title: Graceland (album)

text: Joseph Shabalala also contributed to "Diamonds on the Soles of Her Shoes", with Ladysmith Black Mambazo and the Senegalese singer-percussionist Youssou N'Dour. It was recorded a week following their appearance on "Saturday Night Live". The pennywhistle solo featured on "You Can Call Me Al" was performed by Morris Goldberg, a white South African living in New York. "Homeless" was written jointly by Simon and Shabalala, the lead singer of Ladysmith Black Mambazo, to a melody from a traditional Zulu wedding song. In the song "Under African Skies", "the figure of Joseph becomes the dual image of a dispossessed African black man and the New Testament Joseph." For the song, Simon sent Shabalala a cassette demo, and the two later met at Abbey Road Studios in London, where the rest of the song was completed. "Crazy Love" features music from Stimela, Phiri's group that was very successful in South Africa.


title: Graceland (album)

text: To write lyrics, Simon listened to the recordings made during his time in Johannesburg, identifying patterns in the music to fit to verses. He said:


title: Graceland (album)

text: Simon told "The Village Voice"s Robert Christgau in 1986 that he was bad at writing about politics, and felt his strength was writing about relationships and introspection. In contrast to "Hearts and Bones", "Graceland" subject matter is more upbeat. Simon made an effort to write simply without compromising the language. Composing more personal songs took him significantly longer, as it involved "a lot of avoidance going on". Rewrites were necessary as Simon ended up using overcomplicated words. A perfectionist, Simon rewrote songs only to scrap the newer versions. Songs such as "Graceland" and "The Boy in the Bubble" took three to four months, while others, such as "All Around the World" and "Crazy Love", came together quickly.


title: Graceland (album)

text: "The Boy in the Bubble" discusses starvation and terrorism, but mixes this with wit and optimism. Simon concurred with this assessment: "Hope and dread—that's right. That's the way I see the world, a balance between the two, but coming down on the side of hope." The song retains a variation of the only lyric Simon composed on his South African trip: "The way the camera follows him in slo-mo, the way he smiled at us all." The imagery was inspired by the assassination of John F. Kennedy and the attempted assassination of Ronald Reagan. "Homeless" discusses poverty within the black majority in South Africa. According to Simon's ex-wife Carrie Fisher, the "Graceland" lines "She's come back to tell me she's gone / As if I didn't know that, as if I didn't know my own bed / As if I'd never noticed the way she brushed her hair from her forehead" refer to her. She confirmed she had a habit of brushing her hair from her forehead, and said she felt privileged to be in one of Simon's songs.


title: Graceland (album)

text: Throughout the recording process, Simon remained unsure of the album's thematic connection. He kept dozens of yellow legal pads with random words and phrases he would combine in an attempt to define the album. He derived the album title from the phrase "driving through Wasteland", which he changed to "going to Graceland", a reference to Elvis Presley's Memphis home. Simon believed it represented a spiritual direction: just as he had embarked on a physical journey to collect ideas in Africa, he would spiritually journey to the home of the rock "forefather" to revitalize his love for music.


title: Graceland (album)

text: "Graceland" was released by Warner Bros. with little promotion in September 1986. Before its release, Simon speculated that he was no longer "a viable commercial force in popular music".


title: Graceland (album)

text: By July 1987, "Graceland" had sold six million copies worldwide. That year, "Rolling Stone" David Fricke said the album had become "a daily soundtrack in urban yuppie condos and suburban living rooms and on radio airwaves from Australia to Zimbabwe". In South Africa, it was the best-selling release since Michael Jackson's "Thriller" (1982). It sold 150,000 copies in Australia in 1988, and had sold 470,000 copies there by January 1989. As of 2014, "Graceland" was estimated to have sold more than 16 million copies.


title: Graceland (album)

text: The cover art depicts an Ethiopian Christian icon from the collection of the Peabody Essex Museum dating to around 1500.


title: Graceland (album)

text: Initial reviews of "Graceland" were positive. "Rolling Stone" Rob Tannenbaum characterized it as "lovely, daring and accomplished". Stephen Holden of "The New York Times" wrote: "With his characteristic refinement, Mr. Simon has fashioned that event into the rock album equivalent of a work of literature." In "The Village Voice", Robert Christgau deemed it Simon's best record since his 1972 self-titled album, as well as "a tremendously engaging and inspired piece of work". It went on to top "The Village Voice"s Pazz & Jop critics' poll for that year (1986).


title: Graceland (album)

text: Retrospective reviews have continued to be positive. According to AllMusic's William Ruhlmann, ""Graceland" became the standard against which subsequent musical experiments by major artists were measured." Joe Tangari of "Pitchfork" wrote that "its songs transcend the context as listening experiences. These songs are astute and exciting, spit-shined with the gloss of production that bears a lot of hallmarks of the era but somehow has refused to age. Taken as a whole, the album offers tremendous insight into how we live in our world and how that changes as we get older." Patrick Humphries of BBC Music wrote that "it may well stand as the pinnacle of his remarkable half-century career ... Simon fashioned a record which was truly, blindingly original, and – listening to it a quarter of a century on – modern and timeless." Andy Gill of "The Independent" wrote: "The character of the base music here is overwhelming: complex, ebullient and life-affirming, and in yoking this intricate dance music to his sophisticated New Yorker sensibility, Simon created a transatlantic bridge that neither pandered to nor patronised either culture."


title: Graceland (album)

text: "Graceland" earned Simon the Best International Solo Artist award at the 1987 Brit Awards. It was ranked No. 84 in a 2005 survey by British television's Channel 4 to determine the 100 greatest albums of all time.


title: Graceland (album)

text: "Graceland" was ranked 81st on the 2003 list of "Rolling Stone" magazine's 500 Greatest Albums of All Time, as "an album about isolation and redemption that transcended 'world music' to become the whole world's soundtrack." The ranking increased to 71st in the 2012 revision and 46th in the 2020 list. In 2000 it was voted number 43 in Colin Larkin's "All Time Top 1000 Albums". The song "Graceland" was voted #485 in the list of Rolling Stone's 500 Greatest Songs of All Time.


title: Graceland (album)

text: Following the album's success, Simon faced accusations by organizations such as Artists United Against Apartheid, anti-apartheid musicians including Billy Bragg, Paul Weller, and Jerry Dammers, and James Victor Gbeho, at the time the Ghanaian Ambassador to the United Nations. Saying Simon had broken the cultural boycott imposed by the rest of the world against the apartheid regime in South Africa, they called him "naive" and condemned him for having potentially damaged anti-apartheid solidarity.


title: Graceland (album)

text: Before going to South Africa, Simon sought advice from Harry Belafonte, with whom he had recently collaborated on "We Are the World". Belafonte had mixed feelings and advised him to discuss the matter with the African National Congress (ANC). At an album launch party, Simon said about the controversy: "I'm with the artists. I didn't ask the permission of the ANC. I didn't ask permission of Buthelezi, or Desmond Tutu, or the Pretoria government. And to tell you the truth, I have a feeling that when there are radical transfers of power on either the left or the right, the artists always get screwed."


title: Graceland (album)

text: James Victor Ghebo, former Ghanaian ambassador to the UN, was critical, saying: "When he goes to South Africa, Paul Simon bows to apartheid. He lives in designated hotels for whites. He spends money the way whites have made it possible to spend money there. The money he spends goes to look after white society, not to the townships." Simon denied that he went to South Africa to "take money out of the country", noting that he paid the black artists handsomely and split royalties with them, and was not paid to play to a white audience. Guitarist Ray Phiri said: "We used Paul as much as Paul used us. There was no abuse. He came at the right time and he was what we needed to bring our music into the mainstream."


title: Graceland (album)

text: Some criticized Simon for not addressing apartheid in his lyrics. Simon responded: "Was I supposed to solve things in a song?" He said he was not good at writing protest songs in the vein of Bob Dylan or Bob Geldof, and felt that although it was not overtly political, "Graceland" was its own political statement: "I still think it's the most powerful form of politics, more powerful than saying it right on the money, in which case you're usually preaching to the converted. People get attracted to the music, and once they hear what's going on within it, they say, 'What? They're doing "that" to these people?'"


title: Graceland (album)

text: The United Nations Anti-Apartheid Committee supported "Graceland", as it showcased black South African musicians and offered no support to the South African government, but the ANC protested it as a violation of the boycott. The ANC voted to ban Simon from the country, and he was also added to the United Nations blacklist. He was removed from the blacklist in January 1987, and announced that he had been cleared by the ANC, but Artists Against Apartheid founder Dali Tambo denied this. The "Graceland" concert at London's Royal Albert Hall prompted protests from Dammers, Weller, and Bragg. In 2012, the controversy was revived when Simon returned to London for a 25th-anniversary concert celebrating the album.


title: Graceland (album)

text: In contrast, Simon received praise for encouraging South African music from Hugh Masekela, one of South Africa's most prominent musicians and an exiled opponent of apartheid, who subsequently toured alongside Simon and Miriam Makeba. The album's worldwide success introduced some of the musicians, especially Ladysmith Black Mambazo, to global audiences. South African jazz musician Jonas Gwangwa criticized the notion that Simon was responsible for making South African music popular, asking: "So, it has taken another white man to discover my people?"


title: Graceland (album)

text: Some critics viewed "Graceland" as colonialist, with Simon appropriating the music of another culture to bring to the global market. "Star-Ledger" reporter Tris McCall wrote in 2012, "Does it complicate matters to realize that these musicians were second-class citizens in their own country, one groaning under the weight of apartheid? How could Simon approach them as equal partners when their own government demanded that they treat him as a superior?" In 2012, Andrew Mueller of "Uncut" wrote: "Apartheid was of course a monstrosity, but it would be absurd to suggest that Simon's introduction of South Africa's music to the world prolonged it and quite plausible to suggest that it did some small amount to hasten its undoing."


title: Graceland (album)

text: Simon's choice to feature American singer Linda Ronstadt on "Under African Skies" was criticized, as three years earlier she had accepted $500,000 to perform at Sun City, a South African luxury resort. Nelson George of "Billboard" said her inclusion on "Graceland" was like "using gasoline to put out birthday candles", and Robert Christgau wrote: "Even if the lyric called for total US divestiture, Ronstadt's presence on "Graceland" would be a slap in the face to the world anti-apartheid movement."


