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Saturday, April 20, 2019

Reformation

From Wikipedia, the free encyclopedia

The Reformation (more fully the Protestant Reformation, or the European Reformation) was a movement within Western Christianity in 16th-century Europe that posed a religious and political challenge to the Roman Catholic church – and papal authority in particular. Although the Reformation is usually considered to have started with the publication of the Ninety-five Theses by Martin Luther in 1517, there was no schism between the Catholics and the nascent Lutheran branch until the 1521 Edict of Worms. The edict condemned Luther and officially banned citizens of the Holy Roman Empire from defending or propagating his ideas. The end of the Reformation era is disputed: it could be considered to end with the enactment of the confessions of faith which began the Age of Orthodoxy. Other suggested ending years relate to the Counter-Reformation, the Peace of Westphalia, or that it never ended since there are still Protestants today.
 
Movements had been made towards a Reformation prior to Luther, so some Protestants in the tradition of the Radical Reformation prefer to credit the start of the Reformation to reformers such as Arnold of Brescia, Peter Waldo, Jan Hus, Tomáš Štítný ze Štítného, John Wycliffe, and Girolamo Savonarola. Due to the reform efforts of Hus and others in the Lands of the Bohemian Crown, Utraquist Hussitism was officially acknowledged by both the Pope and the Holy Roman Emperor, although other movements were still subject to persecution, as were the including Lollards in England and Waldensians in Italy and France.

Luther began by criticising the sale of indulgences, insisting that the Pope had no authority over purgatory and that the Treasury of Merit had no foundation in the Bible. The Reformation developed further to include a distinction between Law and Gospel, a complete reliance on Scripture as the only source of proper doctrine (sola scriptura) and the belief that faith in Jesus is the only way to receive God's pardon for sin (sola fide) rather than good works. Although this is generally considered a Protestant belief, a similar formulation was taught by Molinist and Jansenist Catholics. The priesthood of all believers downplayed the need for saints or priests to serve as mediators, and mandatory clerical celibacy was ended. Simul justus et peccator implied that although people could improve, no one could become good enough to earn forgiveness from God. Sacramental theology was simplified and attempts at imposing Aristotelian epistemology were resisted.

Luther and his followers did not see these theological developments as changes. The 1530 Augsburg Confession concluded that "in doctrine and ceremonies nothing has been received on our part against Scripture or the Church Catholic", and even after the Council of Trent, Martin Chemnitz published the 1565–73 Examination of the Council of Trent in order to prove that Trent innovated on doctrine while the Lutherans were following in the footsteps of the Church Fathers and Apostles.

The initial movement in Germany diversified, and other reformers arose independently of Luther such as Zwingli in Zürich and Calvin in Geneva. Depending on the country, the Reformation had varying causes and different backgrounds, and also unfolded differently than in Germany. The spread of Gutenberg's printing press provided the means for the rapid dissemination of religious materials in the vernacular.

During Reformation-era confessionalization, Western Christianity adopted different confessions (Catholic, Lutheran, Reformed, Anglican, Anabaptist, Unitarian, etc.). Radical Reformers, besides forming communities outside state sanction, sometimes employed more extreme doctrinal change, such as the rejection of the tenets of the councils of Nicaea and Chalcedon with the Unitarians of Transylvania. Anabaptist movements were especially persecuted following the German Peasants' War.

Leaders within the Roman Catholic Church responded with the Counter-Reformation, initiated by the Confutatio Augustana in 1530, the Council of Trent in 1545, the Jesuits in 1540, the Defensio Tridentinæ fidei in 1578, and also a series of wars and expulsions of Protestants that continued until the 19th century. Northern Europe, with the exception of most of Ireland, came under the influence of Protestantism. Southern Europe remained predominantly Catholic apart from the much-persecuted Waldensians. Central Europe was the site of much of the Thirty Years' War and there were continued expulsions of Protestants in central Europe up to the 19th century. Following World War II, the removal of ethnic Germans to either East Germany or Siberia reduced Protestantism in the Warsaw Pact countries, although some remain today. Absence of Protestants however, does not necessarily imply a failure of the Reformation. Although Protestants were excommunicated and ended up worshipping in communions separate from Catholics contrary to the original intention of the Reformers, they were also suppressed and persecuted in most of Europe at one point. As a result, some of them lived as crypto-Protestants, also called Nicodemites, contrary to the urging of John Calvin who wanted them to live their faith openly. Some crypto-Protestants have been identified as late as the 19th century after immigrating to Latin America. As a result Reformation impulses continued to affect the Latin Church well past the end of what is usually considered the Reformation era.

Origins and early history

Earlier reform movements

Execution of Jan Hus in Konstanz (1415). Western Christianity was already formally compromised in the Lands of the Bohemian Crown long before Luther with the Basel Compacts (1436) and the Religious peace of Kutná Hora (1485). Utraquist Hussitism was allowed there alongside the Roman Catholic confession. By the time the Reformation arrived, the Kingdom of Bohemia and the Margraviate of Moravia both had majority Hussite populations for decades now.
 
The oldest Protestant churches, such as the Unitas Fratrum and Moravian Church, date their origins to Jan Hus (John Huss) in the early 15th century. As it was led by a Bohemian noble majority, and recognised, for a time, by the Basel Compacts, the Hussite Reformation was Europe's first "Magisterial Reformation" because the ruling magistrates supported it, unlike the "Radical Reformation", which the state did not support.

Common factors that played a role during the Reformation and the Counter-Reformation included the rise of nationalism, simony, the appointment of Cardinal-nephews, and other corruption of the Roman Curia and other ecclesiastical hierarchy, the impact of humanism, the new learning of the Renaissance, the epistemological shift between the schola moderna and schola antiqua within scholasticism, and the Western Schism that eroded loyalty to the Papacy. Unrest due to the Great Schism of Western Christianity (1378–1416) excited wars between princes, uprisings among the peasants, and widespread concern over corruption in the Church, especially from John Wycliffe at Oxford University and from Jan Hus at the Charles University in Prague.

Hus objected to some of the practices of the Roman Catholic Church and wanted to return the church in Bohemia and Moravia to earlier practices: liturgy in the language of the people (i.e. Czech), having lay people receive communion in both kinds (bread and wine – that is, in Latin, communio sub utraque specie), married priests, and eliminating indulgences and the concept of Purgatory. Some of these, like the use of local language as the lithurgic language, were approved by the pope as early as in the 9th century. Hus rejected indulgences and adopted a doctrine of justification by grace through faith alone.

The leaders of the Roman Catholic Church condemned him at the Council of Constance (1414–1417) by burning him at the stake despite a promise of safe-conduct. Wycliffe was posthumously condemned as a heretic and his corpse exhumed and burned in 1428. The Council of Constance confirmed and strengthened the traditional medieval conception of church and empire. The council did not address the national tensions or the theological tensions stirred up during the previous century and could not prevent schism and the Hussite Wars in Bohemia.

Pope Sixtus IV (1471–1484) established the practice of selling indulgences to be applied to the dead, thereby establishing a new stream of revenue with agents across Europe. Pope Alexander VI (1492–1503) was one of the most controversial of the Renaissance popes. He was the father of seven children, including Lucrezia and Cesare Borgia. In response to papal corruption, particularly the sale of indulgences, Luther wrote The Ninety-Five Theses.

A number of theologians in the Holy Roman Empire preached reformational ideas in the 1510s, shortly before or simultaneously with Luther, including Christoph Schappeler in Memmingen (as early as 1513).

Magisterial Reformation

Martin Luther initiated the Reformation with his Ninety-five Theses against the Catholic Church
 
Martin Luther at the Diet of Worms, where he refused to recant his works when asked to by Charles V. (painting from Anton von Werner, 1877, Staatsgalerie Stuttgart)
 
The Reformation is usually dated to 31 October 1517 in Wittenberg, Saxony, when Luther sent his Ninety-Five Theses on the Power and Efficacy of Indulgences to the Archbishop of Mainz. The theses debated and criticised the Church and the papacy, but concentrated upon the selling of indulgences and doctrinal policies about purgatory, particular judgment, and the authority of the pope. He would later in the period 1517–1521 write works on devotion to Virgin Mary, the intercession of and devotion to the saints, the sacraments, mandatory clerical celibacy, further on the authority of the pope, the ecclesiastical law, censure and excommunication, the role of secular rulers in religious matters, the relationship between Christianity and the law, good works, and monasticism. Some nuns left the monastic life when they accepted the Reformation, such as Katharina von Bora and Ursula of Munsterberg, but other orders adopted the Reformation, as Lutherans continue to have monasteries today. In contrast, Reformed areas typically secularized monastic property. 

Reformers and their opponents made heavy use of inexpensive pamphlets as well as vernacular Bibles using the relatively new printing press, so there was swift movement of both ideas and documents. Magdalena Heymair printed pedagogical writings for teaching children Bible stories.

Parallel to events in Germany, a movement began in Switzerland under the leadership of Huldrych Zwingli. These two movements quickly agreed on most issues, but some unresolved differences kept them separate. Some followers of Zwingli believed that the Reformation was too conservative, and moved independently toward more radical positions, some of which survive among modern day Anabaptists.

After this first stage of the Reformation, following the excommunication of Luther in Decet Romanum Pontificem and the condemnation of his followers by the edicts of the 1521 Diet of Worms, the work and writings of John Calvin were influential in establishing a loose consensus among various churches in Switzerland, Scotland, Hungary, Germany and elsewhere.

Although the German Peasants' War of 1524–1525 began as a tax and anti-corruption protest as reflected in the Twelve Articles, its leader Thomas Müntzer gave it a radical Reformation character. It swept through the Bavarian, Thuringian and Swabian principalities, including the Black Company of Florian Geier, a knight from Giebelstadt who joined the peasants in the general outrage against the Catholic hierarchy.In response to reports about the destruction and violence, Luther condemned the revolt in writings such as Against the Murderous, Thieving Hordes of Peasants; Zwingli and Luther's ally Philipp Melanchthon also did not condone the uprising. Some 100,000 peasants were killed by the end of the war.

