232 résultats pour "formed"
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Igneous Rock.
As a magma cools, the first crystals to form will be of minerals that become solid at relatively high temperatures (usually olivine and a type of feldspar known asanorthite). The composition of these early-formed mineral crystals will be different from the initial composition of the magma. Consequently, as these growing crystalstake certain elements out of the magma in certain proportions, the composition of the remaining liquid changes. This process is known as magmatic differentiation.Sometime...
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Mars (planet) - astronomy.
The Martian core is probably much like Earth’s, consisting mostly of iron, with a small amount of nickel. If other light elements, particularly sulfur, exist there as well, thecore may be larger than presently thought. From studying Earth’s magnetic field and core, scientists theorize that the motions of the liquid rock in Earth’s core generateits magnetic field. Mars does not have a significant magnetic field, so scientists believe that Mars’s core is probably solid. However, spacecraft data in...
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Planetary Science - astronomy.
III ORIGINS AND COMPOSITIONS OF PLANETS Astronomers believe that planetary systems are formed of elemental materials that were created in the interiors of giant stars. Some of this material comes from giantstars that shed material into space as they age. Most of the matter to form planets, however, comes from stars that explode as supernovas and spread debris enrichedwith the heavier chemical elements into space. According to the currently accepted views, the most likely first stage in the evo...
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Hawaii (state) - geography.
limestone along the coast. The volcanoes of the Hawaiian Islands are all so-called shield volcanoes, or lava domes. Unlike the volcanoes of Alaska and South America, those of Hawaii were notcreated by very explosive eruptions. Formed mostly by lava flows, they are great rounded mountain masses, rather than steep-sided cones. Mauna Kea, dormant forcenturies, is the highest mountain in the state. It rises to 4,205 m (13,796 ft) above sea level, and its summit is dotted with cinder cones formed by...
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Hawaii (state) - USA History.
limestone along the coast. The volcanoes of the Hawaiian Islands are all so-called shield volcanoes, or lava domes. Unlike the volcanoes of Alaska and South America, those of Hawaii were notcreated by very explosive eruptions. Formed mostly by lava flows, they are great rounded mountain masses, rather than steep-sided cones. Mauna Kea, dormant forcenturies, is the highest mountain in the state. It rises to 4,205 m (13,796 ft) above sea level, and its summit is dotted with cinder cones formed by...
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Moon - astronomy.
B Volcanic Features Maria, domes, rilles, and a few craters display indisputable characteristics of volcanic origin. Maria are plains of dark-colored rock that cover approximately 40 percent ofthe Moon's visible hemisphere. The maria formed when molten rock erupted onto the surface and solidified between 3.16 billion and 3.96 billion years ago. This rockresembles terrestrial basalt, a volcanic rock type widely distributed on Earth, but the rock that formed the maria has a higher iron content an...
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Jupiter (planet) - astronomy.
Beneath the supercritical fluid zone, the pressure reaches 3 million Earth atmospheres. At this depth, the atoms collide so frequently and violently that the hydrogenatoms are ionized—that is, the negatively charged electrons are stripped away from the positively charged protons of the hydrogen nuclei. This ionization results in asea of electrically charged particles that resembles a liquid metal and gives rise to Jupiter’s magnetic field. This liquid metallic hydrogen zone is 30,000 to 40,000 k...
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Uranus (planet) - astronomy.
V COMPOSITION AND STRUCTURE A Interior of Uranus Uranus contains mostly rock and water, with hydrogen and helium (and trace amounts of methane) in its dense atmosphere. Astronomers believe that Uranus, likeNeptune, formed from the same material—principally frozen water and rock—that composes most of the planet’s moons. As the planet grew, pressures andtemperatures in the planet’s interior increased, heating the planet’s frozen water into a hot liquid. Uranus probably has a relatively small roc...
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Carbon - chemistry.