title: Graceland (album)

text: Simon defended Ronstadt, saying: "I know that her intention was never to support the government there ... She made a mistake. She's extremely liberal in her political thinking and unquestionably antiapartheid." He told "Spin" he did not think Ronstadt would play at Sun City again, and did not think she was "incompatible" with the record.


title: Graceland (album)

text: Simon had refused to perform on the 1985 antiapartheid single "Sun City", as the demo had included a list of names shaming artists who had performed at the resort, including Ronstadt's, and as he felt "Graceland" would be "my own statement". He said he had refused two offers to perform at Sun City, and drew a distinction between going to South Africa to perform for a segregated audience, which he felt was unacceptable, and going to record.


title: Graceland (album)

text: The cultural boycott against South Africa was lifted in 1991, five years after "Graceland"'s release. At the invitation of anti-apartheid activist Nelson Mandela and with the African National Congress's support, Simon and his band played five shows, beginning at Ellis Park Stadium in Johannesburg. Before the first concert, hand grenades were thrown into the office of promoter Attie van Wyk, who had booked Simon for the shows. A sect of the militant Azanian People's Organisation (AZAPO) claimed responsibility for the attack, which destroyed the office but caused no injuries.


title: Graceland (album)

text: Simon held a clandestine meeting with AZAPO representatives, offering them proceeds from the tour, but no agreement was reached. At a press conference, AZAPO said there was "potential for violence" if the show proceeded. Though hundreds of protesters threatened violence at one concert, it was protected by 800 policemen and proceeded without incident.


title: Graceland (album)

text: According to guitarist Steven Van Zandt, who was involved in the anti-apartheid movement and met with AZAPO representatives, Simon had been "at the top" of AZAPO's assassination list. Van Zandt said he persuaded them that murdering Simon would not help them achieve their goals, and mollified them by saying he was attempting to "unite the music community" against apartheid.


title: Graceland (album)

text: "That Was Your Mother" features the American zydeco band the Good Rockin' Dopsie and the Twisters. Dopsie felt Simon had derived it from his song "My Baby, She's Gone", and was not credited, but decided not to take legal action.


title: Graceland (album)

text: The American group Los Lobos appears on the last track, "All Around the World or the Myth of Fingerprints". Saxophone player Steve Berlin felt they deserved writing credits:[Simon] quite literally—and in no way do I exaggerate when I say—he stole the song from us ... We go into the studio, and he had quite literally nothing. I mean, he had no ideas, no concepts, and said, "Well, let's just jam." ... Paul goes, "Hey, what's that?" We start playing what we have of it, and it is exactly what you hear on the record." The album sold 13 million copies and we never got paid a penny for it. Not even for the session recording. We bitched about this to the label's president Lenny Waronker nonstop and could not get a straight answer out of him regarding song credit or session payment.


title: Graceland (album)

text: According to Berlin, when he contacted Simon about the lack of credit, Simon responded: "Sue me. See what happens." Simon denied this, and said: "The album came out and we heard nothing. Then six months passed and "Graceland" had become a hit and the first thing I heard about the problem was when my manager got a lawyer's letter. I was shocked."


title: Graceland (album)

text: "New York Times" writer Jon Pareles identified "Graceland" as an album that had popularized African rock in the west, alongside albums such as Peter Gabriel's "So" (1986) and Talking Heads' "Remain in Light" (1980). A 2012 documentary film, "Under African Skies", was directed by Joe Berlinger for the album's 25th anniversary, and includes archival footage, interviews, discussion of the controversy, and coverage of an anniversary reunion concert.


title: Graceland (album)

text: Advocates for "Graceland" feel its music transcends the racial and cultural barriers of its production. ""Graceland" was never just a collection of songs, after all; it was a bridge between cultures, genres and continents, not to mention a global launching pad for the musicians whose popularity had been suppressed under South Africa's white-run apartheid rule", said Andrew Leahey of "American Songwriter". Presenting the album in a modern context, Tris McCall of the "Star-Ledger" writes that "In a sense, Simon was ahead of his time: The curatorial approach he took to assembling full tracks from scraps of songs and pre-existing recordings is closer in execution to that of Kanye West than it is to any of his contemporaries."


title: Graceland (album)

text: The album has influenced musicians including Regina Spektor, Bombay Bicycle Club, Gabby Young, Casiokids, The Very Best, Givers, Lorde, and Vampire Weekend. The latter faced particular criticism that their 2008 debut album was too similar to "Graceland", due to its origins in African music. Simon later defended the band, remarking, "In a way, we were on the same pursuit, but I don't think you're lifting from me, and anyway, you're welcome to it, because everybody's lifting all the time. That's the way music grows and is shaped."


title: Graceland (album)

text: In June 2018, Sony Music and Legacy Records issued "Graceland: The Remixes", featuring remixes of "Graceland" songs by artists including Paul Oakenfold, Groove Armada and Thievery Corporation.


title: Permafrost

text: Permafrost is ground that continuously remains below 0 °C (32 °F) for two or more years, located on land or under the ocean. Most common in the Northern Hemisphere, around 15% of the Northern Hemisphere or 11% of the global surface is underlain by permafrost, with the total area of around 18 million km. This includes substantial areas of Alaska, Greenland, Canada and Siberia. It can also be located on mountaintops in the Southern Hemisphere and beneath ice-free areas in the Antarctic.


title: Permafrost

text: Permafrost does not have to be the first layer that is on the ground. It can be from an inch to several miles deep under the Earth's surface. It frequently occurs in ground ice, but it can also be present in non-porous bedrock. Permafrost is formed from ice holding various types of soil, sand, and rock in combination.


title: Permafrost

text: Permafrost contains large amounts of biomass and decomposed biomass that has been stored as methane and carbon dioxide, making tundra soil a carbon sink. As global warming heats the ecosystem and causes soil thawing, the permafrost carbon cycle accelerates and releases much of these soil-contained greenhouse gases into the atmosphere, creating a feedback cycle that increases climate change. Thawing of permafrost is one of the effects of climate change. While emissions from thawing permafrost will be significant enough to lead to additional warming, they will likely not be enough to trigger a self-reinforcing feedback leading to "runaway warming".


title: Permafrost

text: In contrast to the relative dearth of reports on frozen ground in North America prior to World War II, a vast literature on basic permafrost science and the engineering aspects of permafrost was available in Russian. Some Russian authors relate permafrost research with the name Alexander von Middendorff (1815–1894). However, Russian scientists also realized, that Karl Ernst von Baer must be given the attribute "founder of scientific permafrost research". In 1843, Baer's original study “materials for the study of the perennial ground-ice” was ready to be printed. Baer's detailed study consists of 218 pages and was written in German language, as he was a Baltic German scientist. He was teaching at the University of Königsberg and became a member of the St Petersburg Academy of Sciences. This world's first permafrost textbook was conceived as a complete work and ready for printing in 1843. But it remained lost for around 150 years. However, from 1838 onwards, Baer published several individual publications on permafrost. The Russian Academy of Sciences honoured Baer with the publication of a tentative Russian translation of his study in 1942.


title: Permafrost

text: These facts were completely forgotten after the Second World War. Thus in 2001 the discovery of the typescript from 1843 in the library archives of the University of Giessen and its annotated publication was a scientific sensation. The full text of Baer's original work is available online (234 pages). The editor added to the facsimile reprint a preface in English, two colour permafrost maps of Eurasia and some figures of permafrost features. Baer's text is introduced with detailed comments and references on additional 66 pages written by the Estonian historian Erki Tammiksaar. The work is notable because Baer's observations on permafrost distribution and periglacial morphological descriptions are seen as largely correct to the present day. With his compilation and analysis of all available data on ground ice and permafrost, Baer laid the foundation for the modern permafrost terminology. Baer's southern limit of permafrost in Eurasia drawn in 1843 corresponds well with the actual southern limit on the "Circum-Arctic Map of Permafrost and Ground Ice Conditions" of the International Permafrost Association (edited by J. Brown et al.).


title: Permafrost

text: Beginning in 1942, Siemon William Muller delved into the relevant Russian literature held by the Library of Congress and the U.S. Geological Survey Library so that he was able to furnish the government an engineering field guide and a technical report about permafrost by 1943", the year in which he coined the term as a contraction of permanently frozen ground. Although originally classified (as U.S. Army. Office of the Chief of Engineers, "Strategic Engineering Study", no. 62, 1943), in 1947 a revised report was released publicly, which is regarded as the first North American treatise on the subject.


title: Permafrost

text: Permafrost is soil, rock or sediment that is frozen for more than two consecutive years. In areas not covered by ice, it exists beneath a layer of soil, rock or sediment, which freezes and thaws annually and is called the "active layer". In practice, this means that permafrost occurs at an mean annual temperature of or below. Active layer thickness varies with the season, but is 0.3 to 4 meters thick (shallow along the Arctic coast; deep in southern Siberia and the Qinghai-Tibetan Plateau).


title: Permafrost

text: The extent of permafrost is displayed in terms of permafrost zones, which are defined according to the area underlain by permafrost as continuous (90%–100%), discontinuous (50%–90%), sporadic (10%–50%), and isolated patches (10% or less). These permafrost zones cover together approximately 22% of the Northern Hemisphere. Continuous permafrost zone covers slightly more than half of this area, discontinuous permafrost around 20 percent, and sporadic permafrost together with isolated patches little less than 30 percent. Because permafrost zones are not entirely underlain by permafrost, only 15% of the ice-free area of the Northern Hemisphere is actually underlain by permafrost. Most of this area is found in Siberia, northern Canada, Alaska and Greenland. Beneath the active layer annual temperature swings of permafrost become smaller with depth. The deepest depth of permafrost occurs where geothermal heat maintains a temperature above freezing. Above that bottom limit there may be permafrost with a consistent annual temperature—"isothermal permafrost".


