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Following the American Revolutionary War, the United States faced potential military conflict on the high seas as well as on the western frontier. The United States was a minor military power during this time, having only a modest army, Marine corps, and navy. A traditional distrust of standing armies, combined with faith in the abilities of local militia, precluded the development of well-trained units and a professional officer corps. Jeffersonian leaders preferred a small army and navy, fearing that a large military establishment would involve the United States in excessive foreign wars, and potentially allow a domestic tyrant to seize power. |
After the Civil War, population expansion, railroad construction, and the disappearance of the buffalo herds heightened military tensions on the Great Plains. Several tribes, especially the Sioux and Comanche, fiercely resisted confinement to reservations. The main role of the Army was to keep indigenous peoples on reservations and to end their wars against settlers and each other, William Tecumseh Sherman and Philip Sheridan were in charge. A famous victory for the Plains Nations was the Battle of the Little Big Horn in 1876, when Col. George Armstrong Custer and two hundred plus members of the 7th Cavalry were killed by a force consisting of Native Americans from the Lakota, Northern Cheyenne, and Arapaho nations. The last significant conflict came in 1891. |
Rear Admiral Bradley A. Fiske was at the vanguard of new technology in naval guns and gunnery, thanks to his innovations in fire control 1890–1910. He immediately grasped the potential for air power, and called for the development of a torpedo plane. Fiske, as aide for operations in 1913–15 to Assistant Secretary Franklin D. Roosevelt, proposed a radical reorganization of the Navy to make it a war-fighting instrument. Fiske wanted to centralize authority in a chief of naval operations and an expert staff that would develop new strategies, oversee the construction of a larger fleet, coordinate war planning including force structure, mobilization plans, and industrial base, and ensure that the US Navy possessed the best possible war machines. Eventually, the Navy adopted his reforms and by 1915 started to reorganize for possible involvement in the World War then underway. |
By summer 1918, a million American soldiers, or "doughboys" as they were often called, of the American Expeditionary Forces were in Europe under the command of John J. Pershing, with 25,000 more arriving every week. The failure of Germany's spring offensive exhausted its reserves and they were unable to launch new offensives. The German Navy and home front then revolted and a new German government signed a conditional surrender, the Armistice, ending the war against the western front on November 11, 1918. |
Starting in 1940 (18 months before Pearl Harbor), the nation mobilized, giving high priority to air power. American involvement in World War II in 1940–41 was limited to providing war material and financial support to Britain, the Soviet Union, and the Republic of China. The U.S. entered officially on 8 December 1941 following the Japanese attack on Pearl Harbor, Hawaii. Japanese forces soon seized American, Dutch, and British possessions across the Pacific and Southeast Asia, except for Australia, which became a main American forward base along with Hawaii. |
The Vietnam War was a war fought between 1959 and 1975 on the ground in South Vietnam and bordering areas of Cambodia and Laos (see Secret War) and in the strategic bombing (see Operation Rolling Thunder) of North Vietnam. American advisors came in the late 1950s to help the RVN (Republic of Vietnam) combat Communist insurgents known as "Viet Cong." Major American military involvement began in 1964, after Congress provided President Lyndon B. Johnson with blanket approval for presidential use of force in the Gulf of Tonkin Resolution. |
Before the war, many observers believed the US and its allies could win but might suffer substantial casualties (certainly more than any conflict since Vietnam), and that the tank battles across the harsh desert might rival those of North Africa during World War II. After nearly 50 years of proxy wars, and constant fears of another war in Europe between NATO and the Warsaw Pact, some thought the Persian Gulf War might finally answer the question of which military philosophy would have reigned supreme. Iraqi forces were battle-hardened after 8 years of war with Iran, and they were well equipped with late model Soviet tanks and jet fighters, but the antiaircraft weapons were crippled; in comparison, the US had no large-scale combat experience since its withdrawal from Vietnam nearly 20 years earlier, and major changes in US doctrine, equipment and technology since then had never been tested under fire. |
With the emergence of ISIL and its capture of large areas of Iraq and Syria, a number of crises resulted that sparked international attention. ISIL had perpetrated sectarian killings and war crimes in both Iraq and Syria. Gains made in the Iraq war were rolled back as Iraqi army units abandoned their posts. Cities were taken over by the terrorist group which enforced its brand of Sharia law. The kidnapping and decapitation of numerous Western journalists and aid-workers also garnered interest and outrage among Western powers. The US intervened with airstrikes in Iraq over ISIL held territories and assets in August, and in September a coalition of US and Middle Eastern powers initiated a bombing campaign in Syria aimed at degrading and destroying ISIL and Al-Nusra-held territory. |
Groups that emerged from the American psychedelic scene about the same time included Iron Butterfly, MC5, Blue Cheer and Vanilla Fudge. San Francisco band Blue Cheer released a crude and distorted cover of Eddie Cochran's classic "Summertime Blues", from their 1968 debut album Vincebus Eruptum, that outlined much of the later hard rock and heavy metal sound. The same month, Steppenwolf released its self-titled debut album, including "Born to Be Wild", which contained the first lyrical reference to heavy metal and helped popularise the style when it was used in the film Easy Rider (1969). Iron Butterfly's In-A-Gadda-Da-Vida (1968), with its 17-minute-long title track, using organs and with a lengthy drum solo, also prefigured later elements of the sound. |
From outside the United Kingdom and the United States, the Canadian trio Rush released three distinctively hard rock albums in 1974–75 (Rush, Fly by Night and Caress of Steel) before moving toward a more progressive sound with the 1976 album 2112. The Irish band Thin Lizzy, which had formed in the late 1960s, made their most substantial commercial breakthrough in 1976 with the hard rock album Jailbreak and their worldwide hit "The Boys Are Back in Town", which reached number 8 in the UK and number 12 in the US. Their style, consisting of two duelling guitarists often playing leads in harmony, proved itself to be a large influence on later bands. They reached their commercial, and arguably their artistic peak with Black Rose: A Rock Legend (1979). The arrival of Scorpions from Germany marked the geographical expansion of the subgenre. Australian-formed AC/DC, with a stripped back, riff heavy and abrasive style that also appealed to the punk generation, began to gain international attention from 1976, culminating in the release of their multi-platinum albums Let There Be Rock (1977) and Highway to Hell (1979). Also influenced by a punk ethos were heavy metal bands like Motörhead, while Judas Priest abandoned the remaining elements of the blues in their music, further differentiating the hard rock and heavy metal styles and helping to create the New Wave of British Heavy Metal which was pursued by bands like Iron Maiden, Saxon and Venom. |
Bon Jovi's third album, Slippery When Wet (1986), mixed hard rock with a pop sensitivity and spent a total of 8 weeks at the top of the Billboard 200 album chart, selling 12 million copies in the US while becoming the first hard rock album to spawn three top 10 singles — two of which reached number one. The album has been credited with widening the audiences for the genre, particularly by appealing to women as well as the traditional male dominated audience, and opening the door to MTV and commercial success for other bands at the end of the decade. The anthemic The Final Countdown (1986) by Swedish group Europe was an international hit, reaching number eight on the US charts while hitting the top 10 in nine other countries. This era also saw more glam-infused American hard rock bands come to the forefront, with both Poison and Cinderella releasing their multi-platinum début albums in 1986. Van Halen released 5150 (1986), their first album with Sammy Hagar on lead vocals, which was number one in the US for three weeks and sold over 6 million copies. By the second half of the decade, hard rock had become the most reliable form of commercial popular music in the United States. |
Some established acts continued to enjoy commercial success, such as Aerosmith, with their number one multi-platinum albums: Get a Grip (1993), which produced four Top 40 singles and became the band's best-selling album worldwide (going on to sell over 10 million copies), and Nine Lives (1997). In 1998, Aerosmith released the number one hit "I Don't Want to Miss a Thing", which remains the only single by a hard rock band to debut at number one. AC/DC produced the double platinum Ballbreaker (1995). Bon Jovi appealed to their hard rock audience with songs such as "Keep the Faith" (1992), but also achieved success in adult contemporary radio, with the Top 10 ballads "Bed of Roses" (1993) and "Always" (1994). Bon Jovi's 1995 album These Days was a bigger hit in Europe than it was in the United States, spawning four Top 10 singles on the UK Singles Chart. Metallica's Load (1996) and ReLoad (1997) each sold in excess of 4 million copies in the US and saw the band develop a more melodic and blues rock sound. As the initial impetus of grunge bands faltered in the middle years of the decade, post-grunge bands emerged. They emulated the attitudes and music of grunge, particularly thick, distorted guitars, but with a more radio-friendly commercially oriented sound that drew more directly on traditional hard rock. Among the most successful acts were the Foo Fighters, Candlebox, Live, Collective Soul, Australia's Silverchair and England's Bush, who all cemented post-grunge as one of the most commercially viable subgenres by the late 1990s. Similarly, some post-Britpop bands that followed in the wake of Oasis, including Feeder and Stereophonics, adopted a hard rock or "pop-metal" sound. |
