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145-800: The North Saskatchewan River is a glacier -fed river that flows from the Canadian Rockies continental divide east to central Saskatchewan , where it joins with the South Saskatchewan River to make up the Saskatchewan River . Its water flows eventually into the Hudson Bay . The Saskatchewan River system is the largest shared between the Canadian provinces of Alberta and Saskatchewan. Its watershed includes most of southern and central Alberta and Saskatchewan. The North Saskatchewan River has

290-424: A cirque landform (alternatively known as a corrie or as a cwm ) – a typically armchair-shaped geological feature (such as a depression between mountains enclosed by arêtes ) – which collects and compresses through gravity the snow that falls into it. This snow accumulates and the weight of the snow falling above compacts it, forming névé (granular snow). Further crushing of the individual snowflakes and squeezing

435-449: A temperate climate and a varied view. According to Theodore Roosevelt : We have taken into our language the word prairie , because when our backwoodsmen first reached the land [in the Midwest ] and saw the great natural meadows of long grass—sights unknown to the gloomy forests wherein they had always dwelt—they knew not what to call them, and borrowed the term already in use among

580-407: A cliff (called a buffalo jump ), to kill or injure the bison en masse . The introduction of the horse and the gun greatly expanded the killing power of the plains Natives. That was followed by the policy of indiscriminate killing by European Americans and Canadians for both commercial reasons and to weaken the independence of plains Natives, and caused a dramatic drop in bison numbers from millions to

725-402: A few hundred in a century's time, and almost caused their extinction. The very dense soil plagued the first European settlers who were using wooden plows , which were more suitable for loose forest soil. On the prairie, the plows bounced around, and the soil stuck to them. This problem was solved in 1837 by an Illinois blacksmith named John Deere who developed a steel moldboard plow that

870-711: A generating capacity of 120 megawatts (MW), and has an available water supply that allows it to be the largest producer of hydroelectric electricity in Alberta, with an average of 408,000 megawatt hours (MW⋅h) each year. One of the North Saskatchewan's major tributaries, the Brazeau River , houses the Brazeau Hydroelectric Plant . At 355 MW, the Brazeau Dam is Alberta's largest hydroelectric facility, and

1015-511: A glacier is usually assessed by determining the glacier mass balance or observing terminus behavior. Healthy glaciers have large accumulation zones, more than 60% of their area is snow-covered at the end of the melt season, and they have a terminus with a vigorous flow. Following the Little Ice Age 's end around 1850, glaciers around the Earth have retreated substantially . A slight cooling led to

1160-595: A glacier may flow into a body of water, it forms only on land and is distinct from the much thinner sea ice and lake ice that form on the surface of bodies of water. On Earth, 99% of glacial ice is contained within vast ice sheets (also known as "continental glaciers") in the polar regions , but glaciers may be found in mountain ranges on every continent other than the Australian mainland, including Oceania's high-latitude oceanic island countries such as New Zealand . Between latitudes 35°N and 35°S, glaciers occur only in

1305-411: A glacier via moulins . Streams within or beneath a glacier flow in englacial or sub-glacial tunnels. These tunnels sometimes reemerge at the glacier's surface. Most of the important processes controlling glacial motion occur in the ice-bed contact—even though it is only a few meters thick. The bed's temperature, roughness and softness define basal shear stress, which in turn defines whether movement of

1450-408: A kilometer per year. Eventually, the ice will be surging fast enough that it begins to thin, as accumulation cannot keep up with the transport. This thinning will increase the conductive heat loss, slowing the glacier and causing freezing. This freezing will slow the glacier further, often until it is stationary, whence the cycle can begin again. The flow of water under the glacial surface can have

1595-598: A large channel in which the Minnesota River evident today. The Red River of the North flows northward through a plain formerly covered by Lake Agassiz. Certain extraordinary features were produced when the retreat of the ice sheet had progressed so far as to open an eastward outlet for the marginal lakes. This outlet occurred along the depression between the northward slope of the Appalachian plateau in west-central New York and

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1740-404: A large effect on the motion of the glacier itself. Subglacial lakes contain significant amounts of water, which can move fast: cubic kilometers can be transported between lakes over the course of a couple of years. This motion is thought to occur in two main modes: pipe flow involves liquid water moving through pipe-like conduits, like a sub-glacial river; sheet flow involves motion of water in

1885-478: A length of 1,287 kilometres (800 mi), and a drainage area of 122,800 square kilometres (47,400 sq mi). At its end point at Saskatchewan River Forks it has a mean discharge of 245 cubic metres per second (8,700 cu ft/s). The yearly discharge at the Alberta–Saskatchewan border is more than 7 cubic kilometres (1.7 cu mi). The river begins above 1,800 metres (5,900 ft) at

2030-460: A lower heat conductance, meaning that the basal temperature is also likely to be higher. Bed temperature tends to vary in a cyclic fashion. A cool bed has a high strength, reducing the speed of the glacier. This increases the rate of accumulation, since newly fallen snow is not transported away. Consequently, the glacier thickens, with three consequences: firstly, the bed is better insulated, allowing greater retention of geothermal heat. Secondly,