title: Permafrost

text: Permafrost typically forms in any climate where the mean annual air temperature is lower than the freezing point of water. Exceptions are found in humid boreal forests, such as in Northern Scandinavia and the North-Eastern part of European Russia west of the Urals, where snow acts as an insulating blanket. Glaciated areas may also be exceptions. Since all glaciers are warmed at their base by geothermal heat, temperate glaciers, which are near the pressure-melting point throughout, may have liquid water at the interface with the ground and are therefore free of underlying permafrost. "Fossil" cold anomalies in the Geothermal gradient in areas where deep permafrost developed during the Pleistocene persist down to several hundred metres. This is evident from temperature measurements in boreholes in North America and Europe.


title: Permafrost

text: The below-ground temperature varies less from season to season than the air temperature, with mean annual temperatures tending to increase with depth as a result of the geothermal crustal gradient. Thus, if the mean annual air temperature is only slightly below , permafrost will form only in spots that are sheltered—usually with a northern or southern aspect (in north and south hemispheres respectively) —creating "discontinuous permafrost". Usually, permafrost will remain discontinuous in a climate where the mean annual soil surface temperature is between . In the moist-wintered areas mentioned before, there may not be even discontinuous permafrost down to . Discontinuous permafrost is often further divided into "extensive discontinuous permafrost", where permafrost covers between 50 and 90 percent of the landscape and is usually found in areas with mean annual temperatures between , and "sporadic permafrost", where permafrost cover is less than 50 percent of the landscape and typically occurs at mean annual temperatures between .


title: Permafrost

text: In soil science, the sporadic permafrost zone is abbreviated SPZ and the extensive discontinuous permafrost zone DPZ. Exceptions occur in "un-glaciated" Siberia and Alaska where the present depth of permafrost is a relic of climatic conditions during glacial ages where winters were up to colder than those of today.


title: Permafrost

text: At mean annual soil surface temperatures below the influence of aspect can never be sufficient to thaw permafrost and a zone of "continuous permafrost" (abbreviated to CPZ) forms. A "line of continuous permafrost" in the Northern Hemisphere represents the most southern border where land is covered by continuous permafrost or glacial ice. The line of continuous permafrost varies around the world northward or southward due to regional climatic changes. In the southern hemisphere, most of the equivalent line would fall within the Southern Ocean if there were land there. Most of the Antarctic continent is overlain by glaciers, under which much of the terrain is subject to basal melting. The exposed land of Antarctica is substantially underlain with permafrost, some of which is subject to warming and thawing along the coastline.


title: Permafrost

text: Alpine permafrost occurs at elevations with low enough average temperatures to sustain perennially frozen ground; much alpine permafrost is discontinuous. Estimates of the total area of alpine permafrost vary. Bockheim and Munroe combined three sources and made the tabulated estimates by region, totaling .


title: Permafrost

text: Alpine permafrost in the Andes has not been mapped. Its extent has been modeled to assess the amount of water bound up in these areas. In 2009, a researcher from Alaska found permafrost at the level on Africa's highest peak, Mount Kilimanjaro, approximately 3° south of the equator.


title: Permafrost

text: Subsea permafrost occurs beneath the seabed and exists in the continental shelves of the polar regions. These areas formed during the last ice age, when a larger portion of Earth's water was bound up in ice sheets on land and when sea levels were low. As the ice sheets melted to again become seawater, the permafrost became submerged shelves under relatively warm and salty boundary conditions, compared to surface permafrost. Therefore, subsea permafrost exists in conditions that lead to its diminishment. According to Osterkamp, subsea permafrost is a factor in the "design, construction, and operation of coastal facilities, structures founded on the seabed, artificial islands, sub-sea pipelines, and wells drilled for exploration and production." It also contains gas hydrates in places, which are a "potential abundant source of energy" but may also destabilize as subsea permafrost warms and thaws, producing large amounts of methane gas, which is a potent greenhouse gas. Scientists report with high confidence that the extent of subsea permafrost is decreasing, and 97% of permafrost under Arctic ice shelves is currently thinning.


title: Permafrost

text: Permafrost extends to a base depth where geothermal heat from the Earth and the mean annual temperature at the surface achieve an equilibrium temperature of 0 °C. The base depth of permafrost reaches in the northern Lena and Yana River basins in Siberia. The geothermal gradient is the rate of increasing temperature with respect to increasing depth in the Earth's interior. Away from tectonic plate boundaries, it is about 25–30 °C/km (124–139 °F/mi) near the surface in most of the world. It varies with the thermal conductivity of geologic material and is less for permafrost in soil than in bedrock.


title: Permafrost

text: Calculations indicate that the time required to form the deep permafrost underlying Prudhoe Bay, Alaska was over a half-million years. This extended over several glacial and interglacial cycles of the Pleistocene and suggests that the present climate of Prudhoe Bay is probably considerably warmer than it has been on average over that period. Such warming over the past 15,000 years is widely accepted. The table to the right shows that the first hundred metres of permafrost forms relatively quickly but that deeper levels take progressively longer.


title: Permafrost

text: When the ice content of a permafrost exceeds 250 percent (ice to dry soil by mass) it is classified as "massive" ice. Massive ice bodies can range in composition, in every conceivable gradation from icy mud to pure ice. Massive icy beds have a minimum thickness of at least 2 m and a short diameter of at least 10 m. First recorded North American observations were by European scientists at Canning River, Alaska in 1919. Russian literature provides an earlier date of 1735 and 1739 during the Great North Expedition by P. Lassinius and Kh. P. Laptev, respectively. Two categories of massive ground ice are "buried surface ice" and "intrasedimental ice" (also called "constitutional ice").


title: Permafrost

text: Buried surface ice may derive from snow, frozen lake or sea ice, aufeis (stranded river ice) and—probably the most prevalent—buried glacial ice.


title: Permafrost

text: Intrasedimental ice forms by in-place freezing of subterranean waters and is dominated by segregational ice which results from the crystallizational differentiation taking place during the freezing of wet sediments, accompanied by water migrating to the freezing front.


title: Permafrost

text: Intrasedimental or constitutional ice has been widely observed and studied across Canada and also includes intrusive and injection ice.


title: Permafrost

text: Additionally, ice wedges—a separate type of ground ice—produce recognizable patterned ground or tundra polygons. Ice wedges form in a pre-existing geological substrate and were first described in 1919.


title: Permafrost

text: Permafrost processes manifest themselves in large-scale land forms, such as palsas and pingos and smaller-scale phenomena, such as patterned ground found in arctic, periglacial and alpine areas. In ice-rich permafrost areas, melting of ground ice initiates thermokarst landforms such as thermokarst lakes, thaw slumps, thermal-erosion gullies, and active layer detachments.


title: Permafrost

text: The permafrost carbon cycle (Arctic Carbon Cycle) deals with the transfer of carbon from permafrost soils to terrestrial vegetation and microbes, to the atmosphere, back to vegetation, and finally back to permafrost soils through burial and sedimentation due to cryogenic processes. Some of this carbon is transferred to the ocean and other portions of the globe through the global carbon cycle. The cycle includes the exchange of carbon dioxide and methane between terrestrial components and the atmosphere, as well as the transfer of carbon between land and water as methane, dissolved organic carbon, dissolved inorganic carbon, particulate inorganic carbon and particulate organic carbon.


title: Permafrost

text: Arctic permafrost has been diminishing for decades. Globally, permafrost warmed by about between 2007 and 2016, with stronger warming observed in the continuous permafrost zone relative to the discontinuous zone. The consequence is thawing soil, which may be weaker, and release of methane, which contributes to an increased rate of global warming as part of a feedback loop caused by microbial decomposition. Wetlands drying out from drainage or evaporation compromises the ability of plants and animals to survive. When permafrost continues to diminish, many climate change scenarios will be amplified. In areas where permafrost is high, nearby human infrastructure may be damaged severely by the thawing of permafrost. It is believed that carbon storage in permafrost globally is approximately 1600 gigatons; equivalent to twice the atmospheric pool.


title: Permafrost

text: At the Last Glacial Maximum, continuous permafrost covered a much greater area than it does today, covering all of ice-free Europe south to about Szeged (southeastern Hungary) and the Sea of Azov (then dry land) and East Asia south to present-day Changchun and Abashiri. In North America, only an extremely narrow belt of permafrost existed south of the ice sheet at about the latitude of New Jersey through southern Iowa and northern Missouri, but permafrost was more extensive in the drier western regions where it extended to the southern border of Idaho and Oregon. In the southern hemisphere, there is some evidence for former permafrost from this period in central Otago and Argentine Patagonia, but was probably discontinuous, and is related to the tundra. Alpine permafrost also occurred in the Drakensberg during glacial maxima above about .


title: Permafrost

text: By definition, permafrost is ground that remains frozen for two or more years. The ground can consist of many substrate materials, including bedrock, sediment, organic matter, water or ice. Frozen ground is that which is below the freezing point of water, whether or not water is present in the substrate. Ground ice is not always present, as may be the case with nonporous bedrock, but it frequently occurs and may be present in amounts exceeding the potential hydraulic saturation of the thawed substrate.


title: Permafrost

text: During thaw, the ice content of the soil melts and, as the water drains or evaporates, causes the soil structure to weaken and sometimes become viscous until it regains strength with decreasing moisture content. Thawing can also influence the rate of change of soil gases with the atmosphere. One visible sign of permafrost degradation is the random displacement of trees from their vertical orientation in permafrost areas.


title: Permafrost

text: Over the past century, an increasing number of alpine rock slope failure events in mountain ranges around the world have been recorded. It is expected that the high number of structural failures is due to permafrost thawing, which is thought to be linked to climate change. Permafrost thawing is thought to have contributed to the 1987 Val Pola landslide that killed 22 people in the Italian Alps. In mountain ranges, much of the structural stability can be attributed to glaciers and permafrost. As climate warms, permafrost thaws, which results in a less stable mountain structure, and ultimately more slope failures.