Hard rock developed into a major form of popular music in the 1970s, with bands such as Led Zeppelin, The Who, Deep Purple, Aerosmith, AC/DC and Van Halen. During the 1980s, some hard rock bands moved away from their hard rock roots and more towards pop rock, while others began to return to a hard rock sound. Established bands made a comeback in the mid-1980s and it reached a commercial peak in the 1980s, with glam metal bands like Bon Jovi and Def Leppard and the rawer sounds of Guns N' Roses, which followed up with great success in the later part of that decade. Hard rock began losing popularity with the commercial success of grunge and later Britpop in the 1990s. |
The roots of hard rock can be traced back to the 1950s, particularly electric blues, which laid the foundations for key elements such as a rough declamatory vocal style, heavy guitar riffs, string-bending blues-scale guitar solos, strong beat, thick riff-laden texture, and posturing performances. Electric blues guitarists began experimenting with hard rock elements such as driving rhythms, distorted guitar solos and power chords in the 1950s, evident in the work of Memphis blues guitarists such as Joe Hill Louis, Willie Johnson, and particularly Pat Hare, who captured a "grittier, nastier, more ferocious electric guitar sound" on records such as James Cotton's "Cotton Crop Blues" (1954). Other antecedents include Link Wray's instrumental "Rumble" in 1958, and the surf rock instrumentals of Dick Dale, such as "Let's Go Trippin'" (1961) and "Misirlou" (1962). |
In the early 1970s the Rolling Stones developed their hard rock sound with Exile on Main St. (1972). Initially receiving mixed reviews, according to critic Steve Erlewine it is now "generally regarded as the Rolling Stones' finest album". They continued to pursue the riff-heavy sound on albums including It's Only Rock 'n' Roll (1974) and Black and Blue (1976). Led Zeppelin began to mix elements of world and folk music into their hard rock from Led Zeppelin III (1970) and Led Zeppelin IV (1971). The latter included the track "Stairway to Heaven", which would become the most played song in the history of album-oriented radio. Deep Purple continued to define hard rock, particularly with their album Machine Head (1972), which included the tracks "Highway Star" and "Smoke on the Water". In 1975 guitarist Ritchie Blackmore left, going on to form Rainbow and after the break-up of the band the next year, vocalist David Coverdale formed Whitesnake. 1970 saw The Who release Live at Leeds, often seen as the archetypal hard rock live album, and the following year they released their highly acclaimed album Who's Next, which mixed heavy rock with extensive use of synthesizers. Subsequent albums, including Quadrophenia (1973), built on this sound before Who Are You (1978), their last album before the death of pioneering rock drummer Keith Moon later that year. |
The opening years of the 1980s saw a number of changes in personnel and direction of established hard rock acts, including the deaths of Bon Scott, the lead singer of AC/DC, and John Bonham, drummer with Led Zeppelin. Whereas Zeppelin broke up almost immediately afterwards, AC/DC pressed on, recording the album Back in Black (1980) with their new lead singer, Brian Johnson. It became the fifth-highest-selling album of all time in the US and the second-highest-selling album in the world. Black Sabbath had split with original singer Ozzy Osbourne in 1979 and replaced him with Ronnie James Dio, formerly of Rainbow, giving the band a new sound and a period of creativity and popularity beginning with Heaven and Hell (1980). Osbourne embarked on a solo career with Blizzard of Ozz (1980), featuring American guitarist Randy Rhoads. Some bands, such as Queen, moved away from their hard rock roots and more towards pop rock, while others, including Rush with Moving Pictures (1981), began to return to a hard rock sound. The creation of thrash metal, which mixed heavy metal with elements of hardcore punk from about 1982, particularly by Metallica, Anthrax, Megadeth and Slayer, helped to create extreme metal and further remove the style from hard rock, although a number of these bands or their members would continue to record some songs closer to a hard rock sound. Kiss moved away from their hard rock roots toward pop metal: firstly removing their makeup in 1983 for their Lick It Up album, and then adopting the visual and sound of glam metal for their 1984 release, Animalize, both of which marked a return to commercial success. Pat Benatar was one of the first women to achieve commercial success in hard rock, with three successive Top 5 albums between 1980 and 1982. |
Hard rock entered the 1990s as one of the dominant forms of commercial music. The multi-platinum releases of AC/DC's The Razors Edge (1990), Guns N' Roses' Use Your Illusion I and Use Your Illusion II (both in 1991), Ozzy Osbourne's No More Tears (1991), and Van Halen's For Unlawful Carnal Knowledge (1991) showcased this popularity. Additionally, The Black Crowes released their debut album, Shake Your Money Maker (1990), which contained a bluesy classic rock sound and sold five million copies. In 1992, Def Leppard followed up 1987's Hysteria with Adrenalize, which went multi-platinum, spawned four Top 40 singles and held the number one spot on the US album chart for five weeks. |
The term "retro-metal" has been applied to such bands as Texas based The Sword, California's High on Fire, Sweden's Witchcraft and Australia's Wolfmother. Wolfmother's self-titled 2005 debut album combined elements of the sounds of Deep Purple and Led Zeppelin. Fellow Australians Airbourne's début album Runnin' Wild (2007) followed in the hard riffing tradition of AC/DC. England's The Darkness' Permission to Land (2003), described as an "eerily realistic simulation of '80s metal and '70s glam", topped the UK charts, going quintuple platinum. The follow-up, One Way Ticket to Hell... and Back (2005), reached number 11, before the band broke up in 2006. Los Angeles band Steel Panther managed to gain a following by sending up 80s glam metal. A more serious attempt to revive glam metal was made by bands of the sleaze metal movement in Sweden, including Vains of Jenna, Hardcore Superstar and Crashdïet. |
In the 1960s, American and British blues and rock bands began to modify rock and roll by adding harder sounds, heavier guitar riffs, bombastic drumming, and louder vocals, from electric blues. Early forms of hard rock can be heard in the work of Chicago blues musicians Elmore James, Muddy Waters, and Howlin' Wolf, The Kingsmen's version of "Louie Louie" (1963) which made it a garage rock standard, and the songs of rhythm and blues influenced British Invasion acts, including "You Really Got Me" by The Kinks (1964), "My Generation" by The Who (1965), "Shapes of Things" (1966) by The Yardbirds and "(I Can't Get No) Satisfaction" (1965) by The Rolling Stones. From the late 1960s, it became common to divide mainstream rock music that emerged from psychedelia into soft and hard rock. Soft rock was often derived from folk rock, using acoustic instruments and putting more emphasis on melody and harmonies. In contrast, hard rock was most often derived from blues rock and was played louder and with more intensity. |
Emerging British acts included Free, who released their signature song "All Right Now" (1970), which has received extensive radio airplay in both the UK and US. After the breakup of the band in 1973, vocalist Paul Rodgers joined supergroup Bad Company, whose eponymous first album (1974) was an international hit. The mixture of hard rock and progressive rock, evident in the works of Deep Purple, was pursued more directly by bands like Uriah Heep and Argent. Scottish band Nazareth released their self-titled début album in 1971, producing a blend of hard rock and pop that would culminate in their best selling, Hair of the Dog (1975), which contained the proto-power ballad "Love Hurts". Having enjoyed some national success in the early 1970s, Queen, after the release of Sheer Heart Attack (1974) and A Night at the Opera (1975), gained international recognition with a sound that used layered vocals and guitars and mixed hard rock with heavy metal, progressive rock, and even opera. The latter featured the single "Bohemian Rhapsody", which stayed at number one in the UK charts for nine weeks. |
Often categorised with the New Wave of British Heavy Metal, in 1981 Def Leppard released their second album High 'n' Dry, mixing glam-rock with heavy metal, and helping to define the sound of hard rock for the decade. The follow-up Pyromania (1983), reached number two on the American charts and the singles "Photograph", "Rock of Ages" and "Foolin'", helped by the emergence of MTV, all reached the Top 40. It was widely emulated, particularly by the emerging Californian glam metal scene. This was followed by US acts like Mötley Crüe, with their albums Too Fast for Love (1981) and Shout at the Devil (1983) and, as the style grew, the arrival of bands such as Ratt, White Lion, Twisted Sister and Quiet Riot. Quiet Riot's album Metal Health (1983) was the first glam metal album, and arguably the first heavy metal album of any kind, to reach number one in the Billboard music charts and helped open the doors for mainstream success by subsequent bands. |
While these few hard rock bands managed to maintain success and popularity in the early part of the decade, alternative forms of hard rock achieved mainstream success in the form of grunge in the US and Britpop in the UK. This was particularly evident after the success of Nirvana's Nevermind (1991), which combined elements of hardcore punk and heavy metal into a "dirty" sound that made use of heavy guitar distortion, fuzz and feedback, along with darker lyrical themes than their "hair band" predecessors. Although most grunge bands had a sound that sharply contrasted mainstream hard rock, several, including Pearl Jam, Alice in Chains, Mother Love Bone and Soundgarden, were more strongly influenced by 1970s and 1980s rock and metal, while Stone Temple Pilots managed to turn alternative rock into a form of stadium rock. However, all grunge bands shunned the macho, anthemic and fashion-focused aesthetics particularly associated with glam metal. In the UK, Oasis were unusual among the Britpop bands of the mid-1990s in incorporating a hard rock sound. |
Although Foo Fighters continued to be one of the most successful rock acts, with albums like In Your Honor (2005) reaching number two in the US and UK, many of the first wave of post-grunge bands began to fade in popularity. Acts like Creed, Staind, Puddle of Mudd and Nickelback took the genre into the 2000s with considerable commercial success, abandoning most of the angst and anger of the original movement for more conventional anthems, narratives and romantic songs. They were followed in this vein by new acts including Shinedown and Seether. Acts with more conventional hard rock sounds included Andrew W.K., Beautiful Creatures and Buckcherry, whose breakthrough album 15 (2006) went platinum and spawned the single "Sorry" (2007), which made the Top 10 of the Billboard 100. These were joined by bands with hard rock leanings that emerged in the mid-2000s from the garage rock or post punk revival, including Black Rebel Motorcycle Club and Kings of Leon, and Queens of the Stone Age from the US, Three Days Grace from Canada, Jet from Australia and The Datsuns from New Zealand. In 2009 Them Crooked Vultures, a supergroup that brought together Foo Fighters' Dave Grohl, Queens of the Stone Age's Josh Homme and Led Zeppelin bass player John Paul Jones attracted attention as a live act and released a self-titled debut album that reached the top 20 in the US and UK and the top ten in several other countries. |
