afterwards, and affected climates in other areas. Iceland has many geysers , including Geysir , from which the English word is derived, and the famous Strokkur , which erupts every 8–10 minutes. After
2574-589: A foreign policy orientated towards humanitarian and peacekeeping causes. To that end, Iceland provided aid and expertise to various NATO-led interventions in Bosnia , Kosovo , and Iraq . Iceland joined the European Economic Area in 1994, after which the economy was greatly diversified and liberalised. International economic relations increased further after 2001 when Iceland's newly deregulated banks began to raise great amounts of external debt , contributing to
2772-420: A full rotation about its axis so that the Sun returns to the meridian . The orbital speed of Earth averages about 29.78 km/s (107,200 km/h; 66,600 mph), which is fast enough to travel a distance equal to Earth's diameter, about 12,742 km (7,918 mi), in seven minutes, and the distance from Earth to the Moon, 384,400 km (238,900 mi), in about 3.5 hours. The Moon and Earth orbit
2970-704: A fully sovereign and independent state in a personal union with Denmark. The Government of Iceland established an embassy in Copenhagen and requested that Denmark carry out on its behalf certain defence and foreign affairs matters, subject to consultation with the Althing. Danish embassies around the world displayed two coats of arms and two flags: those of the Kingdom of Denmark and those of the Kingdom of Iceland . Iceland's legal position became comparable to those of countries belonging to
3168-421: A globe-spanning mid-ocean ridge system. At Earth's polar regions , the ocean surface is covered by seasonally variable amounts of sea ice that often connects with polar land, permafrost and ice sheets , forming polar ice caps . Earth's land covers 29.2%, or 149 million km (58 million sq mi) of Earth's surface. The land surface includes many islands around the globe, but most of
3366-466: A low- silica lava associated with effusive volcanism as has occurred also in Hawaii . Iceland, however, has a variety of volcanic types (composite and fissure), many producing more evolved lavas such as rhyolite and andesite . Iceland has hundreds of volcanoes with about 30 active volcanic systems. Surtsey , one of the youngest islands in the world, is part of Iceland. Named after Surtr , it rose above
3564-432: A particle depends on the particle's pitch angle : the angle between its direction of motion and the local magnetic field. An aurora is created by processes that decrease the pitch angle of many individual electrons, freeing them from the magnetic trap and causing them to hit the atmosphere. In the case of diffuse auroras, the electron pitch angles are altered by their interaction with various plasma waves . Each interaction
3762-406: A phase of inactivity, Geysir started erupting again after a series of earthquakes in 2000 . Geysir has since grown quieter and does not erupt often. With the widespread availability of geothermal power and the harnessing of many rivers and waterfalls for hydroelectricity , most residents have access to inexpensive hot water, heating, and electricity. The island is composed primarily of basalt ,
3960-620: A popular holiday destination. In 2016, Prime Minister Sigmundur Davíð Gunnlaugsson resigned after being implicated in the Panama Papers scandal. Early elections in 2016 resulted in a right-wing coalition government of the Independence Party , the Reform Party and Bright Future . This government fell when Bright Future quit the coalition due to a scandal involving then-Prime Minister Bjarni Benediktsson 's father's letter of support for
4158-452: A region of greater field strength nearer to the atmosphere. Thus, it is possible for some particles to return, or mirror, if the angle becomes 90° before entering the atmosphere to collide with the denser molecules there. Other particles that do not mirror enter the atmosphere and contribute to the auroral display over a range of altitudes. Other types of auroras have been observed from space; for example, "poleward arcs" stretching sunward across
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#17328524927284356-429: A republic in 1944, ending the remaining formal ties to Denmark. Although the Althing was suspended from 1799 to 1845, Iceland nevertheless has a claim to sustaining one of the world's longest-running parliaments. Until the 20th century, Iceland relied largely on subsistence fishing and agriculture. Industrialization of the fisheries and Marshall Plan aid after World War II brought prosperity, and Iceland became one of
4554-479: A society where subsistence depended almost entirely on agriculture. The Black Death swept Iceland twice, first in 1402–1404 and again in 1494–1495. The former outbreak killed 50% to 60% of the population, and the latter 30% to 50%. Around the middle of the 16th century, as part of the Protestant Reformation , King Christian III of Denmark began to impose Lutheranism on all his subjects. Jón Arason ,
4752-509: A southward component of the IMF, which can then directly connect to the high latitude geomagnetic field lines. The flow pattern of magnetospheric plasma is mainly from the magnetotail toward Earth, around Earth and back into the solar wind through the magnetopause on the day-side. In addition to moving perpendicular to Earth's magnetic field, some magnetospheric plasma travels down along Earth's magnetic field lines, gains additional energy and loses it to
4950-415: A surfer catching an ocean wave. This constantly-changing wave electric field can accelerate electrons along the field line, causing some of them to hit the atmosphere. Electrons accelerated by this mechanism tend to have a broad energy spectrum, in contrast to the sharply-peaked energy spectrum typical of electrons accelerated by quasi-static electric fields. Earth Earth is the third planet from
5148-499: A velocity typically around 400 km/s, a density of around 5 ions/cm and a magnetic field intensity of around 2–5 nT (for comparison, Earth's surface field is typically 30,000–50,000 nT). During magnetic storms , in particular, flows can be several times faster; the interplanetary magnetic field (IMF) may also be much stronger. Joan Feynman deduced in the 1970s that the long-term averages of solar wind speed correlated with geomagnetic activity. Her work resulted from data collected by
5346-533: A year. These factors combined can lead to minor cyclical changes in the detailed way that the IMF links to the magnetosphere. In turn, this affects the average probability of opening a door through which energy from the solar wind can reach Earth's inner magnetosphere and thereby enhance auroras. Recent evidence in 2021 has shown that individual separate substorms may in fact be correlated networked communities. Just as there are many types of aurora, there are many different mechanisms that accelerate auroral particles into
5544-505: Is a sitka spruce planted in 1949 in Kirkjubæjarklaustur ; it was measured at 25.2 m (83 ft) in 2013. Algae such as Chondrus crispus , Phyllphora truncata and Phyllophora crispa and others have been recorded from Iceland. The only native land mammal when humans arrived was the Arctic fox , which came to the island at the end of the ice age, walking over the frozen sea. On rare occasions, bats have been carried to
5742-456: Is a chemically distinct silicate solid crust, which is underlain by a highly viscous solid mantle. The crust is separated from the mantle by the Mohorovičić discontinuity . The thickness of the crust varies from about 6 kilometres (3.7 mi) under the oceans to 30–50 km (19–31 mi) for the continents. The crust and the cold, rigid, top of the upper mantle are collectively known as
5940-496: Is also where most settlements are situated. The island's interior, the Highlands of Iceland , is a cold and uninhabitable combination of sand, mountains, and lava fields . The major towns are the capital city of Reykjavík , along with its outlying towns of Kópavogur , Hafnarfjörður , and Garðabær , nearby Reykjanesbær where the international airport is located, and the town of Akureyri in northern Iceland. The island of Grímsey on
6138-531: Is approximately 9.8 m/s (32 ft/s ). Local differences in topography, geology, and deeper tectonic structure cause local and broad regional differences in Earth's gravitational field, known as gravity anomalies . The main part of Earth's magnetic field is generated in the core, the site of a dynamo process that converts the kinetic energy of thermally and compositionally driven convection into electrical and magnetic field energy. The field extends outwards from
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6336-435: Is at least somewhat humid and covered by vegetation , while large sheets of ice at Earth's polar deserts retain more water than Earth's groundwater , lakes, rivers and atmospheric water combined. Earth's crust consists of slowly moving tectonic plates , which interact to produce mountain ranges, volcanoes , and earthquakes. Earth has a liquid outer core that generates a magnetosphere capable of deflecting most of
6534-399: Is called the "auroral oval". The oval is displaced by the solar wind, pushing it about 15° away from the geomagnetic pole (not the geographic pole) in the noon direction and 23° away in the midnight direction. The peak equatorward extent of the oval is displaced slightly from geographic midnight. It is centered about 3–5° nightward of the magnetic pole, so that auroral arcs reach furthest toward
6732-456: Is closer to continental Europe than to mainland North America, although it is closest to Greenland (290 kilometres; 155 nautical miles), an island of North America. Iceland is generally included in Europe for geographical, historical, political, cultural, linguistic and practical reasons. Geologically, the island includes parts of both continental plates. The closest bodies of land in Europe are
6930-517: Is contained in 3.45 billion-year-old Australian rocks showing fossils of microorganisms . During the Neoproterozoic , 1000 to 539 Ma , much of Earth might have been covered in ice. This hypothesis has been termed " Snowball Earth ", and it is of particular interest because it preceded the Cambrian explosion , when multicellular life forms significantly increased in complexity. Following