title: Permafrost

text: McSaveney reported massive rock and ice falls (up to 11.8 million m), earthquakes (up to 3.9 Richter), floods (up to 7.8 million m water), and rapid rock-ice flow to long distances (up to 7.5 km at 60 m/s) caused by “instability of slopes” in high mountain permafrost. Instability of slopes in permafrost at elevated temperatures near freezing point in warming permafrost is related to effective stress and buildup of pore-water pressure in these soils. Kia and his co-inventors invented a new filter-less rigid piezometer (FRP) for measuring pore-water pressure in partially frozen soils such as warming permafrost soils. They extended the use of effective stress concept to partially frozen soils for use in slope stability analysis of warming permafrost slopes. The use of effective stress concept has many advantages such as ability to extend the concepts of "Critical State Soil Mechanics" into frozen ground engineering.


title: Permafrost

text: According to the University of Alaska Fairbanks, frozen debris lobes (FDLs) are "slow-moving landslides composed of soil, rocks, trees, and ice that occur in permafrost. As of December 2021, there were 43 frozen debris lobes identified in the southern Brooks Range along the Trans Alaska Pipeline System (TAPS) corridor and the main highway linking Interior Alaska and the Alaska North Slope—the Dalton Highway. By 2012, some FDLs measured over in width, in height, and in length. Based on measurements of a frozen debris-lobe southern Brooks Range in Alaska taken from 2008 to 2010, researchers found accelerated movement as ice in deeper layers of soil melted with rising temperatures. Ice within the soil melts, causing loss of soil strength, accelerated movement, and potential debris flows. They raised concerns of a future potential hazard of one debris lobe to both the Trans Alaska Pipeline System and the main highway linking Interior Alaska and the North Slope—Dalton Highway.


title: Permafrost

text: In the northern circumpolar region, permafrost contains 1700 billion tons of organic material equaling almost half of all organic material in all soils. This pool was built up over thousands of years and is only slowly degraded under the cold conditions in the Arctic. The amount of carbon sequestered in permafrost is four times the carbon that has been released to the atmosphere due to human activities in modern time. One manifestation of this is yedoma, which is an organic-rich (about 2% carbon by mass) Pleistocene-age loess permafrost with ice content of 50–90% by volume.


title: Permafrost

text: Formation of permafrost has significant consequences for ecological systems, primarily due to constraints imposed upon rooting zones, but also due to limitations on den and burrow geometries for fauna requiring subsurface homes. Secondary effects impact species dependent on plants and animals whose habitat is constrained by the permafrost. One of the most widespread examples is the dominance of black spruce in extensive permafrost areas, since this species can tolerate rooting pattern constrained to the near surface.


title: Permafrost

text: The number of bacteria in permafrost soil varies widely, typically from 1 to 1000 million per gram of soil. Most of these bacteria and fungi in permafrost soil cannot be cultured in the laboratory, but the identity of the microorganisms can be revealed by DNA-based techniques.


title: Permafrost

text: Global warming has been increasing permafrost slope disturbances and sediment supplies to fluvial systems, resulting in exceptional increases in river sediment.


title: Permafrost

text: Scientists predict that up to 10 microbes, including fungi and bacteria in addition to viruses, will be released from melting ice per year. Often, these microbes will be released directly into the ocean. Due to the migratory nature of many species of fish and birds, it is possible that these microbes have a high transmission rate.


title: Permafrost

text: Permafrost in eastern Switzerland was analyzed by researchers in 2016 at an alpine permafrost site called “Muot-da-Barba-Peider”.This site had a diverse microbial community with various bacteria and eukaryotic groups present. Prominent bacteria groups included phylum Acidobacteriota, Actinomycetota, AD3, Bacteroidota, Chloroflexota, Gemmatimonadota, OD1, Nitrospirota, Planctomycetota, Pseudomonadota, and Verrucomicrobiota. Prominent eukaryotic fungi included Ascomycota, Basidiomycota, and Zygomycota. In the present species, scientists observed a variety of adaptations for sub-zero conditions, including reduced and anaerobic metabolic processes.


title: Permafrost

text: A 2016 outbreak of anthrax in the Yamal Peninsula is believed to be due to thawing permafrost. Also present in Siberian permafrost are two species of virus: Pithovirus sibericum and Mollivirus sibericum. Both of these are approximately 30,000 years old and considered giant viruses due to the fact that they are larger in size than most bacteria and have genomes larger than other viruses. Both viruses are still infective, as seen by their ability to infect Acanthamoeba, a genus of amoebas.


title: Permafrost

text: Freezing at low temperatures has been shown to preserve the infectivity of viruses. Caliciviruses, influenza A, and enteroviruses (ex. Polioviruses, echoviruses, Coxsackie viruses) have all been preserved in ice and/or permafrost. Scientists have determined three characteristics necessary for a virus to successfully preserve in ice: high abundance, ability to transport in ice, and ability to resume disease cycles upon being released from ice. A direct infection from permafrost or ice to humans has not been demonstrated; such viruses are typically spread through other organisms or abiotic mechanisms.


title: Permafrost

text: A study of late Pleistocene Siberian permafrost samples from Kolyma Lowland (an east siberian lowland) used DNA isolation and gene cloning (specifically 16S rRNA genes) to determine which phyla these microorganisms belonged to. This technique allowed a comparison of known microorganisms to their newly discovered samples and revealed eight phylotypes, which belonged to the phyla Actinomycetota and Pseudomonadota.


title: Permafrost

text: In 2012, Russian researchers proved that permafrost can serve as a natural repository for ancient life forms by reviving of "Silene stenophylla" from 30,000 year old tissue found in an Ice Age squirrel burrow in the Siberian permafrost. This is the oldest plant tissue ever revived. The plant was fertile, producing white flowers and viable seeds. The study demonstrated that tissue can survive ice preservation for tens of thousands of years.


title: Permafrost

text: The International Permafrost Association (IPA) is an integrator of issues regarding permafrost. It convenes International Permafrost Conferences, undertakes special projects such as preparing databases, maps, bibliographies, and glossaries, and coordinates international field programmes and networks. Among other issues addressed by the IPA are: Problems for construction on permafrost owing to the change of soil properties of the ground on which structures are placed and the biological processes in permafrost, e.g. the preservation of organisms frozen "in situ".


title: Permafrost

text: Yakutsk is one of two large cities in the world built in areas of continuous permafrost—that is, where the frozen soil forms an unbroken, below-zero sheet. The other is Norilsk, in Krasnoyarsk Krai, Russia.


title: Permafrost

text: Building on permafrost is difficult because the heat of the building (or pipeline) can warm the permafrost and destabilize the structure. Warming can result in thawing of the soil and its consequent weakening of support for a structure as the ice content turns to water; alternatively, where structures are built on piles, warming can cause movement through creep because of the change of friction on the piles even as the soil remains frozen.


title: Permafrost

text: Three common solutions include: using foundations on wood piles, a technique pioneered by Soviet engineer Mikhail Kim in Norilsk; building on a thick gravel pad (usually 1–2 metres/3.3–6.6 feet thick); or using anhydrous ammonia heat pipes. The Trans-Alaska Pipeline System uses heat pipes built into vertical supports to prevent the pipeline from sinking and the Qingzang railway in Tibet employs a variety of methods to keep the ground cool, both in areas with frost-susceptible soil. Permafrost may necessitate special enclosures for buried utilities, called "utilidors".


title: Permafrost

text: The Melnikov Permafrost Institute in Yakutsk, found that the sinking of large buildings into the ground can be prevented by using pile foundations extending down to or more. At this depth the temperature does not change with the seasons, remaining at about .


title: Permafrost

text: Thawing permafrost represents a threat to industrial infrastructure. In May 2020 thawing permafrost at Norilsk-Taimyr Energy's Thermal Power Plant No. 3 caused an oil storage tank to collapse, spilling 6,000 tonnes of diesel into the land, 15,000 into the water. The rivers Ambarnaya, Daldykan and many smaller rivers were polluted. The pollution reached the lake Pyasino that is important to the water supply of the entire Taimyr Peninsula. State of emergency at the federal level was declared. Many buildings and infrastructure are built on permafrost, which cover 65% of Russian territory, and all those can be damaged as it thaws. The 2020 Norilsk oil spill has been described as the second-largest oil spill in modern Russian history. The thawing can also cause leakage of toxic elements from sites of buried toxic waste.


title: Permafrost

text: There is no ground water available in an area underlain with permafrost. Any substantial settlement or installation needs to make some alternative arrangement to obtain water.


title: Save the Last Dance

text: Save the Last Dance is a 2001 American teen dance film produced by MTV Films, directed by Thomas Carter and distributed by Paramount Pictures. The film stars Julia Stiles and Sean Patrick Thomas as a teenage interracial couple in Chicago who work together to help Stiles' character train for a Juilliard School dance audition.


title: Save the Last Dance

text: Released theatrically in the United States on January 12, 2001, the film received mixed reviews from critics but was a box-office success and grossed $131.7 million worldwide against a $13 million budget.


title: Save the Last Dance

text: Seventeen-year-old Sara Johnson, a promising ballet dancer in suburban Chicago, hopes to be admitted to Juilliard School and implores her mother to attend the audition. She fails the audition and soon learns that her mother was killed in a car accident in her haste to get to it.


title: Save the Last Dance

text: Sara is wracked with guilt and gives up ballet. She moves to the South Side to live with her estranged father Roy, a jazz musician who plays the trumpet at nightclubs. Sara also transfers to a majority-black high school, where she is one of a handful of white students, but quickly befriends Chenille Reynolds, a teenage single mother who is having relationship problems with her ex-boyfriend Kenny. Chenille invites Sara to a dance club called Stepps, where she has her first experience dancing to hip hop rhythms. At Stepps, Sara dances with Derek, Chenille's brother and a student with dreams of attending Georgetown University to become a pediatrician. Derek decides to help Sara develop her dancing skills by incorporating more hip hop into her style. He takes a reluctant Sara to the Joffrey Ballet and, afterwards, she confides in him about her mother and her dreams. Later, they return to the club and amaze others with their dancing. While performing, Derek's ex-girlfriend Nikki interrupts the two and begins dancing with Derek, making Sara retreat to the bar. Afterward, Derek returns to Sara and apologizes for pairing up with Nikki; they subsequently make up and return to Roy's apartment. Having achieved his dream of being accepted into Georgetown, Derek convinces Sara to follow her dreams of Juilliard; they eventually begin a romantic relationship.


