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Saturday, October 7, 2023

Protectionism

From Wikipedia, the free encyclopedia

Protectionism, sometimes referred to as trade protectionism, is the economic policy of restricting imports from other countries through methods such as tariffs on imported goods, import quotas, and a variety of other government regulations. Proponents argue that protectionist policies shield the producers, businesses, and workers of the import-competing sector in the country from foreign competitors. Opponents argue that protectionist policies reduce trade and adversely affect consumers in general (by raising the cost of imported goods) as well as the producers and workers in export sectors, both in the country implementing protectionist policies and, in the countries, protected against.

Protectionism is advocated mainly by parties that hold economic nationalist or left-wing positions (although paleoconservatives have also supported the practice), while economically right-wing political parties generally support free trade.

There is a consensus among economists that protectionism has a negative effect on economic growth and economic welfare, while free trade and the reduction of trade barriers have a significantly positive effect on economic growth. Some scholars, such as Douglas Irwin, have implicated protectionism as the cause of some economic crises, most notably the Great Depression. Although trade liberalization can sometimes result in large and unequally distributed losses and gains, and can, in the short run, cause significant economic dislocation of workers in import-competing sectors, free trade has advantages of lowering costs of goods and services for both producers and consumers.

Protectionist policies

A variety of policies have been used to achieve protectionist goals. These include:

Tariffs and import quotas are the most common types of protectionist policies. A tariff is an excise tax levied on imported goods. Originally imposed to raise government revenue, modern tariffs are now used primarily to protect domestic producers and wage rates from lower-priced importers. An import quota is a limit on the volume of a good that may be legally imported, usually established through an import licensing regime.
Protection of technologies, patents, technical and scientific knowledge.
Restrictions on foreign direct investment, such as restrictions on the acquisition of domestic firms by foreign investors.
Administrative barriers: Countries are sometimes accused of using their various administrative rules (e.g., regarding food safety, environmental standards, electrical safety, etc.) as a way to introduce barriers to imports.
Anti-dumping legislation: "Dumping" is the practice of firms selling to export markets at lower prices than are charged in domestic markets. Supporters of anti-dumping laws argue that they prevent the import of cheaper foreign goods that would cause local firms to close down. However, in practice, anti-dumping laws are usually used to impose trade tariffs on foreign exporters.
Direct subsidies: Government subsidies (in the form of lump-sum payments or cheap loans) are sometimes given to local firms that cannot compete well against imports. These subsidies are purported to "protect" local jobs and to help local firms adjust to the world markets.
Export subsidies: Export subsidies are often used by governments to increase exports. Export subsidies have the opposite effect of export tariffs because exporters get payment, which is a percentage or proportion of the value of exported. Export subsidies increase the amount of trade, and in a country with floating exchange rates, have effects similar to import subsidies.
Exchange rate control: A government may intervene in the foreign exchange market to lower the value of its currency by selling its currency in the foreign exchange market. Doing so will raise the cost of imports and lower the cost of exports, leading to an improvement in its trade balance. However, such a policy is only effective in the short run, as it will lead to higher inflation in the country in the long run, which will, in turn, raise the real cost of exports, and reduce the relative price of imports.
International patent systems: There is an argument for viewing national patent systems as a cloak for protectionist trade policies at a national level. Two strands of this argument exist: one when patents held by one country form part of a system of exploitable relative advantage in trade negotiations against another, and a second where adhering to a worldwide system of patents confers "good citizenship" status despite 'de facto protectionism'. Peter Drahos explains that "States realized that patent systems could be used to cloak protectionist strategies. There were also reputational advantages for states to be seen to be sticking to intellectual property systems. One could attend the various revisions of the Paris and Berne conventions, participate in the cosmopolitan moral dialogue about the need to protect the fruits of authorial labor and inventive genius...knowing all the while that one's domestic intellectual property system was a handy protectionist weapon."
Political campaigns advocating domestic consumption (e.g. the "Buy American" campaign in the United States, which could be seen as an extra-legal promotion of protectionism.)
Preferential governmental spending, such as the Buy American Act, federal legislation which called upon the United States government to prefer US-made products in its purchases.

In the modern trade arena, many other initiatives besides tariffs have been called protectionist. For example, some commentators, such as Jagdish Bhagwati, see developed countries' efforts in imposing their own labor or environmental standards as protectionism. Also, the imposition of restrictive certification procedures on imports is seen in this light.

Further, others point out that free trade agreements often have protectionist provisions such as intellectual property, copyright, and patent restrictions that benefit large corporations. These provisions restrict trade in music, movies, pharmaceuticals, software, and other manufactured items to high-cost producers with quotas from low-cost producers set to zero.

History

In the 18th century, Adam Smith famously warned against the "interested sophistry" of industry, seeking to gain an advantage at the cost of the consumers. Friedrich List saw Adam Smith's views on free trade as disingenuous, believing that Smith advocated for free trade so that British industry could lock out underdeveloped foreign competition.

Some have argued that no major country has ever successfully industrialized without some form of economic protection. Economic historian Paul Bairoch wrote that "historically, free trade is the exception and protectionism the rule".

According to economic historians Douglas Irwin and Kevin O'Rourke, "shocks that emanate from brief financial crises tend to be transitory and have a little long-run effect on trade policy, whereas those that play out over longer periods (the early 1890s, early 1930s) may give rise to protectionism that is difficult to reverse. Regional wars also produce transitory shocks that have little impact on long-run trade policy, while global wars give rise to extensive government trade restrictions that can be difficult to reverse."