2175-551: A stage of 9.03 m (29.6 ft) with a peak instantaneous discharge of 2,710 cubic metres per second (96,000 cu ft/s) on June 23 in Edmonton. This is significantly higher than the Bow River's peak height at 4.1 metres (13 ft) and peak discharge of 1,750 cubic metres per second (62,000 cu ft/s) on June 21, that caused widespread flooding in Calgary . However, due to

2320-667: A substantial portion of global energy needs, and leave fertile land for food production." Unlike corn and soybeans, which are both directly and indirectly major food crops, including livestock feed, prairie grasses are not used for human consumption. Prairie grasses can be grown in infertile soil, eliminating the cost of adding nutrients to the soil. Tilman and his colleagues estimate that prairie grass biofuels would yield 51 percent more energy per acre than ethanol from corn grown on fertile land. Some plants commonly used are lupine, big bluestem (turkey foot), blazing star, switchgrass , and prairie clover . Because rich and thick topsoil made

2465-484: A thin layer. A switch between the two flow conditions may be associated with surging behavior. Indeed, the loss of sub-glacial water supply has been linked with the shut-down of ice movement in the Kamb ice stream. The subglacial motion of water is expressed in the surface topography of ice sheets, which slump down into vacated subglacial lakes. The speed of glacial displacement is partly determined by friction . Friction makes

2610-410: A tremendous impact as the iceberg strikes the water. Tidewater glaciers undergo centuries-long cycles of advance and retreat that are much less affected by climate change than other glaciers. Thermally, a temperate glacier is at a melting point throughout the year, from its surface to its base. The ice of a polar glacier is always below the freezing threshold from the surface to its base, although

2755-672: Is omaka-ty 'big river'. The 49-kilometre section of the North Saskatchewan River that falls within the boundaries of Banff National Park was designated a Canadian Heritage River in 1989, due to its importance in the development of Western Canada . In 2022 the remaining 718 km within Alberta, flowing through 16 municipalities in the province, was nominated to the Canadian Heritage Rivers System, achieving final designation in March of 2024. The river demarcates

2900-574: Is a garden consisting primarily of plants from a prairie. The originally treeless prairies of the upper Mississippi basin began in Indiana and extended westward and north-westward until they merged with the drier region known as the Great Plains . An eastward extension of the same area, originally tree-covered, extended to central Ohio . Thus, the prairies generally lie between the Ohio and Missouri rivers on

3045-468: Is a persistent body of dense ice that is constantly moving downhill under its own weight. A glacier forms where the accumulation of snow exceeds its ablation over many years, often centuries . It acquires distinguishing features, such as crevasses and seracs , as it slowly flows and deforms under stresses induced by its weight. As it moves, it abrades rock and debris from its substrate to create landforms such as cirques , moraines , or fjords . Although

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3190-456: Is above or at freezing at the interface and is able to slide at this contact. This contrast is thought to a large extent to govern the ability of a glacier to effectively erode its bed , as sliding ice promotes plucking at rock from the surface below. Glaciers which are partly cold-based and partly warm-based are known as polythermal . Glaciers form where the accumulation of snow and ice exceeds ablation . A glacier usually originates from

3335-407: Is affected by factors such as slope, ice thickness, snowfall, longitudinal confinement, basal temperature, meltwater production, and bed hardness. A few glaciers have periods of very rapid advancement called surges . These glaciers exhibit normal movement until suddenly they accelerate, then return to their previous movement state. These surges may be caused by the failure of the underlying bedrock,

3480-411: Is because these peaks are located near or in the hyperarid Atacama Desert . Glaciers erode terrain through two principal processes: plucking and abrasion . As glaciers flow over bedrock, they soften and lift blocks of rock into the ice. This process, called plucking, is caused by subglacial water that penetrates fractures in the bedrock and subsequently freezes and expands. This expansion causes

3625-491: Is below the soil surface and will re-grow from its deep (upwards of 20 feet ) roots . Without disturbance , trees will encroach on a grassland and cast shade, which suppresses the understory . Prairie and widely spaced oak trees evolved to coexist in the oak savanna ecosystem. Prairie ecosystems in the United States and Canada are divided into the easternmost tallgrass prairie , the westernmost shortgrass prairie , and

3770-406: Is by basal sliding, where meltwater forms between the ice and the bed itself. Whether a bed is hard or soft depends on the porosity and pore pressure; higher porosity decreases the sediment strength (thus increases the shear stress τ B ). Porosity may vary through a range of methods. Bed softness may vary in space or time, and changes dramatically from glacier to glacier. An important factor

3915-434: Is called glaciology . Glaciers are important components of the global cryosphere . Glaciers are categorized by their morphology, thermal characteristics, and behavior. Alpine glaciers form on the crests and slopes of mountains. A glacier that fills a valley is called a valley glacier , or alternatively, an alpine glacier or mountain glacier . A large body of glacial ice astride a mountain, mountain range, or volcano