Hard rock is a form of loud, aggressive rock music. The electric guitar is often emphasised, used with distortion and other effects, both as a rhythm instrument using repetitive riffs with a varying degree of complexity, and as a solo lead instrument. Drumming characteristically focuses on driving rhythms, strong bass drum and a backbeat on snare, sometimes using cymbals for emphasis. The bass guitar works in conjunction with the drums, occasionally playing riffs, but usually providing a backing for the rhythm and lead guitars. Vocals are often growling, raspy, or involve screaming or wailing, sometimes in a high range, or even falsetto voice. |
Blues rock acts that pioneered the sound included Cream, The Jimi Hendrix Experience, and The Jeff Beck Group. Cream, in songs like "I Feel Free" (1966) combined blues rock with pop and psychedelia, particularly in the riffs and guitar solos of Eric Clapton. Jimi Hendrix produced a form of blues-influenced psychedelic rock, which combined elements of jazz, blues and rock and roll. From 1967 Jeff Beck brought lead guitar to new heights of technical virtuosity and moved blues rock in the direction of heavy rock with his band, The Jeff Beck Group. Dave Davies of The Kinks, Keith Richards of The Rolling Stones, Pete Townshend of The Who, Hendrix, Clapton and Beck all pioneered the use of new guitar effects like phasing, feedback and distortion. The Beatles began producing songs in the new hard rock style beginning with the White Album in 1968 and, with the track "Helter Skelter", attempted to create a greater level of noise than the Who. Stephen Thomas Erlewine of AllMusic has described the "proto-metal roar" of "Helter Skelter," while Ian MacDonald argued that "their attempts at emulating the heavy style were without exception embarrassing." |
In the United States, macabre-rock pioneer Alice Cooper achieved mainstream success with the top ten album School's Out (1972). In the following year blues rockers ZZ Top released their classic album Tres Hombres and Aerosmith produced their eponymous début, as did Southern rockers Lynyrd Skynyrd and proto-punk outfit New York Dolls, demonstrating the diverse directions being pursued in the genre. Montrose, including the instrumental talent of Ronnie Montrose and vocals of Sammy Hagar and arguably the first all American hard rock band to challenge the British dominance of the genre, released their first album in 1973. Kiss built on the theatrics of Alice Cooper and the look of the New York Dolls to produce a unique band persona, achieving their commercial breakthrough with the double live album Alive! in 1975 and helping to take hard rock into the stadium rock era. In the mid-1970s Aerosmith achieved their commercial and artistic breakthrough with Toys in the Attic (1975), which reached number 11 in the American album chart, and Rocks (1976), which peaked at number three. Blue Öyster Cult, formed in the late 60s, picked up on some of the elements introduced by Black Sabbath with their breakthrough live gold album On Your Feet or on Your Knees (1975), followed by their first platinum album, Agents of Fortune (1976), containing the hit single "(Don't Fear) The Reaper", which reached number 12 on the Billboard charts. Journey released their eponymous debut in 1975 and the next year Boston released their highly successful début album. In the same year, hard rock bands featuring women saw commercial success as Heart released Dreamboat Annie and The Runaways débuted with their self-titled album. While Heart had a more folk-oriented hard rock sound, the Runaways leaned more towards a mix of punk-influenced music and hard rock. The Amboy Dukes, having emerged from the Detroit garage rock scene and most famous for their Top 20 psychedelic hit "Journey to the Center of the Mind" (1968), were dissolved by their guitarist Ted Nugent, who embarked on a solo career that resulted in four successive multi-platinum albums between Ted Nugent (1975) and his best selling Double Live Gonzo (1978). |
Established bands made something of a comeback in the mid-1980s. After an 8-year separation, Deep Purple returned with the classic Machine Head line-up to produce Perfect Strangers (1984), which reached number five in the UK, hit the top five in five other countries, and was a platinum-seller in the US. After somewhat slower sales of its fourth album, Fair Warning, Van Halen rebounded with the Top 3 album Diver Down in 1982, then reached their commercial pinnacle with 1984. It reached number two on the Billboard album chart and provided the track "Jump", which reached number one on the singles chart and remained there for several weeks. Heart, after floundering during the first half of the decade, made a comeback with their eponymous ninth studio album which hit number one and contained four Top 10 singles including their first number one hit. The new medium of video channels was used with considerable success by bands formed in previous decades. Among the first were ZZ Top, who mixed hard blues rock with new wave music to produce a series of highly successful singles, beginning with "Gimme All Your Lovin'" (1983), which helped their albums Eliminator (1983) and Afterburner (1985) achieve diamond and multi-platinum status respectively. Others found renewed success in the singles charts with power ballads, including REO Speedwagon with "Keep on Loving You" (1980) and "Can't Fight This Feeling" (1984), Journey with "Don't Stop Believin'" (1981) and "Open Arms" (1982), Foreigner's "I Want to Know What Love Is", Scorpions' "Still Loving You" (both from 1984), Heart’s "What About Love" (1985) and "These Dreams" (1986), and Boston's "Amanda" (1986). |
In the new commercial climate glam metal bands like Europe, Ratt, White Lion and Cinderella broke up, Whitesnake went on hiatus in 1991, and while many of these bands would re-unite again in the late 1990s or early 2000s, they never reached the commercial success they saw in the 1980s or early 1990s. Other bands such as Mötley Crüe and Poison saw personnel changes which impacted those bands' commercial viability during the decade. In 1995 Van Halen released Balance, a multi-platinum seller that would be the band's last with Sammy Hagar on vocals. In 1996 David Lee Roth returned briefly and his replacement, former Extreme singer Gary Cherone, was fired soon after the release of the commercially unsuccessful 1998 album Van Halen III and Van Halen would not tour or record again until 2004. Guns N' Roses' original lineup was whittled away throughout the decade. Drummer Steven Adler was fired in 1990, guitarist Izzy Stradlin left in late 1991 after recording Use Your Illusion I and II with the band. Tensions between the other band members and lead singer Axl Rose continued after the release of the 1993 covers album The Spaghetti Incident? Guitarist Slash left in 1996, followed by bassist Duff McKagan in 1997. Axl Rose, the only original member, worked with a constantly changing lineup in recording an album that would take over fifteen years to complete. |
In the late 1960s, the term heavy metal was used interchangeably with hard rock, but gradually began to be used to describe music played with even more volume and intensity. While hard rock maintained a bluesy rock and roll identity, including some swing in the back beat and riffs that tended to outline chord progressions in their hooks, heavy metal's riffs often functioned as stand-alone melodies and had no swing in them. Heavy metal took on "darker" characteristics after Black Sabbath's breakthrough at the beginning of the 1970s. In the 1980s it developed a number of subgenres, often termed extreme metal, some of which were influenced by hardcore punk, and which further differentiated the two styles. Despite this differentiation, hard rock and heavy metal have existed side by side, with bands frequently standing on the boundary of, or crossing between, the genres. |
By the end of the decade a distinct genre of hard rock was emerging with bands like Led Zeppelin, who mixed the music of early rock bands with a more hard-edged form of blues rock and acid rock on their first two albums Led Zeppelin (1969) and Led Zeppelin II (1969), and Deep Purple, who began as a progressive rock group but achieved their commercial breakthrough with their fourth and distinctively heavier album, In Rock (1970). Also significant was Black Sabbath's Paranoid (1970), which combined guitar riffs with dissonance and more explicit references to the occult and elements of Gothic horror. All three of these bands have been seen as pivotal in the development of heavy metal, but where metal further accentuated the intensity of the music, with bands like Judas Priest following Sabbath's lead into territory that was often "darker and more menacing", hard rock tended to continue to remain the more exuberant, good-time music. |
With the rise of disco in the US and punk rock in the UK, hard rock's mainstream dominance was rivalled toward the later part of the decade. Disco appealed to a more diverse group of people and punk seemed to take over the rebellious role that hard rock once held. Early punk bands like The Ramones explicitly rebelled against the drum solos and extended guitar solos that characterised stadium rock, with almost all of their songs clocking in around two minutes with no guitar solos. However, new rock acts continued to emerge and record sales remained high into the 1980s. 1977 saw the début and rise to stardom of Foreigner, who went on to release several platinum albums through to the mid-1980s. Midwestern groups like Kansas, REO Speedwagon and Styx helped further cement heavy rock in the Midwest as a form of stadium rock. In 1978, Van Halen emerged from the Los Angeles music scene with a sound based around the skills of lead guitarist Eddie Van Halen. He popularised a guitar-playing technique of two-handed hammer-ons and pull-offs called tapping, showcased on the song "Eruption" from the album Van Halen, which was highly influential in re-establishing hard rock as a popular genre after the punk and disco explosion, while also redefining and elevating the role of electric guitar. |