7128-443: Is essentially wave-particle scattering ; the electron energy after interacting with the wave is similar to its energy before interaction, but the direction of motion is altered. If the final direction of motion after scattering is close to the field line (specifically, if it falls within the loss cone ) then the electron will hit the atmosphere. Diffuse auroras are caused by the collective effect of many such scattered electrons hitting
7326-452: Is farthest out from its center of mass at its equatorial bulge, the summit of the volcano Chimborazo in Ecuador (6,384.4 km or 3,967.1 mi) is its farthest point out. Parallel to the rigid land topography the ocean exhibits a more dynamic topography . To measure the local variation of Earth's topography, geodesy employs an idealized Earth producing a geoid shape. Such a shape
7524-516: Is gained if the ocean is idealized, covering Earth completely and without any perturbations such as tides and winds. The result is a smooth but irregular geoid surface, providing a mean sea level (MSL) as a reference level for topographic measurements. Earth's surface is the boundary between the atmosphere, and the solid Earth and oceans. Defined in this way, it has an area of about 510 million km (197 million sq mi). Earth can be divided into two hemispheres : by latitude into
7722-442: Is generally accompanied by decreasing peak emission heights of about 8 km for blue and green emissions and above average solar wind speeds ( c. 500 km/s ). In addition, the aurora and associated currents produce a strong radio emission around 150 kHz known as auroral kilometric radiation (AKR), discovered in 1972. Ionospheric absorption makes AKR only observable from space. X-ray emissions, originating from
7920-520: Is induced within the conductor. The strength of the current depends on a) the rate of relative motion, b) the strength of the magnetic field, c) the number of conductors ganged together and d) the distance between the conductor and the magnetic field, while the direction of flow is dependent upon the direction of relative motion. Dynamos make use of this basic process ("the dynamo effect "), any and all conductors, solid or otherwise are so affected, including plasmas and other fluids. The IMF originates on
8118-484: Is more effectively transferred by the temporary magnetic connection between the field lines of the solar wind and those of the magnetosphere. Unsurprisingly this process is known as magnetic reconnection . As already mentioned, it happens most readily when the interplanetary field is directed southward, in a similar direction to the geomagnetic field in the inner regions of both the north magnetic pole and south magnetic pole . Auroras are more frequent and brighter during
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8316-501: Is now slightly longer than it was during the 19th century due to tidal deceleration , each day varies between 0 and 2 ms longer than the mean solar day. Earth's rotation period relative to the fixed stars , called its stellar day by the International Earth Rotation and Reference Systems Service (IERS), is 86,164.0989 seconds of mean solar time ( UT1 ), or 23 56 4.0989 . Earth's rotation period relative to
8514-612: Is rare, though the alternative spelling Gaia has become common due to the Gaia hypothesis , in which case its pronunciation is / ˈ ɡ aɪ . ə / rather than the more classical English / ˈ ɡ eɪ . ə / . There are a number of adjectives for the planet Earth. The word "earthly" is derived from "Earth". From the Latin Terra comes terran / ˈ t ɛr ə n / , terrestrial / t ə ˈ r ɛ s t r i ə l / , and (via French) terrene / t ə ˈ r iː n / , and from
8712-406: Is regularly derived from ground data and serves as a general measure of auroral activity. Kristian Birkeland deduced that the currents flowed in the east–west directions along the auroral arc, and such currents, flowing from the dayside toward (approximately) midnight were later named "auroral electrojets" (see also Birkeland currents ). Ionosphere can contribute to the formation of auroral arcs via
8910-477: Is that it was formed by accretion from material loosed from Earth after a Mars -sized object with about 10% of Earth's mass, named Theia , collided with Earth. It hit Earth with a glancing blow and some of its mass merged with Earth. Between approximately 4.1 and 3.8 Ga , numerous asteroid impacts during the Late Heavy Bombardment caused significant changes to the greater surface environment of
9108-453: Is the basis for the astronomical unit (AU) and is equal to roughly 8.3 light minutes or 380 times Earth's distance to the Moon . Earth orbits the Sun every 365.2564 mean solar days , or one sidereal year . With an apparent movement of the Sun in Earth's sky at a rate of about 1°/day eastward, which is one apparent Sun or Moon diameter every 12 hours. Due to this motion, on average it takes 24 hours—a solar day—for Earth to complete
9306-462: Is the region's westernmost and most sparsely populated country . Its capital and largest city is Reykjavík , which is home to about 36% of the country's roughly 380,000 residents (excluding nearby towns/suburbs which are separate municipalities). The official language of the country is Icelandic . Iceland is on a rift between tectonic plates , and its geologic activity includes geysers and frequent volcanic eruptions . The interior consists of
9504-573: Is the surface expression of the Iceland Plateau , a large igneous province forming as a result of volcanism from the Iceland hotspot and along the Mid-Atlantic Ridge , the latter of which runs right through it. This means that the island is highly geologically active with many volcanoes including Hekla , Eldgjá , Herðubreið , and Eldfell . The volcanic eruption of Laki in 1783–1784 caused
9702-457: Is tied to that of the Sun. Over the next 1.1 billion years , solar luminosity will increase by 10%, and over the next 3.5 billion years by 40%. Earth's increasing surface temperature will accelerate the inorganic carbon cycle , possibly reducing CO 2 concentration to levels lethally low for current plants ( 10 ppm for C4 photosynthesis ) in approximately 100–900 million years . A lack of vegetation would result in
9900-610: Is visible from areas around the Arctic such as Alaska , Canada , Iceland , Greenland , the Faroe Islands , Scandinavia , Finland , Scotland , and Russia . A geomagnetic storm causes the auroral ovals (north and south) to expand, bringing the aurora to lower latitudes. On rare occasions, the aurora borealis can be seen as far south as the Mediterranean and the southern states of the US while
10098-522: Is why there is a color differential with altitude; at high altitudes oxygen red dominates, then oxygen green and nitrogen blue/purple/red, then finally nitrogen blue/purple/red when collisions prevent oxygen from emitting anything. Green is the most common colour. Then comes pink, a mixture of light green and red, followed by pure red, then yellow (a mixture of red and green), and finally, pure blue. Precipitating protons generally produce optical emissions as incident hydrogen atoms after gaining electrons from
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#173285249272810296-521: The Althing , one of the world's oldest functioning legislative assemblies. After a period of civil strife , Iceland acceded to Norwegian rule in the 13th century. In 1397, Iceland followed Norway's integration into the Kalmar Union along with the kingdoms of Denmark and Sweden, coming under de facto Danish rule upon its dissolution in 1523. The Danish kingdom introduced Lutheranism by force in 1550, and
10494-456: The Boreal Kingdom . Plantlife consists mainly of grassland, which is regularly grazed by livestock. The most common tree native to Iceland is the northern birch ( Betula pubescens ), which formerly formed forests over much of Iceland, along with aspens ( Populus tremula ), rowans ( Sorbus aucuparia ), common junipers ( Juniperus communis ), and other smaller trees, mainly willows. When
10692-476: The Explorer 33 spacecraft. The solar wind and magnetosphere consist of plasma (ionized gas), which conducts electricity. It is well known (since Michael Faraday 's work around 1830) that when an electrical conductor is placed within a magnetic field while relative motion occurs in a direction that the conductor cuts across (or is cut by ), rather than along , the lines of the magnetic field, an electric current
10890-528: The Faroe Islands (420 km; 225 nmi); Jan Mayen Island (570 km; 310 nmi); Shetland and the Outer Hebrides , both about 740 km (400 nmi); and the Scottish mainland and Orkney , both about 750 km (405 nmi). The nearest part of Continental Europe is mainland Norway, about 970 km (525 nmi) away, while mainland North America is 2,070 km (1,120 nmi) away, at
11088-582: The Little Ice Age , and overgrazing by sheep imported by settlers caused a loss of critical topsoil due to erosion . Today, many farms have been abandoned. Three-quarters of Iceland's 100,000 square kilometres (39,000 sq mi) is affected by soil erosion; 18,000 km (6,900 sq mi) is affected to a degree serious enough to make the land useless. Only a few small birch stands now exist in isolated reserves. The Icelandic Forest Service and other forestry groups promote large-scale reforestation in
11286-524: The Mid-Atlantic Ridge , a ridge along which the oceanic crust spreads and forms new crust. This part of the mid-ocean ridge is located above a mantle plume, causing Iceland to be subaerial (above the surface of the sea). The ridge marks the boundary between the Eurasian and North American Plates , and Iceland was created by rifting and accretion through volcanism along the ridge. Many fjords punctuate Iceland's 4,970-km-long (3,088-mi) coastline, which
11484-566: The Milky Way and orbits about 28,000 light-years from its center. It is about 20 light-years above the galactic plane in the Orion Arm . The axial tilt of Earth is approximately 23.439281° with the axis of its orbit plane, always pointing towards the Celestial Poles . Due to Earth's axial tilt, the amount of sunlight reaching any given point on the surface varies over the course of
