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The main feature of the Atlantic Ocean's seabed is a large underwater mountain chain called the Mid-Atlantic Ridge. It runs from north to south under the Ocean. This is at the boundary of four tectonic plates: Eurasian, North American, South American and African. The ridge extends from Iceland in the north to about 58° south.
The salinity of the surface waters of the open ocean ranges from 3337 parts per thousand and varies with latitude and season.
Mercury
Mercury may mean:
Mercury (element)
Mercury, also known as quicksilver or hydrargyrum, is a chemical element. Its symbol on the periodic table is Hg, and its atomic number is 80. Its atomic mass is 200.59.
The symbol "Hg" stands for its Latinized Greek name "hydrargyrum", meaning watery or liquid silver.
No one has the credit for finding mercury. It was known in ancient times. Mercury was found in Egyptian tombs that are from 2000 BC.
Chinese people also knew it from long ago. In China and Tibet, people thought using mercury would make them live longer and have better health. One of China's emperors, Qín Shǐ Huáng Dì, is said to have been buried in a tomb with rivers of flowing mercury. He died from drinking a mixture of mercury and powdered jade because he wanted to live forever. However, this only made him die of liver failure, poisoning, and brain death. The ancient Greeks used mercury in ointments. The Egyptians and the Romans used it in cosmetics. These cosmetics sometimes hurt and made faces uglier.
Mercury is a silvery-white liquid post-transition metal. The reason for mercury being a liquid is complex. It is heavy; a chunk of iron can float on mercury. Compared to other metals, it does not conduct heat well. However, it conducts electricity fairly well. Mercury is the only metal with a known melting point (−38.83 °C) lower than caesium. Mercury is one of the two elements that are liquids at standard temperature and pressure. Bromine is the other one.
Mercury may be seen as a transition metal, but it is normally seen as a post-transition metal. It is in Group 12 of the periodic table. Mercury has seven stable (nonradioactive) isotopes. Hg is the most common isotope. Mercury makes a blue to ultraviolet color in a tube when a spark is passed through it. The ultraviolet light can kill germs or light fluorescent lamps.
Mercury is an unreactive metal. It does not corrode in air unless hydrogen sulfide is also there, similar to silver. Mercury can oxidize to mercury(II) oxide when heated in air. If it is heated further, it decomposes into mercury and oxygen again. It does not dissolve in ordinary acids, but can dissolve in oxidizing acids to make mercury salts. It can make amalgams when mixed with most metals, like aluminium, gold, and zinc. Iron, tantalum, tungsten, and platinum do not make amalgams with mercury. Iron flasks were used to trade mercury because of this.
Mercury can dissolve large amounts of aluminium metal, making it dangerous to transport in aluminium containers. The thin layer of oxide on aluminium stops it from amalgamating (making an amalgam with) aluminium, but the oxide coating can be damaged to expose the metal. Then the aluminium metal is dissolved and oxidizes to aluminium oxide. The aluminium oxide forms a solid and releases the mercury, which amalgamates more aluminium. This process keeps repeating until a large amount of aluminium is dissolved.
Mercury forms chemical compounds in 2 oxidation states: +1 and +2. Mercury(I) compounds are weak oxidizing agents and weak reducing agents. Most of them are colorless. They easily disproportionate to mercury(II) compounds and mercury metal. They react with oxygen in the air to make mercury(II) compounds. Many mercury(I) compounds do not dissolve in water. Mercury(I) chloride is one of the most common mercury(I) compounds. Mercury(II) compounds are strong oxidizing agents and very corrosive. Mercury(II) compounds are red, yellow, or colorless. Mercury(II) oxide and mercury(II) chloride are the most common mercury(II) compounds in the laboratory.
One thing they have in common is that they are all toxic. The soluble ones are more toxic than the insoluble ones.
Also known as mercurous compounds, these are weak reducing agents and weak oxidizing agents. Most of them do not dissolve in water, making them less toxic than mercury(II) compounds. Most of them are colorless or yellow.
Also known as mercuric compounds, these are strong oxidizing agents. Most of them dissolve in water, making them very toxic. They are colorless or red.
These contain mercury reacted with a organic molecule. They are even more toxic than other mercury compounds since they get absorbed very easily.