Radical Reformation

The Radical Reformation was the response to what was believed to be the corruption in both the Roman Catholic Church and the Magisterial Reformation. Beginning in Germany and Switzerland in the 16th century, the Radical Reformation developed radical Protestant churches throughout Europe. The term includes Thomas Müntzer, Andreas Karlstadt, the Zwickau prophets, and Anabaptists like the Hutterites and Mennonites

In parts of Germany, Switzerland and Austria, a majority sympathized with the Radical Reformation despite intense persecution. Although the surviving proportion of the European population that rebelled against Catholic, Lutheran and Zwinglian churches was small, Radical Reformers wrote profusely and the literature on the Radical Reformation is disproportionately large, partly as a result of the proliferation of the Radical Reformation teachings in the United States.

Despite significant diversity among the early Radical Reformers, some “repeating patterns,” emerged among many Anabaptist groups.  Many of these patterns were enshrined in the Schleitheim Confession (1527), and include believers’ (or adult) baptism, memorial view of the Lord’s Supper, belief that Scripture is the final authority on matters of faith and practice, emphasis on the New Testament and the Sermon on the Mount, interpretation of Scripture in community, separation from the world and a two-kingdom theology, pacifism and nonresistance, communalism and economic sharing, belief in the freedom of the will, non-swearing of oaths, “yieldedness” (Gelassenheit) to one’s community and to God, the ban, salvation through divinization (Vergöttung) and ethical living, and discipleship (Nachfolge Christi).

Literacy

Martin Luther's 1534 Bible translated into German. Luther's translation influenced the development of the current Standard German.
 
The Reformation was a triumph of literacy and the new printing press. Luther's translation of the Bible into German was a decisive moment in the spread of literacy, and stimulated as well the printing and distribution of religious books and pamphlets. From 1517 onward, religious pamphlets flooded Germany and much of Europe.

By 1530, over 10,000 publications are known, with a total of ten million copies. The Reformation was thus a media revolution. Luther strengthened his attacks on Rome by depicting a "good" against "bad" church. From there, it became clear that print could be used for propaganda in the Reformation for particular agendas, although the term propaganda derives from the Catholic Congregatio de Propaganda Fide (Congregation for Propagating the Faith) from the Counter-Reformation. Reform writers used existing styles, clichés and stereotypes which they adapted as needed. Especially effective were writings in German, including Luther's translation of the Bible, his Smaller Catechism for parents teaching their children, and his Larger Catechism, for pastors.

Using the German vernacular they expressed the Apostles' Creed in simpler, more personal, Trinitarian language. Illustrations in the German Bible and in many tracts popularised Luther's ideas. Lucas Cranach the Elder (1472–1553), the great painter patronised by the electors of Wittenberg, was a close friend of Luther, and he illustrated Luther's theology for a popular audience. He dramatised Luther's views on the relationship between the Old and New Testaments, while remaining mindful of Luther's careful distinctions about proper and improper uses of visual imagery.

Causes of the Reformation

Erasmus was a Catholic priest who inspired some of the Protestant reformers.
 
The following supply-side factors have been identified as causes of the Reformation:
  • The presence of a printing press in a city by 1500 made Protestant adoption by 1600 far more likely.
  • Protestant literature was produced at greater levels in cities where media markets were more competitive, making these cities more likely to adopt Protestantism.
  • Ottoman incursions decreased conflicts between Protestants and Catholics, helping the Reformation take root.
  • Greater political autonomy increased the likelihood that Protestantism would be adopted.
  • Where Protestant reformers enjoyed princely patronage, they were much more likely to succeed.
  • Proximity to neighbors who adopted Protestantism increased the likelihood of adopting Protestantism.
  • Cities that had higher numbers of students enrolled in heterodox universities and lower numbers enrolled in orthodox universities were more likely to adopt Protestantism.
The following demand-side factors have been identified as causes of the Reformation:
  • Cities with strong cults of saints were less likely to adopt Protestantism.
  • Cities where primogeniture was practiced were less likely to adopt Protestantism.
  • Regions that were poor but had great economic potential and bad political institutions were more likely to adopt Protestantism.
  • The presence of bishoprics made the adoption of Protestantism less likely.
  • The presence of monasteries made the adoption of Protestantism less likely.

Reformation in Germany

Political situation in Germany about 1560
 
Religious situation in Germany and Europe about 1560
 
In 1517, Luther nailed the Ninety-five theses to the Castle Church door, and without his knowledge or prior approval, they were copied and printed across Germany and internationally. Different reformers arose more or less independently of Luther in 1518 (for example Andreas Karlstadt, Philip Melanchthon, Erhard Schnepf, Johannes Brenz and Martin Bucer), 1519 (for example Huldrych Zwingli, Nikolaus von Amsdorf, Ulrich von Hutten) and so on.

After the Heidelberg Disputation (1518) where Luther described the Theology of the Cross as opposed to the Theology of Glory and the Leipzig Disputation (1519), the faith issues were brought to the attention of other German theologians throughout the Empire. Each year drew new theologians to embrace the Reformation and participate in the ongoing, European-wide discussion about faith. The pace of the Reformation proved unstoppable already by 1520. 

The early Reformation in Germany mostly concerns the life of Martin Luther until he was excommunicated by Pope Leo X on 3 January 1521, in the bull Decet Romanum Pontificem. The exact moment Martin Luther realized the key doctrine of Justification by Faith is described in German as the Turmerlebnis. In Table Talk, Luther describes it as a sudden realization. Experts often speak of a gradual process of realization between 1514 and 1518. 

Reformational ideas and Protestant church services were first introduced in cities, being supported by local citizens and also some nobles. The Reformation did not receive overt state support until 1525, although it was only due to the protection of Elector Frederick the Wise who had a strange dream the night prior to October 31st 1517 that Luther survived after being declared an outlaw, both in hiding at Wartburg Castle and afterward his return to Wittenberg. It was more of a movement among the German people between 1517 and 1525, and then also a political one beginning in 1525. Reformer Adolf Clarenbach was burned at the stake near Cologne in 1529. 

The first state to formally adopt a Protestant confession was the Duchy of Prussia (1525). Albert, Duke of Prussia formally declared the "Evangelical" faith to be the state religion. Catholics labeled self-identified Evangelicals "Lutherans" in order to discredit them after the practice of naming a heresy after its founder. Ducal Prussia was followed by many imperial free cities and other minor imperial entities. The next sizeable territories were the Landgraviate of Hesse (1526; at the Synod of Homberg) and the Electorate of Saxony (1527; Luther's homeland), Electoral Palatinate (1530s) and the Duchy of Württemberg (1534). For a more complete list, see the list of states by the date of adoption of the Reformation and the table of the adoption years for the Augsburg Confession. The reformational wave swept first the Holy Roman Empire, and then extended beyond it to the rest of the European continent. 

Germany was home to the greatest number of Protestant reformers. Each state which turned Protestant had their own reformers who contributed towards the Evangelical faith. In Electoral Saxony the Evangelical-Lutheran Church of Saxony was organized and served as an example for other states, although Luther was not dogmatic on questions of polity.

Reformation outside Germany

The Reformation also spread widely throughout Europe, starting with Bohemia, in the Czech lands, and, over the next few decades, to other countries.

Austria

Austria followed the same pattern of the German-speaking states within the Holy Roman Empire, and Lutheranism became the main Protestant confession among its population. Lutheranism gained a significant following in Austria which was concentrated in the eastern half of present-day Austria, while Calvinism was less successful. Eventually the expulsions of the Counter-Reformation reversed the trend. 

Evolution of the Hussite movement in the Lands of the Bohemian Crown from 1419 to 1620, superimposed on modern borders

Czech Lands

The Hussites were a Christian movement in the Kingdom of Bohemia following the teachings of Czech reformer Jan Hus.

Jan Hus

Czech reformer and university professor Jan Hus (c. 1369–1415) became the best-known representative of the Bohemian Reformation and one of the forerunners of the Protestant Reformation. 

Jan Hus was declared heretic and executed – burned at stake – at the Council of Constance in 1415 where he arrived voluntarily to defend his teachings.

Hussite movement

This predominantly religious movement was propelled by social issues and strengthened Czech national awareness. In 1417, two years after the execution of Jan Hus, the Czech reformation quickly became the chief force in the country. 

Jiří Třanovský (1592–1637), the "Luther of the Slavs" who was active in Bohemia, Moravia, and Poland
 
Hussites made up the vast majority of the population, forcing the Council of Basel to recognize in 1437 a system of two "religions" for the first time signing the Compacts of Basel for the kingdom (Catholic and Czech Ultraquism, a Hussite movement). Bohemia later also elected two Protestant kings (George of Poděbrady). 

After Habsburgs took control of the region, the Hussite churches were prohibited and the kingdom partially recatholicized. Even later Lutheranism gained a substantial following, after being permitted by the Habsburgs with the continued persecution of the Czech native Hussite churches. Many Hussites thus declared themselves Lutherans.

Two churches with Hussite roots are now second and third biggest churches in the predominantly agnostic country: Czech Brethren (which gave origin to the international church known as the Moravian Church) and Czechoslovak Hussite Church.

Switzerland

In Switzerland, the teachings of the reformers and especially those of Zwingli and Calvin had a profound effect, despite the frequent quarrels between the different branches of the Reformation.

Huldrych Zwingli

Huldrych Zwingli launched the Reformation in Switzerland. Portrait by Hans Asper.
 
Parallel to events in Germany, a movement began in the Swiss Confederation under the leadership of Huldrych Zwingli. Zwingli was a scholar and preacher who moved to Zurich – the then-leading city state – in 1518, a year after Martin Luther began the Reformation in Germany with his Ninety-five Theses. Although the two movements agreed on many issues of theology, as the recently introduced printing press spread ideas rapidly from place to place, some unresolved differences kept them separate. Long-standing resentment between the German states and the Swiss Confederation led to heated debate over how much Zwingli owed his ideas to Lutheranism. Although Zwinglianism does hold uncanny resemblance to Lutheranism (it even had its own equivalent of the Ninety-five Theses, called the 67 Conclusions), historians have been unable to prove that Zwingli had any contact with Luther's publications before 1520, and Zwingli himself maintained that he had prevented himself from reading them.

The German Prince Philip of Hesse saw potential in creating an alliance between Zwingli and Luther, seeing strength in a united Protestant front. A meeting was held in his castle in 1529, now known as the Colloquy of Marburg, which has become infamous for its complete failure. The two men could not come to any agreement due to their disputation over one key doctrine. Although Luther preached consubstantiation in the Eucharist over transubstantiation, he believed in the real presence of Christ at the Mass. Zwingli, inspired by Dutch theologian Cornelius Hoen, believed that the mass was only representative and memorial – Christ was not present. Luther became so angry that he famously carved into the meeting table in chalk Hoc Est Corpus Meum – a Biblical quotation from the Last Supper meaning 'This is my body'. Zwingli countered this saying that est in that context was the equivalent of the word significant (signifies).

