188 résultats pour "flow"

• Georgia (state) - geography.

  B Rivers and Lakes Most of the rivers of Georgia drain eastward to the Atlantic Ocean proper or southward to the Gulf of Mexico. Only a few flow northward to the Tennessee River, which isa major tributary of the Mississippi River. Most of the rivers flowing to the coasts are navigable by barges and small craft as far upstream as the Fall Line. The major river flowing to the Atlantic is the Savannah River, which, with the Tugaloo River, one of its headwaters, forms most of the state’s eastern bo...

• Georgia (state) - USA History.

  B Rivers and Lakes Most of the rivers of Georgia drain eastward to the Atlantic Ocean proper or southward to the Gulf of Mexico. Only a few flow northward to the Tennessee River, which isa major tributary of the Mississippi River. Most of the rivers flowing to the coasts are navigable by barges and small craft as far upstream as the Fall Line. The major river flowing to the Atlantic is the Savannah River, which, with the Tugaloo River, one of its headwaters, forms most of the state’s eastern bo...

• Invertebrate - biology.

  animals with a five-pointed design. They live in the sea and move with the help of tiny fluid-filled feet—another feature found nowhere else in the animal world. Zoologists recognize several different groups of worms. The phylum known as flatworms contains the simplest animals possessing heads. Nerves and sense organs areconcentrated in the head. Most flatworms are paper-thin and live in a variety of wet or damp habitats, including the digestive systems of other animals. Roundwormsrepresent anot...

• Invertebrate - biology.

  animals with a five-pointed design. They live in the sea and move with the help of tiny fluid-filled feet—another feature found nowhere else in the animal world. Zoologists recognize several different groups of worms. The phylum known as flatworms contains the simplest animals possessing heads. Nerves and sense organs areconcentrated in the head. Most flatworms are paper-thin and live in a variety of wet or damp habitats, including the digestive systems of other animals. Roundwormsrepresent anot...

• Europe - geography.

  movement of a segment of the Earth’s crust against the stable shield during the Caledonian orogeny (about 500 to 395 million years ago) raised the mountains of Ireland,Wales, Scotland, and western Norway. Subsequent erosion has rounded and worn down these mountains in the British Isles, but the peaks of Norway still reach 2,472 m(8,110 ft). The second major geological region, a belt of sedimentary materials, sweeps in an arc from southwestern France northward and eastward through the Low Countri...

• Ocean and Oceanography.

  of sediment. When studied in sedimentary core samples, which can represent many millions of years of deposits, they provide a detailed and continuous history of theearth’s environmental changes. The record is particularly informative for the most recent 2 million to 5 million years, during which major fluctuations in global climatehave occurred. Successive ice ages can be traced by the relative scarcity or abundance of the shells of warm-water and cold-water diatoms in various layers of asedimen...

• Ocean and Oceanography - Geography.

  of sediment. When studied in sedimentary core samples, which can represent many millions of years of deposits, they provide a detailed and continuous history of theearth’s environmental changes. The record is particularly informative for the most recent 2 million to 5 million years, during which major fluctuations in global climatehave occurred. Successive ice ages can be traced by the relative scarcity or abundance of the shells of warm-water and cold-water diatoms in various layers of asedimen...

• Telephone.

  digits is dialed. The development of inexpensive and reliable amplification provided by the introduction of the transistor in the 1960s made practical the design of adialing system based on the transmission of relatively low power tones instead of the higher-power dial pulses. Today most telephones have push buttons instead of a rotary dial. Touch-Tone is an optional service, and telephone companies still maintain the ability to receive pulsedialing. Push-button telephones usually have a switch...

• Brazil - country.

  occasional droughts. Brazil contains a wealth of mineral and plant resources that have not yet been fully explored. It possesses some of the world’s largest deposits of iron ore and containsrich deposits of many other minerals, including gold and copper. Brazil’s fossil fuel resources are modest, but this limitation is offset by the considerable hydroelectricpotential of the nation’s many rivers. Although Brazil is an important producer of tropical crops, areas of highly fertile land are limited...