4060-416: Is called rock flour and is made up of rock grains between 0.002 and 0.00625 mm in size. Abrasion leads to steeper valley walls and mountain slopes in alpine settings, which can cause avalanches and rock slides, which add even more material to the glacier. Glacial abrasion is commonly characterized by glacial striations . Glaciers produce these when they contain large boulders that carve long scratches in

4205-460: Is estimated at over 6,000, and in southern Wisconsin, where it is placed at 5,000. They completely dominate the topography of their districts. A curious deposit of an impalpably fine and unstratified silt, known by the German name bess (or loess ), lies on the older drift sheets near the larger river courses of the upper Mississippi basin. It attains a thickness of 20 ft (6.1 m) or more near

4350-463: Is evidenced by the angularity of its grains (a bank of it will stand without slumping for years), whereas, if it had been transported significantly by water, the grains would have been rounded and polished. Loess is parent material for an extremely fertile, but droughty soil. Southwestern Wisconsin and parts of the adjacent states of Illinois, Iowa, and Minnesota are known as the driftless zone , because, although bordered by drift sheets and moraines, it

4495-400: Is free from glacial deposits. It must therefore have been a sort of oasis, when the ice sheets from the north advanced past it on the east and west, and joined around its southern border. The reason for this exemption from glaciation is the converse of that for the southward convexity of the morainic loops. While they mark the paths of greatest glacial advance along lowland troughs (lake basins),

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4640-628: Is higher, and the mountains above 5,000 m (16,400 ft) usually have permanent snow. Even at high latitudes, glacier formation is not inevitable. Areas of the Arctic , such as Banks Island , and the McMurdo Dry Valleys in Antarctica are considered polar deserts where glaciers cannot form because they receive little snowfall despite the bitter cold. Cold air, unlike warm air, is unable to transport much water vapor. Even during glacial periods of

4785-598: Is in cemetery prairies , railroad rights-of-way, or rocky/sandy/hilly places unsuitable for agriculture. States formerly with landcover in native tallgrass prairie including Iowa, Illinois, Minnesota, Wisconsin, Nebraska, and Missouri have become valued for their highly productive soils and are included in the Corn Belt . As an example of this land use intensity, Illinois and Iowa rank 49th and 50th, out of 50 US states, in total uncultivated land remaining. Drier shortgrass prairies were once used mostly for open-range ranching. With

4930-416: Is not known if that is because of inherent differences in the species or because farmed cattle tend to be confined in smaller areas. Bison dung is a vital source of nutrients for prairie soil, spreads seeds, and supports over 1,000 insect species, including specialist dung beetles which cannot subsist on the feces of any other animal. In spite of long recurrent droughts and occasional torrential rains ,

5075-430: Is now buried under the drift. The most significant area of the prairies, from Indiana to North Dakota , consists of till plains, that is, sheets of unstratified drift. The plains are 30, 50 or even 100 ft (up to 30 m) thick covering the underlying rock surface for thousands of square miles except where postglacial stream erosion has locally laid it bare. The plains have an extraordinarily even surface. The till

5220-519: Is presumably made in part of preglacial soils, but it is largely composed of rock waste mechanically transported by the creeping ice sheets. Although the crystalline rocks from Canada and some of the more resistant stratified rocks south of the Great Lakes occur as boulders and stones, a great part of the till has been crushed and ground to a clayey texture. The till plains, although sweeping in broad swells of slowly changing altitude, often appear level to

5365-593: Is shown on a Hudson's Bay Company (HBC) map from 1760, labelled as the Beaver River . Its Cree name is kisiskâciwanisîpiy , meaning 'swift current'. From this name is derived the name Saskatchewan, used as well for the South Saskatchewan River and the Saskatchewan River (of which both the North and South Saskatchewan rivers are major tributaries), and the province of that name. Its Blackfoot name

5510-400: Is similar to the Appalachian piedmont which though not exhausted by the primeval forest cover, are by no means so rich as the till sheets of the prairies. Moreover, whatever the rocky understructure, the till soil has been averaged by a thorough mechanical mixture of rock grindings. Hence, the prairies are continuously fertile for scores of miles together. The true prairies were once covered with

5655-897: Is termed an ice cap or ice field . Ice caps have an area less than 50,000 km (19,000 sq mi) by definition. Glacial bodies larger than 50,000 km (19,000 sq mi) are called ice sheets or continental glaciers . Several kilometers deep, they obscure the underlying topography. Only nunataks protrude from their surfaces. The only extant ice sheets are the two that cover most of Antarctica and Greenland. They contain vast quantities of freshwater, enough that if both melted, global sea levels would rise by over 70 m (230 ft). Portions of an ice sheet or cap that extend into water are called ice shelves ; they tend to be thin with limited slopes and reduced velocities. Narrow, fast-moving sections of an ice sheet are called ice streams . In Antarctica, many ice streams drain into large ice shelves . Some drain directly into