Established acts benefited from the new commercial climate, with Whitesnake's self-titled album (1987) selling over 17 million copies, outperforming anything in Coverdale's or Deep Purple's catalogue before or since. It featured the rock anthem "Here I Go Again '87" as one of 4 UK top 20 singles. The follow-up Slip of the Tongue (1989) went platinum, but according to critics Steve Erlwine and Greg Prato, "it was a considerable disappointment after the across-the-board success of Whitesnake". Aerosmith's comeback album Permanent Vacation (1987) would begin a decade long revival of their popularity. Crazy Nights (1987) by Kiss was the band's highest charting release in the US since 1979 and the highest of their career in the UK. Mötley Crüe with Girls, Girls, Girls (1987) continued their commercial success and Def Leppard with Hysteria (1987) hit their commercial peak, the latter producing seven hit singles (a record for a hard rock act). Guns N' Roses released the best-selling début of all time, Appetite for Destruction (1987). With a "grittier" and "rawer" sound than most glam metal, it produced three top 10 hits, including the number one "Sweet Child O' Mine". Some of the glam rock bands that formed in the mid-1980s, such as White Lion and Cinderella experienced their biggest success during this period with their respective albums Pride (1987) and Long Cold Winter (1988) both going multi-platinum and launching a series of hit singles. In the last years of the decade, the most notable successes were New Jersey (1988) by Bon Jovi, OU812 (1988) by Van Halen, Open Up and Say... Ahh! (1988) by Poison, Pump (1989) by Aerosmith, and Mötley Crüe's most commercially successful album Dr. Feelgood (1989). New Jersey spawned five Top 10 singles, a record for a hard rock act. In 1988 from 25 June to 5 November, the number one spot on the Billboard 200 album chart was held by a hard rock album for 18 out of 20 consecutive weeks; the albums were OU812, Hysteria, Appetite for Destruction, and New Jersey. A final wave of glam rock bands arrived in the late 1980s, and experienced success with multi-platinum albums and hit singles from 1989 until the early 1990s, among them Extreme, Warrant Slaughter and FireHouse. Skid Row also released their eponymous début (1989), reaching number six on the Billboard 200, but they were to be one of the last major bands that emerged in the glam rock era. |
A few hard rock bands from the 1970s and 1980s managed to sustain highly successful recording careers. Bon Jovi were still able to achieve a commercial hit with "It's My Life" from their double platinum-certified album Crush (2000). and AC/DC released the platinum-certified Stiff Upper Lip (2000) Aerosmith released a number two platinum album, Just Push Play (2001), which saw the band foray further into pop with the Top 10 hit "Jaded", and a blues cover album, Honkin' on Bobo, which reached number five in 2004. Heart achieved their first Top 10 album since the early 90s with Red Velvet Car in 2010, becoming the first female-led hard rock band to earn Top 10 albums spanning five decades. There were reunions and subsequent tours from Van Halen (with Hagar in 2004 and then Roth in 2007), The Who (delayed in 2002 by the death of bassist John Entwistle until 2006) and Black Sabbath (with Osbourne 1997–2006 and Dio 2006–2010) and even a one off performance by Led Zeppelin (2007), renewing the interest in previous eras. Additionally, hard rock supergroups, such as Audioslave (with former members of Rage Against the Machine and Soundgarden) and Velvet Revolver (with former members of Guns N' Roses, punk band Wasted Youth and Stone Temple Pilots singer Scott Weiland), emerged and experienced some success. However, these bands were short-lived, ending in 2007 and 2008, respectively. The long awaited Guns N' Roses album Chinese Democracy was finally released in 2008, but only went platinum and failed to come close to the success of the band's late 1980s and early 1990s material. More successfully, AC/DC released the double platinum-certified Black Ice (2008). Bon Jovi continued to enjoy success, branching into country music with "Who Says You Can't Go Home", which reached number one on the Hot Country Singles chart in 2006, and the rock/country album Lost Highway, which reached number one in 2007. In 2009, Bon Jovi released another number one album, The Circle, which marked a return to their hard rock sound. |
The term "Great Plains", for the region west of about the 96th or 98th meridian and east of the Rocky Mountains, was not generally used before the early 20th century. Nevin Fenneman's 1916 study, Physiographic Subdivision of the United States, brought the term Great Plains into more widespread usage. Before that the region was almost invariably called the High Plains, in contrast to the lower Prairie Plains of the Midwestern states. Today the term "High Plains" is used for a subregion of the Great Plains. |
Much of the Great Plains became open range, or rangeland where cattle roamed free, hosting ranching operations where anyone was theoretically free to run cattle. In the spring and fall, ranchers held roundups where their cowboys branded new calves, treated animals and sorted the cattle for sale. Such ranching began in Texas and gradually moved northward. In 1866-95, cowboys herded 10 million cattle north to rail heads such as Dodge City, Kansas and Ogallala, Nebraska; from there, cattle were shipped eastward. |
With the arrival of Francisco Vázquez de Coronado, a Spanish conquistador, the first recorded history of encounter between Europeans and Native Americans in the Great Plains occurred in Texas, Kansas and Nebraska from 1540-1542. In that same time period, Hernando de Soto crossed a west-northwest direction in what is now Oklahoma and Texas. Today this is known as the De Soto Trail. The Spanish thought the Great Plains were the location of the mythological Quivira and Cíbola, a place said to be rich in gold. |
The 100th meridian roughly corresponds with the line that divides the Great Plains into an area that receive 20 inches (510 millimetres) or more of rainfall per year and an area that receives less than 20 in (510 mm). In this context, the High Plains, as well as Southern Alberta, south-western Saskatchewan and Eastern Montana are mainly semi hot steppe land and are generally characterised by rangeland or marginal farmland. The region (especially the High Plains) is periodically subjected to extended periods of drought; high winds in the region may then generate devastating dust storms. The eastern Great Plains near the eastern boundary falls in the humid subtropical climate zone in the southern areas, and the northern and central areas fall in the humid continental climate. |
After 1870, the new railroads across the Plains brought hunters who killed off almost all the bison for their hides. The railroads offered attractive packages of land and transportation to European farmers, who rushed to settle the land. They (and Americans as well) also took advantage of the homestead laws to obtain free farms. Land speculators and local boosters identified many potential towns, and those reached by the railroad had a chance, while the others became ghost towns. In Kansas, for example, nearly 5000 towns were mapped out, but by 1970 only 617 were actually operating. In the mid-20th century, closeness to an interstate exchange determined whether a town would flourish or struggle for business. |
The rural Plains have lost a third of their population since 1920. Several hundred thousand square miles (several hundred thousand square kilometers) of the Great Plains have fewer than 6 inhabitants per square mile (2.3 inhabitants per square kilometer)—the density standard Frederick Jackson Turner used to declare the American frontier "closed" in 1893. Many have fewer than 2 inhabitants per square mile (0.77 inhabitants per square kilometer). There are more than 6,000 ghost towns in the state of Kansas alone, according to Kansas historian Daniel Fitzgerald. This problem is often exacerbated by the consolidation of farms and the difficulty of attracting modern industry to the region. In addition, the smaller school-age population has forced the consolidation of school districts and the closure of high schools in some communities. The continuing population loss has led some to suggest that the current use of the drier parts of the Great Plains is not sustainable, and there has been a proposal - the "Buffalo Commons" - to return approximately 139,000 square miles (360,000 km2) of these drier parts to native prairie land. |
Although the eastern image of farm life in the prairies emphasized the isolation of the lonely farmer and wife, plains residents created busy social lives for themselves. They often sponsored activities that combined work, food and entertainment such as barn raisings, corn huskings, quilting bees, Grange meetings, church activities and school functions. Women organized shared meals and potluck events, as well as extended visits between families. The Grange was a nationwide farmers' organization, they reserved high offices for women, and gave them a voice in public affairs. |
From the 1950s on, many areas of the Great Plains have become productive crop-growing areas because of extensive irrigation on large landholdings. The United States is a major exporter of agricultural products. The southern portion of the Great Plains lies over the Ogallala Aquifer, a huge underground layer of water-bearing strata dating from the last ice age. Center pivot irrigation is used extensively in drier sections of the Great Plains, resulting in aquifer depletion at a rate that is greater than the ground's ability to recharge. |
The Great Plains is the broad expanse of flat land (a plain), much of it covered in prairie, steppe and grassland, that lies west of the Mississippi River tallgrass prairie states and east of the Rocky Mountains in the United States and Canada. This area covers parts, but not all, of the states of Colorado, Kansas, Montana, Nebraska, New Mexico, North Dakota, Oklahoma, South Dakota, Texas, and Wyoming, and the Canadian provinces of Alberta, Manitoba and Saskatchewan. The region is known for supporting extensive cattle ranching and dry farming. |
The North American Environmental Atlas, produced by the Commission for Environmental Cooperation, a NAFTA agency composed of the geographical agencies of the Mexican, American, and Canadian governments uses the "Great Plains" as an ecoregion synonymous with predominant prairies and grasslands rather than as physiographic region defined by topography. The Great Plains ecoregion includes five sub-regions: Temperate Prairies, West-Central Semi-Arid Prairies, South-Central Semi-Arid Prairies, Texas Louisiana Coastal Plains, and Tamaulipus-Texas Semi-Arid Plain, which overlap or expand upon other Great Plains designations. |
