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Wednesday, October 5, 2022

Joseph Stalin's cult of personality

Poster of Stalin displayed at a public event in Leipzig in 1950
 
A celebration of Stalin's purported 70th birthday in the People's Republic of China
 
Stalin at his 70th birthday ceremony with Marshal Nikolai Bulganin, Chinese Communist Leader Mao Zedong, Mongolian Communist Leader Yumjaagiin Tsedenbal and German Communist Leader Walter Ulbricht

Joseph Stalin's cult of personality became a prominent feature of Soviet popular culture in 1929, after a lavish celebration of his purported 50th birthday. For the rest of Stalin's rule, the Soviet press presented Stalin as an all-powerful, all-knowing leader, with Stalin's name and image appearing everywhere. Historian Archie Brown sets the celebration of Stalin's 50th birthday on 21 December 1929 as the starting point for his cult of personality.

Stalin's image in propaganda and the mass media

Female members of the FDJ carry Stalin's pictures in the 3rd World Festival of Youth and Students in East Berlin

The building of the cult of personality around Stalin had to proceed judiciously, as British historian Ian Kershaw explains in his history of Europe in the first half of the 20th century, To Hell and Back:

A Stalin cult had to be built carefully. This was not just because the man himself was so physically unprepossessing – diminutive and squat, his face dominated by a big walrus mustache and heavily pitted from smallpox – or that he was a secretive, intensely private individual who spoke in a quiet, undemonstrative voice, his Russian couched in a strong Georgian accent that never left him. The real problem was the giant shadow of Lenin. Stalin could not be seen to be usurping the legendary image of the great Bolshevik hero and leader of the revolution. So at first Stalin tread cautiously.

Lenin had not wanted Stalin to succeed him, stating that "Comrade Stalin is too rude" and suggesting that the party find someone "more patient, more loyal, more polite". Stalin did not completely succeed in suppressing Lenin's Testament suggesting that others remove Stalin from his position as leader of the Communist party. Nevertheless, after Lenin's death 500,000 copies of a photograph of Lenin and Stalin apparently chatting as friends on a bench appeared throughout the Soviet Union. Before 1932, most Soviet propaganda posters showed Lenin and Stalin together. This propaganda was embraced by Stalin, who weaponized this relationship in speeches to the proletarian, stating Lenin was "the great teacher of the proletarians of all nations" and subsequently identifying himself with the proletarians by their kinship as mutual students of Lenin. However, eventually the two figures merged in the Soviet press; Stalin became the embodiment of Lenin. Initially, the press attributed any and all success within the Soviet Union to the wise leadership of both Lenin and Stalin, but eventually Stalin alone became the professed cause of Soviet well-being.

The celebrations for Stalin's 50th birthday in December 1929 marked the real beginning of the construction of the cult around Stalin. Publicly, Stalin was modest, rejecting suggestions that he was Lenin's equal, but allowing a dual celebration of the two men to proceed, before later shifting it primarily to himself. By 1933, central Moscow had twice as many busts and images of Stalin as of Lenin, and Stalin would receive ovations at his rare public appearances lasting 15 minutes or more.

The Soviet press constantly praised Stalin, describing him as "Great", "Beloved", "Bold", "Wise", "Inspirer", and "Genius". It portrayed him as a caring yet strong father figure, with the Soviet populace as his "children". From 1936, the Soviet press started to refer to Stalin as the "Father of Nations", reminding the peasantry of their image of their previous ruler, the tsar, who was seen as a "stern family patriarch". After years of revolutions and civil war, the Russian people longed for strong and purposeful leadership.

Interactions between Stalin and children became a key element of the personality cult. Stalin often engaged in publicized gift giving exchanges with Soviet children from a range of different ethnic backgrounds. Beginning in 1935, the phrase, "Thank You Dear Comrade Stalin for a Happy Childhood!" appeared above doorways at nurseries, orphanages, and schools; children also chanted this slogan at festivals.

Speeches described Stalin as "Our Best Collective Farm Worker", "Our Shockworker, Our Best of Best", and "Our Darling, Our Guiding Star". The image of Stalin as a father was one way in which Soviet propagandists aimed to incorporate traditional religious symbols and language into the cult of personality; the title of "father" now first and foremost belonged to Stalin, as opposed to the Russian Orthodox priests. The cult of personality also adopted the Christian traditions of procession and devotion to icons through the use of Stalinist parades and effigies. By reapplying various aspects of religion to the cult of personality, the press hoped to shift devotion away from the church and towards Stalin.

Initially, the press also aimed to demonstrate a direct link between Stalin and the common people; newspapers often published collective letters from farm or industrial workers praising the leader, as well as accounts and poems about meeting Stalin. Shortly after the revolution of October 1917 the Ivan Tovstukha drafted up a biographical section featuring Stalin for the Russian Granat Encyclopedia Dictionary. Even though most of the description of Stalin's career was very much embellished, it had gained so much favor with the public that they released a fourteen-page pamphlet of it alone named Joseph Vissarionovich Stalin: A Short Biography with a print run of 50,000. However, these sorts of accounts declined after World War II; Stalin drew back from public life, and the press instead began to focus on remote contact (i.e. accounts of receiving a telegram from Stalin or seeing the leader from afar). Another prominent part of Stalin's image in the mass media was his close association with Vladimir Lenin. The Soviet press maintained that Stalin had been Lenin's constant companion while the latter was alive, and that as such, Stalin closely followed Lenin's teachings and could continue the Bolshevik legacy after Lenin's death. Stalin fiercely defended the correctness of Lenin's views in public, and in doing so Stalin implied that, as a faithful follower of Leninism, his own leadership was similarly faultless.

Other displays of devotion

Stalin became the focus of literature, poetry, music, paintings and film that exhibited fawning devotion. An example was Alexander O. Avdeenko's "Hymn to Stalin", which came from an earlier speech made by him in 1935:

Thank you, Stalin. Thank you because I am joyful. Thank you because I am well. No matter how old I become, I shall never forget how we received Stalin two days ago. Centuries will pass, and the generations still to come will regard us as the happiest of mortals, as the most fortunate of men, because we lived in the century of centuries, because we were privileged to see Stalin, our inspired leader ... Everything belongs to thee, chief of our great country. And when the woman I love presents me with a child the first word it shall utter will be : Stalin ...

Numerous pictures and statues of Stalin adorned public places. In 1955 a giant monument dedicated to Stalin was constructed in Prague and stood until 1962. The statue was a gift for Stalin's sixty-ninth birthday from Prague to commemorate "Mr. Stalin's personalty, mostly from his ideological features". After 5 years in the making, the massive 17,000-ton monument was finally revealed to the public which depicted Stalin, with one at the front of a group of proletarian workers. Statues of Stalin depicted him at a height and build approximating the very tall Tsar Alexander III, but photographic evidence suggests he was between 5 ft 5 in and 5 ft 6 in (165–168 cm). Stalin-themed art appeared privately, as well: starting in the early 1930s, many private homes included "Stalin rooms" dedicated to the leader and featuring his portrait. Although it was not an official uniform, party leaders throughout the Soviet Union emulated the dictator's usual outfit of dark green jacket, riding breeches, boots, and cap to prove their devotion.

The cult also led to public devotional behavior: by the late 1930s, people would jump out of their seats to stand up whenever Stalin's name was uttered in public meetings and conferences. Nikita Khrushchev described it as "a sort of physical culture we all engaged in."

The advent of the cult also led to a renaming craze: numerous towns, villages and cities were renamed after the Soviet leader. The Stalin Prize and Stalin Peace Prize were also named in his honor, and he accepted several grandiloquent titles (e.g., "Father of Nations", "Builder of Socialism", "Architect of Communism", "Leader of Progressive Humanity") among others.

The cult reached new levels during World War II, with Stalin's name included in the new Soviet national anthem.