5800-814: Is the dominant habitat type in the Southern Canadian agricultural and climatic region which is known as Palliser's Triangle . It was once thought to be completely unarable, but is now one of the most important agricultural regions in Canada thanks to advances in irrigation technology. The dominant plant life in prairies consists of grasses , which may include 40 to 60 different grass species. In addition to grasses, prairies can include over 300 species of flowering plants. The Konza Tallgrass Prairie in Kansas hosts 250 species of native plants and provides habitat for 208 birds, 27 mammals, 25 reptiles, and over 3,000 insects. Some of

5945-733: Is the largest system of urban parks in Canada, and covers both sides of the river valley's course through Edmonton. The River Valley Alliance, a non-profit organization composed of seven municipalities which border the North Saskatchewan River, is currently working to create a continuous trail network from the town of Devon to the city of Fort Saskatchewan – a total of 100 kilometres (62 mi). Fish species include: walleye , sauger , yellow perch , northern pike , goldeye , mooneye , lake sturgeon , mountain whitefish , burbot , longnose sucker , white sucker and shorthead redhorse . The upper North Saskatchewan River contains cutthroat trout (although not native), and bull trout Like all rivers,

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6090-413: Is the region where there is a net loss in glacier mass. The upper part of a glacier, where accumulation exceeds ablation, is called the accumulation zone . The equilibrium line separates the ablation zone and the accumulation zone; it is the contour where the amount of new snow gained by accumulation is equal to the amount of ice lost through ablation. In general, the accumulation zone accounts for 60–70% of

6235-402: Is the underlying geology; glacial speeds tend to differ more when they change bedrock than when the gradient changes. Further, bed roughness can also act to slow glacial motion. The roughness of the bed is a measure of how many boulders and obstacles protrude into the overlying ice. Ice flows around these obstacles by melting under the high pressure on their stoss side ; the resultant meltwater

6380-552: Is then forced into the cavity arising in their lee side , where it re-freezes. As well as affecting the sediment stress, fluid pressure (p w ) can affect the friction between the glacier and the bed. High fluid pressure provides a buoyancy force upwards on the glacier, reducing the friction at its base. The fluid pressure is compared to the ice overburden pressure, p i , given by ρgh. Under fast-flowing ice streams, these two pressures will be approximately equal, with an effective pressure (p i – p w ) of 30 kPa; i.e. all of

6525-952: The Andes , the Himalayas , the Rocky Mountains , the Caucasus , Scandinavian Mountains , and the Alps . Snezhnika glacier in Pirin Mountain, Bulgaria with a latitude of 41°46′09″ N is the southernmost glacial mass in Europe. Mainland Australia currently contains no glaciers, although a small glacier on Mount Kosciuszko was present in the last glacial period . In New Guinea, small, rapidly diminishing, glaciers are located on Puncak Jaya . Africa has glaciers on Mount Kilimanjaro in Tanzania, on Mount Kenya , and in

6670-636: The Faroe and Crozet Islands were completely glaciated. The permanent snow cover necessary for glacier formation is affected by factors such as the degree of slope on the land, amount of snowfall and the winds. Glaciers can be found in all latitudes except from 20° to 27° north and south of the equator where the presence of the descending limb of the Hadley circulation lowers precipitation so much that with high insolation snow lines reach above 6,500 m (21,330 ft). Between 19˚N and 19˚S, however, precipitation

6815-599: The Great Plains ecoregion. The Dust Bowl was a major reason for the Great Depression . Nomadic hunting has been the main human activity on the prairies for the majority of the archaeological record. This once included many now-extinct species of megafauna . After the other extinctions, the main hunted animal on the prairies was the plains bison . Using loud noises and waving large signals, Native peoples would drive bison into fenced pens called buffalo pounds to be killed with bows and arrows or spears, or drive them off

6960-750: The Himalayas , Andes , and a few high mountains in East Africa, Mexico, New Guinea and on Zard-Kuh in Iran. With more than 7,000 known glaciers, Pakistan has more glacial ice than any other country outside the polar regions. Glaciers cover about 10% of Earth's land surface. Continental glaciers cover nearly 13 million km (5 million sq mi) or about 98% of Antarctica 's 13.2 million km (5.1 million sq mi), with an average thickness of ice 2,100 m (7,000 ft). Greenland and Patagonia also have huge expanses of continental glaciers. The volume of glaciers, not including

7105-571: The Peace , Smoky , and Athabasca rivers to the Saskatchewan River Basin . The planned dam had a maximum height of 65 metres (212 ft), with a crest length of 1.76 kilometres (5,760 ft), which would have created a reservoir capable of holding over 4.9 cubic kilometres (4,000,000 acre⋅ft) of water. The reservoir would have affected municipal water works in the City of Fort Saskatchewan,

7250-551: The Quaternary , Manchuria , lowland Siberia , and central and northern Alaska , though extraordinarily cold, had such light snowfall that glaciers could not form. In addition to the dry, unglaciated polar regions, some mountains and volcanoes in Bolivia, Chile and Argentina are high (4,500 to 6,900 m or 14,800 to 22,600 ft) and cold, but the relative lack of precipitation prevents snow from accumulating into glaciers. This