Some followers of Zwingli believed that the Reformation was too conservative and moved independently toward more radical positions, some of which survive among modern day Anabaptists. One famous incident illustrating this was when radical Zwinglians fried and ate sausages during Lent in Zurich city square by way of protest against the Church teaching of good works. Other Protestant movements grew up along the lines of mysticism or humanism (cf. Erasmus and Louis de Berquin who was martyred in 1529), sometimes breaking from Rome or from the Protestants, or forming outside of the churches.

John Calvin

John Calvin was one of the leading figures of the Reformation. His legacy remains in a variety of churches.
 
Following the excommunication of Luther and condemnation of the Reformation by the Pope, the work and writings of John Calvin were influential in establishing a loose consensus among various churches in Switzerland, Scotland, Hungary, Germany and elsewhere. After the expulsion of its Bishop in 1526, and the unsuccessful attempts of the Berne reformer Guillaume (William) Farel, Calvin was asked to use the organisational skill he had gathered as a student of law to discipline the "fallen city" of Geneva. His "Ordinances" of 1541 involved a collaboration of Church affairs with the City council and consistory to bring morality to all areas of life. After the establishment of the Geneva academy in 1559, Geneva became the unofficial capital of the Protestant movement, providing refuge for Protestant exiles from all over Europe and educating them as Calvinist missionaries. These missionaries dispersed Calvinism widely, and formed the French Huguenots in Calvin's own lifetime and spread to Scotland under the leadership of the cantankerous John Knox in 1560. Anne Locke translated some of Calvin's writings to English around this time. The faith continued to spread after Calvin's death in 1563 and reached as far as Constantinople by the start of the 17th century. 

The Reformation foundations engaged with Augustinianism. Both Luther and Calvin thought along lines linked with the theological teachings of Augustine of Hippo. The Augustinianism of the Reformers struggled against Pelagianism, a heresy that they perceived in the Catholic Church of their day. Ultimately, since Calvin and Luther disagreed strongly on certain matters of theology (such as double-predestination and Holy Communion), the relationship between Lutherans and Calvinists was one of conflict.

Nordic countries

The seal of the Diocese of Turku (Finland) during the 16th and 17th centuries featured the finger of St Henry. The post-Reformation diocese included the relic of a pre-Reformation saint in its seal.
 
All of Scandinavia ultimately adopted Lutheranism over the course of the 16th century, as the monarchs of Denmark (who also ruled Norway and Iceland) and Sweden (who also ruled Finland) converted to that faith.

Sweden

In Sweden, the Reformation was spearheaded by Gustav Vasa, elected king in 1523. Friction with the pope over the latter's interference in Swedish ecclesiastical affairs led to the discontinuance of any official connection between Sweden and the papacy from 1523. Four years later, at the Diet of Västerås, the king succeeded in forcing the diet to accept his dominion over the national church. The king was given possession of all church property, church appointments required royal approval, the clergy were subject to the civil law, and the "pure Word of God" was to be preached in the churches and taught in the schools – effectively granting official sanction to Lutheran ideas. The apostolic succession#Lutheran churches was retained in Sweden during the Reformation.

Denmark

Under the reign of Frederick I (1523–33), Denmark remained officially Catholic. But though Frederick initially pledged to persecute Lutherans, he soon adopted a policy of protecting Lutheran preachers and reformers, of whom the most famous was Hans Tausen. During his reign, Lutheranism made significant inroads among the Danish population. Frederick's son, Christian, was openly Lutheran, which prevented his election to the throne upon his father's death. In 1536, the authority of the Catholic bishops was terminated by national assembly. The next year, following his victory in the Count's War, he became king as Christian III and continued the Reformation of the state church with assistance of Johannes Bugenhagen.

Iceland

Luther's influence had already reached Iceland before King Christian's decree. The Germans fished near Iceland's coast, and the Hanseatic League engaged in commerce with the Icelanders. These Germans raised a Lutheran church in Hafnarfjörður as early as 1533. Through German trade connections, many young Icelanders studied in Hamburg. In 1538, when the kingly decree of the new Church ordinance reached Iceland, bishop Ögmundur and his clergy denounced it, threatening excommunication for anyone subscribing to the German 'heresy'. In 1539, the King sent a new governor to Iceland, Klaus von Mervitz, with a mandate to introduce reform and take possession of church property. Von Mervitz seized a monastery in Viðey with the help of his sheriff, Dietrich of Minden, and his soldiers. They drove the monks out and seized all their possessions, for which they were promptly excommunicated by Ögmundur.

England

Church of England

Henry VIII broke England's ties with the Roman Catholic Church, becoming the sole head of the English Church.
 
The separation of the Church of England from Rome under Henry VIII, beginning in 1529 and completed in 1537 brought England alongside this broad Reformation movement. Although Robert Barnes attempted to get Henry VIII to adopt Lutheran theology, he refused to do so in 1538 and burned him at the stake in 1540. Reformers in the Church of England alternated, for decades, between sympathies between Catholic tradition and Reformed principles, gradually developing within the context of robustly Protestant doctrine, a tradition considered a middle way (via media) between the Catholic and Protestant traditions. 

The English Reformation followed a different course from the Reformation in continental Europe. There had long been a strong strain of anti-clericalism. England had already given rise to the Lollard movement of John Wycliffe, which played an important part in inspiring the Hussites in Bohemia. Lollardy was suppressed and became an underground movement, so the extent of its influence in the 1520s is difficult to assess. The different character of the English Reformation came rather from the fact that it was driven initially by the political necessities of Henry VIII. 

Henry had once been a sincere Catholic and had even authored a book strongly criticising Luther. His wife, Catherine of Aragon, bore him only a single child that survived infancy, Mary. Henry strongly wanted a male heir, and many of his subjects might have agreed, if only because they wanted to avoid another dynastic conflict like the Wars of the Roses

Thomas Cranmer proved essential in the development of the English Reformation.
 
King Henry decided to remove the Church of England from the authority of Rome. In 1534, the Act of Supremacy recognized Henry as "the only Supreme Head on earth of the Church of England". Between 1535 and 1540, under Thomas Cromwell, the policy known as the Dissolution of the Monasteries was put into effect. The veneration of some saints, certain pilgrimages and some pilgrim shrines were also attacked. Huge amounts of church land and property passed into the hands of the Crown and ultimately into those of the nobility and gentry. The vested interest thus created made for a powerful force in support of the dissolutions.

There were some notable opponents to the Henrician Reformation, such as Thomas More and Cardinal John Fisher, who were executed for their opposition. There was also a growing party of reformers who were imbued with the Calvinistic, Lutheran and Zwinglian doctrines now current on the Continent. When Henry died he was succeeded by his Protestant son Edward VI, who, through his empowered councillors (with the King being only nine years old at his succession and fifteen at his death) the Duke of Somerset and the Duke of Northumberland, ordered the destruction of images in churches, and the closing of the chantries. Under Edward VI the Church of England moved closer to continental Protestantism. 

Yet, at a popular level, religion in England was still in a state of flux. Following a brief Catholic restoration during the reign of Mary (1553–1558), a loose consensus developed during the reign of Elizabeth I, though this point is one of considerable debate among historians. This "Elizabethan Religious Settlement" largely formed Anglicanism into a distinctive church tradition. The compromise was uneasy and was capable of veering between extreme Calvinism on one hand and Catholicism on the other. But compared to the bloody and chaotic state of affairs in contemporary France, it was relatively successful, in part because Queen Elizabeth lived so long, until the Puritan Revolution or English Civil War in the 17th century.

English dissenters

Oliver Cromwell was a devout Puritan and military leader, who became Lord Protector of England, Scotland, and Ireland.
 
The success of the Counter-Reformation on the Continent and the growth of a Puritan party dedicated to further Protestant reform polarised the Elizabethan Age, although it was not until the 1640s that England underwent religious strife comparable to what its neighbours had suffered some generations before.

The early Puritan movement (late 16th–17th centuries) was Reformed (or Calvinist) and was a movement for reform in the Church of England. Its origins lay in the discontent with the Elizabethan Religious Settlement. The desire was for the Church of England to resemble more closely the Protestant churches of Europe, especially Geneva. The Puritans objected to ornaments and ritual in the churches as idolatrous (vestments, surplices, organs, genuflection), which they castigated as "popish pomp and rags". They also objected to ecclesiastical courts. Their refusal to endorse completely all of the ritual directions and formulas of the Book of Common Prayer and the imposition of its liturgical order by legal force and inspection sharpened Puritanism into a definite opposition movement. 

The later Puritan movement, often referred to as dissenters and nonconformists, eventually led to the formation of various reformed denominations.

The most famous emigration to America was the migration of Puritan separatists from the Anglican Church of England. They fled first to Holland, and then later to America to establish the English colony of Massachusetts in New England, which later became one of the original United States. These Puritan separatists were also known as "the Pilgrims". After establishing a colony at Plymouth (which became part of the colony of Massachusetts) in 1620, the Puritan pilgrims received a charter from the King of England that legitimised their colony, allowing them to do trade and commerce with merchants in England, in accordance with the principles of mercantilism. The Puritans persecuted those of other religious faiths, for example, Anne Hutchinson was banished to Rhode Island during the Antinomian Controversy. Quaker Mary Dyer was hanged in Boston for repeatedly defying a Puritan law banning Quakers from the colony. She was one of the four executed Quakers known as the Boston martyrs. Executions ceased in 1661 when King Charles II explicitly forbade Massachusetts from executing anyone for professing Quakerism. In 1647, Massachusetts passed a law prohibiting any Jesuit Roman Catholic priests from entering territory under Puritan jurisdiction. Any suspected person who could not clear himself was to be banished from the colony; a second offense carried a death penalty.

The Pilgrims held radical Protestant disapproval of Christmas, and its celebration was outlawed in Boston from 1659 to 1681. The ban was revoked in 1681 by the English-appointed governor Edmund Andros, who also revoked a Puritan ban on festivities on Saturday nights. Nevertheless, it was not until the mid-19th century that celebrating Christmas became fashionable in the Boston region.