In December 1949, Stalin celebrated his purported 70th birthday (he had in fact been born in December 1878). His birthday was celebrated extensively throughout the USSR. In the Ukrainian city of Mariupol, the former Sanatorium Avenue was renamed to Stalin Avenue. Various statues and institutions were made to honor him. On 2 December 1949, the Presidium of the Supreme Soviet of the USSR issued a decree to form a government committee centered on Stalin's birthday. 18 days later, the Supreme Soviet awarded the Order of Lenin to Stalin. On 21 December, the day after he was awarded, a ceremonial meeting dedicated to the 70th birthday of Stalin took place in the Bolshoi Theater. Notable world leaders were in attendance, including Chinese leader Mao Zedong and East German Deputy Prime Minister Walter Ulbricht. Marshal of the Mongolian People's Republic Khorloogiin Choibalsan, who was once a favorite of Stalin, did not attend the ceremonies, instead sending General Secretary Yumjaagiin Tsedenbal. For Mao, the celebrations were part of his first state visit to the USSR since taking power.

In many Eastern bloc countries, Stalin's birthday was also celebrated extensively. The Bulgarian city of Varna was renamed to Stalin and Musala was renamed to Stalin Peak. The Gerlachovský štít in Czechoslovakia was also renamed after Stalin.

Stalin and young people

One way Stalin's cult was spread was through the Komsomol, the All-Union Leninist Communist League of Youth in Soviet Russia, created in 1918. The ages of these young people ranged from 9 to 28 years old making it a favorable instrument to reshape the members and ideology of the Soviet Union. This organization was created to raise the next generation into the type of socialist that Stalin envisioned. Being a part of this organization was beneficial to the participants for they were favored over a non-member when it came to getting scholarships and jobs. Just like most youth clubs, they focused on their members' education and health, with sports and physical activities. They also focused on the youths' behavior and character. The children were encouraged to reject anyone who didn't embody the values of a socialist. In cases of lying and cheating on the schoolyard, it resulted to "classroom trials". Stalin wanted the best to prevail in his image of the future Soviet Union so he put into effect a decree that would punish juvenile delinquency to ensure the 'good apples' were the ones paving the road for his ideal society.

Organizations like the Komsomol were not the only influences on the children at the time. Cartoons like The Strangers Voice by Ivan Ivanov-Vano, reinforced the idea of a Soviet culture by depicting foreign thinking and customs as unwanted and strange. Children would play their own version of 'Cowboys and Indians' as 'Reds and Whites' with children fighting to play the main party leaders like Stalin.

Illusion of unanimous support

The cult of personality primarily existed among the Soviet masses; there was no explicit manifestation of the cult among the members of the Politburo and other high-ranking Party officials. However, the fear of being marginalized made oppositionists sometimes hesitant to honestly express their viewpoints. This atmosphere of self-censorship created the illusion of undisputed government support for Stalin, and this perceived support further fueled the cult for the Soviet populace. The politburo and comintern secretariat (E.C.C.I.) also gave the impression of being unanimous in its decisions although this was often not the case. Many top ranking leaders in the politburo such as Zhdanov and Kaganovich sometimes disagreed with Stalin. Not all of Stalin's proposals were passed, but this was not made known to people outside the party leadership. The party leadership discussed and debated various alternatives but always presented themselves as monolithic to the outside world to appear stronger, more credible and unified. Among the leadership this was also considered correct Leninist practice, since the Leninist organizational principle of democratic centralism provided "freedom of debate" but required "unity of action" after a decision had been reached. The minority felt it their duty to submit to the will of the majority and Stalin himself practiced this when losing a vote.

Stalin's opinion of his cult

Stalin disapproved and distrusted the personality cult around him. Like Lenin, Stalin acted modestly and unassumingly in public. John Gunther in 1940 described the politeness and good manners to visitors of "the most powerful single human being in the world". In the 1930s Stalin made several speeches that diminished the importance of individual leaders and disparaged the cult forming around him, painting such a cult as un-Bolshevik; instead, he emphasized the importance of broader social forces, such as the working class. Stalin's public actions seemed to support his professed disdain of the cult: Stalin often edited reports of Kremlin receptions, cutting applause and praise aimed at him and adding applause for other Soviet leaders. Walter Duranty stated that Stalin edited a phrase in a draft of an interview by him of the dictator from "inheritor of the mantle of Lenin" to "faithful servant of Lenin".

A banner in 1934 was to feature Marx, Engels, Lenin and Stalin, but Stalin had his name removed from it, yet by 1938 he was more than comfortable with the banner featuring his name. Still, in 1936, Stalin banned renaming places after him. In some memoirs Molotov claimed that Stalin had resisted the cult of personality, but soon came to be comfortable with it.

The Finnish communist Arvo Tuominen reported a sarcastic toast proposed by Stalin himself at a New Year's Party in 1935, in which he said: "Comrades! I want to propose a toast to our patriarch, life and sun, liberator of nations, architect of socialism [he rattled off all the appellations applied to him in those days] – Josef Vissarionovich Stalin, and I hope this is the first and last speech made to that genius this evening." In the beginning of 1938, Nikolai Yezhov proposed renaming Moscow to "Stalinodar". The question was raised at a session of the Presidium of the Supreme Soviet. Stalin, however, reacted entirely negatively to this idea and, for this reason, the city retained the name Moscow.

Veneration of Stalin by the Soviet people for his role as the leader of the Soviet Union's victory over Nazi Germany in World War II helped to stabilize their belief in the Soviet system, a factor of which Stalin was aware. Historian Archie Brown wrote: "Stalin himself believed that his 'image' ... as a charismatic, almost superhuman, leader helped to solidify support for Communism and to bestow on it legitimacy." It was a constant in Stalin's beliefs that the Russian people, especially the peasants, were used to being ruled by a single person, the tsar, and did not understand the complexities of the structure of power and governance in the Soviet Union. Because of this, there had to be one person who was perceived as the ruler, someone they could, in his words "revere and in whose name to live and labour." In 1940, Gunther noted that "[Stalin] knows the Russians understand a master". The dictator could easily have stopped the adoration but "permitted and encouraged his own virtual deification", he said. "Or perhaps he likes" the worship, Gunther speculated.

However, Stalin discouraged all interest in his private and family life, and divulged only limited personal information. He rarely appeared in public or met with ambassadors, as of 1940 had met only seven foreign journalists for formal interviews in 20 years, and during the first five-year plan made no speeches or public appearances for 18 months.

Nikita Khrushchev in his "Secret Speech" to the 20th Party Congress in February 1956, claimed that Stalin had personally added by hand to the manuscript of the hagiographical Short Biography of Stalin, published in 1948, passages such as: "Although he performed his task as the leader of the party and the people with consummate skill and enjoyed the unreserved support of the entire Soviet people, Stalin never allowed his work to be marred by the slightest hint of vanity, conceit or self-adulation." In addition Khrushchev claimed that Stalin expanded the list of his accomplishments enumerated in the book. Despite this, scholars have cited evidence that cast doubt to Khrushchev's claims. Few scholars today would cite Khrushchev’s speech as a reliable source and it now seems clear that Stalin distrusted the cult of personality around him.

Stories of the childhood of Stalin

On February 16, 1938, after the release of a book called Stories of the Childhood of Stalin, the publishing committee was urged to retract the book, as Stalin claimed that the book was an example of excessive hero worship that elevated his image to idealistic proportions. Stalin spoke disdainfully of this excess, expressing concern that idolatry is no substitute for rigorous Bolshevik study, and could be spun as a fault of Bolshevism by right-deviations in the USSR. Specifically he wrote:

I am absolutely against the publication of "Stories of the childhood of Stalin". The book abounds with a mass of inexactitudes of fact, of alterations, of exaggerations and of unmerited praise. Some amateur writers, scribblers, (perhaps honest scribblers) and some adulators have led the author astray. It is a shame for the author, but a fact remains a fact. But this is not the important thing. The important thing resides in the fact that the book has a tendency to engrave on the minds of Soviet children (and people in general) the personality cult of leaders, of infallible heroes. This is dangerous and detrimental. The theory of "heroes" and the "crowd" is not a Bolshevik, but a SR theory. The heroes make the people, transform them from a crowd into people, thus say the SRs. The people make the heroes, thus reply the Bolsheviks to the SRs. The book carries water to the windmill of the SRs. No matter which book it is that brings the water to the windmill of the SRs, this book is going to drown in our common, Bolshevik cause. I suggest we burn this book.

A more accurate depiction of his childhood and achievements are found in many other areas of writing and genre.