One study shows that sudden shifts in comparative advantage for specific countries have led some countries to become protectionist: "The shift in comparative advantage associated with the opening up of New World frontiers, and the subsequent “grain invasion” of Europe, led to higher agricultural tariffs from the late 1870s onwards, which as we have seen reversed the move toward freer trade that had characterized mid-nineteenth-century Europe. In the decades after World War II, Japan's rapid rise led to trade friction with other countries. Japan's recovery was accompanied by a sharp increase in its exports of certain product categories: cotton textiles in the 1950s, steel in the 1960s, automobiles in the 1970s, and electronics in the 1980s. In each case, the rapid expansion in Japan's exports created difficulties for its trading partners and the use of protectionism as a shock absorber."

In the United States

According to economic historian Douglas Irwin, a common myth about US trade policy is that low tariffs harmed American manufacturers in the early 19th century and then that high tariffs made the United States into a great industrial power in the late 19th century. A review by The Economist of Irwin's 2017 book Clashing over Commerce: A History of US Trade Policy states:

Political dynamics would lead people to see a link between tariffs and the economic cycle that was not there. A boom would generate enough revenue for tariffs to fall, and when the bust came pressure would build to raise them again. By the time that happened, the economy would be recovering, giving the impression that tariff cuts caused the crash and the reverse generated the recovery. 'Mr. Irwin' also attempts to debunk the idea that protectionism made America a great industrial power, a notion believed by some to offer lessons for developing countries today. As its share of global manufacturing powered from 23% in 1870 to 36% in 1913, the admittedly high tariffs of the time came with a cost, estimated at around 0.5% of GDP in the mid-1870s. In some industries, they might have sped up development by a few years. But American growth during its protectionist period was more to do with its abundant resources and openness to people and ideas.

According to Irwin, tariffs have serve three primary purposes in the United States: "to raise revenue for the government, to restrict imports and protect domestic producers from foreign competition, and to reach reciprocity agreements that reduce trade barriers." From 1790 to 1860, average tariffs increased from 20 percent to 60 percent before declining again to 20 percent. From 1861 to 1933, which Irwin characterizes as the "restriction period", the average tariffs increased to 50 percent and remained at that level for several decades. From 1934 onwards, which Irwin characterizes as the "reciprocity period", the average tariff declined substantially until it leveled off at 5 percent.

Economist Paul Bairoch documented that the United States imposed among the highest rates in the world from around the founding of the country until the World War II period, describing the United States as "the mother country and bastion of modern protectionism" since the end of the 18th century and until the post-World War II period. Alexander Hamilton, the first United States Secretary of the Treasury, was of the view, as articulated most famously in his "Report on Manufactures", that developing an industrialized economy was impossible without protectionism because import duties are necessary to shelter domestic "infant industries" until they could achieve economies of scale. The industrial takeoff of the United States occurred under protectionist policies 1816–1848 and under moderate protectionism 1846–1861, and continued under strict protectionist policies 1861–1945. In the late 19th century, higher tariffs were introduced on the grounds that they were needed to protect American wages and to protect American farmers. Between 1824 and the 1940s, the U.S. imposed much higher average tariff rates on manufactured products than did Britain or any other European country, with the exception for a period of time of Spain and Russia. Up until the end of World War II, the United States had the most protectionist economy on Earth.

The Bush administration implemented tariffs on Chinese steel in 2002; according to a 2005 review of existing research on the tariff, all studies found that the tariffs caused more harm than gains to the US economy and employment. The Obama administration implemented tariffs on Chinese tires between 2009 and 2012 as an anti-dumping measure; a 2016 study found that these tariffs had no impact on employment and wages in the US tire industry.

In 2018, EU Trade Commissioner Cecilia Malmström stated that the US was "playing a dangerous game" in applying tariffs on steel and aluminum imports from most countries and stated that she saw the Trump administration's decision to do so as both "pure protectionist" and "illegal".

The tariffs imposed by the Trump administration during the China-United States trade war led to a reduction in the United States trade deficit with China.

In Europe

Europe became increasingly protectionist during the eighteenth century. Economic historians Findlay and O'Rourke write that in "the immediate aftermath of the Napoleonic Wars, European trade policies were almost universally protectionist," with the exceptions being smaller countries such as the Netherlands and Denmark.

Europe increasingly liberalized its trade during the 19th century. Countries such as Britain, the Netherlands, Denmark, Portugal and Switzerland, and arguably Sweden and Belgium, had fully moved towards free trade prior to 1860. Economic historians see the repeal of the Corn Laws in 1846 as the decisive shift toward free trade in Britain. A 1990 study by the Harvard economic historian Jeffrey Williamson showed that the Corn Laws (which imposed restrictions and tariffs on imported grain) substantially increased the cost of living for British workers, and hampered the British manufacturing sector by reducing the disposable incomes that British workers could have spent on manufactured goods. The shift towards liberalization in Britain occurred in part due to "the influence of economists like David Ricardo", but also due to "the growing power of urban interests".

Findlay and O'Rourke characterize 1860 Cobden Chevalier treaty between France and the United Kingdom as "a decisive shift toward European free trade." This treaty was followed by numerous free trade agreements: "France and Belgium signed a treaty in 1861; a Franco-Prussian treaty was signed in 1862; Italy entered the “network of Cobden-Chevalier treaties” in 1863 (Bairoch 1989, 40); Switzerland in 1864; Sweden, Norway, Spain, the Netherlands, and the Hanseatic towns in 1865; and Austria in 1866. By 1877, less than two decades after the Cobden Chevalier treaty and three decades after British Repeal, Germany “had virtually become a free trade country” (Bairoch, 41). Average duties on manufactured products had declined to 9–12% on the Continent, a far cry from the 50% British tariffs, and numerous prohibitions elsewhere, of the immediate post-Waterloo era (Bairoch, table 3, p. 6, and table 5, p. 42)."