11682-722: The Pacific , North American , Eurasian , African , Antarctic , Indo-Australian , and South American . Other notable plates include the Arabian Plate , the Caribbean Plate , the Nazca Plate off the west coast of South America and the Scotia Plate in the southern Atlantic Ocean. The Australian Plate fused with the Indian Plate between 50 and 55 Ma . The fastest-moving plates are
11880-553: The Sun and the only astronomical object known to harbor life . This is enabled by Earth being an ocean world , the only one in the Solar System sustaining liquid surface water . Almost all of Earth's water is contained in its global ocean, covering 70.8% of Earth's crust . The remaining 29.2% of Earth's crust is land, most of which is located in the form of continental landmasses within Earth's land hemisphere . Most of Earth's land
12078-686: The Treaty of Kiel formally ceded Iceland to Denmark in 1814. Influenced by ideals of nationalism after the French Revolution , Iceland's struggle for independence took form and culminated in the Danish–Icelandic Act of Union in 1918, with the establishment of the Kingdom of Iceland , sharing through a personal union the incumbent monarch of Denmark . During the occupation of Denmark in World War II, Iceland voted overwhelmingly to become
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#173285249272812276-456: The Vestmannaeyjar archipelago. Lakes and glaciers cover 14.3% of its surface; only 23% is vegetated. The largest lakes are Þórisvatn reservoir: 83–88 km (32–34 sq mi) and Þingvallavatn : 82 km (32 sq mi); other important lakes include Lagarfljót and Mývatn . Jökulsárlón is the deepest lake, at 248 m (814 ft). Geologically, Iceland is part of
12474-419: The asthenosphere , the solid but less-viscous part of the upper mantle that can flow and move along with the plates. As the tectonic plates migrate, oceanic crust is subducted under the leading edges of the plates at convergent boundaries. At the same time, the upwelling of mantle material at divergent boundaries creates mid-ocean ridges. The combination of these processes recycles the oceanic crust back into
12672-415: The celestial equator , this is equivalent to an apparent diameter of the Sun or the Moon every two minutes; from Earth's surface, the apparent sizes of the Sun and the Moon are approximately the same. Earth orbits the Sun, making Earth the third-closest planet to the Sun and part of the inner Solar System . Earth's average orbital distance is about 150 million km (93 million mi), which
12870-410: The equatorial region receiving more sunlight than the polar regions) drive atmospheric and ocean currents , producing a global climate system with different climate regions , and a range of weather phenomena such as precipitation , allowing components such as nitrogen to cycle . Earth is rounded into an ellipsoid with a circumference of about 40,000 km. It is the densest planet in
13068-417: The feedback instability under high ionospheric resistance conditions, observed at night time and in dark Winter hemisphere. Earth is constantly immersed in the solar wind , a flow of magnetized hot plasma (a gas of free electrons and positive ions) emitted by the Sun in all directions, a result of the two-million-degree temperature of the Sun's outermost layer, the corona . The solar wind reaches Earth with
13266-410: The mesosphere in presence of electron precipitation . Horse-collar auroras (HCA) are auroral features in which the auroral ellipse shifts poleward during the dawn and dusk portions and the polar cap becomes teardrop-shaped. They form during periods when the interplanetary magnetic field (IMF) is permanently northward, when the IMF clock angle is small. Their formation is associated with the closure of
13464-408: The ocean floor form the top of Earth's crust , which together with parts of the upper mantle form Earth's lithosphere . Earth's crust may be divided into oceanic and continental crust. Beneath the ocean-floor sediments, the oceanic crust is predominantly basaltic , while the continental crust may include lower density materials such as granite , sediments and metamorphic rocks. Nearly 75% of
13662-430: The precessing or moving mean March equinox (when the Sun is at 90° on the equator), is 86,164.0905 seconds of mean solar time (UT1) (23 56 4.0905 ) . Thus the sidereal day is shorter than the stellar day by about 8.4 ms. Apart from meteors within the atmosphere and low-orbiting satellites, the main apparent motion of celestial bodies in Earth's sky is to the west at a rate of 15°/h = 15'/min. For bodies near
13860-521: The settlement of Iceland began in 874 AD, when the Norwegian chieftain Ingólfr Arnarson became the island's first permanent settler. In the following centuries, Norwegians , and to a lesser extent other Scandinavians , immigrated to Iceland, bringing with them thralls (i.e., slaves or serfs) of Gaelic origin. The island was governed as an independent commonwealth under the native parliament,
14058-468: The sphere of gravitational influence , of Earth is about 1.5 million km (930,000 mi) in radius. This is the maximum distance at which Earth's gravitational influence is stronger than that of the more distant Sun and planets. Objects must orbit Earth within this radius, or they can become unbound by the gravitational perturbation of the Sun. Earth, along with the Solar System, is situated in
14256-464: The "last ice age", covered large parts of the continents, to the middle latitudes, in ice and ended about 11,700 years ago. Chemical reactions led to the first self-replicating molecules about four billion years ago. A half billion years later, the last common ancestor of all current life arose. The evolution of photosynthesis allowed the Sun's energy to be harvested directly by life forms. The resultant molecular oxygen ( O 2 ) accumulated in
14454-609: The 1850s under the leadership of Jón Sigurðsson , based on the burgeoning Icelandic nationalism inspired by the Fjölnismenn and other Danish-educated Icelandic intellectuals. In 1874, Denmark granted Iceland a constitution and limited home rule. This was expanded in 1904, and Hannes Hafstein served as the first Minister for Iceland in the Danish cabinet. The Danish–Icelandic Act of Union , an agreement with Denmark signed on 1 December 1918 and valid for 25 years, recognised Iceland as
14652-408: The 1960s by many research teams using rockets and satellites to traverse the auroral zone. The main findings have been that auroral arcs and other bright forms are due to electrons that have been accelerated during the final few 10,000 km or so of their plunge into the atmosphere. These electrons often, but not always, exhibit a peak in their energy distribution, and are preferentially aligned along
14850-607: The Arctic Circle contains the northernmost habitation of Iceland, whereas Kolbeinsey contains the northernmost point of Iceland. Iceland has three national parks : Vatnajökull National Park , Snæfellsjökull National Park , and Þingvellir National Park . The country is considered a "strong performer" in environmental protection, having been ranked 13th in Yale University 's Environmental Performance Index of 2012. A geologically young land at 16 to 18 million years old, Iceland
15048-479: The Cambrian explosion, 535 Ma , there have been at least five major mass extinctions and many minor ones. Apart from the proposed current Holocene extinction event, the most recent was 66 Ma , when an asteroid impact triggered the extinction of non-avian dinosaurs and other large reptiles, but largely spared small animals such as insects, mammals , lizards and birds. Mammalian life has diversified over
15246-625: The Commonwealth of Nations, such as Canada, whose sovereign is King Charles III . During World War II, Iceland joined Denmark in asserting neutrality. After the German occupation of Denmark on 9 April 1940, the Althing replaced the King with a regent and declared that the Icelandic government would take control of its own defence and foreign affairs. A month later, British armed forces conducted Operation Fork ,
15444-637: The Earth. Terra is also the name of the planet in some Romance languages , languages that evolved from Latin , like Italian and Portuguese , while in other Romance languages the word gave rise to names with slightly altered spellings, like the Spanish Tierra and the French Terre . The Latinate form Gæa or Gaea ( English: / ˈ dʒ iː . ə / ) of the Greek poetic name Gaia ( Γαῖα ; Ancient Greek : [ɡâi̯.a] or [ɡâj.ja] )
15642-527: The Latin Tellus comes tellurian / t ɛ ˈ l ʊər i ə n / and telluric . The oldest material found in the Solar System is dated to 4.5682 +0.0002 −0.0004 Ga (billion years) ago. By 4.54 ± 0.04 Ga the primordial Earth had formed. 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
15840-677: The Left-Green Movement, headed by Prime Minister Katrín Jakobsdóttir. In April 2024, Bjarni Benediktsson of the Independence party succeeded Katrín Jakobsdóttir as prime minister. Iceland is at the juncture of the North Atlantic and Arctic Oceans. The main island is entirely south of the Arctic Circle , which passes through the small Icelandic island of Grímsey off the main island's northern coast. The country lies between latitudes 63 and 68°N , and longitudes 25 and 13°W . Iceland
16038-426: The Moon and, by inference, to that of Earth. Earth's atmosphere and oceans were formed by volcanic activity and outgassing . Water vapor from these sources condensed into the oceans, augmented by water and ice from asteroids, protoplanets , and comets . Sufficient water to fill the oceans may have been on Earth since it formed. In this model, atmospheric greenhouse gases kept the oceans from freezing when
16236-416: The Solar System . Of the four rocky planets , it is the largest and most massive. Earth is about eight light-minutes away from the Sun and orbits it , taking a year (about 365.25 days) to complete one revolution. Earth rotates around its own axis in slightly less than a day (in about 23 hours and 56 minutes). Earth's axis of rotation is tilted with respect to the perpendicular to its orbital plane around