7395-521: The Rwenzori Mountains . Oceanic islands with glaciers include Iceland, several of the islands off the coast of Norway including Svalbard and Jan Mayen to the far north, New Zealand and the subantarctic islands of Marion , Heard , Grande Terre (Kerguelen) and Bouvet . During glacial periods of the Quaternary, Taiwan , Hawaii on Mauna Kea and Tenerife also had large alpine glaciers, while

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7540-577: The fur trade spearheaded by the North West Company (NWC) and followed by the HBC, the river became an important transportation route for fur trade brigades' York boats , to which it was especially well suited as it follows an eastern trend toward Hudson Bay, the entry point for the HBC into the continent. Many fur trade posts were constructed on the river, including Fort Edmonton (1795) and Rocky Mountain House,

7685-492: The labour costs of fur trade brigades , and hoped steamboat shipping would provide a suitable alternative. Several HBC steamboats navigated the river intermittently for many years, although fluctuating water levels and natural barriers (rapids and sandbars ) hampered efficient operation. With the arrival of the railroad in Western Canada , steamboat shipping on the North Saskatchewan tapered off, but steamboats operated in

7830-536: The "tons upon tons of debris" that had been pushed up against its piers, including a house swept away by the current. Thousands of Edmonton residents watched the flood destroy lumber mills , other industries and dozens of houses along the city's river valley. The river peaked at a stage of 13.73 metres (45.0 ft), a rise of 11.5 metres (38 ft) above low flow, with an estimated peak instantaneous discharge of 5,800 cubic metres per second (200,000 cu ft/s). However, based on high water marks and 1D modelling,

7975-554: The 1910s and was later abandoned. The city remained in debt from financing the project until 1960, and the site still attracts tourists today. During the 1960s and 1970s, a major dam was planned on the North Saskatchewan near the Hamlet of Hairy Hill, Alberta , about 160 kilometres (100 mi) downstream from Edmonton. This dam was part of a larger interbasin water diversion conceived by the Alberta Government to transfer water from

8120-448: The 1990s and 2000s. In a study using data from January 1993 through October 2005, more events were detected every year since 2002, and twice as many events were recorded in 2005 as there were in any other year. Ogives or Forbes bands are alternating wave crests and valleys that appear as dark and light bands of ice on glacier surfaces. They are linked to seasonal motion of glaciers; the width of one dark and one light band generally equals

8265-415: The Edmonton area until the economic crash of 1912-14. A number of dams have been planned and constructed on the North Saskatchewan River and its tributaries . No singular purpose has dominated dam planning in the basin, indeed, hydroelectric development , flood control , and water diversion schemes have all underpinned proposals to construct dams on the river. The first hydroelectric development on

8410-652: The French inhabitants. Prairie ( pronounced [pʁɛʁi] ) is the French word for "meadow", formed ultimately from the Latin root word pratum (which has the same meaning). The formation of the North American Prairies started with the uplift of the Rocky Mountains near Alberta . The mountains created a rain shadow which resulted in lower precipitation rates downwind. The parent material of most prairie soil

8555-451: The North Saskatchewan River joins the South Saskatchewan River at Saskatchewan River Forks to become the Saskatchewan River. From there, the river flows east to Tobin Lake and into Manitoba , eventually emptying into Lake Winnipeg . The river course can be divided into five distinct sections. The first, the eastern slopes of the Rocky Mountains , is the smallest area geographically, although

8700-400: The North Saskatchewan is subject to periodic flooding, beginning with rapid snowmelt in the mountains or prolonged periods of rain in the river basin . With the establishment of permanent communities along the river's course, and the rise of an administrative/government structure, records exist recording floods in the North Saskatchewan for the past century. The Bighorn Dam , constructed in

8845-525: The North Saskatchewan was planned in 1910 near the Town of Drayton Valley . Funding for the plan came from a British syndicate; design and construction were to be carried out by the Edmonton Hydro-Electric Power Scheme. The development was shelved after the outbreak of World War I. The La Colle Falls hydroelectric project east of Prince Albert was a half-built failure. Construction began in

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8990-584: The Saskatchewan River Forks, has many rapids . The valley is more shallow than the previous sections of the river, and the channel is much better defined. There is little prairie and much tree cover in this section. The water flows on then in the Saskatchewan River . The Bridge River Ash is in the vicinity of the North Saskatchewan River, which erupted from the Mount Meager massif in southwestern British Columbia about 2350 years ago. The river

9135-511: The Saskatchewan delivering trade goods and amassing furs for transportation to Europe. The North Saskatchewan also witnessed a lively, although short-lived, era of steamboat shipping during the 1870s, 1880s, and 1890s. The Hudson's Bay Company (HBC) purchased a number of steamboats from companies operating on the Red River and trading at Winnipeg / Fort Garry . The HBC desired to avoid paying