title: Save the Last Dance

text: At school, Nikki picks a fight with Sara. Later, Chenille tells Sara that she did not approve of the fight, but can understand the bitterness since Sara, a white girl, is stealing one of the decent black boys at school. Because of this conversation, Sara and Chenille's friendship becomes strained, and Sara decides to break up with Derek. Meanwhile, Derek deals with his friend Malakai, who is heavily involved in the gang lifestyle that Derek is trying to leave. Derek agrees to help Malakai execute a drive-by at the same time as Sara's audition. Roy has a heart-to-heart talk with Sara and encourages her to go through with the audition.


title: Save the Last Dance

text: After learning what Chenille said to Sara, Derek confronts her about it, as well as explains his true reasons for dumping Nikki. Remorseful for her actions, Chenille admits that what she did was wrong and apologizes. She also tells Derek that Sara did not want to dump him, but Chenille's words hurt her to the point of feeling forced to. Chenille also admits that she has been resentful for how Kenny has been treating her, including not helping her raise their son and not being a good boyfriend to her. She unintentionally took it out on Sara since she has been jealous of her and Derek's relationship. Chenille encourages Derek to be with Sara, admitting that she knows that Sara is in love with him. She also warns Derek not to follow Malakai, knowing that he may lose his chance to attend Georgetown and his future if he is arrested. Derek decides to bail on Malakai to attend Sara's audition, arriving at a crucial point in her performance to offer her encouragement and moral support. Afterward, Sara is accepted into Juilliard and she rekindles her relationship with Derek. Meanwhile, the drive-by is botched and Malakai is arrested. The film closes as Sara, Derek, Chenille, and their friends meet at Stepps to celebrate Sara's successful audition.


title: Save the Last Dance

text: Julia Stiles landed the role as Sara when director Thomas Carter saw her dance scene in the 1999 film "10 Things I Hate About You". To prepare for her role, Stiles did two months of training for the ballet scenes while also rehearsing the choreography for the hip hop scenes. Fatima Robinson was the film's hip hop choreographer.


title: Save the Last Dance

text: The film's soundtrack was released on December 19, 2000, through Hollywood Records and consisted of hip hop and R&B music. The soundtrack was a huge success, and made it to several Billboard charts. It peaked at 3 on the "Billboard" 200, 2 on the Top R&B/Hip-Hop Albums, 6 on the Top Soundtracks, 3 on the Top Internet Albums and 2 on the Canadian Albums Chart, and featured two charting singles "Crazy" and "You". "Save the Last Dance" went both gold and platinum on January 29, 2001, and was certified 2x multi-platinum on May 20, 2002. The soundtrack won the American Music Award for Best Soundtrack in 2002.


title: Save the Last Dance

text: Allmusic rated the soundtrack three out of five stars. RapReviews rated it three and a half out of ten.


title: Save the Last Dance

text: The film debuted at number 1 at the North American box office making $27.5 million in its opening weekend. Though the film had a 44% decline in earnings the following weekend, it was still enough to keep the film at the top spot for another week. It grossed $91,057,006 in the US alone and $131.7 million worldwide.


title: Save the Last Dance

text: The film was released on DVD and VHS on June 19, 2001. It was re-released on DVD on January 24, 2017.


title: Save the Last Dance

text: On Rotten Tomatoes, it has a approval rating based on reviews, with an average score of and a consensus: "This teen romance flick feels like a predictable rehashing of other movies."


title: Save the Last Dance

text: Positive reviews praised the performances of Stiles, Thomas, and Washington. Desson Howe of "The Washington Post" called Stiles and Washington appealing performers and concluded, "Thomas is the movie's best element. He puts so much authority in his performance, he makes this controversial romance seem like the best thing that could happen to anyone. That's no easy task."


title: Save the Last Dance

text: In a three-star review, Roger Ebert said that despite the film's clichéd story and romance, "the development is intelligent, the characters are more complicated than we expect, and the ending doesn't tie everything up in a predictable way." Charles Taylor of Salon wrote, "for all its dumb clichés it offers the basic appeal of teen movies: the pleasure of watching kids be kids, acting as they do among themselves instead of how parents and teachers expect them to act."


title: Save the Last Dance

text: Writing for the "Chicago Tribune", Mark Caro wrote, "On paper the movie is full of cliches recently explored elsewhere...Yet in this case the outline is not the story; the people who inhabit it are," and in this way, ""Save the Last Dance" triumphantly passes the audition."


title: Save the Last Dance

text: Negative reviews criticized the editing style of dance scenes, the film's "after-school special"-like subplot, and the script for not delving enough into the issues of interracial relationships. Critic Wesley Morris wrote "the movie combines the worst of urbansploitation with the worst of teensploitation, and outfits them both in makings of the ultimate racial-crossover melodrama -- teen motherhood, deadbeat teen dads, drive-bys, a dangerous ex-girlfriend, speeches straight from the pages of Terry McMillan." Lisa Schwarzbaum of "Entertainment Weekly" wrote, "director Thomas Carter is afraid to pump up the volume on its own interracial, hip hop Romeo and Juliet story, lest it challenge even one sedated viewer or disturb the peace."


title: Save the Last Dance

text: A sequel to the film, titled "Save the Last Dance 2", was released direct-to-video on October 10, 2006.


title: Dominic Calvert-Lewin

text: Dominic Nathaniel Calvert-Lewin (born 16 March 1997) is an English professional footballer who plays as a striker for club Everton and the England national team.


title: Dominic Calvert-Lewin

text: Calvert-Lewin began his career at local team Sheffield United, making his senior debut on loan at Conference North team Stalybridge Celtic in December 2014. He spent the first half of the 2015–16 season on loan at Northampton Town in League Two, and in August 2016 he joined Everton for a fee of £1.5 million.


title: Dominic Calvert-Lewin

text: Calvert-Lewin was part of the England national under-20 team that won the 2017 FIFA U-20 World Cup, scoring in the final. He made his debut for the England national team in October 2020 and subsequently scored in a 3–0 friendly win against Wales at Wembley Stadium.


title: Dominic Calvert-Lewin

text: Calvert-Lewin joined the Youth Academy of Sheffield United on 28 April 2005. After progressing through the ranks of Sheffield United youth team, he signed a scholarship with the academy when he was sixteen. At this level he played as a box-to-box midfielder.


title: Dominic Calvert-Lewin

text: Calvert-Lewin appeared in the first team as an unused substitute, in a 2–1 win over Aston Villa in the third round of FA Cup on 4 January 2014. After this, he was awarded for the League Football Education's 'The 11'.


title: Dominic Calvert-Lewin

text: On 24 December 2014, Calvert-Lewin was loaned out to Conference North team Stalybridge Celtic for a youth loan, where he began to play as a centre forward. Two days later, he scored twice on his debut, in a 4–2 win at Hyde United and scored against them again in the reverse fixture on 1 January, in a 7–1 win. At the beginning of February 2015, Calvert-Lewin returned to his parent club, having scored six times in five appearances.


title: Dominic Calvert-Lewin

text: In early April 2015, he signed a new long-term deal to keep him at Bramall Lane until summer 2018. Calvert-Lewin made his professional début for the senior team on 25 April in League One, in a 1–1 draw away at Leyton Orient as a 66th-minute substitute. At the end of the 2014–15 season, he went on to make two appearances. In the club's pre-season tour ahead of the 2015–16 season, Calvert-Lewin scored in a friendly match, in a 1–0 win over Ilkeston on 9 July. Following the match, manager Nigel Adkins hinted that Calvert-Lewin earned himself a first team chance in the 2015–16 season.


title: Dominic Calvert-Lewin

text: On 7 August 2015, Calvert-Lewin joined League Two club Northampton Town on loan until January. He made his debut four days later, scoring in a 3–0 home win against Blackpool in the first round of the League Cup. Despite being keen to extend his loan at the club, this did not materialise. By the time he left, he had made 26 appearances and scored 8 times across all competitions.


title: Dominic Calvert-Lewin

text: After his loan spell at Northampton Town came to an end in January 2016, Calvert-Lewin returned to the first team at Sheffield United, and did not make his first appearance until 13 February, in a 1–0 win over Doncaster Rovers. Nevertheless, he went on to make nine appearances for the team in the 2015–16 season.


title: Dominic Calvert-Lewin

text: Ahead of the 2016–17 season, there were hints of Calvert-Lewin making a first team breakthrough, with his former manager Wilder appointed as the new Sheffield United manager. He only made one appearance in the 2016–17 season, which was against Crewe Alexandra, in a 2–1 loss in the EFL Cup campaign.


title: Dominic Calvert-Lewin

text: Calvert-Lewin signed for Everton in a £1.5 million deal on 31 August 2016. He later reflected on the move as "simply too good to resist." He made his debut as a substitute in a 2–1 win over Arsenal on 13 December 2016. After missing out for two months due to ankle injury, Calvert-Lewin scored his first goal for Everton in a Premier League fixture against Hull City on 18 March 2017, a 4–0 win. On 3 May 2017, he signed a five-year contract, keeping him until 2022. At the end of the 2016–17 season, he finished his first season, making 11 appearances and scoring once in all competitions.


title: Dominic Calvert-Lewin

text: Following his World Cup performance, "BBC Sport" expected Calvert-Lewin to make a first team breakthrough ahead of the 2017–18 season. Calvert-Lewin scored the winner for Everton in their Europa League third qualifying round second leg against Slovakian team MFK Ružomberok on 3 August 2017. He scored his first brace for the club in the third round of the EFL Cup against Sunderland on 20 September, ending a run of three games in which Everton did not score. Calvert-Lewin signed a new contract with Everton on 14 December, along with fellow youngsters Jonjoe Kenny and Mason Holgate, keeping him at Goodison Park until June 2023.


title: Dominic Calvert-Lewin

text: On 24 September 2019, in his 100th Everton match, Calvert-Lewin scored both goals of a win at Sheffield Wednesday – rivals of his first club Sheffield United – in the third round of the EFL Cup. The following 6 March with his contract due to expire, and while on 15 goals from 31 games for the season, he signed a new deal to last until June 2025.