• Steam Engine.

  wear caused by this pressure, steam-engine valves are frequently made in a cylindrical form entirely enclosing the piston, so that the pressure is equal all around thevalve and friction is minimized. The development of this type of valve is attributed to the American inventor and manufacturer George Henry Corliss. In other types ofslide valves, the moving portion of the valve is designed so that steam does not press directly on the back of the valve. The linkage between the piston of the engine...

• Alaska - geography.

  depression surrounded by highlands and have the coldest winter and hottest summer temperatures in Alaska. Once the Kuskokwim River passes through theKuskokwim Mountains, it forms the southern edge of a vast lake-studded alluvial plain bounded on the north by the Yukon River. This water-logged lowland is a majorsummer nesting area for birds. Fairbanks is the major city in this region, while Fort Yukon is the major community in the Yukon Flats and Bethel the largest settlementon the Lower Kuskokwi...

• Alaska - USA History.

  depression surrounded by highlands and have the coldest winter and hottest summer temperatures in Alaska. Once the Kuskokwim River passes through theKuskokwim Mountains, it forms the southern edge of a vast lake-studded alluvial plain bounded on the north by the Yukon River. This water-logged lowland is a majorsummer nesting area for birds. Fairbanks is the major city in this region, while Fort Yukon is the major community in the Yukon Flats and Bethel the largest settlementon the Lower Kuskokwi...

• 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...

• 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...

• Idaho - geography.

  Idaho-Montana state line in the southern part of the Bitterroot Mountains. Consequently, nearly all the rivers in the state drain toward the Pacific. Most of Idaho lieswithin the drainage basin of the Columbia River system. The Snake River, which is the chief river in southern and central Idaho, follows a crescent-shaped course forabout 790 km (about 490 mi) across southern Idaho. It then swings northward along the Idaho state line and joins the Columbia River in Washington. Major tributariesof...

• Idaho - USA History.

  Idaho-Montana state line in the southern part of the Bitterroot Mountains. Consequently, nearly all the rivers in the state drain toward the Pacific. Most of Idaho lieswithin the drainage basin of the Columbia River system. The Snake River, which is the chief river in southern and central Idaho, follows a crescent-shaped course forabout 790 km (about 490 mi) across southern Idaho. It then swings northward along the Idaho state line and joins the Columbia River in Washington. Major tributariesof...

• Kansas - geography.

  at the adjoining cities of Kansas City, Kansas, and Kansas City, Missouri. Its chief headstreams are the Republican and Smoky Hill rivers, which join to form the KansasRiver at Junction City. Each of the headstreams has numerous tributaries. The Kansas River proper is only 270 km (170 mi) long, but the Smoky Hill River has a lengthof 870 km (540 mi), and the Republican River has a length of 720 km (450 mi). The main tributary flowing into the Kansas River is the Big Blue River. The Arkansas Rive...

• Kansas - USA History.

  at the adjoining cities of Kansas City, Kansas, and Kansas City, Missouri. Its chief headstreams are the Republican and Smoky Hill rivers, which join to form the KansasRiver at Junction City. Each of the headstreams has numerous tributaries. The Kansas River proper is only 270 km (170 mi) long, but the Smoky Hill River has a lengthof 870 km (540 mi), and the Republican River has a length of 720 km (450 mi). The main tributary flowing into the Kansas River is the Big Blue River. The Arkansas Rive...

• Oregon - geography.

  B Rivers and Lakes The Columbia River forms most of the Oregon-Washington boundary, and with its tributaries this great river drains a large portion of Oregon. From the point where theColumbia first touches the state, at Wallula Gap, the river runs in a shallow gorge, deepening as it approaches the Cascades. This part of the river once had manyrapids and falls, but is now navigable by large vessels because of dams and locks that have been built along much of its length. An important tributary o...

• Oregon - USA History.

