217 résultats pour "rivers"
-
Earth (planet) - astronomy.
Milky Way to complete one revolution around the Galaxy’s center. Earth’s axis of rotation is inclined (tilted) 23.5° relative to its plane of revolution around the Sun. This inclination of the axis creates the seasons and causes the height of the Sun in the sky at noon to increase and decrease as the seasons change. The Northern Hemisphere receives the most energy from the Sun when it is tiltedtoward the Sun. This orientation corresponds to summer in the Northern Hemisphere and winter in the S...
-
Nunavut - Canadian History.
The Arctic Lands is a complex geological area that is centered on the Arctic Ocean. It includes coastal plains, plateaus, and mountains. Coastal plains and plateaus arefound in the western Northwest Territories section of the Arctic Lands, such as on Victoria Island, which is mostly a large, flat plateau. In striking contrast to theserelatively gentle landscapes, the eastern Nunavut section of the Arctic Lands is dominated by a jagged chain of ice-covered mountains. The mountains on EllesmereIsl...
-
Valley - geography.
B Longitudinal Profile A graph of the slope of a river channel at each point along its course is called a longitudinal profile . In most cases, the slope of a river becomes less steep as it flows from its headwaters to the ocean. Slopes as high as 200 m/km (1000 ft/mi) can be found in mountainous terrain, but slopes of about 2 m/km (10 ft/mi) are more typical in themiddle section of such valleys. Slopes as low as 2 cm/km (1 in/mi) can be found in rivers close to the ocean. In most rivers there...
-
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...
-
Virginia (state) - geography.
C Coastline Virginia’s coastline, for both the mainland and the Eastern Shore counties, is 180 km (112 mi) long. The state’s tidal shoreline measures 5,335 km (3,315 mi), includingall bays, inlets, tidal estuaries, and other indentations. Major indentations include Chesapeake Bay; Hampton Roads, the excellent natural harbor on which are locatedNewport News, Norfolk, and Portsmouth; and the wide tidal estuaries of the lower Potomac, James, Rappahannock, and York rivers. Cape Henry, in the southe...
-
Virginia (state) - USA History.
C Coastline Virginia’s coastline, for both the mainland and the Eastern Shore counties, is 180 km (112 mi) long. The state’s tidal shoreline measures 5,335 km (3,315 mi), includingall bays, inlets, tidal estuaries, and other indentations. Major indentations include Chesapeake Bay; Hampton Roads, the excellent natural harbor on which are locatedNewport News, Norfolk, and Portsmouth; and the wide tidal estuaries of the lower Potomac, James, Rappahannock, and York rivers. Cape Henry, in the southe...
-
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...
-
-
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...
-
Northwest Territories - Geography.
million years ago by the severe bending (folding) and faulting (breaking) of sedimentary rock that was once part of the Interior Plains. During the Wisconsin Ice Age,alpine glaciers covered the Cordillera, and the movement of the glaciers created razor-sharp peaks and ridges in these mountains. The moving glaciers also createdbroad U-shaped valleys. To the east of the Interior Plains, the ancient rocks of the Canadian Shield are exposed at the Earth’s surface, resulting in a rough, rolling terra...
-
Northwest Territories - Canadian History.
million years ago by the severe bending (folding) and faulting (breaking) of sedimentary rock that was once part of the Interior Plains. During the Wisconsin Ice Age,alpine glaciers covered the Cordillera, and the movement of the glaciers created razor-sharp peaks and ridges in these mountains. The moving glaciers also createdbroad U-shaped valleys. To the east of the Interior Plains, the ancient rocks of the Canadian Shield are exposed at the Earth’s surface, resulting in a rough, rolling terra...
-
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...
-
Yukon Territory - Geography.
Tourism is the second most important private sector industry in the Yukon. Visitors come to fish, hunt, enjoy the rugged scenery, and see the historic buildings andcreeks associated with the gold rush. Some marten, lynx, muskrat, wolverine, and other fur-bearing animals are still trapped, but the Yukon plays a minor role in Canadian fur production. The Yukon’s manufacturing industries consist almost exclusively of some mineral refining, printing, and sawmilling. Several hydroelectric plants gene...
-
Yukon Territory - Canadian History.
Tourism is the second most important private sector industry in the Yukon. Visitors come to fish, hunt, enjoy the rugged scenery, and see the historic buildings andcreeks associated with the gold rush. Some marten, lynx, muskrat, wolverine, and other fur-bearing animals are still trapped, but the Yukon plays a minor role in Canadian fur production. The Yukon’s manufacturing industries consist almost exclusively of some mineral refining, printing, and sawmilling. Several hydroelectric plants gene...