The railroads opened up the Great Plains for settlement, for now it was possible to ship wheat and other crops at low cost to the urban markets in the East, and Europe. Homestead land was free for American settlers. Railroads sold their land at cheap rates to immigrants in expectation they would generate traffic as soon as farms were established. Immigrants poured in, especially from Germany and Scandinavia. On the plains, very few single men attempted to operate a farm or ranch by themselves; they clearly understood the need for a hard-working wife, and numerous children, to handle the many chores, including child-rearing, feeding and clothing the family, managing the housework, feeding the hired hands, and, especially after the 1930s, handling paperwork and financial details. During the early years of settlement, farm women played an integral role in assuring family survival by working outdoors. After approximately one generation, women increasingly left the fields, thus redefining their roles within the family. New technology including sewing and washing machines encouraged women to turn to domestic roles. The scientific housekeeping movement, promoted across the land by the media and government extension agents, as well as county fairs which featured achievements in home cookery and canning, advice columns for women regarding farm bookkeeping, and home economics courses in the schools. |
During the Cenozoic era, specifically about 25 million years ago during the Miocene and Pliocene epochs, the continental climate became favorable to the evolution of grasslands. Existing forest biomes declined and grasslands became much more widespread. The grasslands provided a new niche for mammals, including many ungulates and glires, that switched from browsing diets to grazing diets. Traditionally, the spread of grasslands and the development of grazers have been strongly linked. However, an examination of mammalian teeth suggests that it is the open, gritty habitat and not the grass itself which is linked to diet changes in mammals, giving rise to the "grit, not grass" hypothesis. |
To allow for agricultural development of the Great Plains and house a growing population, the US passed the Homestead Acts of 1862: it allowed a settler to claim up to 160 acres (65 ha) of land, provided that he lived on it for a period of five years and cultivated it. The provisions were expanded under the Kinkaid Act of 1904 to include a homestead of an entire section. Hundreds of thousands of people claimed such homesteads, sometimes building sod houses out of the very turf of their land. Many of them were not skilled dryland farmers and failures were frequent. Much of the Plains were settled during relatively wet years. Government experts did not understand how farmers should cultivate the prairies and gave advice counter to what would have worked[citation needed]. Germans from Russia who had previously farmed, under similar circumstances, in what is now Ukraine were marginally more successful than other homesteaders. The Dominion Lands Act of 1871 served a similar function for establishing homesteads on the prairies in Canada. |
Infrared radiation is used in industrial, scientific, and medical applications. Night-vision devices using active near-infrared illumination allow people or animals to be observed without the observer being detected. Infrared astronomy uses sensor-equipped telescopes to penetrate dusty regions of space, such as molecular clouds; detect objects such as planets, and to view highly red-shifted objects from the early days of the universe. Infrared thermal-imaging cameras are used to detect heat loss in insulated systems, to observe changing blood flow in the skin, and to detect overheating of electrical apparatus. |
The onset of infrared is defined (according to different standards) at various values typically between 700 nm and 800 nm, but the boundary between visible and infrared light is not precisely defined. The human eye is markedly less sensitive to light above 700 nm wavelength, so longer wavelengths make insignificant contributions to scenes illuminated by common light sources. However, particularly intense near-IR light (e.g., from IR lasers, IR LED sources, or from bright daylight with the visible light removed by colored gels) can be detected up to approximately 780 nm, and will be perceived as red light. Sources providing wavelengths as long as 1050 nm can be seen as a dull red glow in intense sources, causing some difficulty in near-IR illumination of scenes in the dark (usually this practical problem is solved by indirect illumination). Leaves are particularly bright in the near IR, and if all visible light leaks from around an IR-filter are blocked, and the eye is given a moment to adjust to the extremely dim image coming through a visually opaque IR-passing photographic filter, it is possible to see the Wood effect that consists of IR-glowing foliage. |
The concept of emissivity is important in understanding the infrared emissions of objects. This is a property of a surface that describes how its thermal emissions deviate from the ideal of a black body. To further explain, two objects at the same physical temperature will not show the same infrared image if they have differing emissivity. For example, for any pre-set emissivity value, objects with higher emissivity will appear hotter, and those with a lower emissivity will appear cooler. For that reason, incorrect selection of emissivity will give inaccurate results when using infrared cameras and pyrometers. |
Infrared vibrational spectroscopy (see also near-infrared spectroscopy) is a technique that can be used to identify molecules by analysis of their constituent bonds. Each chemical bond in a molecule vibrates at a frequency characteristic of that bond. A group of atoms in a molecule (e.g., CH2) may have multiple modes of oscillation caused by the stretching and bending motions of the group as a whole. If an oscillation leads to a change in dipole in the molecule then it will absorb a photon that has the same frequency. The vibrational frequencies of most molecules correspond to the frequencies of infrared light. Typically, the technique is used to study organic compounds using light radiation from 4000–400 cm−1, the mid-infrared. A spectrum of all the frequencies of absorption in a sample is recorded. This can be used to gain information about the sample composition in terms of chemical groups present and also its purity (for example, a wet sample will show a broad O-H absorption around 3200 cm−1). |
In infrared photography, infrared filters are used to capture the near-infrared spectrum. Digital cameras often use infrared blockers. Cheaper digital cameras and camera phones have less effective filters and can "see" intense near-infrared, appearing as a bright purple-white color. This is especially pronounced when taking pictures of subjects near IR-bright areas (such as near a lamp), where the resulting infrared interference can wash out the image. There is also a technique called 'T-ray' imaging, which is imaging using far-infrared or terahertz radiation. Lack of bright sources can make terahertz photography more challenging than most other infrared imaging techniques. Recently T-ray imaging has been of considerable interest due to a number of new developments such as terahertz time-domain spectroscopy. |
Infrared reflectography (fr; it; es), as called by art conservators, can be applied to paintings to reveal underlying layers in a completely non-destructive manner, in particular the underdrawing or outline drawn by the artist as a guide. This often reveals the artist's use of carbon black, which shows up well in reflectograms, as long as it has not also been used in the ground underlying the whole painting. Art conservators are looking to see whether the visible layers of paint differ from the underdrawing or layers in between – such alterations are called pentimenti when made by the original artist. This is very useful information in deciding whether a painting is the prime version by the original artist or a copy, and whether it has been altered by over-enthusiastic restoration work. In general, the more pentimenti the more likely a painting is to be the prime version. It also gives useful insights into working practices. |
The discovery of infrared radiation is ascribed to William Herschel, the astronomer, in the early 19th century. Herschel published his results in 1800 before the Royal Society of London. Herschel used a prism to refract light from the sun and detected the infrared, beyond the red part of the spectrum, through an increase in the temperature recorded on a thermometer. He was surprised at the result and called them "Calorific Rays". The term 'Infrared' did not appear until late in the 19th century. |
Infrared radiation is popularly known as "heat radiation"[citation needed], but light and electromagnetic waves of any frequency will heat surfaces that absorb them. Infrared light from the Sun accounts for 49% of the heating of Earth, with the rest being caused by visible light that is absorbed then re-radiated at longer wavelengths. Visible light or ultraviolet-emitting lasers can char paper and incandescently hot objects emit visible radiation. Objects at room temperature will emit radiation concentrated mostly in the 8 to 25 µm band, but this is not distinct from the emission of visible light by incandescent objects and ultraviolet by even hotter objects (see black body and Wien's displacement law). |
Infrared tracking, also known as infrared homing, refers to a passive missile guidance system, which uses the emission from a target of electromagnetic radiation in the infrared part of the spectrum to track it. Missiles that use infrared seeking are often referred to as "heat-seekers", since infrared (IR) is just below the visible spectrum of light in frequency and is radiated strongly by hot bodies. Many objects such as people, vehicle engines, and aircraft generate and retain heat, and as such, are especially visible in the infrared wavelengths of light compared to objects in the background. |
High, cold ice clouds such as Cirrus or Cumulonimbus show up bright white, lower warmer clouds such as Stratus or Stratocumulus show up as grey with intermediate clouds shaded accordingly. Hot land surfaces will show up as dark-grey or black. One disadvantage of infrared imagery is that low cloud such as stratus or fog can be a similar temperature to the surrounding land or sea surface and does not show up. However, using the difference in brightness of the IR4 channel (10.3–11.5 µm) and the near-infrared channel (1.58–1.64 µm), low cloud can be distinguished, producing a fog satellite picture. The main advantage of infrared is that images can be produced at night, allowing a continuous sequence of weather to be studied. |
The sensitivity of Earth-based infrared telescopes is significantly limited by water vapor in the atmosphere, which absorbs a portion of the infrared radiation arriving from space outside of selected atmospheric windows. This limitation can be partially alleviated by placing the telescope observatory at a high altitude, or by carrying the telescope aloft with a balloon or an aircraft. Space telescopes do not suffer from this handicap, and so outer space is considered the ideal location for infrared astronomy. |