  B Rivers and Lakes The Columbia River forms most of the Oregon-Washington boundary, and with its tributaries this great river drains a large portion of Oregon. From the point where theColumbia first touches the state, at Wallula Gap, the river runs in a shallow gorge, deepening as it approaches the Cascades. This part of the river once had manyrapids and falls, but is now navigable by large vessels because of dams and locks that have been built along much of its length. An important tributary o...

• Egypt - country.

  Egypt has a wide variety of mineral deposits, some of which, such as gold and red granite, have been exploited since ancient times. The chief mineral resource ofcontemporary value is petroleum, found mainly in the Red Sea coastal region, at Al ‘Alamayn (El ‘Alamein) on the Mediterranean, and on the Sinai Peninsula. Otherminerals include phosphates, manganese, iron ore, and uranium. Natural gas is also extracted. D Plants and Animals The vegetation of Egypt is confined largely to the Nile Delta,...

• Texas - geography.

  D Climate Eastern Texas has a humid subtropical climate, while a semiarid low latitude climate prevails in central areas, and an arid low latitude climate in the extreme west. Alongthe coast the climate is much milder, with fewer extremes in temperatures. Hurricanes sometimes hit the coastal areas of Texas from late July through September, andtornadoes are common in north-central Texas in April and May. D1 Temperature Summers are hot throughout the state, and temperatures exceeding 35°C (95°F)...

• Texas - USA History.

  D Climate Eastern Texas has a humid subtropical climate, while a semiarid low latitude climate prevails in central areas, and an arid low latitude climate in the extreme west. Alongthe coast the climate is much milder, with fewer extremes in temperatures. Hurricanes sometimes hit the coastal areas of Texas from late July through September, andtornadoes are common in north-central Texas in April and May. D1 Temperature Summers are hot throughout the state, and temperatures exceeding 35°C (95°F)...

• Kidney.

  secretion. An additional function of the kidney is the processing of vitamin D; the kidney converts this vitamin to an active form that stimulates bone development. Several hormones are produced in the kidney. One of these, erythropoietin, influences the production of red blood cells in the bone marrow. When the kidney detectsthat the number of red blood cells in the body is declining, it secretes erythropoietin. This hormone travels in the bloodstream to the bone marrow, stimulating theproducti...

• Plato I INTRODUCTION Plato (428?

  one of the individuals escapes from the cave into the light of day. With the aid of the sun, that person sees for the first time the real world and returns to the cave withthe message that the only things they have seen heretofore are shadows and appearances and that the real world awaits them if they are willing to struggle free oftheir bonds. The shadowy environment of the cave symbolizes for Plato the physical world of appearances. Escape into the sun-filled setting outside the cave symbolize...

• Plato.

  one of the individuals escapes from the cave into the light of day. With the aid of the sun, that person sees for the first time the real world and returns to the cave withthe message that the only things they have seen heretofore are shadows and appearances and that the real world awaits them if they are willing to struggle free oftheir bonds. The shadowy environment of the cave symbolizes for Plato the physical world of appearances. Escape into the sun-filled setting outside the cave symbolize...

• Capitalism.

  Physiocracy is the term applied to a school of economic thought that suggested the existence of a natural order in economics, one that does not require direction from the state for people to be prosperous. The leader of the physiocrats, the economist François Quesnay, set forth the basic principles in his Tableau économique (1758), in which he traced the flow of money and goods through the economy. Simply put, this flow was seen to be both circular and self-sustaining. More important, however...

• Rain Forest.

  dropped into the heart of the forest by helicopters. Suspended from the crane’s long, movable arm is a large gondola that functions as a mobile treetop laboratory.Moving from tree to tree, forest researchers collect specimens, conduct experiments, and observe life in the canopy frontier. The highest stratum of the rain forest is made up of the emergent trees, those individuals that stick up above the forest canopy. Emergents, which do not form acontinuous layer, are usually the giants of the for...

• New Mexico - geography.