Some European powers did not liberalize during the 19th century, such as the Russian Empire and Austro-Hungarian Empire which remained highly protectionist. The Ottoman Empire also became increasingly protectionist. In the Ottoman Empire's case, however, it previously had liberal free trade policies during the 18th to early 19th centuries, which British prime minister Benjamin Disraeli cited as "an instance of the injury done by unrestrained competition" in the 1846 Corn Laws debate, arguing that it destroyed what had been "some of the finest manufacturers of the world" in 1812.

The countries of Western Europe began to steadily liberalize their economies after World War II and the protectionism of the interwar period.

In Canada

Since 1971 Canada has protected producers of eggs, milk, cheese, chicken, and turkey with a system of supply management. Though prices for these foods in Canada exceed global prices, the farmers and processors have had the security of a stable market to finance their operations. Doubts about the safety of bovine growth hormone, sometimes used to boost dairy production, led to hearings before the Senate of Canada, resulting in a ban in Canada. Thus, supply management of milk products is consumer protection of Canadians.

In Latin America

Most Latin American Countries became independent in the early 19th century. They revolted against their colonizers (primarily Spain, France, and Portugal) and set off on their own. Following the achievement of their independence, most of the Latin American countries adopted protectionism. They both feared that any foreign competition would stomp out their newly created state and figured that lack of outside resources would drive domestic production.

Another reason for protectionism was that Latin America was frequently attacked by outsiders. Spain, the United States of America, France, and Texas had all invaded or attempted to invade Latin America by the year 1880. It could be said that Latin America was essentially hiding in its shell trying just to survive in the 19th century.

Yet the protectionist behavior continued up until and during the World Wars. No Latin American countries got seriously involved with either side. Rather, they just kept harvesting their crops (mostly fruits, tobacco, and sugar) and increasing their exports under an ever-growing tariff rate. During World War 2, Latin America had, on average, the highest tariffs in the world.

There was a slight decrease in Latin American tariffs after World War 2, when Asia started to become very protectionist in order to rebuild yet the Latin Americans were still there. To this day, there are countries that only trade freely with other Latin American countries.

Impact

There is a broad consensus among economists that protectionism has a negative effect on economic growth and economic welfare, while free trade and the reduction of trade barriers has a positive effect on economic growth.

Protectionism is frequently criticized by economists as harming the people it is meant to help. Mainstream economists instead support free trade. The principle of comparative advantage shows that the gains from free trade outweigh any losses as free trade creates more jobs than it destroys because it allows countries to specialize in the production of goods and services in which they have a comparative advantage. Protectionism results in deadweight loss; this loss to overall welfare gives no-one any benefit, unlike in a free market, where there is no such total loss. According to economist Stephen P. Magee, the benefits of free trade outweigh the losses by as much as 100 to 1.

Living standards

A 2016 study found that "trade typically favors the poor", as they spend a greater share of their earnings on goods, as free trade reduces the costs of goods. Other research found that China's entry to the WTO benefitted US consumers, as the price of Chinese goods were substantially reduced. Harvard economist Dani Rodrik argues that while globalization and free trade does contribute to social problems, "a serious retreat into protectionism would hurt the many groups that benefit from trade and would result in the same kind of social conflicts that globalization itself generates. We have to recognize that erecting trade barriers will help in only a limited set of circumstances and that trade policy will rarely be the best response to the problems [of globalization]".

Growth

According to economic historians Findlay and O'Rourke, there is a consensus in the economics literature that protectionist policies in the interwar period "hurt the world economy overall, although there is a debate about whether the effect was large or small."

Economic historian Paul Bairoch argued that economic protection was positively correlated with economic and industrial growth during the 19th century. For example, GNP growth during Europe's "liberal period" in the middle of the century (where tariffs were at their lowest), averaged 1.7% per year, while industrial growth averaged 1.8% per year. However, during the protectionist era of the 1870s and 1890s, GNP growth averaged 2.6% per year, while industrial output grew at 3.8% per year, roughly twice as fast as it had during the liberal era of low tariffs and free trade. One study found that tariffs imposed on manufactured goods increase economic growth in developing countries, and this growth impact remains even after the tariffs are repealed. However, another study examining the tariff variation across the Australian colonies prior to Federation did not find any association between tariffs and growth.

According to Dartmouth economist Douglas Irwin, "that there is a correlation between high tariffs and growth in the late nineteenth century cannot be denied. But correlation is not causation... there is no reason for necessarily thinking that import protection was a good policy just because the economic outcome was good: the outcome could have been driven by factors completely unrelated to the tariff, or perhaps could have been even better in the absence of protection." Irwin furthermore writes that "few observers have argued outright that the high tariffs caused such growth."

According to Oxford economic historian Kevin O'Rourke, "It seems clear that protection was important for the growth of US manufacturing in the first half of the 19th century; but this does not necessarily imply that the tariff was beneficial for GDP growth. Protectionists have often pointed to German and American industrialization during this period as evidence in favor of their position, but economic growth is influenced by many factors other than trade policy, and it is important to control for these when assessing the links between tariffs and growth."

A prominent 1999 study by Jeffrey A. Frankel and David H. Romer found, contrary to free trade skeptics' claims, while controlling for relevant factors, that trade does indeed have a positive impact on growth and incomes.