Wales

Bishop Richard Davies and dissident Protestant cleric John Penry introduced Calvinist theology to Wales. In 1588, the Bishop of Llandaff published the entire Bible in the Welsh language. The translation had a significant impact upon the Welsh population and helped to firmly establish Protestantism among the Welsh people. The Welsh Protestants used the model of the Synod of Dort of 1618–1619. Calvinism developed through the Puritan period, following the restoration of the monarchy under Charles II, and within Wales' Calvinistic Methodist movement. However few copies of Calvin's writings were available before mid-19th century.

Scotland

John Knox was a leading figure in the Scottish Reformation.
 
The Reformation in Scotland's case culminated ecclesiastically in the establishment of a church along reformed lines, and politically in the triumph of English influence over that of France. John Knox is regarded as the leader of the Scottish reformation. 

The Reformation Parliament of 1560 repudiated the pope's authority by the Papal Jurisdiction Act 1560, forbade the celebration of the Mass and approved a Protestant Confession of Faith. It was made possible by a revolution against French hegemony under the regime of the regent Mary of Guise, who had governed Scotland in the name of her absent daughter Mary, Queen of Scots (then also Queen of France). 

Although Protestantism triumphed relatively easily in Scotland, the exact form of Protestantism remained to be determined. The 17th century saw a complex struggle between Presbyterianism (particularly the Covenanters) and Episcopalianism. The Presbyterians eventually won control of the Church of Scotland, which went on to have an important influence on Presbyterian churches worldwide, but Scotland retained a relatively large Episcopalian minority.

France

Although a Catholic clergyman himself, Cardinal Richelieu allied France with Protestant states.
 
Besides the Waldensians already present in France, Protestantism also spread in from German lands, where the Protestants were nicknamed Huguenots; this eventually led to decades of civil warfare.

Though not personally interested in religious reform, Francis I (reigned 1515–1547) initially maintained an attitude of tolerance, in accordance with his interest in the humanist movement. This changed in 1534 with the Affair of the Placards. In this act, Protestants denounced the Catholic Mass in placards that appeared across France, even reaching the royal apartments. During this time as the issue of religious faith entered into the arena of politics, Francis came to view the movement as a threat to the kingdom's stability. 

Following the Affair of the Placards, culprits were rounded up, at least a dozen heretics were put to death, and the persecution of Protestants increased. One of those who fled France at that time was John Calvin, who emigrated to Basel in 1535 before eventually settling in Geneva in 1536. Beyond the reach of the French kings in Geneva, Calvin continued to take an interest in the religious affairs of his native land including the training of ministers for congregations in France.

As the number of Protestants in France increased, the number of heretics in prisons awaiting trial also grew. As an experimental approach to reduce the caseload in Normandy, a special court just for the trial of heretics was established in 1545 in the Parlement de Rouen. When Henry II took the throne in 1547, the persecution of Protestants grew and special courts for the trial of heretics were also established in the Parlement de Paris. These courts came to known as "La Chambre Ardente" ("the fiery chamber") because of their reputation of meting out death penalties on burning gallows.

Despite heavy persecution by Henry II, the Reformed Church of France, largely Calvinist in direction, made steady progress across large sections of the nation, in the urban bourgeoisie and parts of the aristocracy, appealing to people alienated by the obduracy and the complacency of the Catholic establishment.

French Protestantism, though its appeal increased under persecution, came to acquire a distinctly political character, made all the more obvious by the conversions of nobles during the 1550s. This established the preconditions for a series of destructive and intermittent conflicts, known as the Wars of Religion. The civil wars gained impetus with the sudden death of Henry II in 1559, which began a prolonged period of weakness for the French crown. Atrocity and outrage became the defining characteristics of the time, illustrated at their most intense in the St. Bartholomew's Day massacre of August 1572, when the Catholic party killed between 30,000 and 100,000 Huguenots across France. The wars only concluded when Henry IV, himself a former Huguenot, issued the Edict of Nantes (1598), promising official toleration of the Protestant minority, but under highly restricted conditions. Catholicism remained the official state religion, and the fortunes of French Protestants gradually declined over the next century, culminating in Louis XIV's Edict of Fontainebleau (1685), which revoked the Edict of Nantes and made Catholicism the sole legal religion of France, leading some Huguenots to live as Nicodemites. In response to the Edict of Fontainebleau, Frederick William I, Elector of Brandenburg declared the Edict of Potsdam (October 1685), giving free passage to Huguenot refugees and tax-free status to them for ten years. 

In the late 17th century, 150,000–200,000 Huguenots fled to England, the Netherlands, Prussia, Switzerland, and the English and Dutch overseas colonies. A significant community in France remained in the Cévennes region. A separate Protestant community, of the Lutheran faith, existed in the newly conquered (1639– ) province of Alsace, its status not affected by the Edict of Fontainebleau.

Spain

The New Testament translated by Enzinas, published in Antwerp (1543)
 
The New Testament translated by Joanes Leizarraga into the Basque language (1571) on the orders of Navarre's Calvinist queen, Jeanne III of Navarre
 
In the early 16th century, Spain had a different political and cultural milieu from its Western and Central European neighbors in several respects, which affected the mentality and the reaction of the nation towards the Reformation. Spain, which had only recently managed to complete the reconquest of the Peninsula from the Moors in 1492, had been preoccupied with converting the Muslim and Jewish population of the newly conquered regions through the establishment of the Spanish Inquisition in 1478. The rulers of the nation stressed political, cultural, and religious unity, and by the time of the Lutheran Reformation, the Spanish Inquisition was already 40 years old and had the capability of quickly persecuting with any new movement that the leaders of the Catholic Church perceived or interpreted to be religious heterodoxy. Charles V did not wish to see Spain or the rest of Habsburg Europe divided, and in light of continual threat from the Ottomans, preferred to see the Roman Catholic Church reform itself from within. This led to a Counter-Reformation in Spain in the 1530s. During the 1520s, the Spanish Inquisition had created an atmosphere of suspicion and sought to root out any religious thought seen as suspicious. As early as 1521, the Pope had written a letter to the Spanish monarchy warning against allowing the unrest in Northern Europe to be replicated in Spain. Between 1520 and 1550, printing presses in Spain were tightly controlled and any books of Protestant teaching were prohibited.

Contemporary illustration of the auto-da-fé of Valladolid, in which fourteen Protestants were burned at the stake for their faith, on May 21, 1559
 
Between 1530 and 1540, Protestantism in Spain was still able to gain followers clandestinely, and in cities such as Seville and Valladolid adherents would secretly meet at private houses to pray and study the Bible. Protestants in Spain were estimated at between 1000 and 3000, mainly among intellectuals who had seen writings such as those of Erasmus. Notable reformers included Dr. Juan Gil and Juan Pérez de Pineda who subsequently fled and worked alongside others such as Francisco de Enzinas to translate the Greek New Testament into the Spanish language, a task completed by 1556. Protestant teachings were smuggled into Spain by Spaniards such as Julián Hernández, who in 1557 was condemned by the Inquisition and burnt at the stake. Under Philip II, conservatives in the Spanish church tightened their grip, and those who refused to recant such as Rodrigo de Valer were condemned to life imprisonment. In May 1559, sixteen Spanish Lutherans were burnt at the stake: fourteen were strangled before being burnt, while two were burnt alive. In October another thirty were executed. Spanish Protestants who were able to flee the country were to be found in at least a dozen cities in Europe, such as Geneva, where some of them embraced Calvinist teachings. Those who fled to England were given support by the Church of England.

The Kingdom of Navarre, although by the time of the Protestant Reformation a minor principality territorially restricted to southern France, had French Huguenot monarchs, including Henry IV of France and his mother, Jeanne III of Navarre, a devout Calvinist.

Upon the arrival of the Protestant Reformation, Calvinism reached some Basques through the translation of the Bible into the Basque language by Joanes Leizarraga. As Queen of Navarre, Jeanne III commissioned the translation of the New Testament into Basque and Béarnese for the benefit of her subjects. 

Molinism presented a soteriology similar to Protestants within the Roman Catholic Church.

Portugal

During the Reformation era Protestantism was unsuccessful in Portugal, as its spread was frustrated for similar reasons to those in Spain.

Netherlands

Anabaptist Dirk Willems rescues his pursuer and is subsequently burned at the stake in 1569.
 
The Reformation in the Netherlands, unlike in many other countries, was not initiated by the rulers of the Seventeen Provinces, but instead by multiple popular movements, which in turn were bolstered by the arrival of Protestant refugees from other parts of the continent. While the Anabaptist movement enjoyed popularity in the region in the early decades of the Reformation, Calvinism, in the form of the Dutch Reformed Church, became the dominant Protestant faith in the country from the 1560s onward. In the early 17th century internal theological conflict within the Calvinist church between two tendencies of Calvinism, the Gomarists and the liberal Arminians (or Remonstrants), resulted in Gomarist Calvinism becoming the de facto state religion.

Belgium

The first two Lutheran martyrs were monks from Antwerp, Johann Esch and Heinrich Voes who were burned at the stake when they would not recant. 

Harsh persecution of Protestants by the Spanish government of Philip II contributed to a desire for independence in the provinces, which led to the Eighty Years' War and, eventually, the separation of the largely Protestant Dutch Republic from the Catholic-dominated Southern Netherlands (present-day Belgium). 

In 1566, at the peak of Belgian Reformation, there were an estimated 300,000 Protestants, or 20% of the Belgian population.

Luxembourg

Luxembourg, a part of the Spanish Netherlands, remained Catholic during the Reformation era because Protestantism was illegal until 1768.

Hungary

Stephen Bocskay prevented the Holy Roman Emperor from imposing Catholicism on Hungarians.
 
Much of the population of the Kingdom of Hungary adopted Protestantism during the 16th century. After the 1526 Battle of Mohács, the Hungarian people were disillusioned by the inability of the government to protect them and turned to the faith they felt would infuse them with the strength necessary to resist the invader. They found this in the teaching of Protestant reformers such as Martin Luther. The spread of Protestantism in the country was assisted by its large ethnic German minority, which could understand and translate the writings of Martin Luther. While Lutheranism gained a foothold among the German- and Slovak-speaking populations, Calvinism became widely accepted among ethnic Hungarians.

In the more independent northwest, the rulers and priests, protected now by the Habsburg Monarchy, which had taken the field to fight the Turks, defended the old Catholic faith. They dragged the Protestants to prison and the stake wherever they could. Such strong measures only fanned the flames of protest, however. Leaders of the Protestants included Mátyás Dévai Bíró, Mihály Sztárai, István Szegedi Kis, and Ferenc Dávid.