End of the cult and de-Stalinization

O kulcie jednostki i jego następstwach, Warsaw, March 1956, first edition of the Secret Speech, published for the inner use in the PUWP

De-Stalinization was the process of political reform that took place after Stalin's death, where a majority of Joseph Stalin's actions during his reign were condemned and the government reformed. February 1956 was the beginning of the destruction of his image, leadership, and socialist legality under the thaw of Nikita Khrushchev at the 20th Party Congress. The end of Stalin's leadership was met with positive and negative changes. Changes and consequences revolved around politics, the arts and literature, the economic realm, to the social structure.

His death and the destabilization of his iconic leadership was met with the chance of new reforms and changes to his regime that had originally been immediately locked down under his control. The tight lock he kept on what was published, what was propagated, and what changes to the government and economics, became accessible. With the control that Stalin held being passed on to the government, an endorsed methodology was ideally enacted. There after, a collective leadership system was the result. The result left Nikita Khrushchev, Lavrentiy Beria, Nikolai Bulganin, Georgy Malenkov, Vyacheslav Molotov, and Lazar Kaganovich as members of that committee. The program of de-Stalinization was soon after put into effect by Krushchev as he took on an opposite personality into the government. This allowed for better relations with the West in the future.

First wave of de-Stalinization

After Stalin's death, Nikita Khrushchev's 1956 "Secret Speech" to the Twentieth Party Congress famously denounced Stalin's cult of personality, saying, "It is impermissible and foreign to the spirit of Marxism-Leninism to elevate one person, to transform him into a superman possessing supernatural characteristics akin to those of a god." The "Secret Speech" initiated a political reform known as "the overcoming/exposure of the cult of personality", later called de-Stalinization, that sought to eradicate Stalin's influence on the Soviet society. This also led the people to find the liberation to revolt publicly in Poland and Hungary. These changes were inevitably met with opposition. Even after losing favor with Stalin during his leadership, Molotov still argued in favor of Stalin's regime, opposing de-Stalinization and criticizing Stalin's successors. Mao Zedong along with some other communist leaders, while initially supporting the struggle against the "cult of the individual", criticized Khrushchev as an opportunist who merely sought to attack Stalin's leadership and policies in order to implement new different policies that in the Stalin-era would have been considered anti-Marxist Revisionism.

Under Khrushchev's successor, Leonid Brezhnev, pro-Stalinist forces attempted to re-establish Stalin's reputation as the "Great Leader". Having failed to do so at the 23rd Party Congress in the spring of 1966, they turned to another method, the text of a speech that Brezhnev was scheduled to give in November of that year in Georgia, Stalin's native country. A draft of the speech made by hard-core Stalinists was presented to Brezhnev, who, being a cautious man, distributed it to other officials for their comments. One of his advisors, Georgi Arbatov, with the support of his superior, Yuri Andropov, put the arguments against the draft to Brezhnev: rehabilitating Stalin would complicate the Soviet Union's relations with the Eastern European Communist states, especially those headed by men who had been victims of Stalin's actions; changing the status of Stalin once again, so soon after it had been downgraded, would make things difficult for the Western Communist parties; it would be difficult to reconcile the harsh words spoken against Stalin by prominent Communist leaders at the 20th and 22nd Party Congresses; and finally, it was pointed out that Brezhnev himself had participated in those Congresses, which would raise questions about his own role. As a result of these arguments, the speech was re-written without any mention of rehabilitating Stalin. Even though the anti-Stalinists prevailed in this instance, the use of the phrase "the period of the cult of personality" – referring to 1934-1953 – disappeared, indicating a softening of the official anti-Stalin line. Thus, it became easier for pro-Stalin viewpoints to be published, and harder to get anti-Stalin's works before the public.

Second wave

This changed when Mikhail Gorbachev became General Secretary of the Communist Party of the Soviet Union, the country's top leadership position. In a speech given in November 1987, on the eve of the celebration of the 70th anniversary of the Bolshevik revolution, Gorbachev said

It is sometimes asserted that Stalin did not know the facts about the lawlessness. Documents we have at our disposal speak to the fact that this is not so. The guilt of Stalin and of his closest associates before the party and people for indulging in mass repression and lawlessness is enormous and unforgivable. This is a lesson for all generations.

After this, during the period of glasnost ("openness") and perestroika ("restructuring") initiated by Gorbachev, another wave of de-Stalinization took place. This "second wave" evolved into something more fundamentally anti-communist. It condemned not only Stalin but also the other responsible people in the Soviet power hierarchy. In the end, it adopted something closer to a Western democratic structure in place of the traditional closed communist authoritarian system. This campaign aimed to restructure the Soviet Union entirely, engaging public constituencies to diminish communism and bringing an end to the U.S.S.R.

After the breakup of the Soviet Union, the Russian Federation under Vladimir Putin saw a return of both centralized and authoritarian control of the state and the cult of Stalin, focusing primarily on his role in the defeat of Nazi Germany and the winning of World War II. During this period, in the early 2000s, Russia had lost its role as a global superpower, and restoring the positive legacy of Stalin helped to ameliorate the felt loss of status, bringing back a symbol of the country – albeit the Soviet Union predecessor state – at the height of its power.

Third wave

Nevertheless, a "third wave" of more ambivalent de-Stalinization was still able to get off the ground around 2009. This fostered a reassessment of Stalinism as well as commemorating the victims of his totalitarian regime. For instance, Dmitry Medvedev, the president of Russia, said about the Katyn massacre of Polish officers in World War II by the Soviet Army that "Stalin and his henchmen bear responsibility for this crime," echoing a previous statement by the Russian Parliament: "The Katyn crime was committed on direct order by Stalin and other Soviet leaders." Partly driven by the Russian re-engagement with the West, the new de-Stalinization, unlike that under Gorbachev, has not been accompanied by liberalization and reform of the political system, which remains centralized, authoritarian, and dependent on the repression of the people by the security police, much as in Stalin's time. Such a paradoxical situation, where Stalin's reputation is downgraded, but the state is essentially following in the path blazed by him, leads to the ambivalence of the official position. On the one hand, Moscow city officials were prevented from putting up decorations featuring Stalin for the celebration of the 65th anniversary of the Soviet victory over Nazi Germany, with Medvedev saying that Stalin had "committed many crimes against his people. And even though the country achieved success under his guidance, what was done against his own people cannot be forgiven." On the other hand, there is no shortage of publications and television programs glorifying Stalin. Anti-Stalin sentiment is not being suppressed, but neither are pro-Stalin views. And despite the official statements of Stalin's culpability, those in power are still anxious to use the symbolic value of the dictator in support of their own monopolistic hold on the country.

In classrooms across Russia, students are taught out of a modern textbook which represents Stalin as simply an efficient leader who had the unfortunate responsibility to resort to extreme measures to protect Russia and ensure its leadership role on a global scale. A poll in 2019 found that 70% of Russians believed that Stalin had a positive impact on Russian history despite the fact that only 51% of people in Russia still viewed Stalin with a positive attitude.

Social cleansing

From Wikipedia, the free encyclopedia

Social cleansing (Spanish: limpieza social) is social group-based killing that consists of the elimination of members of society who are considered "undesirable", including, but not limited to, the homeless, criminals, street children, the elderly, the disabled. This phenomenon is caused by a combination of economic and social factors, but killings are notably present in regions with high levels of poverty and disparities of wealth. Perpetrators are usually of the same community as the victims and they are often motivated by the idea that the victims are a drain on the resources of society. Efforts by national and local governments to stop these killings have been largely ineffective. The government and police forces are often involved in the killings, especially in South America.

Causes

Africa

In African countries, social cleansing almost always takes the form of witch hunting which is most common in areas with poor economic circumstances. Several social and economic theories exist as to why such circumstances have arisen and led to accusations of witchcraft, including warfare, natural disasters, unequal patterns of development, and larger forces of globalization. Most scholars agree that the cause of social cleansing efforts is a result of "interaction of economic conditions and cultural factors". All of these theories must be linked to larger societal trends, including the devaluation and social marginalization of women as well as the placement of blame on individuals for their own economic misfortunes in lieu of recognition of global and local economic forces at play. However, several scholars have emphasized the outside groups and circumstances related to these killings to dispute the idea that they are simply a cultural norm.

