20 résultats pour "boundaries"
- Boundaries - geography.
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Plate Tectonics.
ridges. The Mid-Atlantic Ridge is an underwater mountain range created at a divergent plate boundary in the middle of the Atlantic Ocean. It is part of a worldwidesystem of ridges made by seafloor spreading. The Mid-Atlantic Ridge is currently spreading at a rate of 2.5 cm per year (1 in per year). The mid-ocean ridges today are60,000 km (about 40,000 mi) long, forming the largest continuous mountain chain on earth. Earthquakes, faults, underwater volcanic eruptions, and vents, oropenings, along...
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Volcano.
before eruption. Very violent explosive eruptions are called Plinian eruptions, after Roman naturalist Pliny the Elder. These eruptions can last for several hours to daysand eject a large amount of pyroclastic material. Some volcanoes can produce much more energetic eruptions that eject materials farther from the vents because oftheir andesitic and dacitic composition. Andesitic and dacitic lava is generally thicker than basaltic lava. Stiff lava generally produces more-explosive eruptions. B No...
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Earthquake.
III CAUSES Most earthquakes are caused by the sudden slip along geologic faults. The faults slip because of movement of the Earth’s tectonic plates. This concept is called theelastic rebound theory. The rocky tectonic plates move very slowly, floating on top of a weaker rocky layer. As the plates collide with each other or slide past eachother, pressure builds up within the rocky crust. Earthquakes occur when pressure within the crust increases slowly over hundreds of years and finally exceeds...
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International Law.
merchants), modernized the rights of neutrals during maritime war, and required blockades to be effective. The Declaration of Paris also initiated the practice of allowingnations other than the original signatories to accede (become a party to) to an agreement. In 1864 a conference convened in Geneva, Switzerland, at the invitation of the Swiss government. The conference approved a convention for the proper treatment ofwounded soldiers on the battlefield and the protection of medical personnel;...
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Map - geography.
Relief MapRelief maps are three-dimensional models of the terrain in an area; on them, color and scale are used to indicate geographicalfeatures rather than simply to delineate political boundaries. Because of this feature, relief maps are extensively used in engineeringand the military. This map shows portions of Alaska and northwestern Canada.United States Geological Survey Among the most important of the special-purpose maps are hydrographic and aviation charts. Hydrographic charts are used f...
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Statistics
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INTRODUCTION
Statistics, branch of mathematics that deals with the collection, organization, and analysis of numerical data and with such problems as experiment design and decision
making.
Professional pollsters typically conduct their surveys among sample populations of 1,000 people. Statistical measurementsshow that reductions in the margin of error flatten out considerably after the sample size reaches 1,000.© Microsoft Corporation. All Rights Reserved. The raw materials of statistics are sets of numbers obtained from enumerations or measurements. In collecting statistical data, adequate precautions must be taken tosecure complete and accurate information. The first problem of...
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Election.
majority systems usually reduce the number of competitive political parties—for example, the mostly two-party system in the United States. Proportional representation systems boost participation by increasing the value of a vote to smaller or more marginal portions of a national population. In the UnitedStates, plurality or majority systems have reduced the incentive to vote of citizens who do not identify closely with the Democratic or Republican Party. Disillusionmentwith the major parties and...
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National Parks and Preserves.
Some ibex raised in Italy’s 700 sq km (220 sq mi) Gran Paradiso National Park (1922) were transferred to aid herd restoration elsewhere in the country. Switzerlandreturned lynx to Swiss National Park to keep red deer populations in check. The growth of national parks also enabled many European countries to restore forests thathad given way to industrialization by the early 20th century. Africa’s wildlife was hunted heavily from the late 19th century well into the 20th century. By 1920 big-game h...
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Mexico City - geography.
The park houses some of Mexico's most important public buildings, including Chapultepec Castle. Construction of the castle began in 1783. Positioned on the park’shighest elevation, the castle functioned as a fortress during colonial times. It once served as the presidential residence and now houses the National Museum of History,which includes murals by 20th-century Mexican painter Juan O'Gorman. Los Pinos, the official residence and working offices of the president, is also on the grounds, buti...
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Fascism.
values as coming before a radical political transformation. Others argue that a radical political transformation will then be followed by a change in values. Fascists claimthat the nation has entered a dangerous age of mediocrity, weakness, and decline. They are convinced that through their timely action they can save the nation fromitself. Fascists may assert the need to take drastic action against a nation's 'inner' enemies. Fascists promise that with their help the national crisis will end an...