Mercury is a rare metal. It is about as common as silver. Mercury is not expensive like silver because the mercury is very easy to get from the places where it is found. Mercury can be found in elemental (liquid) form in nature, but this is not common. Mercury as an element is the only liquid that is recognized as a mineral by the International Mineralogical Association. It is most often found in the form of cinnabar, a mercury(II) sulfide mineral. The biggest deposits of cinnabar used to be found in Spain, but now are found in China. It also occurs in other minerals like calomel, a mercury(I) chloride mineral.
China and Kyrgyzstan are the two main makers of mercury. Mines in Italy, the United States, and Mexico have been closed. China is opening more mines because the European Union wants to use fluorescent lights, which need mercury.
Mercury is made by roasting cinnabar in a furnace. The sulfide is oxidized to sulfur dioxide, leaving mercury behind.
Mercury has been used in dental fillings until it was replaced with safer materials. They are an amalgam of mercury with another element. An organic mercury compound called thiomersal is used to preserve vaccines. Merbromin, another organic mercury compound, is used as an antiseptic. It has been banned in some countries like the US.
Mercury(I) chloride (also known as calomel or mercurous chloride) has been used as a diuretic, skin disinfectant, and laxative. Together with other mercury compounds, Mercury(II) chloride (also known as mercuric chloride or corrosive sublimate) was used to treat syphilis. The problem with this was that mercury(II) chloride is very toxic. Sometimes the symptoms of its toxicity were confused with those of the syphilis it was believed to treat. It is also used as a disinfectant. , a pill or syrup in which mercury is the main ingredient, was prescribed throughout the 1800s for different conditions such as constipation, depression, child-bearing and toothaches. In the early 20th century, mercury was given to children once a year as a laxative and dewormer. Teething powders for infants also had it in them.
Since the 1930s some vaccines have contained the preservative thiomersal. In the body, this is changed to ethylmercury. At first it was thought that this mercury-based preservative can cause or trigger autism in children, but scientific studies could not show such a link. Because of this, thiomersal has been removed from most U.S. vaccines recommended for children six years of age and under. There are certain exceptions to this rule for influenza vaccines. In some cases, vaccines may still have very small amounts of thiomersal in them.
Cinnabar is still an important component of traditional Chinese, Tibetan, and Ayurvedic medicine. Certain countries do not allow the use of mercury or its compounds in drugs. For this reason, cinnabar has recently been replaced with less toxic products.
Today, the use of mercury in medicine has greatly declined in all respects, especially in developed countries. Thermometers and blood pressure devices using mercury were invented in the early 18th and late 19th centuries, respectively. Now their use is declining and has been banned in some countries, states and medical institutions. In 2002, the U.S. Senate passed legislation to phase out the sale of non-prescription mercury thermometers. In 2003, Washington and Maine became the first states to ban mercury blood pressure devices. Mercury compounds are in some over-the-counter drugs, including topical antiseptics, stimulant laxatives, diaper rash ointment, eye drops, and nasal sprays. The FDA has “inadequate data to establish general recognition of the safety and effectiveness” of the mercury in these products. Mercury is still used in some diuretics, although other things can be used for most therapeutic uses.
Mercury is also used:
In 2017 the worldwide use of mercury was less than half of what it was in 1980.
Mercury is liquid at room temperature, and fumes of mercury are very poisonous. Ingested elemental mercury is less dangerous. The biggest problems are organic mercury compounds which are eaten with food. As with other heavy metals, inorganic compounds such as mercury(II) nitrate are also highly toxic by ingestion (eating) or inhalation (breathing in) of the dust. Mercury can cause both chronic and acute poisoning.
In the year 1810, over 200 people died of mercury poisoning on the ship "Triumph" because a barrel of mercury had leaked.
Mercury is extremely poisonous and has to be used carefully. When mercury is spilled, there are special ways to clean it up. Smaller drops should be combined to a larger drop on hard surfaces to be removed more easily (for example, being pushed into a bag that can be thrown away). Vacuum cleaners and brooms should not be used. This is because they can spread mercury even more. Afterwards, elements such as sulfur or zinc powder should be sprinkled over the place, then collected and cleaned away. It is not easy to clean mercury entirely off clothing, so it is better not to use them anymore. Breathing in mercury vapor is also very dangerous.