9280-494: The actual value may have been closer to 6,300 cubic metres per second (220,000 cu ft/s). The river peaked at a stage of 11.5 metres (38 ft) with a peak instantaneous discharge of 4,520 cubic metres per second (160,000 cu ft/s). Along with many other rivers in central and southern Alberta during late June, the North Saskatchewan saw significantly higher water levels and flow rates. The river peaked at

9425-412: The advance of many alpine glaciers between 1950 and 1985, but since 1985 glacier retreat and mass loss has become larger and increasingly ubiquitous. Glaciers move downhill by the force of gravity and the internal deformation of ice. At the molecular level, ice consists of stacked layers of molecules with relatively weak bonds between layers. When the amount of strain (deformation) is proportional to

9570-520: The air from the snow turns it into "glacial ice". This glacial ice will fill the cirque until it "overflows" through a geological weakness or vacancy, such as a gap between two mountains. When the mass of snow and ice reaches sufficient thickness, it begins to move by a combination of surface slope, gravity, and pressure. On steeper slopes, this can occur with as little as 15 m (49 ft) of snow-ice. In temperate glaciers, snow repeatedly freezes and thaws, changing into granular ice called firn . Under

9715-430: The amount of melting at surface of the glacier, the faster the ice will flow. Basal sliding is dominant in temperate or warm-based glaciers. The presence of basal meltwater depends on both bed temperature and other factors. For instance, the melting point of water decreases under pressure, meaning that water melts at a lower temperature under thicker glaciers. This acts as a "double whammy", because thicker glaciers have

9860-607: The annual log drive downstream to Edmonton prior to the First World War, as a source of ice blocks for home owners' iceboxes. The first bridge across the river opened in 1900, the Low Level Bridge (Edmonton) . The Canadian Northern Railway Bridge (Prince Albert) (1907-9), which also at first carried foot and wheeled traffic, and the Battleford bridge (ca. 1908) followed. Edmonton's North Saskatchewan River valley parks system

10005-713: The annual movement of the glacier. Ogives are formed when ice from an icefall is severely broken up, increasing ablation surface area during summer. This creates a swale and space for snow accumulation in the winter, which in turn creates a ridge. Sometimes ogives consist only of undulations or color bands and are described as wave ogives or band ogives. Glaciers are present on every continent and in approximately fifty countries, excluding those (Australia, South Africa) that have glaciers only on distant subantarctic island territories. Extensive glaciers are found in Antarctica, Argentina, Chile, Canada, Pakistan, Alaska, Greenland and Iceland. Mountain glaciers are widespread, especially in

10150-462: The area is still very prone to extended periods of drought, which can be disastrous for the industry if it is significantly prolonged. Research by David Tilman , ecologist at the University of Minnesota , suggests " Biofuels made from high-diversity mixtures of prairie plants can reduce global warming by removing carbon dioxide from the atmosphere. Even when grown on infertile soils, they can provide

10295-432: The bedrock has frequent fractures on the surface, glacial erosion rates tend to increase as plucking is the main erosive force on the surface; when the bedrock has wide gaps between sporadic fractures, however, abrasion tends to be the dominant erosive form and glacial erosion rates become slow. Glaciers in lower latitudes tend to be much more erosive than glaciers in higher latitudes, because they have more meltwater reaching

10440-445: The bedrock. By mapping the direction of the striations, researchers can determine the direction of the glacier's movement. Similar to striations are chatter marks , lines of crescent-shape depressions in the rock underlying a glacier. They are formed by abrasion when boulders in the glacier are repeatedly caught and released as they are dragged along the bedrock. The rate of glacier erosion varies. Six factors control erosion rate: When

10585-462: The central mixed-grass prairie. Tallgrass prairies receive over 30 inches of rainfall per year, whereas shortgrass prairies are much more arid, receiving only 12 inches or so, and mixed-grass prairies receive intermediate rainfall. Wet, mesic, and dry prairie ecosystems can also form more locally due to soil and terrain characteristics. Wet prairies may form in low-lying areas with poor drainage; dry prairie can be found on uplands or slopes. Dry prairie

10730-559: The created ice's density. The word glacier is a loanword from French and goes back, via Franco-Provençal , to the Vulgar Latin glaciārium , derived from the Late Latin glacia , and ultimately Latin glaciēs , meaning "ice". The processes and features caused by or related to glaciers are referred to as glacial. The process of glacier establishment, growth and flow is called glaciation . The corresponding area of study

10875-467: The deep profile of fjords , which can reach a kilometer in depth as ice is topographically steered into them. The extension of fjords inland increases the rate of ice sheet thinning since they are the principal conduits for draining ice sheets. It also makes the ice sheets more sensitive to changes in climate and the ocean. Although evidence in favor of glacial flow was known by the early 19th century, other theories of glacial motion were advanced, such as

11020-483: The deformation to become a plastic flow rather than elastic. Then, the glacier will begin to deform under its own weight and flow across the landscape. According to the Glen–Nye flow law , the relationship between stress and strain, and thus the rate of internal flow, can be modeled as follows: where: The lowest velocities are near the base of the glacier and along valley sides where friction acts against flow, causing