Protestants likely formed a majority of Hungary's population at the close of the 16th century, but Counter-Reformation efforts in the 17th century reconverted a majority of the kingdom to Catholicism. A significant Protestant minority remained, most of it adhering to the Calvinist faith.

In 1558 the Transylvanian Diet of Turda decreed the free practice of both the Catholic and Lutheran religions, but prohibited Calvinism. Ten years later, in 1568, the Diet extended this freedom, declaring that "It is not allowed to anybody to intimidate anybody with captivity or expulsion for his religion". Four religions were declared to be "accepted" (recepta) religions (the fourth being Unitarianism, which became official in 1583 as the faith of the only Unitarian king, John II Sigismund Zápolya, r. 1540–1571), while Eastern Orthodox Christianity was "tolerated" (though the building of stone Orthodox churches was forbidden). During the Thirty Years' War, Royal (Habsburg) Hungary joined the Catholic side, until Transylvania joined the Protestant side. 

Between 1604 and 1711, there was a series of anti-Habsburg uprisings calling for equal rights and freedom for all Christian denominations, with varying success; the uprisings were usually organised from Transylvania. The Habsburg-sanctioned Counter-Reformation efforts in the 17th century reconverted the majority of the kingdom to Catholicism. 

The centre of Protestant learning in Hungary has for some centuries been the University of Debrecen. Founded in 1538, the University was situated in an area of Eastern Hungary under Ottoman Turkish rule during the 1600s and 1700s, being allowed Islamic toleration and thus avoiding Counter-Reformation persecution.

Romania

Transylvania in what is today's Romania was a "dumping ground for undesirables" by the Habsburg monarchy. People who did not conform to the will of the Habsburgs and the leaders of the Catholic Church were forcibly sent there. Centuries of this practice allowed diverse Protestant traditions to emerge in Romania, including Lutheranism, Calvinism and Unitarianism.

Ukraine

Calvinism was popular among Hungarians who inhabited the southwestern parts of the present-day Ukraine. Their descendants are still there, see the Sub-Carpathian Reformed Church.

Belarus

The first Protestant congregation was founded in Brest-Litovsk in the Reformed tradition, and the Belarusian Evangelical Reformed Church exists today.

Ireland

A devout Catholic, Mary I of England started the first Plantations of Ireland, which, ironically, soon came to be associated with Protestantism.
 
The Reformation in Ireland was a movement for the reform of religious life and institutions that was introduced into Ireland by the English administration at the behest of King Henry VIII of England. His desire for an annulment of his marriage was known as the King's Great Matter. Ultimately Pope Clement VII refused the petition; consequently it became necessary for the King to assert his lordship over the church in his realm to give legal effect to his wishes. The English Parliament confirmed the King's supremacy over the Church in the Kingdom of England. This challenge to Papal supremacy resulted in a breach with the Roman Catholic Church. By 1541, the Irish Parliament had agreed to the change in status of the country from that of a Lordship to that of Kingdom of Ireland.

Unlike similar movements for religious reform on the continent of Europe, the various phases of the English Reformation as it developed in Ireland were largely driven by changes in government policy, to which public opinion in England gradually accommodated itself. However, a number of factors complicated the adoption of the religious innovations in Ireland; the majority of the population there adhered to the Catholic Church. However, in the city of Dublin the reformation took hold under the auspices of George Browne.

Italy

Waldensian symbol Lux lucet in tenebris ("Light glows in the darkness")
 
Word of the Protestant reformers reached Italy in the 1520s but never caught on. Its development was stopped by the Counter-Reformation, the Inquisition and also popular disinterest. Not only was the Church highly aggressive in seeking out and suppressing heresy, but there was a shortage of Protestant leadership. No one translated the Bible into Italian; few tracts were written. No core of Protestantism emerged. The few preachers who did take an interest in "Lutheranism", as it was called in Italy, were suppressed or went into exile to northern countries where their message was well received. As a result, the Reformation exerted almost no lasting influence in Italy, except for strengthening the Catholic Church and pushing for an end to ongoing abuses in Counter-Reformation.

Some Protestants left Italy and became outstanding activists of the European Reformation, mainly in the Polish–Lithuanian Commonwealth (e.g. Giorgio Biandrata, Bernardino Ochino, Giovanni Alciato, Giovanni Battista Cetis, Fausto Sozzini, Francesco Stancaro and Giovanni Valentino Gentile), who propagated Nontrinitarianism there and were chief instigators of the movement of Polish Brethren. Some also fled to England and Switzerland, including Peter Vermigli.

In 1532, the Waldensians, who had been already present centuries before the Reformation, aligned themselves and adopted the Calvinist theology. The Waldensian Church survived in the Western Alps through many persecutions and remains a Protestant church in Italy.

Poland and Lithuania

Jan Łaski sought unity between various Christian churches in the Commonwealth, and participated in the English Reformation.
 
In the first half of the 16th century, the enormous Polish–Lithuanian Commonwealth was a country of many creeds, but Catholicism remained the dominating religion. Reformation reached Poland in the 1520s and quickly gained popularity among mostly German-speaking inhabitants of such major cities as Danzig (now Gdańsk), Thorn (now Toruń) and Elbing (now Elbląg). In Königsberg (now Kaliningrad), in 1530, a Polish-language edition of Luther's Small Catechism was published. The Duchy of Prussia, which was a Polish fief, emerged as a key center of the movement, with numerous publishing houses issuing not only Bibles, but also catechisms, in German, Polish and Lithuanian. 

Lutheranism gained popularity in the northern part of the country, while Calvinism caught the interest of the nobility (known as szlachta), mainly in Lesser Poland and the Grand Duchy of Lithuania. Several publishing houses were opened in Lesser Poland in the mid-16th century in such locations as Słomniki and Raków. At that time, Mennonites and Czech Brothers came to Poland, with the latter settling mostly in Greater Poland around Leszno. In 1565, the Polish Brethren appeared as yet another reformation movement. 

The Commonwealth was unique in Europe in the 16th century for its widespread tolerance confirmed by the Warsaw Confederation. In 1563, the Brest Bible was published (see also Bible translations into Polish). The period of tolerance ended during the reign of King Sigismund III Vasa, who was under the strong influence of Piotr Skarga and other Jesuits. After the Deluge, and other wars of the mid-17th century in which all enemies of Poland were either Protestant or Orthodox Christians, the Poles' attitude changed, and the Counter-Reformation prevailed: in 1658 the Polish Brethren were forced to leave the country, and in 1666, the Sejm banned apostasy from Catholicism to any other religion, under penalty of death. Finally, in 1717, the Silent Sejm banned non-Catholics from becoming deputies of the Parliament.

Among most important Protestants of the Commonwealth were Mikołaj Rej, Marcin Czechowic, Andrzej Frycz Modrzewski and Symon Budny.

Moldova

Reformation in Moldova
 
The Reformation was very insignificant in what is now Moldova and saw single congregations of Hussitism and Calvinism being founded across Besserabia. During the Reformation era, Moldova was repeatedly invaded.

Slovenia

Primož Trubar, a Lutheran reformer in Slovenia
 
Primož Trubar is notable for consolidating the Slovene language and is considered to be the key figure of Slovenian cultural history and in many aspects a major Slovene historical personality. He was the key figure of the Protestant Church of the Slovene Lands, as he was its founder and its first superintendent. The first books in Slovene, Catechismus and Abecedarium, were written by Trubar.

Slovakia

At one point in history, the majority of Slovaks (~60%) were Lutherans. Calvinism was popular among the Hungarians who inhabited the southernmost parts of what is now Slovakia. Back then, Slovakia used to be a part of the Kingdom of Hungary. The Counter-Reformation implemented by the Habsburgs severely damaged Slovakian Protestantism, although in the 2010s Protestants are still a substantial minority (~10%) in the country.

Croatia

Lutheranism reached northern parts of the country.

Serbia

Vojvodina turned partially Lutheran.

Greece

The Protestant teachings of the Western Church were also briefly adopted within the Eastern Orthodox Church through the Greek Patriarch Cyril Lucaris in 1629 with the publishing of the Confessio (Calvinistic doctrine) in Geneva. Motivating factors in their decision to adopt aspects of the Reformation included the historical rivalry and mistrust between the Greek Orthodox and the Roman Catholic Churches along with their concerns of Jesuit priests entering Greek lands in their attempts to propagate the teachings of the Counter-Reformation to the Greek populace. He subsequently sponsored Maximos of Gallipoli's translation of the New Testament into the Modern Greek language and it was published in Geneva in 1638. Upon Lucaris's death in 1638, the conservative factions within the Eastern Orthodox Church held two synods: the Synod of Constantinople (1638) and Synod of Jassy (1642) criticizing the reforms and in the 1672 convocation led by Dositheos, they officially condemned the Calvinistic doctrines.

In 2019, Christos Yannaras told Norman Russell that although he had participated in the Zoë movement, he had come to regard it as Crypto-Protestant.

Spread

The Reformation spread throughout Europe beginning in 1517, reaching its peak between 1545 and 1620. 

Religious fragmentation in Central Europe at the outbreak of the Thirty Years' War (1618).
 
The greatest geographical extent of Protestantism occurred at some point between 1545 and 1620. In 1620, the Battle of White Mountain defeated Protestants in Bohemia (now the Czech Republic) who sought to have the 1609 Letter of Majesty upheld. 

The Reformation at its peak, superimposed on modern European borders
.
The Thirty Years' War began in 1618 and brought a drastic territorial and demographic decline when the House of Habsburg introduced counter-reformational measures throughout their vast possessions in Central Europe. Although the Thirty Years' War concluded with the Peace of Westphalia, the French Wars of the Counter-Reformation continued, as well as the expulsion of Protestants in Austria. 