  New Mexico’s major river is the Río Grande, originating in southern Colorado, and flowing southward for 760 km (470 mi) through the state. Between the San LuisValley and Española Valley the river flows in a deep canyon known as the Río Grande Gorge; then, below White Rock Canyon, it flows through several valleys containingagricultural land. Most of the water of the Río Grande is used to irrigate these valleys. The Río Grande’s waterflow in New Mexico is extremely low. One of the major tributarie...

• New Mexico - USA History.

  New Mexico’s major river is the Río Grande, originating in southern Colorado, and flowing southward for 760 km (470 mi) through the state. Between the San LuisValley and Española Valley the river flows in a deep canyon known as the Río Grande Gorge; then, below White Rock Canyon, it flows through several valleys containingagricultural land. Most of the water of the Río Grande is used to irrigate these valleys. The Río Grande’s waterflow in New Mexico is extremely low. One of the major tributarie...

• Liver.

  by bacterial infections. But hepatitis is most often caused by one of several viruses. The hepatitis A virus (HAV) can produce flulike symptoms and jaundice, but manypeople who contract it have no symptoms. The disease tends to resolve on its own. Because HAV lives in feces in the intestinal tract, hepatitis A is prevalent in areaswhere drinking water is contaminated with raw sewage. Good hygiene practices and a hepatitis A vaccination are effective measures of prevention. Hepatitis B is a more...

• Antarctica - geography.

  The geographic South Pole lies near the center of the continent in East Antarctica. This point is where all map lines of longitude converge at the southern end ofEarth’s axis of rotation. Distinct from the geographic south pole is the south magnetic pole, where the lines of force of Earth’s magnetic field emerge vertically,arching upward over the planet to enter Earth again at the north magnetic pole. The south-seeking end of a compass needle points to the south magnetic pole. Thesouth magnetic...

• Race - biology.

  distributed as a cline, generally varying along a north-south line. Skin color is lightest in northern Europeans, especially in those who live around the Baltic Sea, andbecomes gradually darker as one moves toward southern Europe, the Mediterranean, the Middle East, and into northern Africa and northern subtropical Africa. Skin isdarkest in people who live in the tropical regions of Africa. The lack of clear-cut discontinuities makes any racial boundary based on skin color totally arbitrary. Sim...

• Automobile.

  Electric motors have been used to power automobiles since the late 1800s. Electric power supplied by batteries runs the motor, which rotates a driveshaft, the shaftthat transmits engine power to the axles. Commercial electric car models for specialized purposes were available in the 1980s. General Motors Corporation introduced amass-production all-electric car in the mid-1990s. Automobiles that combine two or more types of engines are called hybrids. A typical hybrid is an electric motor with ba...

• Venezuela - country.

  Venezuela has six navigable rivers. Of the thousand or more streams in the country, the majority flow into the Orinoco. The Orinoco flows east across central Venezuelaand drains approximately four-fifths of the total area of the country. With the tributaries—the Apure, Meta, and Negro rivers—it forms the outlet into the Atlantic Oceanfor the waters of much of the interior of Colombia, as well as of inland Venezuela. F Climate The climate of Venezuela is tropical on the Llanos and along the coas...

• Colorado (river, North America) - Geography.

  sometime between AD 1300 and 1400, but their descendants, the Hopi and Pueblo people, continue to farm and irrigate using the river's waters. The first European to visit the river was probably Spanish soldier and explorer Francisco de Ulloa, who explored the mouth of the Colorado in 1539. In 1540 and 1541another Spaniard, Francisco Vásquez de Coronado, traveled through much of the region around the Colorado River. An exploring party from the Coronado expedition,led by Garcia López de Cárdenas,...

• 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...

• 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...

• South Korea - country.

  forest habitat, and overhunting. The Siberian tiger has not been sighted in the wild in South Korea since the 1920s; the Asiatic black bear can still be found in someremote mountain areas. Several species of deer are indigenous to the peninsula, including the roe deer, water deer, and Siberian musk deer. The musk deer, which hasbeen overhunted for its musk glands, is legally protected as a threatened species. Smaller mammals indigenous to the peninsula include the wild boar, red fox, badger,rabb...