Graphite is black and slippery and conducts electricity. In graphite, the atoms form planar, or flat, layers. Each layer is made up of rings containing six carbon atoms.The rings are linked to each other in a structure that resembles the hexagonal mesh of chicken wire. Each atom has three sigma bonds (with 120° between any two ofthe bonds) and belongs to three neighboring rings. The fourth electron of each atom becomes part of an extensive pi bond system. Graphite conducts electricity,because th...
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Sun - astronomy.
A The Sun’s Place in the Milky Way The Milky Way Galaxy contains about 400 billion stars. All of these stars, and the gas and dust between them, are rotating about a galactic center. Stars that arefarther away from the center move at slower speeds and take longer to go around it. The Sun is located in the outer part of the galaxy, at a distance of 2.6 × 10 17 km (1.6 × 10 17 mi) from the center. The Sun, which is moving around the center at a velocity of 220 km/s (140 mi/s), takes 250 million y...
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Canada.
Six general landform regions are distinguishable in Canada: the Appalachian Region, the Great Lakes and St. Lawrence Lowlands, the Canadian Shield, the Great Plains,the Canadian Cordillera, and the Canadian Arctic Archipelago. B1 Appalachian Region and Great Lakes and St. Lawrence Lowlands Eastern Canada consists of the Appalachian Region and the Great Lakes and St. Lawrence Lowlands. The Appalachian Region embraces Newfoundland Island, NovaScotia, New Brunswick, Prince Edward Island, and the G...
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Canada - country.
Six general landform regions are distinguishable in Canada: the Appalachian Region, the Great Lakes and St. Lawrence Lowlands, the Canadian Shield, the Great Plains,the Canadian Cordillera, and the Canadian Arctic Archipelago. B1 Appalachian Region and Great Lakes and St. Lawrence Lowlands Eastern Canada consists of the Appalachian Region and the Great Lakes and St. Lawrence Lowlands. The Appalachian Region embraces Newfoundland Island, NovaScotia, New Brunswick, Prince Edward Island, and the G...
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Canada - Canadian History.
Six general landform regions are distinguishable in Canada: the Appalachian Region, the Great Lakes and St. Lawrence Lowlands, the Canadian Shield, the Great Plains,the Canadian Cordillera, and the Canadian Arctic Archipelago. B1 Appalachian Region and Great Lakes and St. Lawrence Lowlands Eastern Canada consists of the Appalachian Region and the Great Lakes and St. Lawrence Lowlands. The Appalachian Region embraces Newfoundland Island, NovaScotia, New Brunswick, Prince Edward Island, and the G...
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Latin American Independence.
be inferior and were not permitted a university education. In the lowest caste were the African slaves. As the Spanish monarchy tried to increase its authority, it was hampered by the power of the Catholic Church. The church, including various religious orders, hadacquired great wealth, including large holdings of land, in the colonies. The Jesuit order especially had gained extraordinary wealth and political influence, and it alsocontrolled much of the university and high school education in th...
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Cosmology - astronomy.
In 1917 American scientist Harlow Shapley measured the distance to several groups of stars known as globular clusters. He measured these distances by using amethod developed in 1912 by American astronomer Henrietta Leavitt. Leavitt’s method relates distance to variations in brightness of Cepheid variables, a class of starsthat vary periodically in brightness. Shapley’s distance measurements showed that the clusters were centered around a point far from the Sun. The arrangement of theclusters was...
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Geology.
terminology. Today the geologic time scale is generally agreed upon and used by scientists around the world, dividing time into eons, eras, periods, and epochs. Everyfew years, the numerical time scale is refined based on new evidence, and geologists publish an update. Geologists use several methods to determine geologic time. These methods include physical stratigraphy, or the placement of events in the order of their occurrence,and biostratigraphy, which uses fossils to determine geologic time...
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Labor Union.