16434-458: The Solar System's planetary-sized objects, Earth is the object with the highest density . Earth's mass is approximately 5.97 × 10 kg ( 5.970 Yg ). It is composed mostly of iron (32.1% by mass ), oxygen (30.1%), silicon (15.1%), magnesium (13.9%), sulfur (2.9%), nickel (1.8%), calcium (1.5%), and aluminium (1.4%), with the remaining 1.2% consisting of trace amounts of other elements. Due to gravitational separation ,
16632-663: The Solar System, formed 4.5 billion years ago from gas and dust in the early Solar System . During the first billion years of Earth's history , the ocean formed and then life developed within it. Life spread globally and has been altering Earth's atmosphere and surface, leading to the Great Oxidation Event two billion years ago. Humans emerged 300,000 years ago in Africa and have spread across every continent on Earth. Humans depend on Earth's biosphere and natural resources for their survival, but have increasingly impacted
16830-405: The Sun were rising from an unusual direction. Auroras also occur poleward of the auroral zone as either diffuse patches or arcs, which can be subvisual. Auroras are occasionally seen in latitudes below the auroral zone, when a geomagnetic storm temporarily enlarges the auroral oval. Large geomagnetic storms are most common during the peak of the 11-year sunspot cycle or during the three years after
17028-403: The Sun when the star reaches its maximum radius, otherwise, with tidal effects, it may enter the Sun's atmosphere and be vaporized. Earth has a rounded shape , through hydrostatic equilibrium , with an average diameter of 12,742 kilometres (7,918 mi), making it the fifth largest planetary sized and largest terrestrial object of the Solar System . Due to Earth's rotation it has
17226-515: The Sun, linked to the sunspots , and its field lines (lines of force) are dragged out by the solar wind. That alone would tend to line them up in the Sun-Earth direction, but the rotation of the Sun angles them at Earth by about 45 degrees forming a spiral in the ecliptic plane, known as the Parker spiral . The field lines passing Earth are therefore usually linked to those near the western edge ("limb") of
17424-461: The Sun, producing seasons . Earth is orbited by one permanent natural satellite , the Moon , which orbits Earth at 384,400 km (1.28 light seconds) and is roughly a quarter as wide as Earth. The Moon's gravity helps stabilize Earth's axis, causes tides and gradually slows Earth's rotation . Tidal locking has made the Moon always face Earth with the same side. Earth, like most other bodies in
17622-680: The US Marshall Plan programme, through which Icelanders received the most aid per capita of any European country (at US$ 209, with the war-ravaged Netherlands a distant second at US$ 109). Vigdís Finnbogadóttir assumed Iceland's presidency on 1 August 1980, making her the first elected female head of state in the world. The 1970s were marked by the Cod Wars —several disputes with the United Kingdom over Iceland's extension of its fishing limits to 200 nmi (370 km) offshore. Iceland hosted
17820-425: The atmosphere and due to interaction with ultraviolet solar radiation, formed a protective ozone layer ( O 3 ) in the upper atmosphere. The incorporation of smaller cells within larger ones resulted in the development of complex cells called eukaryotes . True multicellular organisms formed as cells within colonies became increasingly specialized. Aided by the absorption of harmful ultraviolet radiation by
18018-422: The atmosphere in the auroral zones. The cusps of the magnetosphere, separating geomagnetic field lines that close through Earth from those that close remotely allow a small amount of solar wind to directly reach the top of the atmosphere, producing an auroral glow. On 26 February 2008, THEMIS probes were able to determine, for the first time, the triggering event for the onset of magnetospheric substorms . Two of
18216-426: The atmosphere, particularly carbon dioxide (CO 2 ), creates the conditions for both liquid surface water and water vapor to persist via the capturing of energy from the Sun's light . This process maintains the current average surface temperature of 14.76 °C (58.57 °F), at which water is liquid under normal atmospheric pressure. Differences in the amount of captured energy between geographic regions (as with
18414-456: The atmosphere. Electron aurora in Earth's auroral zone (i.e. commonly visible aurora) can be split into two main categories with different immediate causes: diffuse and discrete aurora. Diffuse aurora appear relatively structureless to an observer on the ground, with indistinct edges and amorphous forms. Discrete aurora are structured into distinct features with well-defined edges such as arcs, rays and coronas; they also tend to be much brighter than
18612-444: The atmosphere. Proton auroras are usually observed at lower latitudes. Bright auroras are generally associated with Birkeland currents (Schield et al., 1969; Zmuda and Armstrong, 1973), which flow down into the ionosphere on one side of the pole and out on the other. In between, some of the current connects directly through the ionospheric E layer (125 km); the rest ("region 2") detours, leaving again through field lines closer to
18810-439: The atmosphere. The process is mediated by the plasma waves, which become stronger during periods of high geomagnetic activity , leading to increased diffuse aurora at those times. In the case of discrete auroras, the trapped electrons are accelerated toward Earth by electric fields that form at an altitude of about 4000–12000 km in the "auroral acceleration region". The electric fields point away from Earth (i.e. upward) along
19008-569: The aurora australis can be seen as far north as New Caledonia and the Pilbara region in Western Australia . During the Carrington Event , the greatest geomagnetic storm ever observed, auroras were seen even in the tropics. Auroras seen within the auroral oval may be directly overhead. From farther away, they illuminate the poleward horizon as a greenish glow, or sometimes a faint red, as if
19206-515: The auroral oval to active displays along the darkside and after 1–3 hours they gradually change back. Changes in auroras over time are commonly visualized using keograms . At shorter time scales, auroras can change their appearances and intensity, sometimes so slowly as to be difficult to notice, and at other times rapidly down to the sub-second scale. The phenomenon of pulsating auroras is an example of intensity variations over short timescales, typically with periods of 2–20 seconds. This type of aurora
19404-411: The background magnetic field (comparable to the electron inertial length or ion gyroradius ), Alfvén waves develop a significant electric field parallel to the background magnetic field. This electric field can accelerate electrons to keV energies, significant to produce auroral arcs. If the electrons have a speed close to that of the wave's phase velocity, they are accelerated in a manner analogous to
19602-450: The center, the temperature may be up to 6,000 °C (10,830 °F), and the pressure could reach 360 GPa (52 million psi ). Because much of the heat is provided by radioactive decay, scientists postulate that early in Earth's history, before isotopes with short half-lives were depleted, Earth's heat production was much higher. At approximately 3 Gyr , twice the present-day heat would have been produced, increasing
19800-465: The collision of particles precipitated into the atmosphere. Both incoming electrons and protons may be involved. Excitation energy is lost within the atmosphere by the emission of a photon, or by collision with another atom or molecule: Oxygen is unusual in terms of its return to ground state: it can take 0.7 seconds to emit the 557.7 nm green light and up to two minutes for the red 630.0 nm emission. Collisions with other atoms or molecules absorb
19998-454: The continental crust , particularly during the early stages of Earth's history. New continental crust forms as a result of plate tectonics , a process ultimately driven by the continuous loss of heat from Earth's interior. Over the period of hundreds of millions of years, tectonic forces have caused areas of continental crust to group together to form supercontinents that have subsequently broken apart. At approximately 750 Ma , one of
20196-616: The continental surfaces are covered by sedimentary rocks, although they form about 5% of the mass of the crust. Earth's surface topography comprises both the topography of the ocean surface , and the shape of Earth's land surface. The submarine terrain of the ocean floor has an average bathymetric depth of 4 km, and is as varied as the terrain above sea level. Earth's surface is continually being shaped by internal plate tectonic processes including earthquakes and volcanism ; by weathering and erosion driven by ice, water, wind and temperature; and by biological processes including
20394-419: The core are chaotic; the magnetic poles drift and periodically change alignment. This causes secular variation of the main field and field reversals at irregular intervals averaging a few times every million years. The most recent reversal occurred approximately 700,000 years ago. The extent of Earth's magnetic field in space defines the magnetosphere . Ions and electrons of the solar wind are deflected by
20592-527: The core is primarily composed of the denser elements: iron (88.8%), with smaller amounts of nickel (5.8%), sulfur (4.5%), and less than 1% trace elements. The most common rock constituents of the crust are oxides . Over 99% of the crust is composed of various oxides of eleven elements, principally oxides containing silicon (the silicate minerals ), aluminium, iron, calcium, magnesium, potassium, or sodium. The major heat-producing isotopes within Earth are potassium-40 , uranium-238 , and thorium-232 . At