Economic

In many countries, income disparities have led to social tensions and a climate of "mutual suspicion". The wealthy and powerful are perceived as having obtained their wealth through "evil arts", while the economically disadvantaged are accused of responsibility for misfortunes of the community. There is also evidence that the causes of social cleansing are linked to globalization and economic liberalization, "to the extent that it has stripped entire populations of their means of subsistence, torn communities apart, deepened economic inequalities and forced people to compete for diminishing resources." Many African communities have been destabilized as communal lands have been privatized, local currency has been devalued, and public services have been eliminated. Sometimes these larger economic trends have been linked to more specific events. For example, in Southern Zimbabwe, violent wars led certain areas to be neglected in development efforts, leading to a lack of resources and increasing disparities of wealth in these areas. In Tanzania, scholars have found positive correlations between extreme rainfall (both floods and droughts) and large negative income shocks and famine. These periods have been statistically linked to increases in murder of witches.

Cultural

Several cultural explanations for social cleansing in Africa are related to religion. One that has been offered by scholars is the presence of Pentecostalists, whose focus on the occult has been spread by the media and increased social anxiety. Pentecostalists have been recorded as preaching connections between illness and the devil, which has combined potently with existing indigenous beliefs, most notably in Kenya, Ghana, Nigeria, and Tanzania. In Tanzania, a positive correlation exists between witch killing and areas where populations practice traditional religions, where the belief in witchcraft is strong. While scholars have suggested that the presence of these beliefs is important because it demonstrates the fact that perpetrators generally do believe that their victims are practicing witchcraft, they also recognize the fact that populations with traditional religious beliefs often have a low socio-economic status, which supports their assertion that poverty is still the primary factor in motivating killings.

Latin America

The most widespread myth about social cleansing in Latin America is that these killings are all related to drug use. However, the phenomenon is larger than the drug problem and is related to state ideology, a culture of violence, and inequitable wealth distribution. Within Colombia specifically, economic factors account for many of the reasons behind these killings, but such factors are additionally "aggravated by external political and economic pressures from the United States".

Economic

Latin America has an extremely large number of individuals living below the poverty line, and these individuals are largely blamed for their impoverished state. Many of these individuals are in critical poverty, meaning that they do not even have the ability to secure food and shelter. This critical poverty is connected to inflation rates that has led the cost of living to increase and the minimum salary to be hardly adequate for survival. Since the 1990s, the gap between the rich and poor has widened, and funds for welfare programs and social services has decreased while funding for security forces to protect "the haves from the have-nots" have tripled in Colombia specifically.

Culture of violence

Latin America's history has long been plagued by political violence, which over time has morphed into class-based violence. Despite mostly formally democratic governments, the "legacy of authoritarianism" lingers, and the presence of "armed actors" is prevalent as a result of a long history of violence between military, paramilitary, and guerilla groups. The presence of this culture of violence has had various effects on the underclass in countries in Latin America. The military and especially the police have been known to use violence to harm citizens rather than protect them. Private "vigilante" security forces have likewise used violence against the poor with the idea of promoting law and order, especially in Colombia, Guatemala, and Peru. Though many guerilla groups are much less violent than when they originally emerged, they are a presence and an additional source of violence, especially in Colombia. Tension between political groups has led these guerilla groups, the government, and vigilante actors to suspect peasants of working with their enemy and to intimidate them into leaving land in the countryside for the city. Other poor rural residents have been forced to leave due to general violence or lack of public services. Violence at the local level is also extremely common by organized criminals such as street gangs, drug bosses, vigilante justice groups, and local civil patrols. When poor residents are forced to move to the city, they often must turn to prostitution, crime, or begging in inner-city ghettos, which puts them in an extremely vulnerable position in the presence of these violent groups. Men in particular become even more entrenched in the culture of violence as many join gangs to escape "social exclusion and economic disadvantage" and establish a sense of identity and masculinity. Finally, violence exists at a level even smaller than the community—the home. Children are often victims of "physical, mental, and sexual abuse by adults member of their own families". In Guatemala specifically, social cleansing occurs with the "backdrop of genocide", and homicide rates are still extremely high after "three decades of armed conflict" during the Guatemalan Civil War. Violence experienced across the region has led to an erosion of social capital, which was described by Colombians as including "'social mistrust,' 'lack of unity,' 'fear' and 'lack of social institutions.'"

In Spain

Spain, during times before colonization, demonstrates societal patterns that shaped life in Spain in terms of prejudice and discrimination. The discriminatory practice of Spanish legislation led to a certain caste system, pertaining to those with or without honor. Moreover, one's reputation and the way one was treated was based on aspects such as honor, legitimacy, and the limpieza de sangre, a prejudicial marker that indicates one's purity of blood, relating to their family timeline and deciding how society was to treat them. "Historic meanings of honor included those cultural specific ways that Spaniards had always rationalized discrimination due to defects in birth (illegitimate, nonnoble), religion (non-Catholic), and race (nonwhite)." This discriminatory institution based on these concepts of honor, limpieza, and legitimacy, is expressed through the legislation of Spanish government at the time. An example of this was in 1414 when Pope Benedict XIII approved the constitution of Spanish College's San Bartolomé, which linked these concepts through the school's acceptances. Those accepted into the school had to prove they had pure blood, rather than Jewish, Moorish, or heretical heritage.

In Colonial Latin America

The concept of limpieza de sangre, or purity of blood, was used in societies of Spain and Portugal, originating from Iberian culture, where reputation was inherited from one's ancestors. If someone was found to be a race such as Jewish, a converted Jew, or Muslim in their family timeline, it was said to be a stain on their ancestry. Consequently, one's own ancestry determined their reputation and social standing, impacting other aspects such as access to education, career, and marriage for further generations. This became known as the culture of honor, which resided in such reputational ancestry that came to define how individuals were respected.

Limpieza de sangre affected life for every individual in the Spanish and Portuguese colonies, including the degree to exclusion and racial discrimination. When Europe came to colonize the "New World" these ethics of honor and limpieza de sangre implied that those with blood lacking purity to European standards was inferior. The Europeans were at the "apex" of social structure and everyone who was not identical in blood was inferior. As colonists, the presumed inferiors were the colonized and thus, due to this culture of honor, they became victims of this discrimination. While over time assimilation, miscegenation and admixture complicated this concept of social cleansing, the ideals of "purity of blood" prevailed, and elite was considered to be of European and Christian origins.

The conquest of indigenous people in Latin America strengthened these ideals. The vulnerability of one's identity in colonial America gave way to one's defense of honor, except for the elites and those in power, typically the colonists. As the degree of honor perceived by individuals was reputational, people felt the need to be confirmed by society or by those in good social standing through submission to the given standards that one's place held. The pursuit of this honor led to many disputes, as well as the fear of being rejected by society and losing one's place.

Despite these long-lived standards, during post-colonialism the ideals of Latin America changed with independence and the growth of democratic values. With this, the culture of honor and respect for those with pure bloodlines changed. People began to socially include those who were previously seen as inferior.

In Brazil

Victims and methods

The most common murder victim in Brazil is a young, black male living in a favela, or a Brazilian slum. These young men typically are, or are assumed to be, gang members and criminals. Violence and murder are most common in areas that are economically disadvantaged and socially marginalized. Women are often targets by association, though the effects of social cleansing and violence against women are largely absent in existing research. Killings are often in public places, with victims being beaten or shot in the street. Police groups sometimes simply enter the community in a large armoured vehicle called a "caveirão" and start shooting. This vehicle contributes to the "anonymity and impunity for the perpetrators".

Perpetrators and motivations

Social cleansing in Brazil is the result of a "murky symbiosis [that] has developed between the official security forces and paramilitary and vigilante-type actors" that carry out "law enforcement against the 'marginal classes.'" State actors often act against the poor "as a form or result of exclusion and oppression". Gangs serve as a scapegoat for the levels of violence and lack of security in many communities. Private groups and some gangs perpetrate killings in attempts to take policing into their own hands. While some killings are a result of groups attempting to punish criminals for misdemeanors, others are a result of perceived threats of poor citizens, such as members of workers' movements.