B The Legal Environment The legal environment, which permits certain types of union activities and prohibits others, also influences the extent of union organization. States with right-to-worklaws have much lower unionization rates than other states. In the United States, the states with the lowest unionization rates are North Carolina, South Carolina, SouthDakota, and Arkansas—states that have right-to-work laws. In 2000 the unionization rate in these states ranged from 4.44 percent to 6.7 per...
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Valley.
Except in mountainous terrain, rivers are almost always flanked by floodplains. Floodplains are flat wide deposits of alluvium, river-deposited sediment, on either side of the river channel. During floods, a river overflows its banks and spreads out the sediment near the river to form a floodplain. Floodplains of large rivers, such as thoseof the Mississippi River, can be flat areas tens of kilometers across. River channels migrate back and forth across their floodplains as alluvium is repeate...
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Valley - Geography.
Except in mountainous terrain, rivers are almost always flanked by floodplains. Floodplains are flat wide deposits of alluvium, river-deposited sediment, on either side of the river channel. During floods, a river overflows its banks and spreads out the sediment near the river to form a floodplain. Floodplains of large rivers, such as thoseof the Mississippi River, can be flat areas tens of kilometers across. River channels migrate back and forth across their floodplains as alluvium is repeate...
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From Scott v.
liberty, and the pursuit of happiness; that to secure these rights, Governments are instituted, deriving their just powers from the consent of the governed. The general words above quoted would seem to embrace the whole human family, and if they were used in a similar instrument at this day would be so understood.But it is too clear for dispute that the enslaved African race were not intended to be included, and formed no part of the people who framed and adopted thisdeclaration, for if the lang...
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Saturn - astronomy.
measurements of the magnetic field made by the Voyager space probes in the 1980s. Additional Cassini findings reported in March 2007 suggested that particles originating from geysers on the moon Enceladus may provide a partial explanation for thechange. The neutral gas particles become electrically charged and are captured by Saturn’s magnetic field, forming a disk of hot, ionized gas around the planet’sequator. The charged particles interact with the magnetic field and slow down the rotation of...
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Washington, D.
structures built according to L’Enfant’s plan. During the War of 1812, British troops set fire to the White House, destroying its interior. President James Madison and hisfamily lived in the Octagon while the White House was being rebuilt. South of the Federal Triangle is the Mall, a narrow park stretching roughly 1.6 km (1 mi) from the Capitol to the Washington Monument. Although the Mall officially endsat 14th Street, landscaped greenery extends to the Potomac. The Washington Monument, whose m...
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Lesotho - country.
V GOVERNMENT Under the terms of the constitution of 1965, which was suspended in 1970, Lesotho was a constitutional monarchy with a bicameral legislature. After a coup in 1986,legislative and executive powers were vested in the king but actually exercised by a 6-member military council and a 20-member council of ministers. In 1993 Lesothoadopted a new constitution that redefined the role of the monarchy and altered the legislative branch of the government. The king, who is head of state, has no...
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Fidel Castro.
result, Castro formed a radical branch of the Ortodoxo Party called the Radical Action Orthodox wing. This organization supported Chibás in the 1948 election. PrioSocarrás won the election, despite Castro’s efforts. After Chibás committed suicide in 1951, Castro believed he should become the leader of the Ortodoxo Party and ran for a seat in the Cuban House of Representatives inthe 1952 election. Before that election could occur, however, General Fulgencio Batista staged a bloodless coup d’etat...
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Protests in the 1960s - U.
E Youth Culture Young people played an important role in the movements for social change during the 1960s. Numbers alone made them important; more than 76 million babies wereborn during the post-World War II “baby boom.” In addition, these young people spent more years in school and were more affluent than previous generations. In theearly 20th century, most young Americans had moved quickly from childhood to adulthood. In the 1920s only 1 in 5 Americans graduated from high school, and almostal...