20790-463: The core, through the mantle, and up to Earth's surface, where it is, approximately, a dipole . The poles of the dipole are located close to Earth's geographic poles. At the equator of the magnetic field, the magnetic-field strength at the surface is 3.05 × 10 T , with a magnetic dipole moment of 7.79 × 10 Am at epoch 2000, decreasing nearly 6% per century (although it still remains stronger than its long time average). The convection movements in
20988-566: The country's climate continued to grow colder, resulting in mass emigration to the New World , particularly to the region of Gimli , Manitoba in Canada, which was sometimes referred to as New Iceland . About 15,000 people emigrated, out of a total population of 70,000. A national consciousness arose in the first half of the 19th century, inspired by romantic and nationalist ideas from mainland Europe. An Icelandic independence movement took shape in
21186-416: The country's total exports. Birds, especially seabirds, are an important part of Iceland's animal life. Atlantic puffins , skuas , and black-legged kittiwakes nest on its sea cliffs. Commercial whaling is practised intermittently along with scientific whale hunts. Whale watching has become an important part of Iceland's economy since 1997. Around 1,300 species of insects are known in Iceland. This
21384-417: The country. Due to the reforestation efforts, the forest cover of Iceland increased six-fold since the 1990s. This helps to offset carbon emissions, prevent sand storms and increase the productivity of farms. The planting of new forests has increased the number of trees, but the result does not compare to the original forests. Some of the planted forests include introduced species . The tallest tree in Iceland
21582-468: The currents are the direct result of electron acceleration into the atmosphere by wave/particle interactions. Ionospheric resistance has a complex nature, and leads to a secondary Hall current flow. By a strange twist of physics, the magnetic disturbance on the ground due to the main current almost cancels out, so most of the observed effect of auroras is due to a secondary current, the auroral electrojet . An auroral electrojet index (measured in nanotesla)
21780-469: The days shorter. 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. These same latitudes also experience a midnight sun , where the sun remains visible all day. By astronomical convention, the four seasons can be determined by the solstices—the points in
21978-441: The destructive solar winds and cosmic radiation . Earth has a dynamic atmosphere , which sustains Earth's surface conditions and protects it from most meteoroids and UV-light at entry . It has a composition of primarily nitrogen and oxygen . Water vapor is widely present in the atmosphere, forming clouds that cover most of the planet. The water vapor acts as a greenhouse gas and, together with other greenhouse gases in
22176-416: The diffuse aurora. In both cases, the electrons that eventually cause the aurora start out as electrons trapped by the magnetic field in Earth's magnetosphere . These trapped particles bounce back and forth along magnetic field lines and are prevented from hitting the atmosphere by the magnetic mirror formed by the increasing magnetic field strength closer to Earth. The magnetic mirror's ability to trap
22374-402: The dune aurora phenomenon was discovered by Finnish citizen scientists . It consists of regularly-spaced, parallel stripes of brighter emission in the green diffuse aurora which give the impression of sand dunes. The phenomenon is believed to be caused by the modulation of atomic oxygen density by a large-scale atmospheric wave travelling horizontally in a waveguide through an inversion layer in
22572-605: The earliest known supercontinents, Rodinia , began to break apart. The continents later recombined to form Pannotia at 600–540 Ma , then finally Pangaea , which also began to break apart at 180 Ma . The most recent pattern of ice ages began about 40 Ma , and then intensified during the Pleistocene about 3 Ma . 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. The Last Glacial Period , colloquially called
22770-579: The effect is known as the aurora borealis or the northern lights. The southern counterpart, the aurora australis or the southern lights, has features almost identical to the aurora borealis and changes simultaneously with changes in the northern auroral zone. The aurora australis is visible from high southern latitudes in Antarctica , the Southern Cone , South Africa , Australasia and under exceptional circumstances as far north as Uruguay . The aurora borealis
22968-458: The electric field increases the kinetic energy of all of the electrons transiting downward through the acceleration region by the same amount. This accelerates electrons starting from the magnetosphere with initially low energies (tens of eV or less) to energies required to create an aurora (100s of eV or greater), allowing that large source of particles to contribute to creating auroral light. The accelerated electrons carry an electric current along
23166-408: The entire sky. Auroras are the result of disturbances in the Earth's magnetosphere caused by the solar wind . Major disturbances result from enhancements in the speed of the solar wind from coronal holes and coronal mass ejections . These disturbances alter the trajectories of charged particles in the magnetospheric plasma . These particles, mainly electrons and protons , precipitate into
23364-544: The equally large area of land under permafrost ) or deserts (33%). The pedosphere is the outermost layer of Earth's land surface and is composed of soil and subject to soil formation processes. Soil is crucial for land to be arable. Earth's total arable land is 10.7% of the land surface, with 1.3% being permanent cropland. Earth has an estimated 16.7 million km (6.4 million sq mi) of cropland and 33.5 million km (12.9 million sq mi) of pastureland. The land surface and
23562-454: The equator and closing through the "partial ring current" carried by magnetically trapped plasma. The ionosphere is an ohmic conductor , so some consider that such currents require a driving voltage, which an, as yet unspecified, dynamo mechanism can supply. Electric field probes in orbit above the polar cap suggest voltages of the order of 40,000 volts, rising up to more than 200,000 volts during intense magnetic storms. In another interpretation,
23760-413: The equator when the magnetic pole in question is in between the observer and the Sun , which is called magnetic midnight . Early evidence for a geomagnetic connection comes from the statistics of auroral observations. Elias Loomis (1860), and later Hermann Fritz (1881) and Sophus Tromholt (1881) in more detail, established that the aurora appeared mainly in the auroral zone. In northern latitudes ,
23958-513: The eruption, known as the Mist Hardships ( Icelandic : Móðuharðindin ), over half of all livestock in the country died. Around a quarter of the population starved to death in the ensuing famine . In 1814, following the Napoleonic Wars , Denmark-Norway was broken up into two separate kingdoms via the Treaty of Kiel , but Iceland remained a Danish dependency. Throughout the 19th century,
24156-570: The events known locally as the Turkish Abductions , in which hundreds of residents were taken into slavery in North Africa and dozens killed; this was the only invasion in Icelandic history to have casualties. The 1707–08 Iceland smallpox epidemic is estimated to have killed a quarter to a third of the population. In 1783 the Laki volcano erupted, with devastating effects. In the years following
24354-490: The excitation energy and prevent emission; this process is called collisional quenching . Because the highest parts of the atmosphere contain a higher percentage of oxygen and lower particle densities, such collisions are rare enough to allow time for oxygen to emit red light. Collisions become more frequent progressing down into the atmosphere due to increasing density, so that red emissions do not have time to happen, and eventually, even green light emissions are prevented. This
24552-415: The first permanent residents of Iceland to be documented. The Norwegian-Norse chieftain Ingólfr Arnarson built his homestead in present-day Reykjavík in 874. Ingólfr was followed by many other emigrant settlers, largely Scandinavians and their thralls , many of whom were Irish or Scottish . By 930, most arable land on the island had been claimed; the Althing , a legislative and judicial assembly
24750-413: The five probes, positioned approximately one third the distance to the Moon, measured events suggesting a magnetic reconnection event 96 seconds prior to auroral intensification. Geomagnetic storms that ignite auroras may occur more often during the months around the equinoxes . It is not well understood, but geomagnetic storms may vary with Earth's seasons. Two factors to consider are the tilt of both
24948-463: The greatest migration from Iceland since 1887, with a net emigration of 5,000 people in 2009. Iceland's economy stabilised under the government of Jóhanna Sigurðardóttir and grew by 1.6% in 2012. The centre-right Independence Party was returned to power in coalition with the Progressive Party in the 2013 election. In the following years, Iceland saw a surge in tourism as the country became
25146-432: The ground, while extending at times to more than 1,000 km (620 mi). According to Clark (2007), there are five main forms that can be seen from the ground, from least to most visible: Brekke (1994) also described some auroras as "curtains". The similarity to curtains is often enhanced by folds within the arcs. Arcs can fragment or break up into separate, at times rapidly changing, often rayed features that may fill
25344-638: The growth and decomposition of biomass into soil . Earth's mechanically rigid outer layer of Earth's crust and upper mantle , the lithosphere , is divided into tectonic plates . These plates are rigid segments that move relative to each other at one of three boundaries types: at convergent boundaries , two plates come together; at divergent boundaries , two plates are pulled apart; and at transform boundaries , two plates slide past one another laterally. Along these plate boundaries, earthquakes, volcanic activity , mountain-building , and oceanic trench formation can occur. The tectonic plates ride on top of