11165-541: The development of barbed wire in the 1870s and improved irrigation techniques, this region has mostly been converted to cropland and small fenced pastures. In southern Canada, Palliser's Triangle has been changed into one of the most important sources of wheat in the world as a result of improved methods of watering wheat fields (along with the rest of the Southern prairie provinces which also grow wheat, canola and many other grains). Despite those advances in farming technology,

11310-535: The disturbances of grazing and fire. Native ungulates such as bison , elk , and white-tailed deer roamed the expansive, diverse grasslands before European colonization of the Americas . For 10,000-20,000 years, native people used fire annually as a tool to assist in hunting, transportation, and safety. Evidence of ignition sources of fire in the tall grass prairie are overwhelmingly human as opposed to lightning. Humans, and grazing animals, were active participants in

11455-472: The diverse grasses and herbaceous plants. Prairies also depend on the presence of large grazing animals, particularly bison . Bison are important to the prairie ecosystem because they shape and alter the environment by grazing, trampling areas with their hooves, wallowing, and depositing manure. Bison eat more grass than flowering plants, increasing the diversity of plants in the prairie. Cattle are thought to prefer to eat flowering plants over grasses, but it

11600-431: The dominant grasses of prairies are Indian grass , big bluestem , side-oats grama , Canada wildrye , and switchgrass . Prairies are considered to be fire-dependent ecosystems . Regular controlled burning by Native Americans, practices developed through observation of non-anthropogenic fire and its effects, maintained the biodiversity of the prairie, clearing away dead vegetation and preventing trees from shading out

11745-563: The drift on the under rock. Further south, as far as the entrance of the Ohio River, the Mississippi follows a rock-walled valley 300 to 400 ft (91 to 122 m) deep, with a flood-plain 2 to 4 mi (3.2 to 6.4 km) wide. This valley seems to represent the path of an enlarged early-glacial Mississippi, when much precipitation that is today discharged to Hudson Bay and the Gulf of St. Lawrence

11890-452: The driftless zone is a district protected from ice invasion by reason of the obstruction which the highlands of northern Wisconsin and Michigan (part of the Superior upland) offered to glacial advance. The course of the upper Mississippi River is largely consequent upon glacial deposits. Its sources are in the morainic lakes in northern Minnesota. The drift deposits thereabouts are so heavy that

12035-464: The early 1970s near Nordegg, Alberta , and the Brazeau Dam , constructed in the mid-1960s, have not reduced flooding potential on the North Saskatchewan River (Alberta Environment 1981) The river peaked at a stage of 12.61 metres (41.4 ft) with an estimated peak instantaneous discharge of 5,100 cubic metres per second (180,000 cu ft/s). The 1915 flood of the North Saskatchewan River

12180-508: The eastern tallgrass prairies were plowed and turned into agricultural lands, the prairie grasses with their strong root systems were destroyed. In combination with severe droughts that resulted in the Dust Bowl , a major ecological disaster in which winds picked up the dry, unprotected prairie soil and formed it into "black blizzards" of airborne dirt that blackened the skies for days at a time across 19 states and forced 400,000 people to abandon

12325-670: The escarpment to the lower, Lake Ontario . That gave rise to Niagara Falls . Lake Ontario's outlet for a time ran down the Mohawk Valley to the Hudson River. At the higher elevation, it was known as Lake Iroquois . When ice melted from the northeastern end of the lake, it dropped to a lower level, and drained through the St. Lawrence area creating a lower base level for the Niagara River and increasing its erosive capacity. In certain districts,

12470-418: The essentially correct explanation in the 1840s, although it was several decades before it was fully accepted. The top 50 m (160 ft) of a glacier are rigid because they are under low pressure . This upper section is known as the fracture zone and moves mostly as a single unit over the plastic-flowing lower section. When a glacier moves through irregular terrain, cracks called crevasses develop in

12615-570: The expansive North Saskatchewan River Valley and natural sanctuary/parkland that surrounds it, the City of Edmonton had only minor, isolated flooding, with virtually no major property damage as a result. The North Saskatchewan River has always been a major trade route from Hudson Bay and central Canada across the Canadian Prairies to the Canadian Rockies. During the fur trade era, birch bark canoes and York boats travelled up and down

12760-435: The eye with a view stretching to the horizon. Here and there, faint depressions occur, occupied by marshy sloughs or floored with a rich black soil of postglacial origin. Thus, by sub-glacial aggradation, the prairies have been leveled up to a smooth surface, in contrast to the higher and non-glaciated hilly country just to the south. The great ice sheets formed terminal moraines around their border at various stages. However,

12905-474: The father of waters, like so many other rivers in the Northern states, owes many of its features more or less directly to glacial action. The fertility of the prairies is a natural consequence of their origin. During the mechanical transportation of the till, no vegetation was present to remove the minerals essential to plant growth, as is the case in the soils of normally weathered and dissected peneplains. The soil