-
Pollution.
One of the greatest challenges caused by air pollution is global warming, an increase in Earth’s temperature due to the buildup of certain atmospheric gases such ascarbon dioxide. With the heavy use of fossil fuels in the 20th century, atmospheric concentrations of carbon dioxide have risen dramatically. Carbon dioxide and othergases, known as greenhouse gases, reduce the escape of heat from the planet without blocking radiation coming from the Sun. Because of this greenhouse effect,average glob...
-
-
Arctic - geography.
B Rivers and Lakes Low precipitation is characteristic of the Arctic, so large and elaborate river and lake systems are rare. In many places, however, permafrost (permanently frozen subsoil)restricts the downward drainage of meltwater from snow, and the water accumulates on the surface as shallow lakes, ponds, and marshes. In addition, rivers from morehumid regions flow seaward across the dry Arctic terrain. Several large rivers are in the Russian Arctic, and the Mackenzie and Yukon rivers are...
-
Pittsburgh - geography.
identity, such as Bloomfield (Italian), the South Side and Polish Hill (Polish), and Squirrel Hill (Jewish). The eastern neighborhoods of Point Breeze, Shadyside, and SquirrelHill are attractive city living areas, while other sections of the city afford views of the rivers and the Golden Triangle from houses constructed on steep slopes. Pittsburgh’s black population began to arrive far back in the city’s history, but its biggest growth came in the first half of the 20th century largely through m...
-
Salmon (fish) - biology.
alarm and become one of the most important conservation issues in the Pacific Northwest. Less than 2 percent of the wild salmon population of the Columbia River Basin(including parts of Washington, Oregon, Idaho, Montana, Wyoming, and British Columbia) remains and only one individual sockeye salmon returned to the Snake Riverin Idaho in 1994. Coho salmon in the Snake River have been declared extinct by the U.S. Fish and Wildlife Service, as have 106 other salmon populations on the WestCoast. Man...
-
Middle East - geography.
years.Spectrum Colour Library Apart from the Nile River, which provides much of the water supply and irrigation systems of Egypt, and the Tigris and Euphrates rivers, which supply Iraq, Syria, andTurkey, there are no major rivers or navigable waterways. The Sea of Galilee (Lake Tiberias) in northern Israel, fed from the north by the shallow, unnavigable JordanRiver, provides Israel’s main source of fresh water. With such a limited water supply, access to water for drinking, irrigation, and hydro...
-
From Bulfinch's Mythology: Prometheus and Pandora - anthology.
The world being thus furnished with inhabitants, the first age was an age of innocence and happiness, called the Golden Age. Truth and right prevailed, though not enforced by law, nor was there any magistrate to threaten or punish. The forest had not yet been robbed of its trees to furnish timbers for vessels, nor had men builtfortifications round their towns. There were no such things as swords, spears, or helmets. The earth brought forth all things necessary for man, without his labour inplo...
-
British Columbia - Geography.
hemlock, Douglas fir, Sitka spruce, and various cedars, grows rapidly in the mild, wet climate and produces the largest trees in Canada. In the dry lowlands of thesouthern and central interior, ponderosa and lodgepole pines, aspen, and bunchgrass are characteristic. Spruce dominates the Prince George region. Prairie grasses andstands of aspen are found in the northeastern corner of the province. At elevations higher than about 1,800 m (about 6,000 ft), an alpine vegetation of shrubs, mosses,and...
-
British Columbia - Canadian History.
hemlock, Douglas fir, Sitka spruce, and various cedars, grows rapidly in the mild, wet climate and produces the largest trees in Canada. In the dry lowlands of thesouthern and central interior, ponderosa and lodgepole pines, aspen, and bunchgrass are characteristic. Spruce dominates the Prince George region. Prairie grasses andstands of aspen are found in the northeastern corner of the province. At elevations higher than about 1,800 m (about 6,000 ft), an alpine vegetation of shrubs, mosses,and...
-
New Brunswick - Geography.
Grand Lake, the largest lake in New Brunswick, is in the lowlands, east of Fredericton. Most other lakes are located in the northern and southwestern parts of NewBrunswick. D Climate New Brunswick has a continental climate that is moderated by maritime influences in the coastal areas. As a result, coastal regions are slightly warmer in the winter andslightly cooler in the summer than are interior regions. Annual temperature variations are large, with the January mean usually at least 25 to 28°C...