25542-404: The heat in Earth is lost through plate tectonics, by mantle upwelling associated with mid-ocean ridges . The final major mode of heat loss is through conduction through the lithosphere, the majority of which occurs under the oceans. The gravity of Earth is the acceleration that is imparted to objects due to the distribution of mass within Earth. Near Earth's surface, gravitational acceleration
25740-428: The intense phase of the solar cycle when coronal mass ejections increase the intensity of the solar wind. Earth's magnetosphere is shaped by the impact of the solar wind on Earth's magnetic field. This forms an obstacle to the flow, diverting it, at an average distance of about 70,000 km (11 Earth radii or Re), producing a bow shock 12,000 km to 15,000 km (1.9 to 2.4 Re) further upstream. The width of
25938-401: The interaction of the solar wind with Earth's magnetosphere . The varying intensity of the solar wind produces effects of different magnitudes but includes one or more of the following physical scenarios. The details of these phenomena are not fully understood. However, it is clear that the prime source of auroral particles is the solar wind feeding the magnetosphere, the reservoir containing
26136-476: The invasion and occupation of the country, violating Icelandic neutrality . In 1941, the Government of Iceland, friendly to Britain, invited the then-neutral United States to take over its defence so that Britain could use its troops elsewhere. On 31 December 1943, the Danish–Icelandic Act of Union expired after 25 years. Beginning on 20 May 1944, Icelanders voted in a four-day plebiscite on whether to terminate
26334-523: The island was first settled, it was extensively forested, with around 30% of the land covered in trees. In the late 12th century, Ari the Wise described it in the Íslendingabók as "forested from mountain to sea shore". Permanent human settlement greatly disturbed the isolated ecosystem of thin, volcanic soils and limited species diversity . The forests were heavily exploited over the centuries for firewood and timber. Deforestation , climatic deterioration during
26532-440: The island was then called Garðarshólmur, which means "Garðar's Isle". Then came a Viking named Flóki Vilgerðarson ; his daughter drowned en route, then his livestock starved to death. The sagas say that the rather despondent Flóki climbed a mountain and saw a fjord ( Arnarfjörður ) full of icebergs, which led him to give the island its new and present name. The notion that Iceland's Viking settlers chose that name to discourage
26730-555: The island with the winds, but they are not able to breed there. No native or free-living reptiles or amphibians are on the island. The animals of Iceland include the Icelandic sheep , cattle , chickens , goats , the sturdy Icelandic horse , and the Icelandic Sheepdog , all descendants of animals imported by Europeans. Wild mammals include the Arctic fox, mink , mice, rats, rabbits, and reindeer . Polar bears occasionally visit
26928-415: The island, travelling from Greenland on icebergs, but no Icelandic populations exist. In June 2008, two polar bears arrived in the same month. Marine mammals include the grey seal ( Halichoerus grypus ) and harbour seal ( Phoca vitulina ). Many species of fish live in the ocean waters surrounding Iceland, and the fishing industry is a major part of Iceland's economy, accounting for roughly half of
27126-406: The land surface is taken by the four continental landmasses , which are (in descending order): Africa-Eurasia , America (landmass) , Antarctica , and Australia (landmass) . These landmasses are further broken down and grouped into the continents . The terrain of the land surface varies greatly and consists of mountains, deserts , plains , plateaus , and other landforms . The elevation of
27324-508: The land surface varies from a low point of −418 m (−1,371 ft) at the Dead Sea , to a maximum altitude of 8,848 m (29,029 ft) at the top of Mount Everest . The mean height of land above sea level is about 797 m (2,615 ft). Land can be covered by surface water , snow, ice, artificial structures or vegetation. Most of Earth's land hosts vegetation, but considerable amounts of land are ice sheets (10%, not including
27522-437: The last Catholic bishop of Hólar , was beheaded in 1550 along with two of his sons. The country subsequently became officially Lutheran, and Lutheranism has since remained the dominant religion. In the 17th and 18th centuries, Denmark imposed harsh trade restrictions on Iceland. Natural disasters, including volcanic eruptions and disease, contributed to a decreasing population. In the summer of 1627, Barbary Pirates committed
27720-399: The lithosphere, which is divided into independently moving tectonic plates. Beneath the lithosphere is the asthenosphere , a relatively low-viscosity layer on which the lithosphere rides. Important changes in crystal structure within the mantle occur at 410 and 660 km (250 and 410 mi) below the surface, spanning a transition zone that separates the upper and lower mantle. Beneath
27918-760: The local direction of the magnetic field. Electrons mainly responsible for diffuse and pulsating auroras have, in contrast, a smoothly falling energy distribution, and an angular (pitch-angle) distribution favouring directions perpendicular to the local magnetic field. Pulsations were discovered to originate at or close to the equatorial crossing point of auroral zone magnetic field lines. Protons are also associated with auroras, both discrete and diffuse. Auroras result from emissions of photons in Earth's upper atmosphere , above 80 km (50 mi), from ionized nitrogen atoms regaining an electron, and oxygen atoms and nitrogen based molecules returning from an excited state to ground state . They are ionized or excited by
28116-410: The loss of oxygen in the atmosphere, making current animal life impossible. Due to the increased luminosity, Earth's mean temperature may reach 100 °C (212 °F) in 1.5 billion years, and all ocean water will evaporate and be lost to space, which may trigger a runaway greenhouse effect , within an estimated 1.6 to 3 billion years. Even if the Sun were stable, a fraction of the water in
28314-456: The lowercase when it is preceded by "the", such as "the atmosphere of the earth". It almost always appears in lowercase in colloquial expressions such as "what on earth are you doing?" The name Terra / ˈ t ɛr ə / occasionally is used in scientific writing and especially in science fiction to distinguish humanity's inhabited planet from others, while in poetry Tellus / ˈ t ɛ l ə s / has been used to denote personification of
28512-425: The magnetic field line. Electrons moving downward through these fields gain a substantial amount of energy (on the order of a few keV ) in the direction along the magnetic field line toward Earth. This field-aligned acceleration decreases the pitch angle for all of the electrons passing through the region, causing many of them to hit the upper atmosphere. In contrast to the scattering process leading to diffuse auroras,
28710-432: The magnetic field lines (a Birkeland current ). Since the electric field points in the same direction as the current, there is a net conversion of electromagnetic energy into particle energy in the auroral acceleration region (an electric load ). The energy to power this load is eventually supplied by the magnetized solar wind flowing around the obstacle of Earth's magnetic field, although exactly how that power flows through
28908-421: The magnetic flux at the top of the dayside magnetosphere by the double lobe reconnection (DLR). There are approximately 8 HCA events per month, with no seasonal dependence, and that the IMF must be within 30 degrees of northwards. Conjugate auroras are nearly exact mirror-image auroras found at conjugate points in the northern and southern hemispheres on the same geomagnetic field lines. These generally happen at
29106-413: The magnetosphere abreast of Earth is typically 190,000 km (30 Re), and on the night side a long "magnetotail" of stretched field lines extends to great distances (> 200 Re). The high latitude magnetosphere is filled with plasma as the solar wind passes Earth. The flow of plasma into the magnetosphere increases with additional turbulence, density, and speed in the solar wind. This flow is favoured by
29304-489: The magnetosphere is still an active area of research. While the energy to power the aurora is ultimately derived from the solar wind, the electrons themselves do not travel directly from the solar wind into Earth's auroral zone; magnetic field lines from these regions do not connect to the solar wind, so there is no direct access for solar wind electrons. Some auroral features are also created by electrons accelerated by dispersive Alfvén waves . At small wavelengths transverse to
29502-497: The magnetosphere. During magnetic storms and substorms , charged particles can be deflected from the outer magnetosphere and especially the magnetotail, directed along field lines into Earth's ionosphere , where atmospheric atoms can be excited and ionized, causing an aurora . Earth's rotation period relative to the Sun—its mean solar day—is 86,400 seconds of mean solar time ( 86,400.0025 SI seconds ). Because Earth's solar day
29700-409: The magnetosphere; solar wind pressure compresses the day-side of the magnetosphere, to about 10 Earth radii, and extends the night-side magnetosphere into a long tail. Because the velocity of the solar wind is greater than the speed at which waves propagate through the solar wind, a supersonic bow shock precedes the day-side magnetosphere within the solar wind. Charged particles are contained within
29898-478: The magnetosphere; the plasmasphere is defined by low-energy particles that essentially follow magnetic field lines as Earth rotates. 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, and the Van Allen radiation belts are formed by high-energy particles whose motion is essentially random, but contained in