• Electric Motors and Generators.

  the armature. It is often desirable to generate as high a voltage as possible, and rotating armatures are not practical in such applications because of the possibility of sparkingbetween brushes and slip rings and the danger of mechanical failures that might cause short circuits. Alternators are therefore constructed with a stationary armaturewithin which revolves a rotor composed of a number of field magnets. The principle of operation is exactly the same as that of the AC generator described,...

• Oklahoma - geography.

  portion and the Panhandle are classified as a steppe, where precipitation, typically 250 to 500 mm (10 to 20 in), is the controlling characteristic. January is usually the coldest month with an average of about 3°C (38°F) and extremes from -33°C (-27°F), the lowest ever recorded, to 33°C (92°F). Summer arelong and hot with temperatures in the upper 30°s C (lower 100°s F) common from May until September across the state. The growing season varies from less than 180days in the western Panhandle to...

• Oklahoma - USA History.

  portion and the Panhandle are classified as a steppe, where precipitation, typically 250 to 500 mm (10 to 20 in), is the controlling characteristic. January is usually the coldest month with an average of about 3°C (38°F) and extremes from -33°C (-27°F), the lowest ever recorded, to 33°C (92°F). Summer arelong and hot with temperatures in the upper 30°s C (lower 100°s F) common from May until September across the state. The growing season varies from less than 180days in the western Panhandle to...

• Sewage Disposal.

  greater load on the piping system and the treatment plant. The amount of storm-water drainage to be carried away depends on the amount of rainfall as well as on the runoff or yield of the watershed ( see Drainage). A typical metropolitan area discharges a volume of wastewater equal to about 60 to 80 percent of its total daily water requirements, the rest being used for washingcars and watering lawns, and for manufacturing processes such as food canning and bottling. B Composition The composi...

• 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...

• 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...

• Colorado - geography.

  Although the rivers of Colorado are navigable only by small boats, they are important as a source of irrigation water for use in Colorado and adjoining states. However,the water level of the rivers fluctuates seasonally and from year to year. The level is generally low in winter and high in spring and summer, during the runoff of meltedsnow from the mountains. Colorado has no large lakes of natural origin, but there are numerous small lakes in the mountains. The largest bodies of water in Colora...

• Colorado - USA History.

  Although the rivers of Colorado are navigable only by small boats, they are important as a source of irrigation water for use in Colorado and adjoining states. However,the water level of the rivers fluctuates seasonally and from year to year. The level is generally low in winter and high in spring and summer, during the runoff of meltedsnow from the mountains. Colorado has no large lakes of natural origin, but there are numerous small lakes in the mountains. The largest bodies of water in Colora...

• Switzerland - country.

  formation over higher elevations. The wind reverses direction about sundown and moves down the valley as a cool downdraft. The foehn, which occurs during the wintermonths, is a dry and relatively warm airflow that is drawn northward over the Alps. The foehn can quickly melt snow and ice, increasing the risk of mudslides andavalanches. D Natural Resources Waterpower is the chief natural resource of Switzerland. The principal source of water is runoff from the considerable annual precipitation th...

• Montana - geography.

  (191 sq mi), is Montana’s largest lake, and the largest natural freshwater lake in the contiguous states west of the Mississippi River. C Climate Climatic regions in Montana coincide roughly with the two major physiographic regions. In western Montana, as compared with the eastern plains area, winters tend tobe milder while summers are cooler. Precipitation is more evenly distributed throughout the year in the west, and it is cloudier and somewhat more humid in all seasons.In addition, the grow...

• Montana - USA History.

  (191 sq mi), is Montana’s largest lake, and the largest natural freshwater lake in the contiguous states west of the Mississippi River. C Climate Climatic regions in Montana coincide roughly with the two major physiographic regions. In western Montana, as compared with the eastern plains area, winters tend tobe milder while summers are cooler. Precipitation is more evenly distributed throughout the year in the west, and it is cloudier and somewhat more humid in all seasons.In addition, the grow...