Near-infrared is the region closest in wavelength to the radiation detectable by the human eye, mid- and far-infrared are progressively further from the visible spectrum. Other definitions follow different physical mechanisms (emission peaks, vs. bands, water absorption) and the newest follow technical reasons (the common silicon detectors are sensitive to about 1,050 nm, while InGaAs's sensitivity starts around 950 nm and ends between 1,700 and 2,600 nm, depending on the specific configuration). Unfortunately, international standards for these specifications are not currently available. |
Heat is energy in transit that flows due to temperature difference. Unlike heat transmitted by thermal conduction or thermal convection, thermal radiation can propagate through a vacuum. Thermal radiation is characterized by a particular spectrum of many wavelengths that is associated with emission from an object, due to the vibration of its molecules at a given temperature. Thermal radiation can be emitted from objects at any wavelength, and at very high temperatures such radiations are associated with spectra far above the infrared, extending into visible, ultraviolet, and even X-ray regions (i.e., the solar corona). Thus, the popular association of infrared radiation with thermal radiation is only a coincidence based on typical (comparatively low) temperatures often found near the surface of planet Earth. |
Thermographic cameras detect radiation in the infrared range of the electromagnetic spectrum (roughly 900–14,000 nanometers or 0.9–14 μm) and produce images of that radiation. Since infrared radiation is emitted by all objects based on their temperatures, according to the black body radiation law, thermography makes it possible to "see" one's environment with or without visible illumination. The amount of radiation emitted by an object increases with temperature, therefore thermography allows one to see variations in temperature (hence the name). |
The infrared portion of the spectrum has several useful benefits for astronomers. Cold, dark molecular clouds of gas and dust in our galaxy will glow with radiated heat as they are irradiated by imbedded stars. Infrared can also be used to detect protostars before they begin to emit visible light. Stars emit a smaller portion of their energy in the infrared spectrum, so nearby cool objects such as planets can be more readily detected. (In the visible light spectrum, the glare from the star will drown out the reflected light from a planet.) |
Infrared is used in night vision equipment when there is insufficient visible light to see. Night vision devices operate through a process involving the conversion of ambient light photons into electrons that are then amplified by a chemical and electrical process and then converted back into visible light. Infrared light sources can be used to augment the available ambient light for conversion by night vision devices, increasing in-the-dark visibility without actually using a visible light source. |
IR data transmission is also employed in short-range communication among computer peripherals and personal digital assistants. These devices usually conform to standards published by IrDA, the Infrared Data Association. Remote controls and IrDA devices use infrared light-emitting diodes (LEDs) to emit infrared radiation that is focused by a plastic lens into a narrow beam. The beam is modulated, i.e. switched on and off, to encode the data. The receiver uses a silicon photodiode to convert the infrared radiation to an electric current. It responds only to the rapidly pulsing signal created by the transmitter, and filters out slowly changing infrared radiation from ambient light. Infrared communications are useful for indoor use in areas of high population density. IR does not penetrate walls and so does not interfere with other devices in adjoining rooms. Infrared is the most common way for remote controls to command appliances. Infrared remote control protocols like RC-5, SIRC, are used to communicate with infrared. |
In the semiconductor industry, infrared light can be used to characterize materials such as thin films and periodic trench structures. By measuring the reflectance of light from the surface of a semiconductor wafer, the index of refraction (n) and the extinction Coefficient (k) can be determined via the Forouhi-Bloomer dispersion equations. The reflectance from the infrared light can also be used to determine the critical dimension, depth, and sidewall angle of high aspect ratio trench structures. |
Infrared cleaning is a technique used by some Motion picture film scanner, film scanners and flatbed scanners to reduce or remove the effect of dust and scratches upon the finished scan. It works by collecting an additional infrared channel from the scan at the same position and resolution as the three visible color channels (red, green, and blue). The infrared channel, in combination with the other channels, is used to detect the location of scratches and dust. Once located, those defects can be corrected by scaling or replaced by inpainting. |
Earth's surface and the clouds absorb visible and invisible radiation from the sun and re-emit much of the energy as infrared back to atmosphere. Certain substances in the atmosphere, chiefly cloud droplets and water vapor, but also carbon dioxide, methane, nitrous oxide, sulfur hexafluoride, and chlorofluorocarbons, absorb this infrared, and re-radiate it in all directions including back to Earth. Thus, the greenhouse effect keeps the atmosphere and surface much warmer than if the infrared absorbers were absent from the atmosphere. |
Biodiversity, a contraction of "biological diversity," generally refers to the variety and variability of life on Earth. One of the most widely used definitions defines it in terms of the variability within species, between species, and between ecosystems. It is a measure of the variety of organisms present in different ecosystems. This can refer to genetic variation, ecosystem variation, or species variation (number of species) within an area, biome, or planet. Terrestrial biodiversity tends to be greater near the equator, which seems to be the result of the warm climate and high primary productivity. Biodiversity is not distributed evenly on Earth. It is richest in the tropics. Marine biodiversity tends to be highest along coasts in the Western Pacific, where sea surface temperature is highest and in the mid-latitudinal band in all oceans. There are latitudinal gradients in species diversity. Biodiversity generally tends to cluster in hotspots, and has been increasing through time, but will be likely to slow in the future. |
This multilevel construct is consistent with Dasmann and Lovejoy. An explicit definition consistent with this interpretation was first given in a paper by Bruce A. Wilcox commissioned by the International Union for the Conservation of Nature and Natural Resources (IUCN) for the 1982 World National Parks Conference. Wilcox's definition was "Biological diversity is the variety of life forms...at all levels of biological systems (i.e., molecular, organismic, population, species and ecosystem)...". The 1992 United Nations Earth Summit defined "biological diversity" as "the variability among living organisms from all sources, including, 'inter alia', terrestrial, marine, and other aquatic ecosystems, and the ecological complexes of which they are part: this includes diversity within species, between species and of ecosystems". This definition is used in the United Nations Convention on Biological Diversity. |
On the other hand, changes through the Phanerozoic correlate much better with the hyperbolic model (widely used in population biology, demography and macrosociology, as well as fossil biodiversity) than with exponential and logistic models. The latter models imply that changes in diversity are guided by a first-order positive feedback (more ancestors, more descendants) and/or a negative feedback arising from resource limitation. Hyperbolic model implies a second-order positive feedback. The hyperbolic pattern of the world population growth arises from a second-order positive feedback between the population size and the rate of technological growth. The hyperbolic character of biodiversity growth can be similarly accounted for by a feedback between diversity and community structure complexity. The similarity between the curves of biodiversity and human population probably comes from the fact that both are derived from the interference of the hyperbolic trend with cyclical and stochastic dynamics. |
Interspecific crop diversity is, in part, responsible for offering variety in what we eat. Intraspecific diversity, the variety of alleles within a single species, also offers us choice in our diets. If a crop fails in a monoculture, we rely on agricultural diversity to replant the land with something new. If a wheat crop is destroyed by a pest we may plant a hardier variety of wheat the next year, relying on intraspecific diversity. We may forgo wheat production in that area and plant a different species altogether, relying on interspecific diversity. Even an agricultural society which primarily grows monocultures, relies on biodiversity at some point. |
In absolute terms, the planet has lost 52% of its biodiversity since 1970 according to a 2014 study by the World Wildlife Fund. The Living Planet Report 2014 claims that "the number of mammals, birds, reptiles, amphibians and fish across the globe is, on average, about half the size it was 40 years ago". Of that number, 39% accounts for the terrestrial wildlife gone, 39% for the marine wildlife gone, and 76% for the freshwater wildlife gone. Biodiversity took the biggest hit in Latin America, plummeting 83 percent. High-income countries showed a 10% increase in biodiversity, which was canceled out by a loss in low-income countries. This is despite the fact that high-income countries use five times the ecological resources of low-income countries, which was explained as a result of process whereby wealthy nations are outsourcing resource depletion to poorer nations, which are suffering the greatest ecosystem losses. |
A 2007 study conducted by the National Science Foundation found that biodiversity and genetic diversity are codependent—that diversity among species requires diversity within a species, and vice versa. "If any one type is removed from the system, the cycle can break down, and the community becomes dominated by a single species." At present, the most threatened ecosystems are found in fresh water, according to the Millennium Ecosystem Assessment 2005, which was confirmed by the "Freshwater Animal Diversity Assessment", organised by the biodiversity platform, and the French Institut de recherche pour le développement (MNHNP). |