30096-417: The mantle, an extremely low viscosity liquid outer core lies above a solid inner core . Earth's inner core may be rotating at a slightly higher angular velocity than the remainder of the planet, advancing by 0.1–0.5° per year, although both somewhat higher and much lower rates have also been proposed. The radius of the inner core is about one-fifth of that of Earth. The density increases with depth. Among
30294-600: The mantle. Due to this recycling, most of the ocean floor is less than 100 Ma old. The oldest oceanic crust is located in the Western Pacific and is estimated to be 200 Ma old. By comparison, the oldest dated continental crust is 4,030 Ma , although zircons have been found preserved as clasts within Eoarchean sedimentary rocks that give ages up to 4,400 Ma , indicating that at least some continental crust existed at that time. The seven major plates are
30492-548: The modern oceans will descend to the mantle , due to reduced steam venting from mid-ocean ridges. The Sun will evolve to become a red giant in about 5 billion years . Models predict that the Sun will expand to roughly 1 AU (150 million km; 93 million mi), about 250 times its present radius. Earth's fate is less clear. 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
30690-399: The mother of Thor . Historically, "Earth" has been written in lowercase. Beginning with the use of Early Middle English , its definite sense as "the globe" was expressed as "the earth". By the era of Early Modern English , capitalization of nouns began to prevail , and the earth was also written the Earth , particularly when referenced along with other heavenly bodies. More recently,
30888-424: The name is sometimes simply given as Earth , by analogy with the names of the other planets , though "earth" and forms with "the earth" remain common. House styles now vary: Oxford spelling recognizes the lowercase form as the more common, with the capitalized form an acceptable variant. Another convention capitalizes "Earth" when appearing as a name, such as a description of the "Earth's atmosphere", but employs
31086-425: The newly forming Sun had only 70% of its current luminosity . By 3.5 Ga , Earth's magnetic field was established, which helped prevent the atmosphere from being stripped away by the solar wind . As the molten outer layer of Earth cooled it formed the first solid crust , which is thought to have been mafic in composition. The first continental crust , which was more felsic in composition, formed by
31284-472: The northeastern hinterland. The temperature records for Reykjavík are 26.2 °C (79.2 °F) on 30 July 2008, and −24.5 °C (−12.1 °F) on 21 January 1918. The entire country is in a single ecoregion , the Iceland boreal birch forests and alpine tundra . Some areas are covered by glaciers . Phytogeographically , Iceland belongs to the Arctic province of the Circumboreal Region within
31482-410: The northern tip of Labrador . Iceland is the world's 18th-largest island , and Europe's second-largest island after Great Britain and before Ireland. The main island covers 101,826 km (39,315 sq mi), but the entire country is 103,000 km (40,000 sq mi) in size, of which 62.7% is tundra . Iceland contains about 30 minor islands, including the lightly populated Grímsey and
31680-401: The ocean in a series of volcanic eruptions between 8 November 1963 and 5 June 1968. Only scientists researching the growth of new life are allowed to visit the island. The country has around 30 active volcanic systems. Within each are volcano-tectonic fissure systems and many, but not all of them, also have at least one central volcano (mostly in the form of a stratovolcano , sometimes of
31878-586: The ocean may have covered Earth completely. The world ocean is commonly divided into the Pacific Ocean, Atlantic Ocean, Indian Ocean, Antarctic or Southern Ocean , and Arctic Ocean, from largest to smallest. The ocean covers Earth's oceanic crust , with the shelf seas covering the shelves of the continental crust to a lesser extent. The oceanic crust forms large oceanic basins with features like abyssal plains , seamounts , submarine volcanoes , oceanic trenches , submarine canyons , oceanic plateaus , and
32076-648: The oceanic plates, with the Cocos Plate advancing at a rate of 75 mm/a (3.0 in/year) and the Pacific Plate moving 52–69 mm/a (2.0–2.7 in/year). At the other extreme, the slowest-moving plate is the South American Plate, progressing at a typical rate of 10.6 mm/a (0.42 in/year). Earth's interior, like that of the other terrestrial planets, is divided into layers by their chemical or physical ( rheological ) properties. The outer layer
32274-497: The opposite order. Until about 1963, it was thought that these changes are due to the rotation of the Earth under a pattern fixed with respect to the Sun. Later, it was found by comparing all-sky films of auroras from different places (collected during the International Geophysical Year ) that they often undergo global changes in a process called auroral substorm . They change in a few minutes from quiet arcs all along
32472-581: The orbit of maximum axial tilt toward or away from the Sun—and the equinoxes , when Earth's rotational axis is aligned with its orbital axis. 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. In the Southern Hemisphere, the situation is reversed, with
32670-472: The otherwise dark sky (e.g., "rosy-fingered dawn"). The words borealis and australis are derived from the names of the ancient gods of the north wind ( Boreas ) and the south wind ( Auster ) in Greco-Roman mythology . Auroras are most commonly observed in the "auroral zone", a band approximately 6° (~660 km) wide in latitude centered on 67° north and south. The region that currently displays an aurora
32868-566: The ozone layer, life colonized Earth's surface. Among the earliest fossil evidence for life is microbial mat fossils found in 3.48 billion-year-old sandstone in Western Australia , biogenic graphite found in 3.7 billion-year-old metasedimentary rocks in Western Greenland , and remains of biotic material found in 4.1 billion-year-old rocks in Western Australia. The earliest direct evidence of life on Earth
33066-469: The partial melting of this mafic crust. The presence of grains of the mineral zircon of Hadean age in Eoarchean sedimentary rocks suggests that at least some felsic crust existed as early as 4.4 Ga , only 140 Ma after Earth's formation. There are two main models of how this initial small volume of continental crust evolved to reach its current abundance: (1) a relatively steady growth up to
33264-453: The particles associated with auroras, have also been detected. Aurora noise , similar to a crackling noise, begins about 70 m (230 ft) above Earth's surface and is caused by charged particles in an inversion layer of the atmosphere formed during a cold night. The charged particles discharge when particles from the Sun hit the inversion layer, creating the noise. In 2016, more than fifty citizen science observations described what
33462-501: The past 66 Mys , and several million years ago, an African ape species gained the ability to stand upright. This facilitated tool use and encouraged communication that provided the nutrition and stimulation needed for a larger brain, which led to the evolution of humans . The development of agriculture , and then civilization , led to humans having an influence on Earth and the nature and quantity of other life forms that continues to this day. Earth's expected long-term future
33660-412: The peak. An electron spirals (gyrates) about a field line at an angle that is determined by its velocity vectors, parallel and perpendicular, respectively, to the local geomagnetic field vector B. This angle is known as the "pitch angle" of the particle. The distance, or radius, of the electron from the field line at any time is known as its Larmor radius. The pitch angle increases as the electron travels to
33858-507: The personal union with Denmark, abolish the monarchy, and establish a republic. The vote was 97% to end the union, and 95% in favour of the new republican constitution. Iceland formally became a republic on 17 June 1944, with Sveinn Björnsson as its first president. In 1946, the US Defence Force Allied left Iceland. The nation formally became a member of NATO on 30 March 1949, amid domestic controversy and riots . On 5 May 1951,
34056-478: The planet's environment . Humanity's current impact on Earth's climate and biosphere is unsustainable , threatening the livelihood of humans and many other forms of life, and causing widespread extinctions . The Modern English word Earth developed, via Middle English , from an Old English noun most often spelled eorðe . It has cognates in every Germanic language , and their ancestral root has been reconstructed as * erþō . In its earliest attestation,
34254-421: The polar Northern and Southern hemispheres; or by longitude into the continental Eastern and Western hemispheres. Most of Earth's surface is ocean water: 70.8% or 361 million km (139 million sq mi). This vast pool of salty water is often called the world ocean , and makes Earth with its dynamic hydrosphere a water world or ocean world . Indeed, in Earth's early history
34452-454: The polar cap, the related "theta aurora", and "dayside arcs" near noon. These are relatively infrequent and poorly understood. Other interesting effects occur such as pulsating aurora, "black aurora" and their rarer companion "anti-black aurora" and subvisual red arcs. In addition to all these, a weak glow (often deep red) observed around the two polar cusps, the field lines separating the ones that close through Earth from those that are swept into
34650-490: The present day, which is supported by the radiometric dating of continental crust globally and (2) an initial rapid growth in the volume of continental crust during the Archean , forming the bulk of the continental crust that now exists, which is supported by isotopic evidence from hafnium in zircons and neodymium in sedimentary rocks. The two models and the data that support them can be reconciled by large-scale recycling of