Economist Arvind Panagariya criticizes the view that protectionism is good for growth. Such arguments, according to him, arise from "revisionist interpretation" of East Asian "tigers"' economic history. The Asian tigers achieved a rapid increase in per capita income without any "redistributive social programs", through free trade, which advanced Western economies took a century to achieve.

Developing world

There is broad consensus among economists that free trade helps workers in developing countries, even though they are not subject to the stringent health and labor standards of developed countries. This is because "the growth of manufacturing—and of the myriad other jobs that the new export sector creates—has a ripple effect throughout the economy" that creates competition among producers, lifting wages and living conditions. The Nobel laureates, Milton Friedman and Paul Krugman, have argued for free trade as a model for economic development. Alan Greenspan, former chair of the American Federal Reserve, has criticized protectionist proposals as leading "to an atrophy of our competitive ability. ... If the protectionist route is followed, newer, more efficient industries will have less scope to expand, and overall output and economic welfare will suffer."

Protectionists postulate that new industries may require protection from entrenched foreign competition in order to develop. Mainstream economists do concede that tariffs can in the short-term help domestic industries to develop but are contingent on the short-term nature of the protective tariffs and the ability of the government to pick the winners. The problems are that protective tariffs will not be reduced after the infant industry reaches a foothold, and that governments will not pick industries that are likely to succeed. Economists have identified a number of cases across different countries and industries where attempts to shelter infant industries failed.

Economists such as Paul Krugman have speculated that those who support protectionism ostensibly to further the interests of workers in the least developed countries are in fact being disingenuous, seeking only to protect jobs in developed countries. Additionally, workers in the least developed countries only accept jobs if they are the best on offer, as all mutually consensual exchanges must be of benefit to both sides, or else they wouldn't be entered into freely. That they accept low-paying jobs from companies in developed countries shows that their other employment prospects are worse. A letter reprinted in the May 2010 edition of Econ Journal Watch identifies a similar sentiment against protectionism from 16 British economists at the beginning of the 20th century.

Conflict

Protectionism has also been accused of being one of the major causes of war. Proponents of this theory point to the constant warfare in the 17th and 18th centuries among European countries whose governments were predominantly mercantilist and protectionist, the American Revolution, which came about ostensibly due to British tariffs and taxes, as well as the protective policies preceding both World War I and World War II. According to a slogan of Frédéric Bastiat (1801–1850), "When goods cannot cross borders, armies will."

Current world trends

Certain policies of First World governments have been criticized as protectionist, however, such as the Common Agricultural Policy in the European Union, longstanding agricultural subsidies and proposed "Buy American" provisions in economic recovery packages in the United States.

Heads of the G20 meeting in London on 2 April 2009 pledged "We will not repeat the historic mistakes of protectionism of previous eras". Adherence to this pledge is monitored by the Global Trade Alert, providing up-to-date information and informed commentary to help ensure that the G20 pledge is met by maintaining confidence in the world trading system, deterring beggar-thy-neighbor acts and preserving the contribution that exports could play in the future recovery of the world economy.

Although they were reiterating what they had already committed to, last November in Washington, 17 of these 20 countries were reported by the World Bank as having imposed trade restrictive measures since then. In its report, the World Bank says most of the world's major economies are resorting to protectionist measures as the global economic slowdown begins to bite. Economists who have examined the impact of new trade-restrictive measures using detailed bilaterally monthly trade statistics estimated that new measures taken through late 2009 were distorting global merchandise trade by 0.25% to 0.5% (about $50 billion a year).

Since then, however, President Donald Trump announced in January 2017 the U.S. was abandoning the TPP (Trans-Pacific Partnership) deal, saying, “We’re going to stop the ridiculous trade deals that have taken everybody out of our country and taken companies out of our country, and it’s going to be reversed.”

Basalt

From Wikipedia, the free encyclopedia
https://en.wikipedia.org/wiki/Basalt

Basalt
Composition
Igneous rock

Primary	Mafic: plagioclase, amphibole, and pyroxene
Secondary	Sometimes feldspathoids or olivine

Basalt (UK: /ˈbæsɔːlt, -əlt/; US: /bəˈsɔːlt, ˈbeɪsɔːlt/) is an aphanitic (fine-grained) extrusive igneous rock formed from the rapid cooling of low-viscosity lava rich in magnesium and iron (mafic lava) exposed at or very near the surface of a rocky planet or moon. More than 90% of all volcanic rock on Earth is basalt. Rapid-cooling, fine-grained basalt is chemically equivalent to slow-cooling, coarse-grained gabbro. The eruption of basalt lava is observed by geologists at about 20 volcanoes per year. Basalt is also an important rock type on other planetary bodies in the Solar System. For example, the bulk of the plains of Venus, which cover ~80% of the surface, are basaltic; the lunar maria are plains of flood-basaltic lava flows; and basalt is a common rock on the surface of Mars.

Molten basalt lava has a low viscosity due to its relatively low silica content (between 45% and 52%), resulting in rapidly moving lava flows that can spread over great areas before cooling and solidifying. Flood basalts are thick sequences of many such flows that can cover hundreds of thousands of square kilometres and constitute the most voluminous of all volcanic formations.

Basaltic magmas within Earth are thought to originate from the upper mantle. The chemistry of basalts thus provides clues to processes deep in Earth's interior.

Definition and characteristics

Basalt is field B in the TAS classification.

Vesicular basalt at Sunset Crater, Arizona. US quarter (24mm) for scale.