title: Dominic Calvert-Lewin

text: On 13 September 2020, he started the 2020–21 season by scoring the winning goal with a header in a 1–0 win over Tottenham Hotspur, followed by his first Premier League hat-trick in a 5–2 victory over West Bromwich Albion. On 30 September, he scored a hat-trick in a 4–1 win against West Ham United in the EFL Cup. That made Calvert-Lewin the first Everton player to score two hat-tricks in one month since Dixie Dean in November 1931. Calvert-Lewin scored in the fourth succession in the Premier League with a towering header against Brighton & Hove Albion in a 4–2 victory at Goodison Park on 3 October 2020. He was named as the Premier League Player of the Month for September 2020 after scoring five league goals that month. Calvert-Lewin scored in the fifth succession in the Premier League with another header against Liverpool in a 2–2 draw at Goodison Park on 17 October 2020. Calvert-Lewin scored another brace, including his ninth and 10th league goal of the season, in a 3–2 away win against Fulham on 22 November 2020. After scoring 21 goals in 33 matches in all competitions across the 2020–21 season, Calvert-Lewin was awarded Everton's Player of the Year award at their end of season awards evening.


title: Dominic Calvert-Lewin

text: In September 2021, he had a fractured toe which kept him off the field for four months. On 19 May 2022, he scored the winning goal in a 3–2 victory over Crystal Palace, to secure his club's safety from relegation in the 2021–22 season.


title: Dominic Calvert-Lewin

text: Calvert-Lewin made his England U20 debut on 1 September 2016, in a 1–1 draw against Brazil U20, followed up scoring in his second appearance, in a 2–1 loss three days later. He later scored against Germany U20 (twice) and Senegal U20.


title: Dominic Calvert-Lewin

text: Calvert-Lewin was selected to play for England in the 2017 FIFA U-20 World Cup in South Korea. He scored two goals in the tournament; his first was the first goal of tournament for England scored in the match against Argentina, the last was the winning goal in the final as they beat Venezuela 1–0. He joined Geoff Hurst and Martin Peters as the only England players to score in a World Cup Final.


title: Dominic Calvert-Lewin

text: On 27 May 2019, Calvert-Lewin was included in England's 23-man squad for the 2019 UEFA European Under-21 Championship.


title: Dominic Calvert-Lewin

text: Calvert-Lewin received his first England call-up by Gareth Southgate on 1 October 2020 after scoring eight goals in five appearances, including two hat-tricks, for Everton in the opening weeks of the 2020–21 season. He scored with a header in his maiden appearance for England, a 3–0 friendly win against Wales at Wembley Stadium on 8 October. He scored his first brace on 26 March 2021 in a 5–0 win against San Marino.


title: Dominic Calvert-Lewin

text: Sheffield United staff Keith Briggs and Neill Collins reacted positively about Calvert-Lewin, including his attitude, while Chris Short described him as "football mad and a special talent." Manager Nigel Clough said of him: "He's a big lad who is good technically for the stage he's at and he's going to win headers against anybody", while manager Nigel Adkins described Calvert-Lewin's impressive performance in a training session: "He took the ball with his back to goal, controlled it and popped an overhead kick straight in the top corner. Brilliant stuff." Carlo Ancelotti suggested Calvert-Lewin has all the qualities to be a top striker: "He is fantastic with the head, clever in the box and sharp. I think he is going to be at the top in England and in Europe."


title: Dominic Calvert-Lewin

text: Born and brought up in Sheffield, South Yorkshire, Calvert-Lewin supported Sheffield United. During his time at Northampton Town, he resided with his then teammate Ryan Cresswell and developed a good friendship.


title: Dominic Calvert-Lewin

text: Calvert-Lewin has been noted by fashion journalists for his choice of clothing, and in November 2021 he appeared on the front cover of "Arena Homme +" wearing a suit, flared shorts and a pink Prada handbag. In April 2022, he featured in British "GQ" with a Chanel handbag from his own collection.


title: Dominic Calvert-Lewin

text: In February 2020, he and Everton teammate Tom Davies used a break in the season to attend New York Fashion Week.


title: Mathematical optimization

text: Mathematical optimization (alternatively spelled "optimisation") or mathematical programming is the selection of a best element, with regard to some criterion, from some set of available alternatives. It is generally divided into two subfields: discrete optimization and continuous optimization. Optimization problems of sorts arise in all quantitative disciplines from computer science and engineering to operations research and economics, and the development of solution methods has been of interest in mathematics for centuries.


title: Mathematical optimization

text: In the more general approach, an optimization problem consists of maximizing or minimizing a real function by systematically choosing input values from within an allowed set and computing the value of the function. The generalization of optimization theory and techniques to other formulations constitutes a large area of applied mathematics. More generally, optimization includes finding "best available" values of some objective function given a defined domain (or input), including a variety of different types of objective functions and different types of domains.


title: Mathematical optimization

text: Optimization problems can be divided into two categories, depending on whether the variables are continuous or discrete:


title: Mathematical optimization

text: Such a formulation is called an optimization problem or a mathematical programming problem (a term not directly related to computer programming, but still in use for example in linear programming – see History below). Many real-world and theoretical problems may be modeled in this general framework.


title: Mathematical optimization

text: it suffices to solve only minimization problems. However, the opposite perspective of considering only maximization problems would be valid, too.


title: Mathematical optimization

text: Problems formulated using this technique in the fields of physics may refer to the technique as "energy minimization", speaking of the value of the function as representing the energy of the system being modeled. In machine learning, it is always necessary to continuously evaluate the quality of a data model by using a cost function where a minimum implies a set of possibly optimal parameters with an optimal (lowest) error.


title: Mathematical optimization

text: Typically, is some subset of the Euclidean space , often specified by a set of "constraints", equalities or inequalities that the members of have to satisfy. The domain of is called the "search space" or the "choice set", while the elements of are called "candidate solutions" or "feasible solutions".


title: Mathematical optimization

text: The function is called, variously, an "objective function", a "loss function" or "cost function" (minimization), a "utility function" or "fitness function" (maximization), or, in certain fields, an "energy function" or "energy functional". A feasible solution that minimizes (or maximizes, if that is the goal) the objective function is called an "optimal solution".


title: Mathematical optimization

text: that is to say, on some region around all of the function values are greater than or equal to the value at that element.


title: Mathematical optimization

text: While a local minimum is at least as good as any nearby elements, a global minimum is at least as good as every feasible element.


title: Mathematical optimization

text: Generally, unless the objective function is convex in a minimization problem, there may be several local minima.


title: Mathematical optimization

text: In a convex problem, if there is a local minimum that is interior (not on the edge of the set of feasible elements), it is also the global minimum, but a nonconvex problem may have more than one local minimum not all of which need be global minima.


title: Mathematical optimization

text: A large number of algorithms proposed for solving the nonconvex problems – including the majority of commercially available solvers – are not capable of making a distinction between locally optimal solutions and globally optimal solutions, and will treat the former as actual solutions to the original problem. Global optimization is the branch of applied mathematics and numerical analysis that is concerned with the development of deterministic algorithms that are capable of guaranteeing convergence in finite time to the actual optimal solution of a nonconvex problem.


title: Mathematical optimization

text: This denotes the minimum value of the objective function , when choosing from the set of real numbers . The minimum value in this case is 1, occurring at .


title: Mathematical optimization

text: asks for the maximum value of the objective function , where may be any real number. In this case, there is no such maximum as the objective function is unbounded, so the answer is "infinity" or "undefined".


title: Mathematical optimization

text: This represents the value (or values) of the argument in the interval that minimizes (or minimize) the objective function (the actual minimum value of that function is not what the problem asks for). In this case, the answer is , since is infeasible, that is, it does not belong to the feasible set.


title: Mathematical optimization

text: represents the pair (or pairs) that maximizes (or maximize) the value of the objective function , with the added constraint that lie in the interval (again, the actual maximum value of the expression does not matter). In this case, the solutions are the pairs of the form and , where ranges over all integers.


title: Mathematical optimization

text: Operators and are sometimes also written as and , and stand for "argument of the minimum" and "argument of the maximum".


title: Mathematical optimization

text: Fermat and Lagrange found calculus-based formulae for identifying optima, while Newton and Gauss proposed iterative methods for moving towards an optimum.


title: Mathematical optimization

text: The term "linear programming" for certain optimization cases was due to George B. Dantzig, although much of the theory had been introduced by Leonid Kantorovich in 1939. ("Programming" in this context does not refer to computer programming, but comes from the use of "program" by the United States military to refer to proposed training and logistics schedules, which were the problems Dantzig studied at that time.) Dantzig published the Simplex algorithm in 1947, and John von Neumann developed the theory of duality in the same year.


title: Mathematical optimization

text: In a number of subfields, the techniques are designed primarily for optimization in dynamic contexts (that is, decision making over time):


title: Mathematical optimization

text: Adding more than one objective to an optimization problem adds complexity. For example, to optimize a structural design, one would desire a design that is both light and rigid. When two objectives conflict, a trade-off must be created. There may be one lightest design, one stiffest design, and an infinite number of designs that are some compromise of weight and rigidity. The set of trade-off designs that improve upon one criterion at the expense of another is known as the Pareto set. The curve created plotting weight against stiffness of the best designs is known as the Pareto frontier.


title: Mathematical optimization

text: A design is judged to be "Pareto optimal" (equivalently, "Pareto efficient" or in the Pareto set) if it is not dominated by any other design: If it is worse than another design in some respects and no better in any respect, then it is dominated and is not Pareto optimal.


title: Mathematical optimization

text: The choice among "Pareto optimal" solutions to determine the "favorite solution" is delegated to the decision maker. In other words, defining the problem as multi-objective optimization signals that some information is missing: desirable objectives are given but combinations of them are not rated relative to each other. In some cases, the missing information can be derived by interactive sessions with the decision maker.


title: Mathematical optimization

text: Multi-objective optimization problems have been generalized further into vector optimization problems where the (partial) ordering is no longer given by the Pareto ordering.


title: Mathematical optimization

text: Optimization problems are often multi-modal; that is, they possess multiple good solutions. They could all be globally good (same cost function value) or there could be a mix of globally good and locally good solutions. Obtaining all (or at least some of) the multiple solutions is the goal of a multi-modal optimizer.