In Colombia

In the 1980s, "social cleansing" groups started to be created. Their main mission was "to make justice" by killing all non-appropriate people in social terms, like prostitutes, street-living people, trans people, and drug addicts.

Victims and methods

Victims of social cleansing in Colombia are members of society who are considered "undesirable" and "disposable". They are economically disadvantaged, usually live on the streets, and are considered to be a burden on society, "the cause of the country's problems, rather than a consequence of them".

Street children

One of these groups is street children, who are without homes due to abuse, forced displacement, or the death of their parents. Death rates for street children have been as high as six to eight children per day. Children are often shot in their sleep or stabbed to death on the streets or in the police station. A 1993 case in which a nine-year-old girl was strangled to death in Bogota brought attention to this problem and led to nominal reforms. The National Police targets street children specifically under the assumption that they are drug users and criminals. This is to some extent true, as many use drugs to relieve pain and avoid hunger and must shoplift to survive. Despite living in conditions of extreme vulnerability to "aggression and danger", the National Police poses the greatest threat to street children's survival, as they drive them off the streets and target them in social cleansing.

Poor criminals, drug users, and drug dealers

Poor criminals, drug users, and drug dealers are also common targets. From 1988 to 1993, these individuals collectively comprised 56% of social cleansing victims. These individuals are often victims of physical and sexual abuse by the police and vigilante groups known as "comas". One common method of killing these individuals in the city of Bogota is the Choachí run, in which victims are taken to the top of a mountain in the town of Choachí, executed, and thrown off the mountain. In some cases, they are released to attempt escape, but die by falling down the mountain or being shot at as they run. A similar method is known as "the ride", in which victims are forced into a vehicle, killed, and left in a desolate area. Death squads have employed other means for killing suspected criminals, such as murdering them, then cutting off their hands and putting them in small boxes in public spaces to intimidate other criminals. Another group has been known to shoot victims and then cast their bodies into the municipal stadium.

Sex workers and sexual minorities

Sex workers and sexual minorities are treated quite similarly in regards to social cleansing, as both are hard to identify and victims of heavy discrimination despite the fact that both homosexuality and prostitution are legal. Many female sex workers are forced into the line of work due to poverty and domestic violence. Both male and female sex workers are often harassed by the police, and males specifically are demanded to pay a "tax" where "failure to pay results in beatings or imprisonment". In an upside-down system, encounters with dishonest police are preferable to honest police, as the dishonest will accept bribes, while the honest are more likely to kill. Sexual minorities are particularly difficult to identify, because not only do some male sex workers participate in gay sex out of economic necessity, but victims are only considered homosexual if they were dressed as females at the time of death.

Beggars and recyclers

Another group includes those individuals in the most extreme form of poverty. These individuals subsist by asking for money and/or collecting garbage. The police have been known to kill these victims in especially cruel ways, such as pouring gasoline on them and setting them on fire. It is also notable that at least 14 destitute individuals have been killed by security guards at one Colombian university for the use of their bodies as cadavers in the medical school.

Perpetrators and motivations

National Police

The National Police has played a large role in carrying out class-based killings in Colombia. The police created the term "disposable" (Spanish: desechable) to define economically disadvantaged people who are considered to have no value to society. Whether directly or through "paramilitary clients", the National Police was responsible for 74% of deaths related to social cleansing in 1992. Motivations include "security, aesthetics, economic well-being, morals, and religion". In regards to safety and economic well-being, rationales include the idea that the poor are or look like criminals and decrease public safety and drive customers away from businesses. Moral arguments include protection from homosexuals and prostitutes.

Death squads and paramilitary groups

The distinction between death squads and paramilitary groups and the National Police is not always clear. Not only are policemen often members of these groups, but these groups typically enjoy the protection of the police. Other members include businessmen, industrialists, guerillas, and soldiers. Death squads emerged in the late 1970s, one of the first being the Black Hand, a group that murdered suspected criminals. Their reasoning behind these killings is the flawed legal system, which convicts less than 3% of criminals. Death squads and other groups believe it necessary to step in where the legal system has failed by eliminating these suspected criminals. As of 1995, there were no less than 40 of these squads operating in Colombia.

Other factors

National government

The role of the national government in Colombia has largely been complicit cooperation with the National Police. By failing to deal with crime and then also effectively granting impunity to police and military groups, the state has allowed safety issues to be addressed with violence and has perpetuated a "cycle of crime, lack of public safety, violent response, and impunity" due to "terrifying inefficiency and unwillingness to hold people accountable for their acts". While the government at least tries to protect street children through programs to put them in state-run homes, these programs often do not align with their actual needs and have largely failed. There have been limited attempts to protect those in poverty in the legal system, and one case of harassment against the poor resulted in a judge calling for their equal treatment and compensation from the offending policemen. However, the decision was not enforced.

In Guatemala

Victims and methods

Social cleansing and gang killings make up a large portion of the homicides in Guatemala. Since gangs typically make no effort to cover up crimes and leave bodies at the place of death, "signs of torture", as well as location of the body, "serve as indicators of the existence of social cleansing", according to Elizabeth Sanford. According to a study by the Human Rights Ombudsman, "the increase in the number of women killed whose bodies bore marks of torture and other sadistic abuse accounted for 40 percent of the total increase in female murders in 2005." Though female victims account for 10% of all homicides, over 18% of cadavers with signs of torture indicating social cleansing were female. Furthermore, 2% of female victims of homicide are prostitutes, a common victim group of social cleansing efforts. Furthermore, young and destitute male gang members, especially those blamed for homicide of females, have been common victims of social cleansing. The most common form of killing, indicated by the 305 cadavers found in 2005, is strangulation. Other common methods included victims being beaten, shot in the head, bound by their hands and feet, and in the case of female victims, sexual abuse. Victims are abducted, taken to a different location, are tortured and killed, and finally have their body dumped in a different location.

Perpetrators and motivations

Perpetrators include the Guatemalan government as well as private groups either directly or indirectly complicit with the state. Social cleansing efforts are targeted against gangs and other perceived and actual criminals, who are blamed for the high rates of homicide. The perpetrators intend to both exterminate victims and intimidate other members of the target group. Intimidation is carried out both through torture tactics used as well as propaganda including flyers and stickers that support social cleansing as a "method of social control". Because perpetrators are directly or indirectly tied to the state, they naturally have impunity.

Origins

The use of "social cleansing" efforts to eliminate criminals and other persons deemed to be socially dangerous has its origins during the period of military dictatorship and civil war (1954–1996). During the 1960s and 70s, many state-operated paramilitary front organizations (so-called "death squads") emerged with the express purpose of exterminating suspected communists and other enemies of the state. These groups included the MANO, NOA, CADEG, 'Ojo por Ojo' and others. While nominally employed against political targets, the use of "death squads" came to be seen by the Guatemalan police forces (specifically the National Police) as a crime fighting tool, particularly after the election of Col. Arana Osorio in 1970 and the subsequent "state of siege". One early example of the use of "death squads" against non-political targets was a phantom organization called the 'Avenging Vulture', which specifically targeted criminals.

In Tanzania

Victims and methods

The most common victims of social cleansing efforts in Tanzania are elderly women, the majority of whom are of low socioeconomic status, but several groups of people who are considered burdens to the community, such as children, the sick, infants, and the handicapped, are also victims. These people are usually accused of witchcraft following deaths or other misfortunes in society and tend to flee, choosing homelessness over death. Those who do not flee successfully are killed violently in their homes. Sometimes those considered burdens are simply reduced to zero consumption and are starved to death. This occurs particularly among infants, who have no ability to flee or attempt to provide for themselves.

Perpetrators and motivations

Victims are typically killed by members of their own families, who blame them for economic suffering and household misfortune. Accusations and subsequent killings are often incited by death or illness in the family or the family's livestock. However, general misfortune in the form of "failed crops, lost jobs, and bad dreams also arouse suspicion". While often accusations are raised to the effect of creating a scapegoat, not all forms of social cleansing are connected to witch hunting. The extreme scarcity theory suggests that some families to drive out or starve unproductive family members to provide more nutrients for other members. Many of these perpetrators are young, unemployed men who see the elderly as a burden on their potential for success. Another key perpetrator of social cleansing in Tanzania are the Sungusungu, councils of male elders that operate under the premise of promoting village security. These groups formed under the premise that the government was not able to prevent crimes such as theft, and they serve as a form of vigilante justice.