Basalt is composed mostly of oxides of silicon, iron, magnesium, potassium, aluminum, titanium,and calcium. Geologists classify igneous rock by its mineral content whenever possible, with the relative volume percentages of quartz (crystalline silica (SiO₂)), alkali feldspar, plagioclase, and feldspathoid (QAPF) being particularly important. An aphanitic (fine-grained) igneous rock is classified as basalt when its QAPF fraction is composed of less than 10% feldspathoid and less than 20% quartz, with plagioclase making up at least 65% of its feldspar content. This places basalt in the basalt/andesite field of the QAPF diagram. Basalt is further distinguished from andesite by its silica content of under 52%.

It is often not practical to determine the mineral composition of volcanic rocks, due to their very fine grain size, and geologists then classify the rocks chemically, with the total content of alkali metal oxides and silica (TAS) being particularly important. Basalt is then defined as volcanic rock with a content of 45% to 52% silica and not more than 5% alkali metal oxides. This places basalt in the B field of the TAS diagram. Such a composition is described as mafic.

Basalt is usually dark grey to black in colour, due to its high content of augite or other dark-coloured pyroxene minerals, but can exhibit a wide range of shading. Some basalts are quite light-coloured due to a high content of plagioclase, and these are sometimes described as leucobasalts. Lighter basalt can be difficult to distinguish from andesite, but a common rule of thumb, used in field research, is that basalt has a color index of 35 or greater.

The physical properties of basalt reflect its relatively low silica content and typically high iron and magnesium content. The average density of basalt is 2.9 g/cm³, compared with a typical density for granite of 2.7 g/cm³. The viscosity of basaltic magma is relatively low, around 10⁴ to 10⁵ cP, although this is still many orders of magnitude higher than water (which has a viscosity of about 1 cP). The viscosity of basaltic magma is similar to that of ketchup.

Basalt is often porphyritic, containing larger crystals (phenocrysts) formed prior to the extrusion that brought the magma to the surface, embedded in a finer-grained matrix. These phenocrysts usually are of augite, olivine, or a calcium-rich plagioclase, which have the highest melting temperatures of the typical minerals that can crystallize from the melt and are therefore the first to form solid crystals.

Basalt often contains vesicles, formed when dissolved gases bubble out of the magma as it decompresses during its approach to the surface, and the erupted lava then solidifies before the gases can escape. When vesicles make up a substantial fraction of the volume of the rock, the rock is described as scoria.

The term basalt is at times applied to shallow intrusive rocks with a composition typical of basalt, but rocks of this composition with a phaneritic (coarser) groundmass are more properly referred to as diabase (also called dolerite) or, when more coarse-grained (crystals over 2 mm across), as gabbro. Diabase and gabbro are thus the hypabyssal and plutonic equivalents of basalt.

Columnar basalt at Szent György Hill, Hungary

In the Hadean, Archean, and early Proterozoic eons of Earth's history, the chemistry of erupted magmas was significantly different from today's, due to immature crustal and asthenosphere differentiation. These ultramafic volcanic rocks, with silica (SiO₂) contents below 45% are usually classified as komatiites.

Etymology

The word "basalt" is ultimately derived from Late Latin basaltes, a misspelling of Latin basanites "very hard stone", which was imported from Ancient Greek βασανίτης (basanites), from βάσανος (basanos, "touchstone"). The modern petrological term basalt describing a particular composition of lava-derived rock, originates from its use by Georgius Agricola in 1546 in his work De Natura Fossilium. Agricola applied "basalt" to the volcanic black rock beneath the Bishop of Meissen's Stolpen castle, believing it to be the same as the "basaniten" described by Pliny the Elder in AD 77 in Naturalis Historiae.

Types

Large masses must cool slowly to form a polygonal joint pattern, as here at the Giant's Causeway in Northern Ireland

Columns of basalt near Bazaltove, Ukraine

On Earth, most basalt forms by decompression melting of the mantle. The high pressure in the upper mantle (due to the weight of the overlying rock) raises the melting point of mantle rock, so that almost all of the upper mantle is solid. However, mantle rock is ductile (the solid rock slowly deforms under high stress). When tectonic forces cause hot mantle rock to creep upwards, the decrease of the pressure on the ascending rock can cause its melting point to drop enough for the rock to partially melt. This produces basaltic magma.

Decompression melting can occur in a variety of tectonic settings. These include continental rifts zones, at mid-ocean ridges, above hotspots, and in back-arc basins. Basalt is also produced in subduction zones, where mantle rock rises into a mantle wedge above the descending slab. Decompression melting in this setting is enhanced by further lowering of the melting point by water vapor and other volatiles released from the slab. Each such setting produces basalt with distinctive characteristics.