title: Mathematical optimization

text: Classical optimization techniques due to their iterative approach do not perform satisfactorily when they are used to obtain multiple solutions, since it is not guaranteed that different solutions will be obtained even with different starting points in multiple runs of the algorithm.


title: Mathematical optimization

text: Common approaches to global optimization problems, where multiple local extrema may be present include evolutionary algorithms, Bayesian optimization and simulated annealing.


title: Mathematical optimization

text: The "satisfiability problem", also called the "feasibility problem", is just the problem of finding any feasible solution at all without regard to objective value. This can be regarded as the special case of mathematical optimization where the objective value is the same for every solution, and thus any solution is optimal.


title: Mathematical optimization

text: Many optimization algorithms need to start from a feasible point. One way to obtain such a point is to relax the feasibility conditions using a slack variable; with enough slack, any starting point is feasible. Then, minimize that slack variable until the slack is null or negative.


title: Mathematical optimization

text: The extreme value theorem of Karl Weierstrass states that a continuous real-valued function on a compact set attains its maximum and minimum value. More generally, a lower semi-continuous function on a compact set attains its minimum; an upper semi-continuous function on a compact set attains its maximum point or view.


title: Mathematical optimization

text: One of Fermat's theorems states that optima of unconstrained problems are found at stationary points, where the first derivative or the gradient of the objective function is zero (see first derivative test). More generally, they may be found at critical points, where the first derivative or gradient of the objective function is zero or is undefined, or on the boundary of the choice set. An equation (or set of equations) stating that the first derivative(s) equal(s) zero at an interior optimum is called a 'first-order condition' or a set of first-order conditions.


title: Mathematical optimization

text: Optima of equality-constrained problems can be found by the Lagrange multiplier method. The optima of problems with equality and/or inequality constraints can be found using the 'Karush–Kuhn–Tucker conditions'.


title: Mathematical optimization

text: While the first derivative test identifies points that might be extrema, this test does not distinguish a point that is a minimum from one that is a maximum or one that is neither. When the objective function is twice differentiable, these cases can be distinguished by checking the second derivative or the matrix of second derivatives (called the Hessian matrix) in unconstrained problems, or the matrix of second derivatives of the objective function and the constraints called the bordered Hessian in constrained problems. The conditions that distinguish maxima, or minima, from other stationary points are called 'second-order conditions' (see 'Second derivative test'). If a candidate solution satisfies the first-order conditions, then the satisfaction of the second-order conditions as well is sufficient to establish at least local optimality.


title: Mathematical optimization

text: The envelope theorem describes how the value of an optimal solution changes when an underlying parameter changes. The process of computing this change is called comparative statics.


title: Mathematical optimization

text: The maximum theorem of Claude Berge (1963) describes the continuity of an optimal solution as a function of underlying parameters.


title: Mathematical optimization

text: For unconstrained problems with twice-differentiable functions, some critical points can be found by finding the points where the gradient of the objective function is zero (that is, the stationary points). More generally, a zero subgradient certifies that a local minimum has been found for minimization problems with convex functions and other locally Lipschitz functions.


title: Mathematical optimization

text: Further, critical points can be classified using the definiteness of the Hessian matrix: If the Hessian is "positive" definite at a critical point, then the point is a local minimum; if the Hessian matrix is negative definite, then the point is a local maximum; finally, if indefinite, then the point is some kind of saddle point.


title: Mathematical optimization

text: Constrained problems can often be transformed into unconstrained problems with the help of Lagrange multipliers. Lagrangian relaxation can also provide approximate solutions to difficult constrained problems.


title: Mathematical optimization

text: When the objective function is a convex function, then any local minimum will also be a global minimum. There exist efficient numerical techniques for minimizing convex functions, such as interior-point methods.


title: Mathematical optimization

text: More generally, if the objective function is not a quadratic function, then many optimization methods use other methods to ensure that some subsequence of iterations converges to an optimal solution. The first and still popular method for ensuring convergence relies on line searches, which optimize a function along one dimension. A second and increasingly popular method for ensuring convergence uses trust regions. Both line searches and trust regions are used in modern methods of non-differentiable optimization. Usually, a global optimizer is much slower than advanced local optimizers (such as BFGS), so often an efficient global optimizer can be constructed by starting the local optimizer from different starting points.


title: Mathematical optimization

text: To solve problems, researchers may use algorithms that terminate in a finite number of steps, or iterative methods that converge to a solution (on some specified class of problems), or heuristics that may provide approximate solutions to some problems (although their iterates need not converge).


title: Mathematical optimization

text: The iterative methods used to solve problems of nonlinear programming differ according to whether they evaluate Hessians, gradients, or only function values. While evaluating Hessians (H) and gradients (G) improves the rate of convergence, for functions for which these quantities exist and vary sufficiently smoothly, such evaluations increase the computational complexity (or computational cost) of each iteration. In some cases, the computational complexity may be excessively high.


title: Mathematical optimization

text: One major criterion for optimizers is just the number of required function evaluations as this often is already a large computational effort, usually much more effort than within the optimizer itself, which mainly has to operate over the N variables. The derivatives provide detailed information for such optimizers, but are even harder to calculate, e.g. approximating the gradient takes at least N+1 function evaluations. For approximations of the 2nd derivatives (collected in the Hessian matrix), the number of function evaluations is in the order of N². Newton's method requires the 2nd-order derivatives, so for each iteration, the number of function calls is in the order of N², but for a simpler pure gradient optimizer it is only N. However, gradient optimizers need usually more iterations than Newton's algorithm. Which one is best with respect to the number of function calls depends on the problem itself.


title: Mathematical optimization

text: Besides (finitely terminating) algorithms and (convergent) iterative methods, there are heuristics. A heuristic is any algorithm which is not guaranteed (mathematically) to find the solution, but which is nevertheless useful in certain practical situations. List of some well-known heuristics:


title: Mathematical optimization

text: Problems in rigid body dynamics (in particular articulated rigid body dynamics) often require mathematical programming techniques, since you can view rigid body dynamics as attempting to solve an ordinary differential equation on a constraint manifold; the constraints are various nonlinear geometric constraints such as "these two points must always coincide", "this surface must not penetrate any other", or "this point must always lie somewhere on this curve". Also, the problem of computing contact forces can be done by solving a linear complementarity problem, which can also be viewed as a QP (quadratic programming) problem.


title: Mathematical optimization

text: Many design problems can also be expressed as optimization programs. This application is called design optimization. One subset is the engineering optimization, and another recent and growing subset of this field is multidisciplinary design optimization, which, while useful in many problems, has in particular been applied to aerospace engineering problems.


title: Mathematical optimization

text: Economics is closely enough linked to optimization of agents that an influential definition relatedly describes economics "qua" science as the "study of human behavior as a relationship between ends and scarce means" with alternative uses. Modern optimization theory includes traditional optimization theory but also overlaps with game theory and the study of economic equilibria. The "Journal of Economic Literature" codes classify mathematical programming, optimization techniques, and related topics under .


title: Mathematical optimization

text: In microeconomics, the utility maximization problem and its dual problem, the expenditure minimization problem, are economic optimization problems. Insofar as they behave consistently, consumers are assumed to maximize their utility, while firms are usually assumed to maximize their profit. Also, agents are often modeled as being risk-averse, thereby preferring to avoid risk. Asset prices are also modeled using optimization theory, though the underlying mathematics relies on optimizing stochastic processes rather than on static optimization. International trade theory also uses optimization to explain trade patterns between nations. The optimization of portfolios is an example of multi-objective optimization in economics.


title: Mathematical optimization

text: Since the 1970s, economists have modeled dynamic decisions over time using control theory. For example, dynamic search models are used to study labor-market behavior. A crucial distinction is between deterministic and stochastic models. Macroeconomists build dynamic stochastic general equilibrium (DSGE) models that describe the dynamics of the whole economy as the result of the interdependent optimizing decisions of workers, consumers, investors, and governments.


title: Mathematical optimization

text: Some common applications of optimization techniques in electrical engineering include active filter design, stray field reduction in superconducting magnetic energy storage systems, space mapping design of microwave structures, handset antennas, electromagnetics-based design. Electromagnetically validated design optimization of microwave components and antennas has made extensive use of an appropriate physics-based or empirical surrogate model and space mapping methodologies since the discovery of space mapping in 1993.


title: Mathematical optimization

text: Optimization has been widely used in civil engineering. Construction management and transportation engineering are among the main branches of civil engineering that heavily rely on optimization. The most common civil engineering problems that are solved by optimization are cut and fill of roads, life-cycle analysis of structures and infrastructures, resource leveling, water resource allocation, traffic management and schedule optimization.


title: Mathematical optimization

text: Another field that uses optimization techniques extensively is operations research. Operations research also uses stochastic modeling and simulation to support improved decision-making. Increasingly, operations research uses stochastic programming to model dynamic decisions that adapt to events; such problems can be solved with large-scale optimization and stochastic optimization methods.


title: Mathematical optimization

text: Mathematical optimization is used in much modern controller design. High-level controllers such as model predictive control (MPC) or real-time optimization (RTO) employ mathematical optimization. These algorithms run online and repeatedly determine values for decision variables, such as choke openings in a process plant, by iteratively solving a mathematical optimization problem including constraints and a model of the system to be controlled.


title: Mathematical optimization

text: Optimization techniques are regularly used in geophysical parameter estimation problems. Given a set of geophysical measurements, e.g. seismic recordings, it is common to solve for the physical properties and geometrical shapes of the underlying rocks and fluids. The majority of problems in geophysics are nonlinear with both deterministic and stochastic methods being widely used.


title: Mathematical optimization

text: Optimization techniques are used in many facets of computational systems biology such as model building, optimal experimental design, metabolic engineering, and synthetic biology. Linear programming has been applied to calculate the maximal possible yields of fermentation products, and to infer gene regulatory networks from multiple microarray datasets as well as transcriptional regulatory networks from high-throughput data. Nonlinear programming has been used to analyze energy metabolism and has been applied to metabolic engineering and parameter estimation in biochemical pathways.