Other actors

Although the Tanzanian government has made public witchcraft accusations illegal, the efforts to stop them have been unsuccessful. Conviction levels are extremely low, as "only seven of 1,622 individuals arrested in connection with witch killings during the 1970s and 1980s were convicted, and since then the conviction rate as apparently fallen even lower," according to Edward Miguel. The perception of the government and police force as unable to control crime has led groups such as Sungusungu to take matters into their own hands, though studies suggest that the police may sometimes be involved in witch killings.

Igneous rock

From Wikipedia, the free encyclopedia
 
Geologic provinces of the world (USGS)

Igneous rock (derived from the Latin word ignis meaning fire), or magmatic rock, is one of the three main rock types, the others being sedimentary and metamorphic. Igneous rock is formed through the cooling and solidification of magma or lava.

The magma can be derived from partial melts of existing rocks in either a planet's mantle or crust. Typically, the melting is caused by one or more of three processes: an increase in temperature, a decrease in pressure, or a change in composition. Solidification into rock occurs either below the surface as intrusive rocks or on the surface as extrusive rocks. Igneous rock may form with crystallization to form granular, crystalline rocks, or without crystallization to form natural glasses.

Igneous rocks occur in a wide range of geological settings: shields, platforms, orogens, basins, large igneous provinces, extended crust and oceanic crust.

Volcanic eruptions of lava are major sources of igneous rocks. (Mayon volcano in the Philippines, erupting in 2009)
 
Natural columns of igneous rock separated from each other by columnar joints, in Madeira

Geological significance

Igneous and metamorphic rocks make up 90–95% of the top 16 kilometres (9.9 mi) of the Earth's crust by volume. Igneous rocks form about 15% of the Earth's current land surface. Most of the Earth's oceanic crust is made of igneous rock.

Igneous rocks are also geologically important because:

  • their minerals and global chemistry give information about the composition of the lower crust or upper mantle from which their parent magma was extracted, and the temperature and pressure conditions that allowed this extraction;
  • their absolute ages can be obtained from various forms of radiometric dating and can be compared to adjacent geological strata, thus permitting calibration of the geological time scale;
  • their features are usually characteristic of a specific tectonic environment, allowing tectonic reconstructions (see plate tectonics);
  • in some special circumstances they host important mineral deposits (ores): for example, tungsten, tin, and uranium are commonly associated with granites and diorites, whereas ores of chromium and platinum are commonly associated with gabbros.

Geological setting

Formation of igneous rock

Igneous rocks can be either intrusive (plutonic and hypabyssal) or extrusive (volcanic).

Intrusive

Basic types of intrusions:

Intrusive igneous rocks make up the majority of igneous rocks and are formed from magma that cools and solidifies within the crust of a planet. Bodies of intrusive rock are known as intrusions and are surrounded by pre-existing rock (called country rock). The country rock is an excellent thermal insulator, so the magma cools slowly, and intrusive rocks are coarse-grained (phaneritic). The mineral grains in such rocks can generally be identified with the naked eye. Intrusions can be classified according to the shape and size of the intrusive body and its relation to the bedding of the country rock into which it intrudes. Typical intrusive bodies are batholiths, stocks, laccoliths, sills and dikes. Common intrusive rocks are granite, gabbro, or diorite.

The central cores of major mountain ranges consist of intrusive igneous rocks. When exposed by erosion, these cores (called batholiths) may occupy huge areas of the Earth's surface.

Intrusive igneous rocks that form at depth within the crust are termed plutonic (or abyssal) rocks and are usually coarse-grained. Intrusive igneous rocks that form near the surface are termed subvolcanic or hypabyssal rocks and they are usually much finer-grained, often resembling volcanic rock. Hypabyssal rocks are less common than plutonic or volcanic rocks and often form dikes, sills, laccoliths, lopoliths, or phacoliths.

Extrusive

Extrusive igneous rock is made from lava released by volcanoes
 
Sample of basalt (an extrusive igneous rock), found in Massachusetts

Extrusive igneous rock, also known as volcanic rock, is formed by the cooling of molten magma on the earth's surface. The magma, which is brought to the surface through fissures or volcanic eruptions, rapidly solidifies. Hence such rocks are fine-grained (aphanitic) or even glassy. Basalt is the most common extrusive igneous rock and forms lava flows, lava sheets and lava plateaus. Some kinds of basalt solidify to form long polygonal columns. The Giant's Causeway in Antrim, Northern Ireland is an example.

The molten rock, which typically contains suspended crystals and dissolved gases, is called magma. It rises because it is less dense than the rock from which it was extracted. When magma reaches the surface, it is called lava. Eruptions of volcanoes into air are termed subaerial, whereas those occurring underneath the ocean are termed submarine. Black smokers and mid-ocean ridge basalt are examples of submarine volcanic activity.

The volume of extrusive rock erupted annually by volcanoes varies with plate tectonic setting. Extrusive rock is produced in the following proportions:

The behaviour of lava depends upon its viscosity, which is determined by temperature, composition, and crystal content. High-temperature magma, most of which is basaltic in composition, behaves in a manner similar to thick oil and, as it cools, treacle. Long, thin basalt flows with pahoehoe surfaces are common. Intermediate composition magma, such as andesite, tends to form cinder cones of intermingled ash, tuff and lava, and may have a viscosity similar to thick, cold molasses or even rubber when erupted. Felsic magma, such as rhyolite, is usually erupted at low temperature and is up to 10,000 times as viscous as basalt. Volcanoes with rhyolitic magma commonly erupt explosively, and rhyolitic lava flows are typically of limited extent and have steep margins because the magma is so viscous.

Felsic and intermediate magmas that erupt often do so violently, with explosions driven by the release of dissolved gases—typically water vapour, but also carbon dioxide. Explosively erupted pyroclastic material is called tephra and includes tuff, agglomerate and ignimbrite. Fine volcanic ash is also erupted and forms ash tuff deposits, which can often cover vast areas.

Because volcanic rocks are mostly fine-grained or glassy, it is much more difficult to distinguish between the different types of extrusive igneous rocks than between different types of intrusive igneous rocks. Generally, the mineral constituents of fine-grained extrusive igneous rocks can only be determined by examination of thin sections of the rock under a microscope, so only an approximate classification can usually be made in the field. Although classification by mineral makeup is preferred by the IUGS, this is often impractical, and chemical classification is done instead using the TAS classification.

Classification

Close-up of granite (an intrusive igneous rock) exposed in Chennai, India

Igneous rocks are classified according to mode of occurrence, texture, mineralogy, chemical composition, and the geometry of the igneous body.

The classification of the many types of igneous rocks can provide important information about the conditions under which they formed. Two important variables used for the classification of igneous rocks are particle size, which largely depends on the cooling history, and the mineral composition of the rock. Feldspars, quartz or feldspathoids, olivines, pyroxenes, amphiboles, and micas are all important minerals in the formation of almost all igneous rocks, and they are basic to the classification of these rocks. All other minerals present are regarded as nonessential in almost all igneous rocks and are called accessory minerals. Types of igneous rocks with other essential minerals are very rare, but include carbonatites, which contain essential carbonates.

In a simplified classification, igneous rock types are separated on the basis of the type of feldspar present, the presence or absence of quartz, and in rocks with no feldspar or quartz, the type of iron or magnesium minerals present. Rocks containing quartz (silica in composition) are silica-oversaturated. Rocks with feldspathoids are silica-undersaturated, because feldspathoids cannot coexist in a stable association with quartz.

Igneous rocks that have crystals large enough to be seen by the naked eye are called phaneritic; those with crystals too small to be seen are called aphanitic. Generally speaking, phaneritic implies an intrusive origin; aphanitic an extrusive one.

An igneous rock with larger, clearly discernible crystals embedded in a finer-grained matrix is termed porphyry. Porphyritic texture develops when some of the crystals grow to considerable size before the main mass of the magma crystallizes as finer-grained, uniform material.

Igneous rocks are classified on the basis of texture and composition. Texture refers to the size, shape, and arrangement of the mineral grains or crystals of which the rock is composed.