Tholeiitic basalt is relatively rich in iron and poor in alkali metals and aluminium. Included in this category are most basalts of the ocean floor, most large oceanic islands, and continental flood basalts such as the Columbia River Plateau.
- High and low titanium basalt. Basalt rocks are in some cases classified after their titanium (Ti) content in High-Ti and Low-Ti varieties. High-Ti and Low-Ti basalt has been distinguished in the Paraná and Etendeka traps and the Emeishan Traps.
- Mid-ocean ridge basalt (MORB) is a tholeiitic basalt commonly erupted only at ocean ridges and is characteristically low in incompatible elements. Although all MORBs are chemically similar, geologists recognize that they vary significantly in how depleted they are in incompatible elements. Their presence in close proximity along mid-ocean ridges is interpreted as evidence for mantle inhomogeneity.
  - E-MORB, enriched MORB, is relatively undepleted in incompatible elements. E-MORB was once thought to be typical of hot spots along mid-ocean ridges, such as Iceland, but is now known to be present in many locations along mid-ocean ridges.
  - N-MORB, normal MORB, is average in its content of incompatible elements.
  - D-MORB, depleted MORB, is highly depleted in incompatible elements.
Alkali basalt is relatively rich in alkali metals. It is silica-undersaturated and may contain feldspathoids, alkali feldspar, phlogopite, and kaersutite. Augite in alkali basalts is titanium-enriched augite, and low-calcium pyroxenes are never present. They are characteristic of continental rifting and hotspot volcanism.
High-alumina basalt has greater than 17% alumina (Al₂O₃) and is intermediate in composition between tholeiitic basalt and alkali basalt. Its relatively alumina-rich composition is based on rocks without phenocrysts of plagioclase. These represent the low silica end of the calc-alkaline magma series and are characteristic of volcanic arcs above subduction zones.
Boninite is a high-magnesium form of basalt that is erupted generally in back-arc basins, distinguished by its low titanium content and trace-element composition.
Ocean island basalts include both tholeiites and alkali basalts, with tholeiite predominating early in the eruptive history of the island. These basalts are characterized by elevated concentrations of incompatible elements. This suggests that their source mantle rock has produced little magma in the past (it is undepleted).

Petrology

The mineralogy of basalt is characterized by a preponderance of calcic plagioclase feldspar and pyroxene. Olivine can also be a significant constituent. Accessory minerals present in relatively minor amounts include iron oxides and iron-titanium oxides, such as magnetite, ulvöspinel, and ilmenite. Because of the presence of such oxide minerals, basalt can acquire strong magnetic signatures as it cools, and paleomagnetic studies have made extensive use of basalt.

In tholeiitic basalt, pyroxene (augite and orthopyroxene or pigeonite) and calcium-rich plagioclase are common phenocryst minerals. Olivine may also be a phenocryst, and when present, may have rims of pigeonite. The groundmass contains interstitial quartz or tridymite or cristobalite. Olivine tholeiitic basalt has augite and orthopyroxene or pigeonite with abundant olivine, but olivine may have rims of pyroxene and is unlikely to be present in the groundmass.

Alkali basalts typically have mineral assemblages that lack orthopyroxene but contain olivine. Feldspar phenocrysts typically are labradorite to andesine in composition. Augite is rich in titanium compared to augite in tholeiitic basalt. Minerals such as alkali feldspar, leucite, nepheline, sodalite, phlogopite mica, and apatite may be present in the groundmass.

Basalt has high liquidus and solidus temperatures—values at the Earth's surface are near or above 1200 °C (liquidus) and near or below 1000 °C (solidus); these values are higher than those of other common igneous rocks.

The majority of tholeiitic basalts are formed at approximately 50–100 km depth within the mantle. Many alkali basalts may be formed at greater depths, perhaps as deep as 150–200 km. The origin of high-alumina basalt continues to be controversial, with disagreement over whether it is a primary melt or derived from other basalt types by fractionation.

Geochemistry

Relative to most common igneous rocks, basalt compositions are rich in MgO and CaO and low in SiO₂ and the alkali oxides, i.e., Na₂O + K₂O, consistent with their TAS classification. Basalt contains more silica than picrobasalt and most basanites and tephrites but less than basaltic andesite. Basalt has a lower total content of alkali oxides than trachybasalt and most basanites and tephrites.

Basalt generally has a composition of 45–52 wt% SiO₂, 2–5 wt% total alkalis, 0.5–2.0 wt% TiO₂, 5–14 wt% FeO and 14 wt% or more Al₂O₃. Contents of CaO are commonly near 10 wt%, those of MgO commonly in the range 5 to 12 wt%.

High-alumina basalts have aluminium contents of 17–19 wt% Al₂O₃; boninites have magnesium (MgO) contents of up to 15 percent. Rare feldspathoid-rich mafic rocks, akin to alkali basalts, may have Na₂O + K₂O contents of 12% or more.

The abundances of the lanthanide or rare-earth elements (REE) can be a useful diagnostic tool to help explain the history of mineral crystallisation as the melt cooled. In particular, the relative abundance of europium compared to the other REE is often markedly higher or lower, and called the europium anomaly. It arises because Eu²⁺ can substitute for Ca²⁺ in plagioclase feldspar, unlike any of the other lanthanides, which tend to only form ³⁺ cations.

Mid-ocean ridge basalts (MORB) and their intrusive equivalents, gabbros, are the characteristic igneous rocks formed at mid-ocean ridges. They are tholeiitic basalts particularly low in total alkalis and in incompatible trace elements, and they have relatively flat REE patterns normalized to mantle or chondrite values. In contrast, alkali basalts have normalized patterns highly enriched in the light REE, and with greater abundances of the REE and of other incompatible elements. Because MORB basalt is considered a key to understanding plate tectonics, its compositions have been much studied. Although MORB compositions are distinctive relative to average compositions of basalts erupted in other environments, they are not uniform. For instance, compositions change with position along the Mid-Atlantic Ridge, and the compositions also define different ranges in different ocean basins. Mid-ocean ridge basalts have been subdivided into varieties such as normal (NMORB) and those slightly more enriched in incompatible elements (EMORB).

Isotope ratios of elements such as strontium, neodymium, lead, hafnium, and osmium in basalts have been much studied to learn about the evolution of the Earth's mantle. Isotopic ratios of noble gases, such as ³He/⁴He, are also of great value: for instance, ratios for basalts range from 6 to 10 for mid-ocean ridge tholeiitic basalt (normalized to atmospheric values), but to 15–24 and more for ocean-island basalts thought to be derived from mantle plumes.