-
-
New Brunswick - Canadian History.
Grand Lake, the largest lake in New Brunswick, is in the lowlands, east of Fredericton. Most other lakes are located in the northern and southwestern parts of NewBrunswick. D Climate New Brunswick has a continental climate that is moderated by maritime influences in the coastal areas. As a result, coastal regions are slightly warmer in the winter andslightly cooler in the summer than are interior regions. Annual temperature variations are large, with the January mean usually at least 25 to 28°C...
-
Minnesota - geography.
C Climate Minnesota’s climate is classified as humid continental because normally there is a sufficient amount of precipitation to provide at least some surplus for runoff, andbecause Minnesota’s temperature conditions are largely controlled by its location in the interior of the large landmass of North America. The result is extreme seasonaltemperature variations. The average January temperature is about -18°C (about 0°F) in the northwest and about -10°C (about 14°F) in the south, but thetherm...
-
Minnesota - USA History.
C Climate Minnesota’s climate is classified as humid continental because normally there is a sufficient amount of precipitation to provide at least some surplus for runoff, andbecause Minnesota’s temperature conditions are largely controlled by its location in the interior of the large landmass of North America. The result is extreme seasonaltemperature variations. The average January temperature is about -18°C (about 0°F) in the northwest and about -10°C (about 14°F) in the south, but thetherm...
-
West Virginia - geography.
Forests, mostly of hardwood varieties, cover 79 percent of West Virginia. The principal commercial species are the oak, yellow poplar, maple, birch, beech, black walnut,hickory, and gum. Softwoods include pines and hemlock firs. Flowering trees include the wild crab apple, dogwood, hawthorn, and redbud. Among the many floweringbushes and plants are the rhododendron, which is the state flower, the laurel, blueberry, hepatica, wild geranium, and black-eyed Susan. Insects and disease, mostly introd...
-
West Virginia - USA History.
Forests, mostly of hardwood varieties, cover 79 percent of West Virginia. The principal commercial species are the oak, yellow poplar, maple, birch, beech, black walnut,hickory, and gum. Softwoods include pines and hemlock firs. Flowering trees include the wild crab apple, dogwood, hawthorn, and redbud. Among the many floweringbushes and plants are the rhododendron, which is the state flower, the laurel, blueberry, hepatica, wild geranium, and black-eyed Susan. Insects and disease, mostly introd...
-
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...
-
Ohio - geography.
conflict with modified Gulf air and causing frontal or cyclonic storms. Gulf air is dominant in summer. In fall, polar air passing over Lake Erie is modified, delaying thekilling frost along the adjacent shoreline. C1 Temperatures The mean annual temperatures for the state range from 9° C (48° F) in the northeast to 13° C (55° F) in the south. Average January temperatures range from -4° C(24° F) in the west to 2° C (35° F) in the south. July averages are 24° C (76° F) in the south and 23° C (73...
-
-
Ohio - USA History.
conflict with modified Gulf air and causing frontal or cyclonic storms. Gulf air is dominant in summer. In fall, polar air passing over Lake Erie is modified, delaying thekilling frost along the adjacent shoreline. C1 Temperatures The mean annual temperatures for the state range from 9° C (48° F) in the northeast to 13° C (55° F) in the south. Average January temperatures range from -4° C(24° F) in the west to 2° C (35° F) in the south. July averages are 24° C (76° F) in the south and 23° C (73...
-
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...
-
New Hampshire - geography.
Washington. D1 Temperature The coldest parts of the state are in the White Mountains and the extreme north. Average January temperatures range from about -11° C (about 12° F) along theCanadian border to about -3° C (about 26° F) along the coast. July temperatures range from about 17° C (about 63° F) in the mountains to about 21° C (about 70° F)in the south. D2 Precipitation Precipitation is evenly distributed throughout the year over most of the state. However, the higher peaks of the White Mo...
-
New Hampshire - USA History.
Washington. D1 Temperature The coldest parts of the state are in the White Mountains and the extreme north. Average January temperatures range from about -11° C (about 12° F) along theCanadian border to about -3° C (about 26° F) along the coast. July temperatures range from about 17° C (about 63° F) in the mountains to about 21° C (about 70° F)in the south. D2 Precipitation Precipitation is evenly distributed throughout the year over most of the state. However, the higher peaks of the White Mo...
-
Kentucky - geography.