Africa
Africa is the second largest continent in the world. It makes up about a fifth of the world's land. It is surrounded by large areas of water. There are 54 fully recognised and independent countries in Africa, and 14.7% (1.216 billion) of the world's population lives there. It is thought to be the continent where the first humans evolved.
The history of Africa begins from the first modern human beings and leads to its present difficult state as a politically developing continent.
Africa's ancient historic period includes the rise of Egyptian civilization, the further development of societies outside the Nile River Valley and the interaction between them and civilizations outside of Africa. In the late 7th century North and East Africa were heavily influenced by the spread of Islam. That led to the appearance of new cultures such as those of the Swahili people, and the Mali Empire, whose king, Musa Keita I, became one of the richest and most influential people of the early 14th century. This also led to an increase in the slave trade that had a very bad influence for the development of the whole continent until the 19th century.
Slavery has long been practiced in Africa, just like the rest of the world. But two new slave trades would create a much bigger and more violent version of slavery.
Between the seventh and twentieth centuries, the Arab slave trade took 18 million slaves from Africa via trans-Saharan and Indian Ocean routes. Between the fifteenth and the nineteenth centuries (500 years), the Atlantic slave trade took an estimated 7–12 million slaves to the Americas. While some Africans collaborated with European and Asian slave traders, many were very opposed to it and avoided, protested, or violently fought slavery.
Africans who had been captured and sent to the French colony of Saint Domingue on slave ships would play an important role in ending the Atlantic slave trade. They began the Haitian Revolution, which created Haiti, the first country to permanently ban slavery. After this revolution, European empires began to reduce slave trading and abolitionism became more popular. Between 1808 and 1860, the British Navy captured approximately 1,600 slave ships and freed 150,000 Africans who were aboard.
In the late nineteenth century, the European powers occupied much of the continent, creating many colonial and dependent territories. They left only three fully independent states: Darwiish State, (also spelled Daraawiish State), Ethiopia (known to Europeans as "Abyssinia"), and Liberia. Taleh, then capital of Darawiish, was the only African capital city which survived the scramble for Africa.
Egypt and Sudan were never formally incorporated into any European colonial empire. However, after the British occupation of 1882, Egypt was effectively under British administration until 1922.
African independence movements had their first success in 1951 when Libya became the first former colony to become independent. Modern African history has been full of revolutions and wars as well as the growth of modern African economies and democratization across the continent.
A civil war in the Democratic Republic of the Congo (formerly Zaire) began in 1998. Neighbouring African countries have become involved. Since the conflict began, 5,5 million are estimated to have died because of it.
Political associations such as the African Union offer hope for greater co-operation and peace between the continent's many countries.
From north to south, Africa has most types of climate. In sequence from the north:
Running north-east to the south is the East African Great Rift Valley. This has mountains, volcanoes, deep rifts and valleys, rivers and lakes.
In fact Africa has examples of most of the Earth's climate types.
Much of North Africa is dry and hot: it is dominated by the Sahara Desert and does not receive much rain. In Saharan Africa there are few rivers or other water sources. Underground water sources, such as springs are very important in the desert. These often form oases. An oasis is an area of vegetation (plant life) surrounded by desert.
In that part of the world the wind comes mostly from the east. That does bring rain, but the Himalayas and the Tibetan Plateau blocks the monsoon rain and prevents it getting to North Africa. Also, the Atlas Mountains near the north coast
of Africa prevent rain from coming in from the north. That is another rain shadow.
These two rain shadows are mainly responsible for the Sahara desert.
Conditions and winds are different further south, where huge amounts of rain falls near the equator. The equator runs across the middle of Africa (see red line drawn on map). That means much of Africa is between the two tropics:
Africa has a lot of wildlife. There are many types of animals there. In particular, it is now the only continent that has many native species of large mammals. Some of them occur in very large numbers. There are antelope, buffalo, zebra, cheetah, elephant, lion, giraffe, rhinoceros, apes, hyaena, and a lot more. Over 2,000 types of fish live in African lakes and rivers.
The African Union (AU) is an international organisation. It aims to transform the African Economic Community, a federated commonwealth, into a state under established international conventions. The African Union has a parliamentary government, known as the African Union Government, consisting of legislative, judicial and executive organs. It is led by the African Union President and Head of State, who is also the President of the Pan African Parliament. A person becomes President of the AU by being elected to the PAP, and then gaining majority support in the PAP.