Source rocks for the partial melts that produce basaltic magma probably include both peridotite and pyroxenite.

Morphology and textures

The shape, structure and texture of a basalt is diagnostic of how and where it erupted—for example, whether into the sea, in an explosive cinder eruption or as creeping pāhoehoe lava flows, the classic image of Hawaiian basalt eruptions.

Subaerial eruptions

Basalt that erupts under open air (that is, subaerially) forms three distinct types of lava or volcanic deposits: scoria; ash or cinder (breccia); and lava flows.

Basalt in the tops of subaerial lava flows and cinder cones will often be highly vesiculated, imparting a lightweight "frothy" texture to the rock. Basaltic cinders are often red, coloured by oxidized iron from weathered iron-rich minerals such as pyroxene.

ʻAʻā types of blocky cinder and breccia flows of thick, viscous basaltic lava are common in Hawaiʻi. Pāhoehoe is a highly fluid, hot form of basalt which tends to form thin aprons of molten lava which fill up hollows and sometimes forms lava lakes. Lava tubes are common features of pāhoehoe eruptions.

Basaltic tuff or pyroclastic rocks are less common than basaltic lava flows. Usually basalt is too hot and fluid to build up sufficient pressure to form explosive lava eruptions but occasionally this will happen by trapping of the lava within the volcanic throat and buildup of volcanic gases. Hawaiʻi's Mauna Loa volcano erupted in this way in the 19th century, as did Mount Tarawera, New Zealand in its violent 1886 eruption. Maar volcanoes are typical of small basalt tuffs, formed by explosive eruption of basalt through the crust, forming an apron of mixed basalt and wall rock breccia and a fan of basalt tuff further out from the volcano.

Amygdaloidal structure is common in relict vesicles and beautifully crystallized species of zeolites, quartz or calcite are frequently found.

Columnar basalt

During the cooling of a thick lava flow, contractional joints or fractures form. If a flow cools relatively rapidly, significant contraction forces build up. While a flow can shrink in the vertical dimension without fracturing, it cannot easily accommodate shrinking in the horizontal direction unless cracks form; the extensive fracture network that develops results in the formation of columns. These structures are predominantly hexagonal in cross-section, but polygons with three to twelve or more sides can be observed. The size of the columns depends loosely on the rate of cooling; very rapid cooling may result in very small (<1 cm diameter) columns, while slow cooling is more likely to produce large columns.

Submarine eruptions

The character of submarine basalt eruptions is largely determined by depth of water, since increased pressure restricts the release of volatile gases and results in effusive eruptions. It has been estimated that at depths greater than 500 metres (1,600 ft), explosive activity associated with basaltic magma is suppressed. Above this depth, submarine eruptions are often explosive, tending to produce pyroclastic rock rather than basalt flows. These eruptions, described as Surtseyan, are characterised by large quantities of steam and gas and the creation of large amounts of pumice.

Pillow basalts

When basalt erupts underwater or flows into the sea, contact with the water quenches the surface and the lava forms a distinctive pillow shape, through which the hot lava breaks to form another pillow. This "pillow" texture is very common in underwater basaltic flows and is diagnostic of an underwater eruption environment when found in ancient rocks. Pillows typically consist of a fine-grained core with a glassy crust and have radial jointing. The size of individual pillows varies from 10 cm up to several metres.

When pāhoehoe lava enters the sea it usually forms pillow basalts. However, when ʻaʻā enters the ocean it forms a littoral cone, a small cone-shaped accumulation of tuffaceous debris formed when the blocky ʻaʻā lava enters the water and explodes from built-up steam.

The island of Surtsey in the Atlantic Ocean is a basalt volcano which breached the ocean surface in 1963. The initial phase of Surtsey's eruption was highly explosive, as the magma was quite fluid, causing the rock to be blown apart by the boiling steam to form a tuff and cinder cone. This has subsequently moved to a typical pāhoehoe-type behaviour.

Volcanic glass may be present, particularly as rinds on rapidly chilled surfaces of lava flows, and is commonly (but not exclusively) associated with underwater eruptions.

Pillow basalt is also produced by some subglacial volcanic eruptions.

Distribution

Earth

Basalt is the most common volcanic rock type on Earth, making up over 90% of all volcanic rock on the planet. The crustal portions of oceanic tectonic plates are composed predominantly of basalt, produced from upwelling mantle below the ocean ridges. Basalt is also the principal volcanic rock in many oceanic islands, including the islands of Hawaiʻi, the Faroe Islands, and Réunion. The eruption of basalt lava is observed by geologists at about 20 volcanoes per year.

Basalt is the rock most typical of large igneous provinces. These include continental flood basalts, the most voluminous basalts found on land. Examples of continental flood basalts included the Deccan Traps in India, the Chilcotin Group in British Columbia, Canada, the Paraná Traps in Brazil, the Siberian Traps in Russia, the Karoo flood basalt province in South Africa, and the Columbia River Plateau of Washington and Oregon.

Basalt also is common around volcanic arcs, specially those on thin crust.

Ancient Precambrian basalts are usually only found in fold and thrust belts, and are often heavily metamorphosed. These are known as greenstone belts, because low-grade metamorphism of basalt produces chlorite, actinolite, epidote and other green minerals.

Other bodies in the Solar System

As well as forming large parts of the Earth's crust, basalt also occurs in other parts of the Solar System. Basalt commonly erupts on Io (the third largest moon of Jupiter), and has also formed on the Moon, Mars, Venus, and the asteroid Vesta.