The climate of Kentucky is characterized by warm or hot summers and cool winters. Throughout the year, temperatures do not vary greatly from place to place,although they are generally slightly lower in the Appalachian Plateaus region than elsewhere in the state. Average July temperatures are usually from 24° to 27°C (76°to 80°F) in the central and western areas and from 23° to 24°C (74° to 76°F) in the east. January averages range from below 1°C (34°F) in the northern Bluegrassregion to more tha...
-
Kentucky - USA History.
The climate of Kentucky is characterized by warm or hot summers and cool winters. Throughout the year, temperatures do not vary greatly from place to place,although they are generally slightly lower in the Appalachian Plateaus region than elsewhere in the state. Average July temperatures are usually from 24° to 27°C (76°to 80°F) in the central and western areas and from 23° to 24°C (74° to 76°F) in the east. January averages range from below 1°C (34°F) in the northern Bluegrassregion to more tha...
-
China - country.
North China lies between the Mongolian Steppe on the north and the Yangtze River Basin on the south. It stretches west from the Bo Hai gulf and the Yellow Sea to theeastern edge of the Tibetan Plateau. Administratively, North China includes Beijing and Tianjin municipalities; Shandong and Shanxi provinces; most of Hebei, Henan,and Shaanxi provinces; and portions of Ningxia Hui Autonomous Region and of Jiangsu, Anhui, and Gansu provinces. Humans have lived in the agriculturally rich region of Nor...
-
-
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...
-
Sweden - country.
mi) and is Sweden’s second largest lake, after Vänern. The two lakes, together with several smaller lakes, rivers, and canals, form an internal water route called theGöta Canal. Built in the early 19th century, the Göta Canal extends for about 386 km (about 240 mi) and provides a scenic transportation link between the Baltic Sea,at Stockholm, and the Kattegat. Sweden’s other large lakes in the district include Mälaren, Hjälmaren, and the famously picturesque Siljan. D Climate Although one-seven...
-
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...
-
Ontario - Geography.
governed Ontario’s initial settlement and development. The province’s most important river is the St. Lawrence. Its route was much improved and enlarged by dredgingand canal building in the mid-20th century. This enabled large ocean-going vessels to reach Great Lake ports ( see St. Lawrence Seaway). The Ottawa River was an important early route to the interior for fur traders and timber merchants. The Niagara River, because of its falls, is a great center of hydroelectric power as well as aninte...
-
Ontario - Canadian History.
governed Ontario’s initial settlement and development. The province’s most important river is the St. Lawrence. Its route was much improved and enlarged by dredgingand canal building in the mid-20th century. This enabled large ocean-going vessels to reach Great Lake ports ( see St. Lawrence Seaway). The Ottawa River was an important early route to the interior for fur traders and timber merchants. The Niagara River, because of its falls, is a great center of hydroelectric power as well as aninte...
-
Japan - country.
island’s fertile soils support agriculture and provide the vast majority of Japan’s pasturelands. In addition, Hokkaidō contains coal deposits, and the cold currents off itsshores supply cold-water fish. Winters are long and harsh, so most of Hokkaid ō is lightly settled, housing about 5 percent of Japan’s population on approximately 20 percent of its land area. However,its snowy winters and unspoiled natural beauty attract many skiers and tourists. Hokkaid ō is thought of as Japan’s northern fr...
-
Pittsburgh - geography.
College of Allegheny County (1966), with branches in the city and suburbs. Pittsburgh has many outstanding cultural institutions. The Oakland district is where Carnegie Mellon University and the University of Pittsburgh are located. The CarnegieMuseums of Pittsburgh include The Carnegie Museum of Art (including the Scaife Galleries), which holds a distinguished motion-picture and video collection and a uniquestudy of architecture; the Carnegie Museum of Natural History, which displays an extensi...
-
-
Spain - country.
B Natural Resources Spain has a number of mineral resources. The largest known deposits are of iron ore, zinc, and lead. Spain also produces significant quantities of copper and mercury.These deposits are mined mainly in Huelva province in southwestern Spain, around Cartagena on the Mediterranean, and at various points along the Bay of Biscay inthe north. Additionally, uranium is mined in the region of Extremadura, near the Portuguese frontier, where pyrites, fluorspar, gypsum, tungsten, and po...
-
Thailand - country.
E Natural Resources Thailand possesses a range of mineral resources. Tin is mined in the peninsula. Important gemstones, such as sapphires, are found in the southeast, and coal reserves,particularly lignite, are in the north. Fish are abundant in rivers and coastal waters. In addition to being consumed domestically, fish are also exported. F Climate Thailand experiences a typical monsoon climate. Winds blow from the northeast during the winter months of October to March or April (known as the...