Extensive human rights abuses still occur in several parts of Africa, often under the oversight of the state. Most of such violations occur for political reasons, often as a side effect of civil war. Countries where major human rights violations have been reported in recent times include Uganda, Sierra Leone, Liberia, Sudan, Zimbabwe, and Côte d'Ivoire. There are 54 UN member states in Africa.
People who come from Africa are called Africans. People in the north are called North Africans and people in the south are called South Africans. Languages in eastern Africa include Swahili, Oromo and Amharic. Languages in western Africa include Lingala, Igbo and Fulani. The most populated country in Africa is Nigeria.
Countries with significant African descendents outside Africa:
Butter
Butter is a dairy food. It is made by moving the cream from whole milk for a long time. The fat in the milk separates from the liquid. The fat is butter.
Butter is often put on on bread, as a main ingredient in biscuits, as a shortening agent in some baking and cooking recipes, and for frying foods.
Often, butter is made from cows' milk, butter can also be made from the milk of other mammals, like sheep, goats, bison, and yaks. Salt, flavorings and preservatives are sometimes added to butter.
Many people use butter in their foods instead of oil.
It has a melting point of about .
Cultured butter is a butter made from fermented cream. Sweet cream butter is butter made from pasteurized fresh cream. Raw cream butter is butter made from fresh or cultured unpasteurized cream.
Cold War
The Cold War was the tense relationship between the United States (and its allies), and the Soviet Union (the USSR and its allies) between the end of World War II and the fall of the Soviet Union. It is called the "Cold" War because the US and the USSR never actually fought each other directly. Instead, they opposed each other in conflicts known as proxy wars, where each country chose a side to support.
Most of the countries on one side were allied in NATO whose most powerful country was the United States. Most of the countries on the other side were allied in the Warsaw Pact whose most powerful country was the Soviet Union.
The Western Bloc was the name of the capitalist countries led by the United States. The North Atlantic Treaty Organization (NATO) is an alliance created in 1949 which included the US, United Kingdom, France, West Germany, Canada, Netherlands, Belgium, Luxembourg, Spain, Portugal, Italy, Norway, Iceland (until 1981), Denmark, Mexico (until 1990), Greece, and Turkey. Other countries allied with the Western Bloc include Israel, Brazil, South Korea, Kenya (1960-1991), Bangladesh (1964-1968), Pakistan, North Yemen, Malaysia, Saudi Arabia, Philippines, South Africa, Australia and New Zealand.
The Eastern Bloc was the group of socialist countries led by the Soviet Union (USSR). The Warsaw Pact was an alliance created in 1955 which included the USSR, Albania, Bulgaria, Czechoslovakia, East Germany, Hungary (until 1976), Poland, and Romania. Other countries allied with the Eastern Bloc included Angola (1975–1991), Cuba, Bolivia, Cambodia (1977–1979), South Yemen, Tunisia, Nepal, Bhutan, Libya (1974–1991), Mongolia (1976–1988), Jamaica, North Korea, China and Laos (1975–1991).
In February 1917, Tsar (King) Nicholas II of the Russian Empire was overthrown because people were unhappy with their living conditions, especially during World War I. The new government in Russia was a democratic socialist government. Unfortunately, it was ineffective, and people were still unhappy. In November 1917, a communist group called the Bolsheviks led by Vladimir Lenin overthrew the new government. They were supported by groups of workers called Soviets. The Bolsheviks created a new communist government called the Russian Soviet Federation Socialist Republic (called simply Soviet Russia or the Russian SFSR).
However, not everyone supported the communists. Many countries that had been a part of the Russian Empire had left, such as Latvia, Lithuania, Estonia, and Belarus. The Russian Civil War began, with the Russian SFSR's "Red Army" fighting against the "White Army", the group of all Russians against the communists. The White Army was not very united or organized. The Allied Powers of World War I, such as the United States, United Kingdom, and France, invaded Russia to support the White Army. Soviet Russia eventually won the war in 1922, and established the Union of Soviet Socialist Republics (Soviet Union), along with the newly formed Socialist Republics of Ukraine, Armenia, Azerbaijan and Georgia.