The Moon

The dark areas visible on Earth's moon, the lunar maria, are plains of flood basaltic lava flows. These rocks were sampled both by the crewed American Apollo program and the robotic Russian Luna program, and are represented among the lunar meteorites.

Lunar basalts differ from their Earth counterparts principally in their high iron contents, which typically range from about 17 to 22 wt% FeO. They also possess a wide range of titanium concentrations (present in the mineral ilmenite), ranging from less than 1 wt% TiO₂, to about 13 wt.%. Traditionally, lunar basalts have been classified according to their titanium content, with classes being named high-Ti, low-Ti, and very-low-Ti. Nevertheless, global geochemical maps of titanium obtained from the Clementine mission demonstrate that the lunar maria possess a continuum of titanium concentrations, and that the highest concentrations are the least abundant.

Lunar basalts show exotic textures and mineralogy, particularly shock metamorphism, lack of the oxidation typical of terrestrial basalts, and a complete lack of hydration. Most of the Moon's basalts erupted between about 3 and 3.5 billion years ago, but the oldest samples are 4.2 billion years old, and the youngest flows, based on the age dating method of crater counting, are estimated to have erupted only 1.2 billion years ago.

Venus

From 1972 to 1985, five Venera and two VEGA landers successfully reached the surface of Venus and carried out geochemical measurements using X-ray fluorescence and gamma-ray analysis. These returned results consistent with the rock at the landing sites being basalts, including both tholeiitic and highly alkaline basalts. The landers are thought to have landed on plains whose radar signature is that of basaltic lava flows. These constitute about 80% of the surface of Venus. Some locations show high reflectivity consistent with unweathered basalt, indicating basaltic volcanism within the last 2.5 million years.

Mars

Basalt is also a common rock on the surface of Mars, as determined by data sent back from the planet's surface, and by Martian meteorites.

Vesta

Analysis of Hubble Space Telescope images of Vesta suggests this asteroid has a basaltic crust covered with a brecciated regolith derived from the crust. Evidence from Earth-based telescopes and the Dawn mission suggest that Vesta is the source of the HED meteorites, which have basaltic characteristics. Vesta is the main contributor to the inventory of basaltic asteroids of the main Asteroid Belt.

Io

Lava flows represent a major volcanic terrain on Io. Analysis of the Voyager images led scientists to believe that these flows were composed mostly of various compounds of molten sulfur. However, subsequent Earth-based infrared studies and measurements from the Galileo spacecraft indicate that these flows are composed of basaltic lava with mafic to ultramafic compositions. This conclusion is based on temperature measurements of Io's "hotspots", or thermal-emission locations, which suggest temperatures of at least 1,300 K and some as high as 1,600 K. Initial estimates suggesting eruption temperatures approaching 2,000 K have since proven to be overestimates because the wrong thermal models were used to model the temperatures.

Alteration of basalt

Weathering

Compared to granitic rocks exposed at the Earth's surface, basalt outcrops weather relatively rapidly. This reflects their content of minerals that crystallized at higher temperatures and in an environment poorer in water vapor than granite. These minerals are less stable in the colder, wetter environment at the Earth's surface. The finer grain size of basalt and the volcanic glass sometimes found between the grains also hasten weathering. The high iron content of basalt causes weathered surfaces in humid climates to accumulate a thick crust of hematite or other iron oxides and hydroxides, staining the rock a brown to rust-red colour.Because of the low potassium content of most basalts, weathering converts the basalt to calcium-rich clay (montmorillonite) rather than potassium-rich clay (illite). Further weathering, particularly in tropical climates, converts the montmorillonite to kaolinite or gibbsite. This produces the distinctive tropical soil known as laterite. The ultimate weathering product is bauxite, the principal ore of aluminium.

Chemical weathering also releases readily water-soluble cations such as calcium, sodium and magnesium, which give basaltic areas a strong buffer capacity against acidification. Calcium released by basalts binds CO₂ from the atmosphere forming CaCO₃ acting thus as a CO₂ trap.

Metamorphism

Intense heat or great pressure transforms basalt into its metamorphic rock equivalents. Depending on the temperature and pressure of metamorphism, these may include greenschist, amphibolite, or eclogite. Basalts are important rocks within metamorphic regions because they can provide vital information on the conditions of metamorphism that have affected the region.

Metamorphosed basalts are important hosts for a variety of hydrothermal ores, including deposits of gold, copper and volcanogenic massive sulfides.

Life on basaltic rocks

The common corrosion features of underwater volcanic basalt suggest that microbial activity may play a significant role in the chemical exchange between basaltic rocks and seawater. The significant amounts of reduced iron, Fe(II), and manganese, Mn(II), present in basaltic rocks provide potential energy sources for bacteria. Some Fe(II)-oxidizing bacteria cultured from iron-sulfide surfaces are also able to grow with basaltic rock as a source of Fe(II). Fe- and Mn- oxidizing bacteria have been cultured from weathered submarine basalts of Kamaʻehuakanaloa Seamount (formerly Loihi). The impact of bacteria on altering the chemical composition of basaltic glass (and thus, the oceanic crust) and seawater suggest that these interactions may lead to an application of hydrothermal vents to the origin of life.

Uses

Basalt is used in construction (e.g. as building blocks or in the groundwork), making cobblestones (from columnar basalt) and in making statues. Heating and extruding basalt yields stone wool, which has potential to be an excellent thermal insulator.

Carbon sequestration in basalt has been studied as a means of removing carbon dioxide, produced by human industrialization, from the atmosphere. Underwater basalt deposits, scattered in seas around the globe, have the added benefit of the water serving as a barrier to the re-release of CO₂ into the atmosphere.

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