The Reformation & the Counter-Reformation—both at their end—and superimposed on modern European borders

Conclusion and legacy

There is no universal agreement on the exact or approximate date the Reformation ended. Various interpretations emphasize different dates, entire periods, or argue that the Reformation never really ended. However, there are a few popular interpretations.
  • In the history of theology or philosophy, the Reformation era ended with the Age of Orthodoxy. The Orthodox Period, also termed the Scholastic Period, succeeded the Reformation with the 1545–1563 Council of Trent, the 1562 Anglican Thirty-nine Articles, the 1580 Book of Concord, and other confessions of faith. The Orthodox Era ended with the development of both Pietism and the Enlightenment.
  • The Peace of Westphalia is considered by some to be the event that ended the Reformation.
  • According to other interpretations, the Reformation could truly be considered to have ended in the middle 18th century, as the Peace of Westphalia did not specify, nor did it mean that it concluded; that is around time the First Great Awakening (1730–1755) took place. People who hold this interpretation often argue that the emergence of Pietism prolonged the Reformation up to this point;
  • Some argue that the Reformation never ended as new churches have splintered from the Catholic Church (e.g., Old Catholics, Polish National Catholic Church, etc.), as well as all the various Protestant churches that exist today. No church splintering from the Catholic Church since the 17th century has done so on the basis of the same issues animating the Reformation, however.

Thirty Years' War: 1618–1648

Treaty of Westphalia allowed Calvinism to be freely exercised, reducing the need for Crypto-Calvinism
 
The Reformation and Counter-Reformation era conflicts are termed the European wars of religion. In particular, the Thirty Years' War (1618–1648) devastated much of Germany, killing between 25% and 40% of its entire population. Catholic House of Habsburg and its allies fought against the Protestant princes of Germany, supported at various times by Denmark, Sweden and France. The Habsburgs, who ruled Spain, Austria, the Crown of Bohemia, Hungary, Slovene Lands, the Spanish Netherlands and much of Germany and Italy, were staunch defenders of the Catholic Church. Some historians believe that the era of the Reformation came to a close when Catholic France allied itself with Protestant states against the Habsburg dynasty.

Two main tenets of the Peace of Westphalia, which ended the Thirty Years' War, were:
  • All parties would now recognise the Peace of Augsburg of 1555, by which each prince would have the right to determine the religion of his own state, the options being Catholicism, Lutheranism, and now Calvinism (the principle of cuius regio, eius religio).
  • Christians living in principalities where their denomination was not the established church were guaranteed the right to practice their faith in public during allotted hours and in private at their will.
The treaty also effectively ended the Papacy's pan-European political power. Pope Innocent X declared the treaty "null, void, invalid, iniquitous, unjust, damnable, reprobate, inane, empty of meaning and effect for all times" in his bull Zelo Domus Dei. European sovereigns, Catholic and Protestant alike, ignored his verdict.

Clathrate gun hypothesis

From Wikipedia, the free encyclopedia

Methane clathrate is released as gas into the surrounding water column or soils when ambient temperature increases
 
The clathrate gun hypothesis is the popular name given to the idea that increases in sea temperatures or drops in sea levels can trigger a strong positive feedback effect on climate: first, warming causes a sudden release of methane from methane clathrate compounds buried in seabeds and seabed permafrost; second, because methane itself is a powerful greenhouse gas, temperatures rise further, and the cycle repeats. This runaway process, once started, could be as irreversible as the firing of a gun.

In its original form, the hypothesis proposed that the "clathrate gun" could cause abrupt runaway warming on a time scale less than a human lifetime. A 2018 published review concluded that the clathrate gun hypothesis remains controversial, but that better understanding is vital.

General

Studies published in 2000 attributed the hypothesis to be responsible for warming events in and at the end of the Last Glacial Maximum, but this is now thought to be unlikely. At one point there seemed to be stronger evidence that runaway methane clathrate breakdown may have caused drastic alteration of the ocean environment (such as ocean acidification and ocean stratification) and of the atmosphere over timescales of tens of thousands of years during the Paleocene–Eocene Thermal Maximum 56 million years ago, and most notably the Permian–Triassic extinction event, when up to 96% of all marine species became extinct, 252 million years ago. However, the pattern of isotope shifts expected to result from a massive release of methane does not match the patterns seen there. First, the isotope shift is too large for this hypothesis, as it would require five times as much methane as is postulated for the PETM, and then, it would have to be reburied at an unrealistically high rate to account for the rapid increases in the 13C/12C ratio throughout the early Triassic before it was released again several times. Yet, it is still argued that a potential positive feedback mechanism from clathrate dissociation would amplify future global warming. However, past hydrate dissociation at Svalbard eight thousand years ago has been attributed to isostatic rebound (continental uplift following deglaciation).

The SWIPA 2017 report notes, "Arctic sources and sinks of greenhouse gases are still hampered by data and knowledge gaps."

Possible release events

Two events possibly linked to methane excursions are the Permian–Triassic extinction event and the Paleocene–Eocene Thermal Maximum (PETM). Equatorial permafrost methane clathrate may have had a role in the sudden warm-up of "Snowball Earth", 630 million years ago. However, warming at the end of the last ice age is not thought to be due to methane release. A similar event is the methane hydrate releases, following ice-sheet retreat during the last glacial period, around 12,000 years ago, in response to the Bølling-Allerød warming.

Mechanism

Specific structure of a gas hydrate piece, from the subduction zone off Oregon
 
Gas hydrate-bearing sediment, from the subduction zone off Oregon
 
Methane clathrate, also known commonly as methane hydrate, is a form of water ice that contains a large amount of methane within its crystal structure. Potentially large deposits of methane clathrate have been found under sediments on the ocean floors of the Earth, although the estimates of total resource size given by various experts differ by many orders of magnitude, leaving doubt as to the size of methane clathrate deposits (particularly in the viability of extracting them as a fuel resource). Indeed, cores of greater than 10 centimeters' contiguous depth had only been found in three sites as of 2000, and some resource reserve size estimates for specific deposits/locations have been based primarily on seismology.

The sudden release of large amounts of natural gas from methane clathrate deposits in runaway climate change could be a cause of past, future, and present climate changes. The release of this trapped methane is a potential major outcome of a rise in temperature; some have suggested that this was a main factor in the planet warming 6 °C, which happened during the end-Permian extinction, as methane is much more powerful as a greenhouse gas than carbon dioxide. Despite its atmospheric lifetime of around 12 years, it has a global warming potential of 72 over 20 years, 25 over 100 years, and 33 when accounted for aerosol interactions. The theory also predicts this will greatly affect available oxygen and hydroxyl radical content of the atmosphere.

Subsea permafrost

Subsea permafrost occurs beneath the seabed and exists in the continental shelves of the polar regions. This source of methane is different from methane clathrates, but contributes to the overall outcome and feedbacks. 

From sonar measurements in recent years researchers quantified the density of bubbles emanating from subsea permafrost into the ocean (a process called ebullition), and found that 100–630 mg methane per square meter is emitted daily along the East Siberian Shelf, into the water column. They also found that during storms, when wind accelerates air-sea gas exchange, methane levels in the water column drop dramatically. Observations suggest that methane release from seabed permafrost will progress slowly, rather than abruptly. However, Arctic cyclones, fueled by global warming, and further accumulation of greenhouse gases in the atmosphere could contribute to more rapid methane release from this source.

Metastable methane clathrates

Another kind of exception is in clathrates associated with the Arctic ocean, where clathrates can exist in shallower water stabilized by lower temperatures rather than higher pressures; these may potentially be marginally stable much closer to the surface of the sea-bed, stabilized by a frozen 'lid' of permafrost preventing methane escape. 

The so-called self-preservation phenomenon has been studied by Russian geologists starting in the late 1980s. This metastable clathrate state can be a basis for release events of methane excursions, such as during the interval of the Last Glacial Maximum. A study from 2010 concluded with the possibility for a trigger of abrupt climate warming based on metastable methane clathrates in the East Siberian Arctic Shelf (ESAS) region.

Ocean anoxia

Euxinic (i.e. sulfidic) and anoxic events happened in the past on different time scales ranging from decades to centuries (from impact events) or through climate change within tens of thousands of years or a few million years. According to Gregory Ryskin, such a scenario could lead to the release of methane and other gases (e.g., CO
2
, H
2
S
) into the atmosphere, from the ocean. Following atmospheric methane excursions he postulates explosions and burning of methane would produce lots of smoke and dust, which would first lead to global cooling. And likely after a relatively short geological period following stratospheric cooling, global warming would take over.

Current outlook

Most deposits of methane clathrate are in sediments too deep to respond rapidly, and modelling by Archer (2007) suggests the methane forcing should remain a minor component of the overall greenhouse effect. Clathrate deposits destabilize from the deepest part of their stability zone, which is typically hundreds of metres below the seabed. A sustained increase in sea temperature will warm its way through the sediment eventually, and cause the shallowest, most marginal clathrate to start to break down; but it will typically take on the order of a thousand years or more for the temperature signal to get through. However, there is also a possibility for the formation of gas migration pathways within fault zones in the East Siberian Arctic Shelf, through the process of talik formation, or pingo-like features.

According to data released by the EPA, atmospheric methane (CH4) concentrations in parts per billion (ppb) remained between 400–800ppb in the years 600,000 BC to 1900 AD, and since 1900 AD have risen to levels between 1600–1800ppb. Global averaged monthly mean atmospheric methane is currently at ~1860 ppb CH4, increases between 8.8 ± 2.6 through 2017 compare to an average annual increase of 5.7 ± 1.1 ppb between 2007 and 2013.

A USGS metastudy in 2017 by the USGS Gas Hydrates Project concluded:
Our review is the culmination of nearly a decade of original research by the USGS, my coauthor Professor John Kessler at the University of Rochester, and many other groups in the community,” said USGS geophysicist Carolyn Ruppel, who is the paper’s lead author and oversees the USGS Gas Hydrates Project. “After so many years spent determining where gas hydrates are breaking down and measuring methane flux at the sea-air interface, we suggest that conclusive evidence for release of hydrate-related methane to the atmosphere is lacking.