The start of the Cold War in 1947 was due to a belief that all governments would become either communist or capitalist. The Western allies feared that the Soviet Union would use force to expand its influence in Europe, and was especially concerned that Soviet agents had obtained information on making the Atom Bomb after the war.
Both groups of nations had opposed Nazi Germany. The Soviet Union had sporadically co-operated with Germany and shared in the division of Poland in 1939, but Germany turned against the Soviet Union in June 1941 with Operation Barbarossa.
After Second World War, Germany was left in ruins. The victorious Allies that occupied it split it into four parts. In the western half of Germany, one part was given to the United States, one to the United Kingdom, and one to France. The Eastern half was occupied by the USSR. The city of Berlin was also split among the four countries, even though it was entirely within the Eastern half.
The Federal Republic of Germany ("Bundesrepublik Deutschland" or BRD), or West Germany, was recognized by the Western allies in June 1949. It was a capitalist democracy. West Berlin was considered a part of the country. The USSR named their section of Germany the German Democratic Republic ("Deutsche Demokratische Republik" or DDR), or East Germany, later in 1949. It was a communist dictatorship.
From April 1948 to May 1949, the Soviets blockaded West Berlin to prevent the city from using West Germany's currency. The United States and its allies supplied the city through airplanes until September 1949 in what became known as the Berlin Airlift. Many East Germans wanted to live in West Germany due to its greater quality of life and political freedoms. Thus, in 1961, the East German government built the Berlin Wall, dividing the two halves of the city. It was heavily guarded to prevent people from escaping to the West. It was considered a symbol of the Cold War and the Iron Curtain that divided Europe.
Espionage, "spying" has been around for a long time, and was very important during the Cold War. After its successful nuclear espionage in the Manhattan Project the USSR built up its spy organs, especially the KGB. The Central Intelligence Agency led US efforts abroad, while the FBI did counterespionage. Catching foreign spies was among KGB functions, as well as fighting domestic subversion.
In the USSR, the dictator Joseph Stalin died and Nikolai Bulganin and Nikita Khrushchev (1953) took his place. Khrushchev later took sole control of the USSR. Khrushchev's Secret Speech marked a period of de-Stalinization and Khrushchev tried to undo many of the things Stalin did (such as the Gulag prison camps and 'cult of personality').
In the United States, there was a "Red Scare", and when the USSR detonated its own atom bomb, there was a great deal of political fallout. Famous people, in many fields who had been Communist sympathizers in the past lost their positions. Many actors were 'blacklisted' and were not hired to act in movies, ruining their careers. Senator Joseph McCarthy accused some important Americans of being communists, including some high government officials.
The 1950s were the beginning of the space race between the United States and USSR. It began with the USSR putting the Sputnik 1 satellite into orbit around the Earth, making the Soviet Union the first country in space. The United States responded by starting NASA, and soon sent up its own satellites. The Soviet Union also sent the first man (Yuri Gagarin) into Earth orbit, claiming that this proved communism was the better ideology.
In the 1950s, the United States (under president Dwight Eisenhower) created a policy called "New Look," cutting defense spending and increasing the number of nuclear weapons as a deterrent in order to prevent the Soviet Union from attacking the USA. The USSR also increased their nuclear force, resulting in mutual assured destruction.
In the Suez Crisis of 1956, the Cold War alliances were broken for the first time with the Soviet Union and United States favoring one side, and Britain and France the other. Later that year, the Western allies did not interfere when Soviet troops suppressed an anti-communist revolution in Hungary.
United States Vice-President Richard Nixon engaged in several talks with Nikita Khrushchev during the 1950s. One of these was the 1959 "Kitchen Debate" in a model kitchen in Moscow. These debates highlighted the political and economic differences between the USA and the USSR. The following year, the United States U-2 spy plane crashed in the Soviet Union. Tensions between the two countries increased.
After the United States tried to invade Cuba and failed (Bay of Pigs), the Soviet Union attempted to supply Cuba with nuclear missiles. These missiles in Cuba would have allowed the Soviet Union to effectively target almost the entire United States. In response the United States sent a large number of ships to blockade Cuba thus preventing the Soviet Union from delivering these weapons. The United States and Soviet Union came to agreement that the Soviet Union would no longer give nuclear weapons to Cuba as long as the United States does not invade Cuba again. This was the highest period of tension during the Cold War and it was the closest the world came to a nuclear war, with possible global conflict to follow.