title: Nuclear fallout

text: Nuclear fallout is the residual radioactive material propelled into the upper atmosphere following a nuclear blast, so called because it "falls out" of the sky after the explosion and the shock wave has passed. It commonly refers to the radioactive dust and ash created when a nuclear weapon explodes. The amount and spread of fallout is a product of the size of the weapon and the altitude at which it is detonated. Fallout may get entrained with the products of a pyrocumulus cloud and fall as black rain (rain darkened by soot and other particulates, which fell within 30–40 minutes of the atomic bombings of Hiroshima and Nagasaki). This radioactive dust, usually consisting of fission products mixed with bystanding atoms that are neutron-activated by exposure, is a form of radioactive contamination.


title: Nuclear fallout

text: Fallout comes in two varieties. The first is a small amount of carcinogenic material with a long half-life. The second, depending on the height of detonation, is a large quantity of radioactive dust and sand with a short half-life.


title: Nuclear fallout

text: All nuclear explosions produce fission products, un-fissioned nuclear material, and weapon residues vaporized by the heat of the fireball. These materials are limited to the original mass of the device, but include radioisotopes with long lives. When the nuclear fireball does not reach the ground, this is the only fallout produced. Its amount can be estimated from the fission-fusion design and yield of the weapon.


title: Nuclear fallout

text: After the detonation of a weapon at or above the fallout-free altitude (an "air burst"), fission products, un-fissioned nuclear material, and weapon residues vaporized by the heat of the fireball condense into a suspension of particles 10 nm to 20 µm in diameter. This size of particulate matter, lifted to the stratosphere, may take months or years to settle, and may do so anywhere in the world. Its radioactive characteristics increase the statistical cancer risk. Elevated atmospheric radioactivity remains measurable after the widespread nuclear testing of the 1950s.


title: Nuclear fallout

text: Radioactive fallout has occurred around the world; for example, people have been exposed to iodine-131 from atmospheric nuclear testing. Fallout accumulates on vegetation, including fruits and vegetables. Starting from 1951 people may have gotten exposure, depending on whether they were outside, the weather, and whether they consumed contaminated milk, vegetables or fruit. Exposure can be on an intermediate time scale or long term. The intermediate time scale results from fallout that has been put into the troposphere and ejected by precipitation during the first month. Long-term fallout can sometimes occur from deposition of tiny particles carried in the stratosphere. By the time that stratospheric fallout has begun to reach the earth, the radioactivity is very much decreased. Also, after a year it is estimated that a sizable quantity of fission products move from the northern to the southern stratosphere. The intermediate time scale is between 1 and 30 days, with long term fallout occurring after that.


title: Nuclear fallout

text: Examples of both intermediate and long term fallout occurred after the 1986 Chernobyl accident, which contaminated over of land in Ukraine and Belarus. The main fuel of the reactor was uranium, and surrounding this was graphite, both of which were vaporized by the hydrogen explosion that destroyed the reactor and breached its containment. An estimated 31 people died within a few weeks after this happened, including two plant workers killed at the scene. Although residents were evacuated within 36 hours, people started to complain of vomiting, migraines and other major signs of radiation sickness. The officials of Ukraine had to close off an 18-mile area. Long term effects included at least 6,000 cases of thyroid cancer, mainly among children. Fallout spread throughout Western Europe, with Northern Scandinavia receiving a heavy dose, contaminating reindeer herds in Lapland, and salad greens becoming almost unavailable in France.


title: Nuclear fallout

text: During detonations of devices at ground level ("surface burst"), below the fallout-free altitude, or in shallow water, heat vaporizes large amounts of earth or water, which is drawn up into the radioactive cloud. This material becomes radioactive when it combines with fission products or other radio-contaminants, or when it is neutron-activated.


title: Nuclear fallout

text: The table below summarizes the abilities of common isotopes to form fallout. Some radiation taints large amounts of land and drinking water causing formal mutations throughout animal and human life.


title: Nuclear fallout

text: A surface burst generates large amounts of particulate matter, composed of particles from less than 100 nm to several millimeters in diameter—in addition to very fine particles that contribute to worldwide fallout. The larger particles spill out of the stem and cascade down the outside of the fireball in a downdraft even as the cloud rises, so fallout begins to arrive near ground zero within an hour. More than half the total bomb debris lands on the ground within about 24 hours as local fallout. Chemical properties of the elements in the fallout control the rate at which they are deposited on the ground. Less volatile elements deposit first.


title: Nuclear fallout

text: Severe local fallout contamination can extend far beyond the blast and thermal effects, particularly in the case of high yield surface detonations. The ground track of fallout from an explosion depends on the weather from the time of detonation onward. In stronger winds, fallout travels faster but takes the same time to descend, so although it covers a larger path, it is more spread out or diluted. Thus, the width of the fallout pattern for any given dose rate is reduced where the downwind distance is increased by higher winds. The total amount of activity deposited up to any given time is the same irrespective of the wind pattern, so overall casualty figures from fallout are generally independent of winds. But thunderstorms can bring down activity as rain allows fallout to drop more rapidly, particularly if the mushroom cloud is low enough to be below ("washout"), or mixed with ("rainout"), the thunderstorm.


title: Nuclear fallout

text: Whenever individuals remain in a radiologically contaminated area, such contamination leads to an immediate external radiation exposure as well as a possible later internal hazard from inhalation and ingestion of radiocontaminants, such as the rather short-lived iodine-131, which is accumulated in the thyroid.


title: Nuclear fallout

text: There are two main considerations for the location of an explosion: height and surface composition. A nuclear weapon detonated in the air, called an air burst, produces less fallout than a comparable explosion near the ground. A nuclear explosion in which the fireball touches the ground pulls soil and other materials into the cloud and neutron activates it before it falls back to the ground. An air burst produces a relatively small amount of the highly radioactive heavy metal components of the device itself.


title: Nuclear fallout

text: In case of water surface bursts, the particles tend to be rather lighter and smaller, producing less local fallout but extending over a greater area. The particles contain mostly sea salts with some water; these can have a cloud seeding effect causing local rainout and areas of high local fallout. Fallout from a seawater burst is difficult to remove once it has soaked into porous surfaces because the fission products are present as metallic ions that chemically bond to many surfaces. Water and detergent washing effectively removes less than 50% of this chemically bonded activity from concrete or steel. Complete decontamination requires aggressive treatment like sandblasting, or acidic treatment. After the "Crossroads" underwater test, it was found that wet fallout must be immediately removed from ships by continuous water washdown (such as from the fire sprinkler system on the decks).


title: Nuclear fallout

text: Parts of the sea bottom may become fallout. After the Castle Bravo test, white dust—contaminated calcium oxide particles originating from pulverized and calcined corals—fell for several hours, causing beta burns and radiation exposure to the inhabitants of the nearby atolls and the crew of the "Daigo Fukuryū Maru" fishing boat. The scientists called the fallout "Bikini snow".


title: Nuclear fallout

text: For subsurface bursts, there is an additional phenomenon present called "base surge". The base surge is a cloud that rolls outward from the bottom of the subsiding column, which is caused by an excessive density of dust or water droplets in the air. For underwater bursts, the visible surge is, in effect, a cloud of liquid (usually water) droplets with the property of flowing almost as if it were a homogeneous fluid. After the water evaporates, an invisible base surge of small radioactive particles may persist.


title: Nuclear fallout

text: For subsurface land bursts, the surge is made up of small solid particles, but it still behaves like a fluid. A soil earth medium favors base surge formation in an underground burst. Although the base surge typically contains only about 10% of the total bomb debris in a subsurface burst, it can create larger radiation doses than fallout near the detonation, because it arrives sooner than fallout, before much radioactive decay has occurred.


title: Nuclear fallout

text: Meteorological conditions greatly influence fallout, particularly local fallout. Atmospheric winds are able to bring fallout over large areas. For example, as a result of a "Castle Bravo" surface burst of a 15 Mt thermonuclear device at Bikini Atoll on March 1, 1954, a roughly cigar-shaped area of the Pacific extending over 500 km downwind and varying in width to a maximum of 100 km was severely contaminated. There are three very different versions of the fallout pattern from this test, because the fallout was measured only on a small number of widely spaced Pacific Atolls. The two alternative versions both ascribe the high radiation levels at north Rongelap to a downwind hot spot caused by the large amount of radioactivity carried on fallout particles of about 50–100 micrometres size.


title: Nuclear fallout

text: After "Bravo", it was discovered that fallout landing on the ocean disperses in the top water layer (above the thermocline at 100 m depth), and the land equivalent dose rate can be calculated by multiplying the ocean dose rate at two days after burst by a factor of about 530. In other 1954 tests, including "Yankee" and "Nectar," hot spots were mapped out by ships with submersible probes, and similar hot spots occurred in 1956 tests such as "Zuni" and "Tewa".


title: Nuclear fallout

text: Snow and rain, especially if they come from considerable heights, accelerate local fallout. Under special meteorological conditions, such as a local rain shower that originates above the radioactive cloud, limited areas of heavy contamination just downwind of a nuclear blast may be formed.


title: Nuclear fallout

text: A wide range of biological changes may follow the irradiation of animals. These vary from rapid death following high doses of penetrating whole-body radiation, to essentially normal lives for a variable period of time until the development of delayed radiation effects, in a portion of the exposed population, following low dose exposures.


title: Nuclear fallout

text: The unit of actual "exposure" is the röntgen, defined in ionisations per unit volume of air. All ionisation based instruments (including geiger counters and ionisation chambers) measure exposure. However, effects depend on the energy per unit mass, not the exposure measured in air. A deposit of 1 joule per kilogram has the unit of 1 gray (Gy). For 1 MeV energy gamma rays, an exposure of 1 röntgen in air produces a dose of about 0.01 gray (1 centigray, cGy) in water or surface tissue. Because of shielding by the tissue surrounding the bones, the bone marrow only receives about 0.67 cGy when the air exposure is 1 röntgen and the surface skin dose is 1 cGy. Some lower values reported for the amount of radiation that would kill 50% of personnel (the ) refer to bone marrow dose, which is only 67% of the air dose.