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Comet - astronomy.
may exceed the planet Jupiter in size, however. Observations from telescopes on Earth and in space indicate that most of the gases in the coma and tail of a comet are fragmentary molecules, or radicals, of the mostcommon elements in space: hydrogen, carbon, nitrogen, and oxygen. The radicals, for example, of CH, NH, and OH may be broken away from the stable molecules CH 4 (methane), NH 3 (ammonia), and H 2O (water), which may exist as ices or more complex, very cold compounds in the nucleus. Al...
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Russian Revolutions of 1917 (Histoire) .
as Marxists. They believed that the working class—with its struggles to organize trade unions and to bring about political reforms of benefit to the majority ofpeople—would become the primary force for revolutionary change. The Russian Marxists formed the Russian Social Democratic Labor Party (RSDLP) in 1898. By 1903,however, the RSDLP had split into two factions. The faction called the Bolsheviks (from the Russian word for “majority”), led by Vladimir Ilich Lenin, favored a more centralized a...
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Arizona - geography.
of the Mogollon Rim, the Little Colorado draws very little water from a relatively large watershed, usually containing a mere trickle of water in its riverbed. The ColoradoRiver’s principal tributary is the Gila River, which flows all the way across the southern part of the state from New Mexico to the California border. From the mountainsand plateaus of central Arizona, the Gila River receives the Salt, Agua Fria, and Hassayampa rivers. The Salt River is itself fed by the Verde River. The Gila...
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Arizona - USA History.
of the Mogollon Rim, the Little Colorado draws very little water from a relatively large watershed, usually containing a mere trickle of water in its riverbed. The ColoradoRiver’s principal tributary is the Gila River, which flows all the way across the southern part of the state from New Mexico to the California border. From the mountainsand plateaus of central Arizona, the Gila River receives the Salt, Agua Fria, and Hassayampa rivers. The Salt River is itself fed by the Verde River. The Gila...
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Molecule - chemistry.
attracted to the negatively charged electrons between them. The electrons belong to the molecule as a whole. However, each hydrogen atom now has a complete outershell of two electrons. The formula H 2 describes a hydrogen molecule, a discrete unit. When a molecule contains just two atoms, such as the hydrogen molecule does, it is called a diatomic molecule. Some atoms can form covalent bonds with more than one other atom and thus create a larger molecule. Atoms form molecules with covalent bo...
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African American History - U.
In their day-to-day lives, slaves and servants shared similar grievances and frequently formed alliances. Advertisements seeking the return of slaves and servants whohad run away together filled colonial newspapers. When a slave named Charles escaped in 1740, the Pennsylvania Gazette reported that two white servants, a 'Scotch man' and an Englishman, escaped with him. Sometimes interracial alliances involved violence. During Bacon's Rebellion in 1676, slaves and servants took up armsagainst Na...
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Missouri - geography.
Saint Francois Mountains, at the eastern end of the crest of the dome. Only in these mountains have the sedimentary rocks been sufficiently eroded away so that theunderlying igneous rocks are exposed. They form the rounded, knoblike peaks of an old mountain range. The peaks project, in isolation or in clusters, between 230 and300 m (750 and 1,000 ft) above the surrounding sedimentary basins. One of these knobs, Taum Sauk Mountain, reaches 540 m (1,772 ft) above sea level and is thehighest point...
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Missouri - USA History.
Saint Francois Mountains, at the eastern end of the crest of the dome. Only in these mountains have the sedimentary rocks been sufficiently eroded away so that theunderlying igneous rocks are exposed. They form the rounded, knoblike peaks of an old mountain range. The peaks project, in isolation or in clusters, between 230 and300 m (750 and 1,000 ft) above the surrounding sedimentary basins. One of these knobs, Taum Sauk Mountain, reaches 540 m (1,772 ft) above sea level and is thehighest point...
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United Provinces of Central America.