After the agreement that ended the Cuban Missile Crisis, relations between the two sides eased up. Several treaties, designed to reduce the number of nuclear weapons, were signed. In 1964, the USA under the Lyndon Johnson administration invaded North Vietnam, which resulted in a humiliating defeat for the USA and South Vietnam in 1975. During this period of Détente, the United States began building a good relationship with the People's Republic of China, a previous ally of the Soviet Union.
The policy of détente ended in 1981, when the U.S. president Ronald Reagan ordered a massive military massing to challenge the Soviet Union's influence around the world. The United States began to support anti-communists all over the world with money and weapons. The idea was to help them overthrow their communist governments.
The Soviet Union had a slow economy during this decade because military spending was at an all-time high. They tried to keep up with the United States in military spending, but could not. In the Soviet war in Afghanistan starting in 1979, the Soviet Union had a difficult time fighting resistance groups, some of them armed and trained by the United States. The Soviet Union's failed invasion of Afghanistan is often compared to the United States' failure during the Vietnam War.
In the late 1980s the new Soviet President Mikhail Gorbachev made an effort to make an ally of the United States to fix world problems caused by the war, with the ultimate aim of eliminating nuclear weapons completely. However, this did not take place because the President of the United States, Ronald Reagan, insisted on having a nuclear missile defense system. The people of the Soviet Union were divided on their feelings about this. Some wanted President Gorbachev to fight harder to eliminate nuclear weapons, while others did not want him to be talking to the United States at all. These mixed feelings created an atmosphere of political in-fighting, and the people were no longer united behind one goal. Because of this, the Communist Party started to crumble.
After the fall of the Berlin Wall in 1989 and without Communist rule holding together the countries that comprised the Soviet Union, the USSR broke into smaller countries, like Russia, Ukraine, Lithuania and Georgia. The nations of Eastern Europe returned to capitalism, and the period of the Cold War was over. The Soviet Union ended in December 1991.
Not all historians agree on when the Cold War ended. Some think it ended when the Berlin Wall fell. Others think it ended when the Soviet Union collapsed in 1991.
Mainland China
Mainland China, also called the Chinese Mainland, is the part of China not including the Republic of China controlling Taiwan, Kinmen, Matsu, and the Pescadores. The term also excludes Hong Kong and Macau.
In the Qing Dynasty (Manchu Dynasty), all of Mainland China, Hong Kong, Macau, Taiwan, Kinmen, Matsu, the Pescadores, and Mongolia were part of the Manchu Empire. Taiwan, Hong Kong, and Macau were colonized by foreigners for some years (Taiwan to the Japanese, Hong Kong to the British, and Macau to the Portuguese).
By the end the Qing Empire, China became Nationalist China (the Republic of China) and it got Taiwan back in 1945. After the Communists (the People's Republic of China) took over most of China, the Nationalists kept only Taiwan, Kinmen, Matsu, and the Pescadores. Mongolia became an independent state later.
Since then, Communist China only includes the part on the continent (mainland) and some small islands that are very near (the largest communist island is Hainan). This region is Mainland China.
Later Hong Kong and Macau were returned to the government of China, but because the government calls them "special administrative regions" under a "one country, two systems" idea, they are still not thought of as part of Mainland China.
Capital city
A capital city, or capital town or capital, is a city or town, specified by law or constitution, by the government of a country, or part of a country, such as a state, province, or county. It usually serves as the location of the government's central meeting place and offices. Most of the country's leaders, embassy and officials work in the capital city.
Capitals are usually among the largest cities in their regions and often are the biggest. For example, Montevideo is Uruguay's capital and its biggest city. The capital may also be the most important center of commerce, as in London or Bangkok.
However, a capital is not always the largest city in a country. For example, the capital of the India is New Delhi, which is smaller than Mumbai. The capital of Pakistan is Islamabad, which is smaller than Karachi.
In countries with subdivisions like the United States, the capitals of the federated states are often not the biggest cities. For example, New York City is the biggest city in the United States and in New York State, but is not the capital of either. The capital the country is Washington, DC, and the capital of the state is Albany.