Finally, an introduced species may unintentionally injure a species that depends on the species it replaces. In Belgium, Prunus spinosa from Eastern Europe leafs much sooner than its West European counterparts, disrupting the feeding habits of the Thecla betulae butterfly (which feeds on the leaves). Introducing new species often leaves endemic and other local species unable to compete with the exotic species and unable to survive. The exotic organisms may be predators, parasites, or may simply outcompete indigenous species for nutrients, water and light. |
The forests play a vital role in harbouring more than 45,000 floral and 81,000 faunal species of which 5150 floral and 1837 faunal species are endemic. Plant and animal species confined to a specific geographical area are called endemic species. In reserved forests, rights to activities like hunting and grazing are sometimes given to communities living on the fringes of the forest, who sustain their livelihood partially or wholly from forest resources or products. The unclassed forests covers 6.4 percent of the total forest area and they are marked by the following characteristics: |
Global agreements such as the Convention on Biological Diversity, give "sovereign national rights over biological resources" (not property). The agreements commit countries to "conserve biodiversity", "develop resources for sustainability" and "share the benefits" resulting from their use. Biodiverse countries that allow bioprospecting or collection of natural products, expect a share of the benefits rather than allowing the individual or institution that discovers/exploits the resource to capture them privately. Bioprospecting can become a type of biopiracy when such principles are not respected.[citation needed] |
Rapid environmental changes typically cause mass extinctions. More than 99 percent of all species, amounting to over five billion species, that ever lived on Earth are estimated to be extinct. Estimates on the number of Earth's current species range from 10 million to 14 million, of which about 1.2 million have been documented and over 86 percent have not yet been described. The total amount of related DNA base pairs on Earth is estimated at 5.0 x 1037, and weighs 50 billion tonnes. In comparison, the total mass of the biosphere has been estimated to be as much as 4 TtC (trillion tons of carbon). |
The history of biodiversity during the Phanerozoic (the last 540 million years), starts with rapid growth during the Cambrian explosion—a period during which nearly every phylum of multicellular organisms first appeared. Over the next 400 million years or so, invertebrate diversity showed little overall trend, and vertebrate diversity shows an overall exponential trend. This dramatic rise in diversity was marked by periodic, massive losses of diversity classified as mass extinction events. A significant loss occurred when rainforests collapsed in the carboniferous. The worst was the Permian-Triassic extinction event, 251 million years ago. Vertebrates took 30 million years to recover from this event. |
Jared Diamond describes an "Evil Quartet" of habitat destruction, overkill, introduced species, and secondary extinctions. Edward O. Wilson prefers the acronym HIPPO, standing for Habitat destruction, Invasive species, Pollution, human over-Population, and Over-harvesting. The most authoritative classification in use today is IUCN's Classification of Direct Threats which has been adopted by major international conservation organizations such as the US Nature Conservancy, the World Wildlife Fund, Conservation International, and BirdLife International. |
Endemic species can be threatened with extinction through the process of genetic pollution, i.e. uncontrolled hybridization, introgression and genetic swamping. Genetic pollution leads to homogenization or replacement of local genomes as a result of either a numerical and/or fitness advantage of an introduced species. Hybridization and introgression are side-effects of introduction and invasion. These phenomena can be especially detrimental to rare species that come into contact with more abundant ones. The abundant species can interbreed with the rare species, swamping its gene pool. This problem is not always apparent from morphological (outward appearance) observations alone. Some degree of gene flow is normal adaptation, and not all gene and genotype constellations can be preserved. However, hybridization with or without introgression may, nevertheless, threaten a rare species' existence. |
The age of the Earth is about 4.54 billion years old. The earliest undisputed evidence of life on Earth dates at least from 3.5 billion years ago, during the Eoarchean Era after a geological crust started to solidify following the earlier molten Hadean Eon. There are microbial mat fossils found in 3.48 billion-year-old sandstone discovered in Western Australia. Other early physical evidence of a biogenic substance is graphite in 3.7 billion-year-old metasedimentary rocks discovered in Western Greenland. More recently, in 2015, "remains of biotic life" were found in 4.1 billion-year-old rocks in Western Australia. According to one of the researchers, "If life arose relatively quickly on Earth ... then it could be common in the universe." |
The fossil record suggests that the last few million years featured the greatest biodiversity in history. However, not all scientists support this view, since there is uncertainty as to how strongly the fossil record is biased by the greater availability and preservation of recent geologic sections. Some scientists believe that corrected for sampling artifacts, modern biodiversity may not be much different from biodiversity 300 million years ago., whereas others consider the fossil record reasonably reflective of the diversification of life. Estimates of the present global macroscopic species diversity vary from 2 million to 100 million, with a best estimate of somewhere near 9 million, the vast majority arthropods. Diversity appears to increase continually in the absence of natural selection. |
Agricultural diversity can also be divided by whether it is ‘planned’ diversity or ‘associated’ diversity. This is a functional classification that we impose and not an intrinsic feature of life or diversity. Planned diversity includes the crops which a farmer has encouraged, planted or raised (e.g.: crops, covers, symbionts and livestock, among others), which can be contrasted with the associated diversity that arrives among the crops, uninvited (e.g.: herbivores, weed species and pathogens, among others). |
Biodiversity's relevance to human health is becoming an international political issue, as scientific evidence builds on the global health implications of biodiversity loss. This issue is closely linked with the issue of climate change, as many of the anticipated health risks of climate change are associated with changes in biodiversity (e.g. changes in populations and distribution of disease vectors, scarcity of fresh water, impacts on agricultural biodiversity and food resources etc.) This is because the species most likely to disappear are those that buffer against infectious disease transmission, while surviving species tend to be the ones that increase disease transmission, such as that of West Nile Virus, Lyme disease and Hantavirus, according to a study done co-authored by Felicia Keesing, an ecologist at Bard College, and Drew Harvell, associate director for Environment of the Atkinson Center for a Sustainable Future (ACSF) at Cornell University. |
Since life began on Earth, five major mass extinctions and several minor events have led to large and sudden drops in biodiversity. The Phanerozoic eon (the last 540 million years) marked a rapid growth in biodiversity via the Cambrian explosion—a period during which the majority of multicellular phyla first appeared. The next 400 million years included repeated, massive biodiversity losses classified as mass extinction events. In the Carboniferous, rainforest collapse led to a great loss of plant and animal life. The Permian–Triassic extinction event, 251 million years ago, was the worst; vertebrate recovery took 30 million years. The most recent, the Cretaceous–Paleogene extinction event, occurred 65 million years ago and has often attracted more attention than others because it resulted in the extinction of the dinosaurs. |
The number of species invasions has been on the rise at least since the beginning of the 1900s. Species are increasingly being moved by humans (on purpose and accidentally). In some cases the invaders are causing drastic changes and damage to their new habitats (e.g.: zebra mussels and the emerald ash borer in the Great Lakes region and the lion fish along the North American Atlantic coast). Some evidence suggests that invasive species are competitive in their new habitats because they are subject to less pathogen disturbance. Others report confounding evidence that occasionally suggest that species-rich communities harbor many native and exotic species simultaneously while some say that diverse ecosystems are more resilient and resist invasive plants and animals. An important question is, "do invasive species cause extinctions?" Many studies cite effects of invasive species on natives, but not extinctions. Invasive species seem to increase local (i.e.: alpha diversity) diversity, which decreases turnover of diversity (i.e.: beta diversity). Overall gamma diversity may be lowered because species are going extinct because of other causes, but even some of the most insidious invaders (e.g.: Dutch elm disease, emerald ash borer, chestnut blight in North America) have not caused their host species to become extinct. Extirpation, population decline, and homogenization of regional biodiversity are much more common. Human activities have frequently been the cause of invasive species circumventing their barriers, by introducing them for food and other purposes. Human activities therefore allow species to migrate to new areas (and thus become invasive) occurred on time scales much shorter than historically have been required for a species to extend its range. |
Brazil's Atlantic Forest is considered one such hotspot, containing roughly 20,000 plant species, 1,350 vertebrates, and millions of insects, about half of which occur nowhere else.[citation needed] The island of Madagascar and India are also particularly notable. Colombia is characterized by high biodiversity, with the highest rate of species by area unit worldwide and it has the largest number of endemics (species that are not found naturally anywhere else) of any country. About 10% of the species of the Earth can be found in Colombia, including over 1,900 species of bird, more than in Europe and North America combined, Colombia has 10% of the world’s mammals species, 14% of the amphibian species, and 18% of the bird species of the world. Madagascar dry deciduous forests and lowland rainforests possess a high ratio of endemism.[citation needed] Since the island separated from mainland Africa 66 million years ago, many species and ecosystems have evolved independently.[citation needed] Indonesia's 17,000 islands cover 735,355 square miles (1,904,560 km2) and contain 10% of the world's flowering plants, 12% of mammals, and 17% of reptiles, amphibians and birds—along with nearly 240 million people. Many regions of high biodiversity and/or endemism arise from specialized habitats which require unusual adaptations, for example, alpine environments in high mountains, or Northern European peat bogs.[citation needed] |