Arctic Ocean

Potential Methane release in the Eastern Siberian Arctic Shelf

Research carried out in 2008 in the Siberian Arctic showed millions of tons of methane being released, apparently through perforations in the seabed permafrost, with concentrations in some regions reaching up to 100 times normal levels. The excess methane has been detected in localized hotspots in the outfall of the Lena River and the border between the Laptev Sea and the East Siberian Sea. At the time, some of the melting was thought to be the result of geological heating, but more thawing was believed to be due to the greatly increased volumes of meltwater being discharged from the Siberian rivers flowing north. The current methane release had previously been estimated at 0.5 megatonnes per year. Shakhova et al. (2008) estimate that not less than 1,400 gigatonnes of carbon is presently locked up as methane and methane hydrates under the Arctic submarine permafrost, and 5–10% of that area is subject to puncturing by open taliks. They conclude that "release of up to 50 gigatonnes of predicted amount of hydrate storage [is] highly possible for abrupt release at any time". That would increase the methane content of the planet's atmosphere by a factor of twelve, equivalent in greenhouse effect to a doubling in the current level of CO
2

This is what led to the original Clathrate gun hypothesis, and in 2008 the United States Department of Energy National Laboratory system and the United States Geological Survey's Climate Change Science Program both identified potential clathrate destabilization in the Arctic as one of four most serious scenarios for abrupt climate change, which have been singled out for priority research. The USCCSP released a report in late December 2008 estimating the gravity of this risk. A 2012 assessment of the literature identifies methane hydrates on the Shelf of East Arctic Seas as a potential trigger.

Hong et al. 2017 studied methane seepage in the shallow arctic seas at the Barents Sea close to Svalbard. Temperature at the seabed has fluctuated seasonally over the last century, between -1.8 and 4.8 °C, it has only affected release of methane to a depth of about 1.6 meters at the sediment-water interface. Hydrates can be stable through the top 60 meters of the sediments and the current observed releases originate from deeper below the sea floor. They conclude that the increased methane flux started hundreds to thousands of years ago, noted about it, "..episodic ventilation of deep reservoirs rather than warming-induced gas hydrate dissociation." Summarizing his research, Hong stated:
The results of our study indicate that the immense seeping found in this area is a result of natural state of the system. Understanding how methane interacts with other important geological, chemical and biological processes in the Earth system is essential and should be the emphasis of our scientific community.

Continental slopes

Profile illustrating the continental shelf, slope and rise
 
A trapped gas deposit on the continental slope off Canada in the Beaufort Sea, located in an area of small conical hills on the ocean floor is just 290 meters below sea level and considered the shallowest known deposit of methane hydrate. However, the ESAS region averages 45 meters in depth, and it is assumed that below the seafloor, sealed by sub-sea permafrost layers, hydrates deposits are located.

Seismic observation in 2012 of destabilizing methane hydrate along the continental slope of the eastern United States, following the intrusion of warmer ocean currents, suggests that underwater landslides could release methane. The estimated amount of methane hydrate in this slope is 2.5 gigatonnes (about 0.2% of the amount required to cause the PETM), and it is unclear if the methane could reach the atmosphere. However, the authors of the study caution: "It is unlikely that the western North Atlantic margin is the only area experiencing changing ocean currents; our estimate of 2.5 gigatonnes of destabilizing methane hydrate may therefore represent only a fraction of the methane hydrate currently destabilizing globally." 

Bill McGuire notes, "There may be a threat of submarine landslides around the margins of Greenland, which are less well explored. Greenland is already uplifting, reducing the pressure on the crust beneath and also on submarine methane hydrates in the sediment around its margins, and increased seismic activity may be apparent within decades as active faults beneath the ice sheet are unloaded. This could provide the potential for the earthquake or methane hydrate destabilisation of submarine sediment, leading to the formation of submarine slides and, perhaps, tsunamis in the North Atlantic."

Research by Klaus Wallmann et al. 2018 concluded that hydrate dissociation at Svalbard 8,000 years ago was due to the rebound of the seabed following ice-sheet retreat. As a result the water depth got shallower with less hydrostatic pressure, without further warming. The study, also found that today's deposits at the site become unstable at a depth of ~ 400 meters, due to seasonal bottom water warming, and it remains unclear if this is due to natural variability or anthropogenic warming.

Model simulations

A study of the effects for the original hypothesis, based on a coupled climate–carbon cycle model (GCM) assessed a 1000-fold (from less than 1 to 1000 ppmv) methane increase—within a single pulse, from methane hydrates (based on carbon amount estimates for the PETM, with ~2000 GtC), and concluded it would increase atmospheric temperatures by more than 6 °C within 80 years. Further, carbon stored in the land biosphere would decrease by less than 25%, suggesting a critical situation for ecosystems and farming, especially in the tropics.

In fiction

Anoxic event

From Wikipedia, the free encyclopedia

Red circles show the location and size of many dead zones.  Black dots show Ocean dead zones of unknown size.

The size and number of marine dead zones—areas where the deep water is so low in dissolved oxygen that sea creatures can't survive—have grown explosively in the past half-century.NASA Earth Observatory
 
This world perspective on oceanic currents demonstrates the interdependencies of transnational regions on circulating currents.

Oceanic anoxic events or anoxic events (anoxia conditions) were intervals in the Earth's past where portions of oceans become depleted in oxygen (O2) at depths over a large geographic area. During some of these events, euxinia, waters that contained H
2
S
hydrogen sulfide, developed. Although anoxic events have not happened for millions of years, the geological record shows that they happened many times in the past. Anoxic events coincided with several mass extinctions and may have contributed to them. These mass extinctions include some that geobiologists use as time markers in biostratigraphic dating. Many geologists believe oceanic anoxic events are strongly linked to slowing of ocean circulation, climatic warming, and elevated levels of greenhouse gases. Researchers have proposed enhanced volcanism (the release of CO2) as the "central external trigger for euxinia".

Background

The concept of the oceanic anoxic event (OAE) was first proposed in 1976 by Seymour Schlanger (1927–1990) and geologist Hugh Jenkyns and arose from discoveries made by the Deep Sea Drilling Project (DSDP) in the Pacific Ocean. It was the finding of black carbon-rich shales in Cretaceous sediments that had accumulated on submarine volcanic plateaus (Shatsky Rise, Manihiki Plateau), coupled with the fact that they were identical in age with similar deposits cored from the Atlantic Ocean and known from outcrops in Europe - particularly in the geological record of the otherwise limestone-dominated Apennines chain in Italy - that led to the realization that these widespread similar strata recorded highly unusual oxygen-depleted conditions in the world ocean during several discrete periods of geological time.

Sedimentological investigations of these organic-rich sediments, which have continued to this day, typically reveal the presence of fine laminations undisturbed by bottom-dwelling fauna, indicating anoxic conditions on the sea floor, believed to be coincident with a low lying poisonous layer of hydrogen sulfide. Furthermore, detailed organic geochemical studies have recently revealed the presence of molecules (so-called biomarkers) that derive from both purple sulfur bacteria and green sulfur bacteria: organisms that required both light and free hydrogen sulfide (H2S), illustrating that anoxic conditions extended high into the illuminated upper water column. 

There are currently several places on earth that are exhibiting the features of anoxic events on a localized scale such as algal/bacterial blooms and localized "dead zones". Dead zones exist off the East Coast of the United States in the Chesapeake Bay, in the Scandinavian strait Kattegat, the Black Sea (which may have been anoxic in its deepest levels for millennia, however), in the northern Adriatic as well as a dead zone off the coast of Louisiana. The current surge of jellyfish worldwide is sometimes regarded as the first stirrings of an anoxic event. Other marine dead zones have appeared in coastal waters of South America, China, Japan, and New Zealand. A 2008 study counted 405 dead zones worldwide.

This is a recent understanding. This picture was only pieced together during the last three decades. The handful of known and suspected anoxic events have been tied geologically to large-scale production of the world's oil reserves in worldwide bands of black shale in the geologic record. Likewise the high relative temperatures believed linked to so called "super-greenhouse events".

Euxinia

Oceanic anoxic events with euxinic (i.e. sulfidic) conditions have been linked to extreme episodes of volcanic outgassing. Thus, volcanism contributed to the buildup of CO2 in the atmosphere, increased global temperatures, causing an accelerated hydrological cycle that introduced nutrients to the oceans to stimulate planktonic productivity. These processes potentially acted as a trigger for euxinia in restricted basins where water-column stratification could develop. Under anoxic to euxinic conditions, oceanic phosphate is not retained in sediment and could hence be released and recycled, aiding continued high productivity.

Mechanism

Temperatures throughout the Jurassic and Cretaceous are generally thought to have been relatively warm, and consequently dissolved oxygen levels in the ocean were lower than today - making anoxia easier to achieve. However, more specific conditions are required to explain the short-period (less than a million years) oceanic anoxic events. Two hypotheses, and variations upon them, have proved most durable. 

One hypothesis suggests that the anomalous accumulation of organic matter relates to its enhanced preservation under restricted and poorly oxygenated conditions, which themselves were a function of the particular geometry of the ocean basin: such a hypothesis, although readily applicable to the young and relatively narrow Cretaceous Atlantic (which could be likened to a large-scale Black Sea, only poorly connected to the World Ocean), fails to explain the occurrence of coeval black shales on open-ocean Pacific plateaus and shelf seas around the world. There are suggestions, again from the Atlantic, that a shift in oceanic circulation was responsible, where warm, salty waters at low latitudes became hypersaline and sank to form an intermediate layer, at 500 to 1,000 m (1,640 to 3,281 ft) depth, with a temperature of 20 °C (68 °F) to 25 °C (77 °F).

The second hypothesis suggests that oceanic anoxic events record a major change in the fertility of the oceans that resulted in an increase in organic-walled plankton (including bacteria) at the expense of calcareous plankton such as coccoliths and foraminifera. Such an accelerated flux of organic matter would have expanded and intensified the oxygen minimum zone, further enhancing the amount of organic carbon entering the sedimentary record. Essentially this mechanism assumes a major increase in the availability of dissolved nutrients such as nitrate, phosphate and possibly iron to the phytoplankton population living in the illuminated layers of the oceans. 

For such an increase to occur would have required an accelerated influx of land-derived nutrients coupled with vigorous upwelling, requiring major climate change on a global scale. Geochemical data from oxygen-isotope ratios in carbonate sediments and fossils, and magnesium/calcium ratios in fossils, indicate that all major oceanic anoxic events were associated with thermal maxima, making it likely that global weathering rates, and nutrient flux to the oceans, were increased during these intervals. Indeed, the reduced solubility of oxygen would lead to phosphate release, further nourishing the ocean and fuelling high productivity, hence a high oxygen demand - sustaining the event through a positive feedback.

Here is another way of looking at oceanic anoxic events. Assume that the earth releases a huge volume of carbon dioxide during an interval of intense volcanism; global temperatures rise due to the greenhouse effect; global weathering rates and fluvial nutrient flux increase; organic productivity in the oceans increases; organic-carbon burial in the oceans increases (OAE begins); carbon dioxide is drawn down due to both burial of organic matter and weathering of silicate rocks (inverse greenhouse effect); global temperatures fall, and the ocean–atmosphere system returns to equilibrium (OAE ends).