34848-538: The radiation zones and temporarily magnetically trapped particles confined by the geomagnetic field, coupled with particle acceleration processes. The immediate cause of the ionization and excitation of atmospheric constituents leading to auroral emissions was discovered in 1960, when a pioneering rocket flight from Fort Churchill in Canada revealed a flux of electrons entering the atmosphere from above. Since then an extensive collection of measurements has been acquired painstakingly and with steadily improving resolution since
35046-493: The rates of mantle convection and plate tectonics, and allowing the production of uncommon igneous rocks such as komatiites that are rarely formed today. The mean heat loss from Earth is 87 mW m , for a global heat loss of 4.42 × 10 W . A portion of the core's thermal energy is transported toward the crust by mantle plumes , a form of convection consisting of upwellings of higher-temperature rock. These plumes can produce hotspots and flood basalts . More of
35244-423: The ribbon). The processes that cause STEVE are also associated with a picket-fence aurora, although the latter can be seen without STEVE. It is an aurora because it is caused by precipitation of electrons in the atmosphere but it appears outside the auroral oval, closer to the equator than typical auroras. When the picket-fence aurora appears with STEVE, it is below. First reported in 2020, and confirmed in 2021,
35442-621: The settlement of their verdant isle is most likely a myth. According to both Landnámabók and Íslendingabók , monks known as the Papar lived in Iceland before Scandinavian settlers arrived, possibly members of a Hiberno-Scottish mission . An archaeological excavation has revealed the ruins of a cabin in Hafnir on the Reykjanes peninsula . Carbon dating indicates that it was abandoned sometime between 770 and 880. In 2016, archaeologists uncovered
35640-515: The shape of an ellipsoid , bulging at its Equator ; its diameter is 43 kilometres (27 mi) longer there than at its poles . Earth's shape also has local topographic variations; the largest local variations, like the Mariana Trench (10,925 metres or 35,843 feet below local sea level), shortens Earth's average radius by 0.17% and Mount Everest (8,848 metres or 29,029 feet above local sea level) lengthens it by 0.14%. Since Earth's surface
35838-597: The signing of the Old Covenant in 1262, which ended the Commonwealth and brought Iceland under the Norwegian crown. Possession of Iceland passed from the Kingdom of Norway (872–1397) to the Kalmar Union in 1415, when the kingdoms of Norway, Denmark, and Sweden were united. After the break-up of the union in 1523, it remained a Norwegian dependency, as a part of Denmark–Norway . Infertile soil, volcanic eruptions, deforestation, and an unforgiving climate made for harsh life in
36036-470: The smallest population of any NATO member and is the only one with no standing army , possessing only a lightly armed coast guard . The Sagas of Icelanders say that a Norwegian named Naddodd (or Naddador) was the first Norseman to reach Iceland; in the ninth century, he named it Snæland or "Snowland" because it was snowing. Following Naddodd, the Swede Garðar Svavarsson arrived, and so
36234-416: The solar and Earth's axis to the ecliptic plane. As Earth orbits throughout a year, it experiences an interplanetary magnetic field (IMF) from different latitudes of the Sun, which is tilted at 8 degrees. Similarly, the 23-degree tilt of Earth's axis about which the geomagnetic pole rotates with a diurnal variation changes the daily average angle that the geomagnetic field presents to the incident IMF throughout
36432-463: The south coast is warmer, wetter, and windier than the north. The Central Highlands are the coldest part of the country. Low-lying inland areas in the north are the aridest. Snowfall in winter is more common in the north than in the south. The highest air temperature recorded was 30.5 °C (86.9 °F) on 22 June 1939 at Teigarhorn on the southeastern coast. The lowest was −38 °C (−36.4 °F) on 22 January 1918 at Grímsstaðir and Möðrudalur in
36630-455: The summer and winter solstices exchanged and the spring and autumnal equinox dates swapped. Iceland Iceland ( Icelandic : Ísland , pronounced [ˈistlant] ) is a Nordic island country between the North Atlantic and Arctic Oceans , on the Mid-Atlantic Ridge between North America and Europe . It is culturally and politically linked with Europe and
36828-510: The tail and close remotely. Early work on the imaging of the auroras was done in 1949 by the University of Saskatchewan using the SCR-270 radar. The altitudes where auroral emissions occur were revealed by Carl Størmer and his colleagues, who used cameras to triangulate more than 12,000 auroras. They discovered that most of the light is produced between 90 and 150 km (56 and 93 mi) above
37026-408: The time of the equinoxes , when there is little difference in the orientation of the north and south geomagnetic poles to the sun. Attempts were made to image conjugate auroras by aircraft from Alaska and New Zealand in 1967, 1968, 1970, and 1971, with some success. A full understanding of the physical processes which lead to different types of auroras is still incomplete, but the basic cause involves
37224-483: The upper atmosphere ( thermosphere / exosphere ). The resulting ionization and excitation of atmospheric constituents emit light of varying colour and complexity. The form of the aurora, occurring within bands around both polar regions, is also dependent on the amount of acceleration imparted to the precipitating particles. Most of the planets in the Solar System , some natural satellites , brown dwarfs , and even comets also host auroras. The term aurora borealis
37422-405: The visible Sun at any time. The solar wind and the magnetosphere, being two electrically conducting fluids in relative motion, should be able in principle to generate electric currents by dynamo action and impart energy from the flow of the solar wind. However, this process is hampered by the fact that plasmas conduct readily along magnetic field lines, but less readily perpendicular to them. Energy
37620-504: The whole sky. These are also known as discrete auroras , which are at times bright enough to read a newspaper by at night. These forms are consistent with auroras being shaped by Earth's magnetic field. The appearances of arcs, rays, curtains, and coronas are determined by the shapes of the luminous parts of the atmosphere and a viewer's position . Auroras change with time. Over the night they begin with glows and progress toward coronas, although they may not reach them. They tend to fade in
37818-456: The word eorðe was used to translate the many senses of Latin terra and Greek γῆ gē : the ground, its soil , dry land, the human world, the surface of the world (including the sea), and the globe itself. As with Roman Terra /Tellūs and Greek Gaia , Earth may have been a personified goddess in Germanic paganism : late Norse mythology included Jörð ("Earth"), a giantess often given as
38016-534: The world with similar climates include the Aleutian Islands , the Alaska Peninsula , and Tierra del Fuego , although these regions are closer to the equator. Despite its proximity to the Arctic, the island's coasts remain ice-free through the winter. Ice incursions are rare, with the last having occurred on the north coast in 1969. The climate varies between different parts of the island. Generally speaking,
38214-680: The world's wealthiest and most developed nations. In 1994 it became a part of the European Economic Area , further diversifying its economy into sectors such as finance, biotechnology, and manufacturing . Iceland has a market economy with relatively low taxes , compared to other OECD countries, as well as the highest trade union membership in the world . It maintains a Nordic social welfare system that provides universal health care and tertiary education . Iceland ranks highly in international comparisons of national performance, such as quality of life, education, protection of civil liberties, government transparency, and economic freedom. It has
38412-598: The year. This causes the seasonal change in climate, with summer in the Northern Hemisphere occurring when the Tropic of Cancer is facing the Sun, and in the Southern Hemisphere when the Tropic of Capricorn faces the Sun. In each instance, winter occurs simultaneously in the opposite hemisphere. During the summer, the day lasts longer, and the Sun climbs higher in the sky. In winter, the climate becomes cooler and
38610-507: Was adopted by consensus around 999–1000, although Norse paganism persisted among segments of the population for some years afterward. The Icelandic Commonwealth lasted until the 13th century when the political system devised by the original settlers proved unable to cope with the increasing power of Icelandic chieftains. The internal struggles and civil strife of the Age of the Sturlungs led to
38808-580: Was coined by Galileo in 1619, from the Roman Aurora, goddess of the dawn , and the Greek Boreas, god of the cold north wind . The word aurora is derived from the name of the Roman goddess of the dawn, Aurora , who travelled from east to west announcing the coming of the Sun . Ancient Greek poets used the corresponding name " Eos " metaphorically to refer to dawn, often mentioning its play of colours across
39006-539: Was initiated to regulate the Icelandic Commonwealth . The lack of arable land also served as an impetus to the settlement of Greenland starting in 986. The period of these early settlements coincided with the Medieval Warm Period , when temperatures were similar to those of the early 20th century. At this time about 25% of Iceland was covered with forest, compared to 1% in the present day. Christianity
39204-424: Was to them an unknown type of aurora which they named " STEVE ", for "Strong Thermal Emission Velocity Enhancement". STEVE is not an aurora but is caused by a 25 km (16 mi) wide ribbon of hot plasma at an altitude of 450 km (280 mi), with a temperature of 3,000 °C (3,270 K; 5,430 °F) and flowing at a speed of 6 km/s (3.7 mi/s) (compared to 10 m/s (33 ft/s) outside
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