IV REUNION EFFORTS Efforts to reunite the Central American federation in the 1840s all failed. But unity was still seen as a desirable goal—to give the states more power when dealing withforeign nations and to tie together people with a common heritage. But as conservatives came to power in each of the states, they rejected a restored federation,associating the idea too closely with the hated Morazán and his liberal policies. Carrera’s Guatemala was the first formally to declare itself an inde...
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Big Bang Theory - astronomy.
hydrogen atoms. Hydrogen atoms can only absorb and emit specific colors, or wavelengths, of light. The formation of atoms allowed many other wavelengths of light,wavelengths that had been interfering with the free electrons prior to the cooling of the universe, to travel much farther than before. This change set free radiation thatwe can detect today. After billions of years of cooling, this cosmic background radiation is at about 3 K (-270°C/-454°F).The cosmic background radiation was first d...
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Neptune (planet) - astronomy.
The gaseous atmosphere of Neptune contains hydrogen, helium, and about 3 percent methane. It extends about 5,000 km (about 3,000 mi) above the planet’s ocean.Light reflected from Neptune’s deep atmosphere is blue, because the atmospheric methane absorbs red and orange light but scatters blue light. In 1998 astronomersalso identified molecules of methyl in Neptune’s atmosphere. Methyl molecules each contain one carbon atom and three hydrogen atoms. Methyl molecules are knownas hydrocarbon radical...
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Glacier.
covered. In spring the snow cover begins to melt in the lower reaches, exposing the ice surface. As temperatures increase, the melting moves up the glacier. Thesnowline is the highest position the melting reaches during the year. Firn is old granular snow. The firn limit may not exactly coincide with the annual snowline since insome years rapid melting leaves behind firn patches below the snowline. Some glaciers exhibit features called ice streams and icefalls. Ice streams are valley glaciers th...
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Vladimir Lenin
I
INTRODUCTION
Vladimir Lenin (1870-1924), Russian revolutionary leader and theorist, who presided over the first government of Soviet Russia and then that of the Union of Soviet
Socialist Republics (USSR).
with Japan ( see Russo-Japanese War). A string of military defeats and the strains placed on society by the war made for a tense atmosphere in Saint Petersburg, and by the beginning of 1905 various segments of Russian society, including students and liberal members of the nobility, were calling for political reform. When an unarmedcrowd of workers marched to the city’s Winter Palace on January 9 (or January 22, in the Western, or New Style, calendar) to submit a petition to Emperor Nicholas II,s...
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Vladimir Lenin.
with Japan ( see Russo-Japanese War). A string of military defeats and the strains placed on society by the war made for a tense atmosphere in Saint Petersburg, and by the beginning of 1905 various segments of Russian society, including students and liberal members of the nobility, were calling for political reform. When an unarmedcrowd of workers marched to the city’s Winter Palace on January 9 (or January 22, in the Western, or New Style, calendar) to submit a petition to Emperor Nicholas II,s...
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Vladimir Lenin .
with Japan ( see Russo-Japanese War). A string of military defeats and the strains placed on society by the war made for a tense atmosphere in Saint Petersburg, and by the beginning of 1905 various segments of Russian society, including students and liberal members of the nobility, were calling for political reform. When an unarmedcrowd of workers marched to the city’s Winter Palace on January 9 (or January 22, in the Western, or New Style, calendar) to submit a petition to Emperor Nicholas II,s...
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Galaxy - astronomy.
Astronomers have obtained images of young galaxies using the Keck Telescope in Hawaii and the Hubble Space Telescope, which resides in an orbit high above Earth’satmosphere and thus avoids atmospheric interference. Photos from the HST show galaxies that are as far as 13 billion light-years away from Earth, which means theyformed soon after the universe formed about 13.7 billion years ago. The galaxies appear to be spherical in shape, and may be early precursors of elliptical and spiralgalaxies....