In this way, an oceanic anoxic event can be viewed as the Earth’s response to the injection of excess carbon dioxide into the atmosphere and hydrosphere. One test of this notion is to look at the age of large igneous provinces (LIPs), the extrusion of which would presumably have been accompanied by rapid effusion of vast quantities of volcanogenic gases such as carbon dioxide. Intriguingly, the age of three LIPs (Karoo-Ferrar flood basalt, Caribbean large igneous province, Ontong Java Plateau) correlates uncannily well with that of the major Jurassic (early Toarcian) and Cretaceous (early Aptian and Cenomanian–Turonian) oceanic anoxic events, indicating that a causal link is feasible.

Occurrence

Oceanic anoxic events most commonly occurred during periods of very warm climate characterized by high levels of carbon dioxide (CO2) and mean surface temperatures probably in excess of 25 °C (77 °F). The Quaternary levels, the current period, are just 13 °C (55 °F) in comparison. Such rises in carbon dioxide may have been in response to a great outgassing of the highly flammable natural gas (methane) that some call an "oceanic burp". Vast quantities of methane are normally locked into the Earth's crust on the continental plateaus in one of the many deposits consisting of compounds of methane hydrate, a solid precipitated combination of methane and water much like ice. Because the methane hydrates are unstable, except at cool temperatures and high (deep) pressures, scientists have observed smaller "burps" due to tectonic events. Studies suggest the huge release of natural gas could be a major climatological trigger, methane itself being a greenhouse gas many times more powerful than carbon dioxide. However, anoxia was also rife during the Hirnantian (late Ordovician) ice age.

Oceanic anoxic events have been recognized primarily from the already warm Cretaceous and Jurassic Periods, when numerous examples have been documented, but earlier examples have been suggested to have occurred in the late Triassic, Permian, Devonian (Kellwasser event), Ordovician and Cambrian

The Paleocene–Eocene Thermal Maximum (PETM), which was characterized by a global rise in temperature and deposition of organic-rich shales in some shelf seas, shows many similarities to oceanic anoxic events.

Typically, oceanic anoxic events lasted for less than a million years, before a full recovery.

Consequences

Oceanic anoxic events have had many important consequences. It is believed that they have been responsible for mass extinctions of marine organisms both in the Paleozoic and Mesozoic. The early Toarcian and Cenomanian-Turonian anoxic events correlate with the Toarcian and Cenomanian-Turonian extinction events of mostly marine life forms. Apart from possible atmospheric effects, many deeper-dwelling marine organisms could not adapt to an ocean where oxygen penetrated only the surface layers.

An economically significant consequence of oceanic anoxic events is the fact that the prevailing conditions in so many Mesozoic oceans has helped produce most of the world's petroleum and natural gas reserves. During an oceanic anoxic event, the accumulation and preservation of organic matter was much greater than normal, allowing the generation of potential petroleum source rocks in many environments across the globe. Consequently, some 70 percent of oil source rocks are Mesozoic in age, and another 15 percent date from the warm Paleogene: only rarely in colder periods were conditions favorable for the production of source rocks on anything other than a local scale.

Atmospheric effects

A model put forward by Lee Kump, Alexander Pavlov and Michael Arthur in 2005 suggests that oceanic anoxic events may have been characterized by upwelling of water rich in highly toxic hydrogen sulfide gas, which was then released into the atmosphere. This phenomenon would probably have poisoned plants and animals and caused mass extinctions. Furthermore, it has been proposed that the hydrogen sulfide rose to the upper atmosphere and attacked the ozone layer, which normally blocks the deadly ultraviolet radiation of the Sun. The increased UV radiation caused by this ozone depletion would have amplified the destruction of plant and animal life. Fossil spores from strata recording the Permian-Triassic extinction event show deformities consistent with UV radiation. This evidence, combined with fossil biomarkers of green sulfur bacteria, indicates that this process could have played a role in that mass extinction event, and possibly other extinction events. The trigger for these mass extinctions appears to be a warming of the ocean caused by a rise of carbon dioxide levels to about 1000 parts per million.

Ocean chemistry effects

Reduced oxygen levels are expected to lead to increased seawater concentrations of redox-sensitive metals. The reductive dissolution of ironmanganese oxyhydroxides in seafloor sediments under low-oxygen conditions would release those metals and associated trace metals. Sulfate reduction in such sediments could release other metals such as barium. When heavy-metal-rich anoxic deep water entered continental shelves and encountered increased O2 levels, precipitation of some of the metals, as well as poisoning of the local biota, would have occurred. In the late Silurian mid-Pridoli event, increases are seen in the Fe, Cu, As, Al, Pb, Ba, Mo and Mn levels in shallow-water sediment and microplankton; this is associated with a marked increase in the malformation rate in chitinozoans and other microplankton types, likely due to metal toxicity. Similar metal enrichment has been reported in sediments from the mid-Silurian Ireviken event.

Anoxic events in Earth's history

Cretaceous

Sulfidic (or euxinic) conditions, which exist today in many water bodies from ponds to various land-surrounded mediterranean seas such as the Black Sea, were particularly prevalent in the Cretaceous Atlantic but also characterized other parts of the world ocean. In an ice-free sea of these supposed super-greenhouse worlds, oceanic waters were as much as 200 meters higher, in some eras. During the time spans in question, the continental plates are believed to have been well separated, and the mountains we know today were (mostly) future tectonic events—meaning the overall landscapes were generally much lower— and even the half super-greenhouse climates would have been eras of highly expedited water erosion carrying massive amounts of nutrients into the world oceans fueling an overall explosive population of microorganisms and their predator species in the oxygenated upper layers. 

Detailed stratigraphic studies of Cretaceous black shales from many parts of the world have indicated that two oceanic anoxic events (OAEs) were particularly significant in terms of their impact on the chemistry of the oceans, one in the early Aptian (~120 Ma), sometimes called the Selli Event (or OAE 1a) after the Italian geologist, Raimondo Selli (1916–1983), and another at the CenomanianTuronian boundary (~93 Ma), sometimes called the Bonarelli Event (or OAE 2) after the Italian geologist, Guido Bonarelli (1871–1951). OAE1a lasted for ~1.0 to 1.3 Myr. The duration of OAE2 is estimated to be ~820 kyr based on a high-resolution study of the significantly expanded OAE2 interval in southern Tibet, China.
  • Insofar as the Cretaceous OAEs can be represented by type localities, it is the striking outcrops of laminated black shales within the vari-colored claystones and pink and white limestones near the town of Gubbio in the Italian Apennines that are the best candidates.
  • The 1-meter thick black shale at the Cenomanian–Turonian boundary that crops out near Gubbio is termed the ‘Livello Bonarelli’ after the man who first described it in 1891.
More minor oceanic anoxic events have been proposed for other intervals in the Cretaceous (in the Valanginian, Hauterivian, Albian and ConiacianSantonian stages), but their sedimentary record, as represented by organic-rich black shales, appears more parochial, being dominantly represented in the Atlantic and neighboring areas, and some researchers relate them to particular local conditions rather than being forced by global change.

Jurassic

The only oceanic anoxic event documented from the Jurassic took place during the early Toarcian (~183 Ma). Because no DSDP (Deep Sea Drilling Project) or ODP (Ocean Drilling Program) cores have recovered black shales of this age – there being little or no Toarcian ocean crust remaining in the world ocean – the samples of black shale primarily come from outcrops on land. These outcrops, together with material from some commercial oil wells, are found on all major continents and this event seems similar in kind to the two major Cretaceous examples.

Paleozoic

The boundary between the Ordovician and Silurian periods is marked by repetitive periods of anoxia, interspersed with normal, oxic conditions. In addition, anoxic periods are found during the Silurian. These anoxic periods occurred at a time of low global temperatures (although CO
2
levels were high), in the midst of a glaciation.

Jeppsson (1990) proposes a mechanism whereby the temperature of polar waters determines the site of formation of downwelling water. If the high latitude waters are below 5 °C (41 °F), they will be dense enough to sink; as they are cool, oxygen is highly soluble in their waters, and the deep ocean will be oxygenated. If high latitude waters are warmer than 5 °C (41 °F), their density is too low for them to sink below the cooler deep waters. Therefore, thermohaline circulation can only be driven by salt-increased density, which tends to form in warm waters where evaporation is high. This warm water can dissolve less oxygen, and is produced in smaller quantities, producing a sluggish circulation with little deep water oxygen. The effect of this warm water propagates through the ocean, and reduces the amount of CO
2
that the oceans can hold in solution, which makes the oceans release large quantities of CO
2
into the atmosphere in a geologically short time (tens or thousands of years). The warm waters also initiate the release of clathrates, which further increases atmospheric temperature and basin anoxia. Similar positive feedbacks operate during cold-pole episodes, amplifying their cooling effects. 

The periods with cold poles are termed "P-episodes" (short for primo), and are characterised by bioturbated deep oceans, a humid equator and higher weathering rates, and terminated by extinction events - for example, the Ireviken and Lau events. The inverse is true for the warmer, oxic "S-episodes" (secundo), where deep ocean sediments are typically graptolitic black shales. A typical cycle of secundo-primo episodes and ensuing event typically lasts around 3 Ma.

The duration of events is so long compared to their onset because the positive feedbacks must be overwhelmed. Carbon content in the ocean-atmosphere system is affected by changes in weathering rates, which in turn is dominantly controlled by rainfall. Because this is inversely related to temperature in Silurian times, carbon is gradually drawn down during warm (high CO
2
) S-episodes, while the reverse is true during P-episodes. On top of this gradual trend is overprinted the signal of Milankovic cycles, which ultimately trigger the switch between P- and S- episodes.

These events become longer during the Devonian; the enlarging land plant biota probably acted as a large buffer to carbon dioxide concentrations.

The end-Ordovician Hirnantian event may alternatively be a result of algal blooms, caused by sudden supply of nutrients through wind-driven upwelling or an influx of nutrient-rich meltwater from melting glaciers, which by virtue of its fresh nature would also slow down oceanic circulation.

Archean and Proterozoic

It has been thought that through most of Earth's history, oceans were largely oxygen-deficient. During the Archean, euxinia was largely absent because of low availability of sulfate in the oceans, but during the Proterozoic, it would become more common.

Operator (computer programming)

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