The existence of a "global carrying capacity", limiting the amount of life that can live at once, is debated, as is the question of whether such a limit would also cap the number of species. While records of life in the sea shows a logistic pattern of growth, life on land (insects, plants and tetrapods)shows an exponential rise in diversity. As one author states, "Tetrapods have not yet invaded 64 per cent of potentially habitable modes, and it could be that without human influence the ecological and taxonomic diversity of tetrapods would continue to increase in an exponential fashion until most or all of the available ecospace is filled." |
From 1950 to 2011, world population increased from 2.5 billion to 7 billion and is forecast to reach a plateau of more than 9 billion during the 21st century. Sir David King, former chief scientific adviser to the UK government, told a parliamentary inquiry: "It is self-evident that the massive growth in the human population through the 20th century has had more impact on biodiversity than any other single factor." At least until the middle of the 21st century, worldwide losses of pristine biodiverse land will probably depend much on the worldwide human birth rate. |
The control of associated biodiversity is one of the great agricultural challenges that farmers face. On monoculture farms, the approach is generally to eradicate associated diversity using a suite of biologically destructive pesticides, mechanized tools and transgenic engineering techniques, then to rotate crops. Although some polyculture farmers use the same techniques, they also employ integrated pest management strategies as well as strategies that are more labor-intensive, but generally less dependent on capital, biotechnology and energy. |
National park and nature reserve is the area selected by governments or private organizations for special protection against damage or degradation with the objective of biodiversity and landscape conservation. National parks are usually owned and managed by national or state governments. A limit is placed on the number of visitors permitted to enter certain fragile areas. Designated trails or roads are created. The visitors are allowed to enter only for study, cultural and recreation purposes. Forestry operations, grazing of animals and hunting of animals are prohibited. Exploitation of habitat or wildlife is banned. |
During the last century, decreases in biodiversity have been increasingly observed. In 2007, German Federal Environment Minister Sigmar Gabriel cited estimates that up to 30% of all species will be extinct by 2050. Of these, about one eighth of known plant species are threatened with extinction. Estimates reach as high as 140,000 species per year (based on Species-area theory). This figure indicates unsustainable ecological practices, because few species emerge each year.[citation needed] Almost all scientists acknowledge that the rate of species loss is greater now than at any time in human history, with extinctions occurring at rates hundreds of times higher than background extinction rates. As of 2012, some studies suggest that 25% of all mammal species could be extinct in 20 years. |
Habitat size and numbers of species are systematically related. Physically larger species and those living at lower latitudes or in forests or oceans are more sensitive to reduction in habitat area. Conversion to "trivial" standardized ecosystems (e.g., monoculture following deforestation) effectively destroys habitat for the more diverse species that preceded the conversion. In some countries lack of property rights or lax law/regulatory enforcement necessarily leads to biodiversity loss (degradation costs having to be supported by the community).[citation needed] |
Not all introduced species are invasive, nor all invasive species deliberately introduced. In cases such as the zebra mussel, invasion of US waterways was unintentional. In other cases, such as mongooses in Hawaii, the introduction is deliberate but ineffective (nocturnal rats were not vulnerable to the diurnal mongoose). In other cases, such as oil palms in Indonesia and Malaysia, the introduction produces substantial economic benefits, but the benefits are accompanied by costly unintended consequences. |
Less than 1% of all species that have been described have been studied beyond simply noting their existence. The vast majority of Earth's species are microbial. Contemporary biodiversity physics is "firmly fixated on the visible [macroscopic] world". For example, microbial life is metabolically and environmentally more diverse than multicellular life (see e.g., extremophile). "On the tree of life, based on analyses of small-subunit ribosomal RNA, visible life consists of barely noticeable twigs. The inverse relationship of size and population recurs higher on the evolutionary ladder—"to a first approximation, all multicellular species on Earth are insects". Insect extinction rates are high—supporting the Holocene extinction hypothesis. |
The number and variety of plants, animals and other organisms that exist is known as biodiversity. It is an essential component of nature and it ensures the survival of human species by providing food, fuel, shelter, medicines and other resources to mankind. The richness of biodiversity depends on the climatic conditions and area of the region. All species of plants taken together are known as flora and about 70,000 species of plants are known till date. All species of animals taken together are known as fauna which includes birds, mammals, fish, reptiles, insects, crustaceans, molluscs, etc. |
The term biological diversity was used first by wildlife scientist and conservationist Raymond F. Dasmann in the year 1968 lay book A Different Kind of Country advocating conservation. The term was widely adopted only after more than a decade, when in the 1980s it came into common usage in science and environmental policy. Thomas Lovejoy, in the foreword to the book Conservation Biology, introduced the term to the scientific community. Until then the term "natural diversity" was common, introduced by The Science Division of The Nature Conservancy in an important 1975 study, "The Preservation of Natural Diversity." By the early 1980s TNC's Science program and its head, Robert E. Jenkins, Lovejoy and other leading conservation scientists at the time in America advocated the use of the term "biological diversity". |
Biodiversity provides critical support for drug discovery and the availability of medicinal resources. A significant proportion of drugs are derived, directly or indirectly, from biological sources: at least 50% of the pharmaceutical compounds on the US market are derived from plants, animals, and micro-organisms, while about 80% of the world population depends on medicines from nature (used in either modern or traditional medical practice) for primary healthcare. Only a tiny fraction of wild species has been investigated for medical potential. Biodiversity has been critical to advances throughout the field of bionics. Evidence from market analysis and biodiversity science indicates that the decline in output from the pharmaceutical sector since the mid-1980s can be attributed to a move away from natural product exploration ("bioprospecting") in favor of genomics and synthetic chemistry, indeed claims about the value of undiscovered pharmaceuticals may not provide enough incentive for companies in free markets to search for them because of the high cost of development; meanwhile, natural products have a long history of supporting significant economic and health innovation. Marine ecosystems are particularly important, although inappropriate bioprospecting can increase biodiversity loss, as well as violating the laws of the communities and states from which the resources are taken. |
In agriculture and animal husbandry, the Green Revolution popularized the use of conventional hybridization to increase yield. Often hybridized breeds originated in developed countries and were further hybridized with local varieties in the developing world to create high yield strains resistant to local climate and diseases. Local governments and industry have been pushing hybridization. Formerly huge gene pools of various wild and indigenous breeds have collapsed causing widespread genetic erosion and genetic pollution. This has resulted in loss of genetic diversity and biodiversity as a whole. |
Originally based on the English alphabet, ASCII encodes 128 specified characters into seven-bit integers as shown by the ASCII chart on the right. The characters encoded are numbers 0 to 9, lowercase letters a to z, uppercase letters A to Z, basic punctuation symbols, control codes that originated with Teletype machines, and a space. For example, lowercase j would become binary 1101010 and decimal 106. ASCII includes definitions for 128 characters: 33 are non-printing control characters (many now obsolete) that affect how text and space are processed and 95 printable characters, including the space (which is considered an invisible graphic:223). |
The code itself was patterned so that most control codes were together, and all graphic codes were together, for ease of identification. The first two columns (32 positions) were reserved for control characters.:220, 236 § 8,9) The "space" character had to come before graphics to make sorting easier, so it became position 20hex;:237 § 10 for the same reason, many special signs commonly used as separators were placed before digits. The committee decided it was important to support uppercase 64-character alphabets, and chose to pattern ASCII so it could be reduced easily to a usable 64-character set of graphic codes,:228, 237 § 14 as was done in the DEC SIXBIT code. Lowercase letters were therefore not interleaved with uppercase. To keep options available for lowercase letters and other graphics, the special and numeric codes were arranged before the letters, and the letter A was placed in position 41hex to match the draft of the corresponding British standard.:238 § 18 The digits 0–9 were arranged so they correspond to values in binary prefixed with 011, making conversion with binary-coded decimal straightforward. |
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