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African Theater
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INTRODUCTION
African Theater, traditional, historical, and contemporary dramatic forms in Africa south of the Sahara.
The period after World War II ended in 1945 led to the struggle for and achievement of independence in many African countries. The new nation-states were oftenestablished along colonial boundaries and power was handed over to a bourgeois class who had been educated in Europe. The epoch-making era of nationalismproduced a number of African playwrights who merged African theatrical traditions with European forms. These plays are still widely performed and read in many partsof the continent. Nigeri...
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African Theater
I
INTRODUCTION
African Theater, traditional, historical, and contemporary dramatic forms in Africa south of the Sahara.
The period after World War II ended in 1945 led to the struggle for and achievement of independence in many African countries. The new nation-states were oftenestablished along colonial boundaries and power was handed over to a bourgeois class who had been educated in Europe. The epoch-making era of nationalismproduced a number of African playwrights who merged African theatrical traditions with European forms. These plays are still widely performed and read in many partsof the continent. Nigeri...
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São Paulo (city) - geography.
universities include the State University Paulista Júlio de Mesquita Filho (1976), and the even larger University of São Paulo (1934), which incorporates the city’s famousand influential Faculty of Law. Important private universities are Mackenzie University, originally founded by Presbyterian missionaries from the United States (1870);the Paulista University (1972); the Pontifical Catholic University of São Paulo (1946); and the University São Judas Tadeu (1971). The city is home to the São Pau...
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United States (Overview) - country.
parts. IV UNITED STATES PEOPLE When Europeans first reached North America in the 1520s, they encountered other people—Native Americans—and they also encountered a new geography. Someimagined they were entering “a howling wilderness”—an environment filled with exotic flora and fauna but sparsely populated. In reality, they found their way to alandmass that was widely settled. But soon after the Europeans’ arrival, the population of the Americas plummeted, largely because Native Americans lacked...
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Optics
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INTRODUCTION
Mirage
Mirages appear because differences in air temperature cause light rays from an object to take different paths to a viewer's
eye.
Refraction of Light by DiamondsThe brilliance of diamonds is due to their high refractive index, a measure of how strongly a transparent material bendslight rays. The skill of the gem-cutter lies in angling the facets of the stone so that each light ray entering it is reflectedmany times before it emerges again.Spencer Grant/Photo Researchers, Inc. The amount of light reflected depends on the ratio of the refractive indexes for the two media. The plane of incidence contains the incident ray and...
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Native American Policy.
of white settlement dominated policy during the second quarter of the 19th century. IV REMOVAL PERIOD The idea of moving Native Americans to a different part of the country was not new. After the Louisiana Purchase in 1803, President Thomas Jefferson had suggestedthat tracts of land in this vast new territory could be given to native peoples if they agreed to cede their lands in the eastern part of the country. Transfers occurred in apiecemeal way, but no consistent removal program developed u...
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Philadelphia (city, Pennsylvania) - geography.
national trend of migration from eastern cities to the warmer climate of the Sun Belt. Whereas in 1950 Philadelphia contained more than 2 million people and ranked as the third largest city in America, the city's population plunged to 1,517,550 by 2000.In 2006, the city's population was estimated at 1,448,394. While the city proper was decreasing in population, the metropolitan area centered on Philadelphia grew. In 2006 the region had 6.2 million inhabitants. Philadelphiaranked as the nation’s...
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Asia - Geography.
Borneo, the world’s third largest island after Greenland and New Guinea. To the southeast is the Timor Sea separating the Asian island of Timor from the Australiancontinent. The Indian subcontinent is flanked by the Bay of Bengal on the east and the Arabian Sea on the west. The island of Sri Lanka and the much smaller Maldives andNicobar Islands trail away to the south. The Arabian Sea’s Gulf of Aden, the Red Sea, the Mediterranean Sea, and the Black Sea form an arc along the western rim of Asia...
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Asia - History.
Borneo, the world’s third largest island after Greenland and New Guinea. To the southeast is the Timor Sea separating the Asian island of Timor from the Australiancontinent. The Indian subcontinent is flanked by the Bay of Bengal on the east and the Arabian Sea on the west. The island of Sri Lanka and the much smaller Maldives andNicobar Islands trail away to the south. The Arabian Sea’s Gulf of Aden, the Red Sea, the Mediterranean Sea, and the Black Sea form an arc along the western rim of Asia...