Texture

Gabbro specimen showing phaneritic texture, from Rock Creek Canyon, eastern Sierra Nevada, California
 

Texture is an important criterion for the naming of volcanic rocks. The texture of volcanic rocks, including the size, shape, orientation, and distribution of mineral grains and the intergrain relationships, will determine whether the rock is termed a tuff, a pyroclastic lava or a simple lava. However, the texture is only a subordinate part of classifying volcanic rocks, as most often there needs to be chemical information gleaned from rocks with extremely fine-grained groundmass or from airfall tuffs, which may be formed from volcanic ash.

Textural criteria are less critical in classifying intrusive rocks where the majority of minerals will be visible to the naked eye or at least using a hand lens, magnifying glass or microscope. Plutonic rocks also tend to be less texturally varied and less prone to showing distinctive structural fabrics. Textural terms can be used to differentiate different intrusive phases of large plutons, for instance porphyritic margins to large intrusive bodies, porphyry stocks and subvolcanic dikes. Mineralogical classification is most often used to classify plutonic rocks. Chemical classifications are preferred to classify volcanic rocks, with phenocryst species used as a prefix, e.g. "olivine-bearing picrite" or "orthoclase-phyric rhyolite".

Basic classification scheme for igneous rocks based on their mineral composition. If the approximate volume fractions of minerals in the rock are known, the rock name and silica content can be read off the diagram. This is not an exact method, because the classification of igneous rocks also depends on other components, yet in most cases it is a good first guess.

Mineralogical classification

The IUGS recommends classifying igneous rocks by their mineral composition whenever possible. This is straightforward for coarse-grained intrusive igneous rock, but may require examination of thin sections under a microscope for fine-grained volcanic rock, and may be impossible for glassy volcanic rock. The rock must then be classified chemically.

Mineralogical classification of an intrusive rock begins by determining if the rock is ultramafic, a carbonatite, or a lamprophyre. An ultramafic rock contains more than 90% of iron- and magnesium-rich minerals such as hornblende, pyroxene, or olivine, and such rocks have their own classification scheme. Likewise, rocks containing more than 50% carbonate minerals are classified as carbonatites, while lamprophyres are rare ultrapotassic rocks. Both are further classified based on detailed mineralogy.

In the great majority of cases, the rock has a more typical mineral composition, with significant quartz, feldspars, or feldspathoids. Classification is based on the percentages of quartz, alkali feldspar, plagioclase, and feldspathoid out of the total fraction of the rock composed of these minerals, ignoring all other minerals present. These percentages place the rock somewhere on the QAPF diagram, which often immediately determines the rock type. In a few cases, such as the diorite-gabbro-anorthite field, additional mineralogical criteria must be applied to determine the final classification.

Where the mineralogy of an volcanic rock can be determined, it is classified using the same procedure, but with a modified QAPF diagram whose fields correspond to volcanic rock types.

Chemical classification and petrology

Total alkali versus silica classification scheme (TAS) as proposed in Le Maitre's 2002 Igneous Rocks – A classification and glossary of terms Blue area is roughly where alkaline rocks plot; yellow area is where subalkaline rocks plot.

When it is impractical to classify a volcanic rock by mineralogy, the rock must be classified chemically.

There are relatively few minerals that are important in the formation of common igneous rocks, because the magma from which the minerals crystallize is rich in only certain elements: silicon, oxygen, aluminium, sodium, potassium, calcium, iron, and magnesium. These are the elements that combine to form the silicate minerals, which account for over ninety percent of all igneous rocks. The chemistry of igneous rocks is expressed differently for major and minor elements and for trace elements. Contents of major and minor elements are conventionally expressed as weight percent oxides (e.g., 51% SiO2, and 1.50% TiO2). Abundances of trace elements are conventionally expressed as parts per million by weight (e.g., 420 ppm Ni, and 5.1 ppm Sm). The term "trace element" is typically used for elements present in most rocks at abundances less than 100 ppm or so, but some trace elements may be present in some rocks at abundances exceeding 1,000 ppm. The diversity of rock compositions has been defined by a huge mass of analytical data—over 230,000 rock analyses can be accessed on the web through a site sponsored by the U. S. National Science Foundation (see the External Link to EarthChem).

The single most important component is silica, SiO2, whether occurring as quartz or combined with other oxides as feldspars or other minerals. Both intrusive and volcanic rocks are grouped chemically by total silica content into broad categories.

  • Felsic rocks have the highest content of silica, and are predominantly composed of the felsic minerals quartz and feldspar. These rocks (granite, rhyolite) are usually light coloured, and have a relatively low density.
  • Intermediate rocks have a moderate content of silica, and are predominantly composed of feldspars. These rocks (diorite, andesite) are typically darker in colour than felsic rocks and somewhat more dense.
  • Mafic rocks have a relatively low silica content and are composed mostly of pyroxenes, olivines and calcic plagioclase. These rocks (basalt, gabbro) are usually dark coloured, and have a higher density than felsic rocks.
  • Ultramafic rock is very low in silica, with more than 90% of mafic minerals (komatiite, dunite).

This classification is summarized in the following table:


Composition
Mode of occurrence Felsic
(>63% SiO2)
Intermediate
(52% to 63% SiO2)
Mafic
(45% to 52% SiO2)
Ultramafic
(<45% SiO2)
Intrusive Granite Diorite Gabbro Peridotite
Extrusive Rhyolite Andesite Basalt Komatiite

The percentage of alkali metal oxides (Na2O plus K2O) is second only to silica in its importance for chemically classifying volcanic rock. The silica and alkali metal oxide percentages are used to place volcanic rock on the TAS diagram, which is sufficient to immediately classify most volcanic rocks. Rocks in some fields, such as the trachyandesite field, are further classified by the ratio of potassium to sodium (so that potassic trachyandesites are latites and sodic trachyandesites are benmoreites). Some of the more mafic fields are further subdivided or defined by normative mineralogy, in which an idealized mineral composition is calculated for the rock based on its chemical composition. For example, basanite is distinguished from tephrite by having a high normative olivine content.

Other refinements to the basic TAS classification include:

  • Ultrapotassic – rocks containing molar K2O/Na2O >3.
  • Peralkaline – rocks containing molar (K2O + Na2O)/Al2O3 >1.
  • Peraluminous – rocks containing molar (K2O + Na2O + CaO)/Al2O3 <1.

In older terminology, silica oversaturated rocks were called silicic or acidic where the SiO2 was greater than 66% and the family term quartzolite was applied to the most silicic. A normative feldspathoid classifies a rock as silica-undersaturated; an example is nephelinite.

AFM ternary diagram showing the relative proportions of Na2O + K2O (A for Alkali earth metals), FeO + Fe2O3 (F), and MgO (M) with arrows showing the path of chemical variation in tholeiitic and calc-alkaline series magmas

Magmas are further divided into three series:

The alkaline series is distinguishable from the other two on the TAS diagram, being higher in total alkali oxides for a given silica content, but the tholeiitic and calc-alkaline series occupy approximately the same part of the TAS diagram. They are distinguished by comparing total alkali with iron and magnesium content.

These three magma series occur in a range of plate tectonic settings. Tholeiitic magma series rocks are found, for example, at mid-ocean ridges, back-arc basins, oceanic islands formed by hotspots, island arcs and continental large igneous provinces.

All three series are found in relatively close proximity to each other at subduction zones where their distribution is related to depth and the age of the subduction zone. The tholeiitic magma series is well represented above young subduction zones formed by magma from relatively shallow depth. The calc-alkaline and alkaline series are seen in mature subduction zones, and are related to magma of greater depths. Andesite and basaltic andesite are the most abundant volcanic rock in island arc which is indicative of the calc-alkaline magmas. Some island arcs have distributed volcanic series as can be seen in the Japanese island arc system where the volcanic rocks change from tholeiite—calc-alkaline—alkaline with increasing distance from the trench.

History of classification

Some igneous rock names date to before the modern era of geology. For example, basalt as a description of a particular composition of lava-derived rock dates to Georgius Agricola in 1546 in his work De Natura Fossilium. The word granite goes back at least to the 1640s and is derived either from French granit or Italian granito, meaning simply "granulate rock". The term rhyolite was introduced in 1860 by the German traveler and geologist Ferdinand von Richthofen The naming of new rock types accelerated in the 19th century and peaked in the early 20th century.