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Latin America.
adequate housing and services, most were forced to live in shantytowns that came to encircle all large Latin American cities. One of the key problems facing Latin America in the late 20th century was the rapid rise of external debt during the 1980s. The borrowed money had been used bycorrupt, or at best inefficient, governments in non-productive projects. These large debts meant that many countries had to spend up to 30 percent of their net incometo pay interest on their loans. Some countries, s...
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Indianapolis - geography.
Amateur athletic competitions are frequent in Indianapolis. Each summer it is the site for the finals of the Hoosier State Games, with athletes of all ages and skill levelscompeting in 21 sports. In 1987 Indianapolis hosted the Tenth Pan American Games, and is often the site for numerous Olympic trials and collegiate sportschampionships. Among the many sports facilities are those for tennis, bicycle racing, skating, and track and field. The city’s professional football team, the Indianapolis Col...
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Venus (planet) - astronomy.
level winds circle the planet at 360 km/h (225 mph), making a complete rotation in only four days. These winds are said to super-rotate because they travel muchfaster than the rotation of the planet itself. These high-speed winds cover the planet completely, blowing toward the west at virtually every latitude from equator topole. The motions of descending probes, however, have shown that the bulk of Venus’s tremendously dense atmosphere, closer to the planet’s surface, is almoststagnant. From th...
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Nicaraguan Revolution.
Directorate. Within a year Robelo and Violeta Chamorro left the junta, and the Council of State was reorganized to guarantee an overwhelming Sandinista majority.Elections were postponed, restrictions were placed on the media, and relations with the Roman Catholic Church became increasingly tense. Two non-Sandinistasreplaced Robelo and Chamorro on the junta, but they had little power, and the government’s relations with opposition political parties and the private business sectordeteriorated. A D...
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Antarctica - Geography.
The maximum area of sea ice surrounding Antarctica each winter varies from year to year. A marked decline during the 1970s appears to have reversed in more recentdecades, except in the Antarctic Peninsula area. This area has lost almost 40 percent of its sea ice since the start of the 1980s. Sea ice is important to marine life. Krillfeed on algae that live under the sea ice and are released when the ice melts in spring and summer. In turn, many marine animals feed on krill. Emperor penguinsbreed...
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Iowa - geography.
Okoboji, Lost Island, Silver, and West Swan lakes. In addition, reservoirs have been created by damming several smaller Iowa rivers. There are a number of largereservoirs behind dams on the Mississippi River along the Iowa state line. C Climate Iowa’s climate is characterized by warm, generally moist summers and cold winters. Temperatures vary considerably from season to season and, at times, from day today. However, monthly averages are relatively uniform throughout the state and usually vary...
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Iowa - USA History.
Okoboji, Lost Island, Silver, and West Swan lakes. In addition, reservoirs have been created by damming several smaller Iowa rivers. There are a number of largereservoirs behind dams on the Mississippi River along the Iowa state line. C Climate Iowa’s climate is characterized by warm, generally moist summers and cold winters. Temperatures vary considerably from season to season and, at times, from day today. However, monthly averages are relatively uniform throughout the state and usually vary...
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California - geography.
The Basin and Range province is an arid area of mountain ranges, basins, and deserts. In California it is represented primarily by parts of the Great Basin and SonoranDesert sections. Within the Great Basin lies Death Valley, whose lowest elevation, 86 m (282 ft) below sea level, is the lowest point in the Western Hemisphere. TheSonoran Desert section is characterized by numerous flat plains separated by low but rugged ranges. It includes the extensive Mojave, or Mohave, Desert. Also in thisprov...
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California - USA History.
The Basin and Range province is an arid area of mountain ranges, basins, and deserts. In California it is represented primarily by parts of the Great Basin and SonoranDesert sections. Within the Great Basin lies Death Valley, whose lowest elevation, 86 m (282 ft) below sea level, is the lowest point in the Western Hemisphere. TheSonoran Desert section is characterized by numerous flat plains separated by low but rugged ranges. It includes the extensive Mojave, or Mohave, Desert. Also in thisprov...