Much of the early classification of igneous rocks was based on the geological age and occurrence of the rocks. However, in 1902, the American petrologists Charles Whitman Cross, Joseph P. Iddings, Louis V. Pirsson, and Henry Stephens Washington proposed that all existing classifications of igneous rocks should be discarded and replaced by a "quantitative" classification based on chemical analysis. They showed how vague, and often unscientific, much of the existing terminology was and argued that as the chemical composition of an igneous rock was its most fundamental characteristic, it should be elevated to prime position.

Geological occurrence, structure, mineralogical constitution—the hitherto accepted criteria for the discrimination of rock species—were relegated to the background. The completed rock analysis is first to be interpreted in terms of the rock-forming minerals which might be expected to be formed when the magma crystallizes, e.g., quartz feldspars, olivine, akermannite, Feldspathoids, magnetite, corundum, and so on, and the rocks are divided into groups strictly according to the relative proportion of these minerals to one another. This new classification scheme created a sensation, but was criticized for its lack of utility in fieldwork, and the classification scheme was abandoned by the 1960s. However, the concept of normative mineralogy has endured, and the work of Cross and his coinvestigators inspired a flurry of new classification schemes.

Among these was the classification scheme of M.A. Peacock, which divided igneous rocks into four series: the alkalic, the alkali-calcic, the calc-alkali, and the calcic series. His definition of the alkali series, and the term calc-alkali, continue in use as part of the widely used Irvine-Barager classification, along with W.Q. Kennedy's tholeiitic series.

By 1958, there were some 12 separate classification schemes and at least 1637 rock type names in use. In that year, Albert Streckeisen wrote a review article on igneous rock classification that ultimately led to the formation of the IUGG Subcommission of the Systematics of Igneous Rocks. By 1989 a single system of classification had been agreed upon, which was further revised in 2005. The number of recommended rock names was reduced to 316. These included a number of new names promulgated by the Subcommission.

Origin of magmas

The Earth's crust averages about 35 kilometres (22 mi) thick under the continents, but averages only some 7–10 kilometres (4.3–6.2 mi) beneath the oceans. The continental crust is composed primarily of sedimentary rocks resting on a crystalline basement formed of a great variety of metamorphic and igneous rocks, including granulite and granite. Oceanic crust is composed primarily of basalt and gabbro. Both continental and oceanic crust rest on peridotite of the mantle.

Rocks may melt in response to a decrease in pressure, to a change in composition (such as an addition of water), to an increase in temperature, or to a combination of these processes.

Other mechanisms, such as melting from a meteorite impact, are less important today, but impacts during the accretion of the Earth led to extensive melting, and the outer several hundred kilometers of our early Earth was probably an ocean of magma. Impacts of large meteorites in the last few hundred million years have been proposed as one mechanism responsible for the extensive basalt magmatism of several large igneous provinces.

Decompression

Decompression melting occurs because of a decrease in pressure.

The solidus temperatures of most rocks (the temperatures below which they are completely solid) increase with increasing pressure in the absence of water. Peridotite at depth in the Earth's mantle may be hotter than its solidus temperature at some shallower level. If such rock rises during the convection of solid mantle, it will cool slightly as it expands in an adiabatic process, but the cooling is only about 0.3 °C per kilometer. Experimental studies of appropriate peridotite samples document that the solidus temperatures increase by 3 °C to 4 °C per kilometer. If the rock rises far enough, it will begin to melt. Melt droplets can coalesce into larger volumes and be intruded upwards. This process of melting from the upward movement of solid mantle is critical in the evolution of the Earth.

Decompression melting creates the ocean crust at mid-ocean ridges. It also causes volcanism in intraplate regions, such as Europe, Africa and the Pacific sea floor. There, it is variously attributed either to the rise of mantle plumes (the "Plume hypothesis") or to intraplate extension (the "Plate hypothesis").

Effects of water and carbon dioxide

The change of rock composition most responsible for the creation of magma is the addition of water. Water lowers the solidus temperature of rocks at a given pressure. For example, at a depth of about 100 kilometers, peridotite begins to melt near 800 °C in the presence of excess water, but near or above about 1,500 °C in the absence of water. Water is driven out of the oceanic lithosphere in subduction zones, and it causes melting in the overlying mantle. Hydrous magmas composed of basalt and andesite are produced directly and indirectly as results of dehydration during the subduction process. Such magmas, and those derived from them, build up island arcs such as those in the Pacific Ring of Fire. These magmas form rocks of the calc-alkaline series, an important part of the continental crust.

The addition of carbon dioxide is relatively a much less important cause of magma formation than the addition of water, but genesis of some silica-undersaturated magmas has been attributed to the dominance of carbon dioxide over water in their mantle source regions. In the presence of carbon dioxide, experiments document that the peridotite solidus temperature decreases by about 200 °C in a narrow pressure interval at pressures corresponding to a depth of about 70 km. At greater depths, carbon dioxide can have more effect: at depths to about 200 km, the temperatures of initial melting of a carbonated peridotite composition were determined to be 450 °C to 600 °C lower than for the same composition with no carbon dioxide. Magmas of rock types such as nephelinite, carbonatite, and kimberlite are among those that may be generated following an influx of carbon dioxide into mantle at depths greater than about 70 km.

Temperature increase

Increase in temperature is the most typical mechanism for formation of magma within continental crust. Such temperature increases can occur because of the upward intrusion of magma from the mantle. Temperatures can also exceed the solidus of a crustal rock in continental crust thickened by compression at a plate boundary. The plate boundary between the Indian and Asian continental masses provides a well-studied example, as the Tibetan Plateau just north of the boundary has crust about 80 kilometers thick, roughly twice the thickness of normal continental crust. Studies of electrical resistivity deduced from magnetotelluric data have detected a layer that appears to contain silicate melt and that stretches for at least 1,000 kilometers within the middle crust along the southern margin of the Tibetan Plateau. Granite and rhyolite are types of igneous rock commonly interpreted as products of the melting of continental crust because of increases in temperature. Temperature increases also may contribute to the melting of lithosphere dragged down in a subduction zone.

Magma evolution

Schematic diagrams showing the principles behind fractional crystallisation in a magma. While cooling, the magma evolves in composition because different minerals crystallize from the melt. 1: olivine crystallizes; 2: olivine and pyroxene crystallize; 3: pyroxene and plagioclase crystallize; 4: plagioclase crystallizes. At the bottom of the magma reservoir, a cumulate rock forms.
 

Most magmas are fully melted only for small parts of their histories. More typically, they are mixes of melt and crystals, and sometimes also of gas bubbles. Melt, crystals, and bubbles usually have different densities, and so they can separate as magmas evolve.

As magma cools, minerals typically crystallize from the melt at different temperatures (fractional crystallization). As minerals crystallize, the composition of the residual melt typically changes. If crystals separate from the melt, then the residual melt will differ in composition from the parent magma. For instance, a magma of gabbroic composition can produce a residual melt of granitic composition if early formed crystals are separated from the magma. Gabbro may have a liquidus temperature near 1,200 °C, and the derivative granite-composition melt may have a liquidus temperature as low as about 700 °C. Incompatible elements are concentrated in the last residues of magma during fractional crystallization and in the first melts produced during partial melting: either process can form the magma that crystallizes to pegmatite, a rock type commonly enriched in incompatible elements. Bowen's reaction series is important for understanding the idealised sequence of fractional crystallisation of a magma. Clinopyroxene thermobarometry is used to determine temperature and pressure conditions at which magma differentiation occurred for specific igneous rocks.

Magma composition can be determined by processes other than partial melting and fractional crystallization. For instance, magmas commonly interact with rocks they intrude, both by melting those rocks and by reacting with them. Magmas of different compositions can mix with one another. In rare cases, melts can separate into two immiscible melts of contrasting compositions.

Etymology

The word igneous is derived from the Latin ignis, meaning "of fire". Volcanic rocks are named after Vulcan, the Roman name for the god of fire. Intrusive rocks are also called "plutonic" rocks, named after Pluto, the Roman god of the underworld.

Copper in renewable energy

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