13050-475: The fracture zone. Crevasses form because of differences in glacier velocity. If two rigid sections of a glacier move at different speeds or directions, shear forces cause them to break apart, opening a crevasse. Crevasses are seldom more than 46 m (150 ft) deep but, in some cases, can be at least 300 m (1,000 ft) deep. Beneath this point, the plasticity of the ice prevents the formation of cracks. Intersecting crevasses can create isolated peaks in

13195-484: The glacial base and facilitate sediment production and transport under the same moving speed and amount of ice. Material that becomes incorporated in a glacier is typically carried as far as the zone of ablation before being deposited. Glacial deposits are of two distinct types: Prairie In the U.S., the area is constituted by most or all of the states, from north to south, of North Dakota , South Dakota , Nebraska , Kansas , and Oklahoma , and sizable parts of

13340-453: The glacier to melt, creating a water source that is especially important for plants, animals and human uses when other sources may be scant. However, within high-altitude and Antarctic environments, the seasonal temperature difference is often not sufficient to release meltwater. Since glacial mass is affected by long-term climatic changes, e.g., precipitation , mean temperature , and cloud cover , glacial mass changes are considered among

13485-428: The glacier will be accommodated by motion in the sediments, or if it'll be able to slide. A soft bed, with high porosity and low pore fluid pressure, allows the glacier to move by sediment sliding: the base of the glacier may even remain frozen to the bed, where the underlying sediment slips underneath it like a tube of toothpaste. A hard bed cannot deform in this way; therefore the only way for hard-based glaciers to move

13630-450: The glacier's surface area, more if the glacier calves icebergs. Ice in the accumulation zone is deep enough to exert a downward force that erodes underlying rock. After a glacier melts, it often leaves behind a bowl- or amphitheater-shaped depression that ranges in size from large basins like the Great Lakes to smaller mountain depressions known as cirques . The accumulation zone can be subdivided based on its melt conditions. The health of

13775-461: The grasslands of the Great Plains were not subject to great soil erosion . The root systems of native prairie grasses firmly held the soil in place to prevent run-off of soil. When the plant died, the fungi and bacteria returned its nutrients to the soil. These deep roots also helped native prairie plants reach water in even the driest conditions. Native grasses suffer much less damage from dry conditions than many farm crops currently grown. When

13920-417: The head of the gorges are now occupied by little lakes. The most significant stage in this series of changes occurred when the glacio-marginal lake waters were lowered so that the long escarpment of Niagara limestone was laid bare in western New York. The previously confluent waters were then divided into two lakes. The higher one, Lake Erie , supplied the outflowing Niagara River , which poured its waters down

14065-614: The ice at the bottom of the glacier move more slowly than ice at the top. In alpine glaciers, friction is also generated at the valley's sidewalls, which slows the edges relative to the center. Mean glacial speed varies greatly but is typically around 1 m (3 ft) per day. There may be no motion in stagnant areas; for example, in parts of Alaska, trees can establish themselves on surface sediment deposits. In other cases, glaciers can move as fast as 20–30 m (70–100 ft) per day, such as in Greenland's Jakobshavn Isbræ . Glacial speed

14210-416: The ice of the last glacial epoch had retreated so far that its front border lay on a northward slope, belonging to the drainage area of the Great Lakes, bodies of water accumulated in front of the ice margin, forming glacio-marginal lakes. The lakes were small at first, and each had its own outlet at the lowest depression of land to the south. As the ice melted further back, neighboring lakes became confluent at

14355-483: The ice sheets advanced in lobes along the lowlands of the Great Lakes . Neighboring morainic loops join each other in re-entrants (north-pointing cusps), where two adjacent glacial lobes came together and formed their moraines in largest volume. The moraines are of too small relief to be shown on any maps except of the largest scale. Small as they are, they are the chief relief of the prairie states, and, in association with

14500-471: The ice sheets extended to the land sloping southward to the Ohio River , Mississippi River and Missouri River , the drift-laden streams flowed freely away from the ice border. As the streams escaped from their subglacial channels, they spread into broader channels and deposited some of their load, and thus aggraded their courses. Local sheets or aprons of gravel and sand are spread more or less abundantly along

14645-420: The ice sheets of Antarctica and Greenland, has been estimated at 170,000 km . Glacial ice is the largest reservoir of fresh water on Earth, holding with ice sheets about 69 percent of the world's freshwater. Many glaciers from temperate , alpine and seasonal polar climates store water as ice during the colder seasons and release it later in the form of meltwater as warmer summer temperatures cause

14790-544: The ice to act as a lever that loosens the rock by lifting it. Thus, sediments of all sizes become part of the glacier's load. If a retreating glacier gains enough debris, it may become a rock glacier , like the Timpanogos Glacier in Utah. Abrasion occurs when the ice and its load of rock fragments slide over bedrock and function as sandpaper, smoothing and polishing the bedrock below. The pulverized rock this process produces

14935-488: The ice, called seracs . Crevasses can form in several different ways. Transverse crevasses are transverse to flow and form where steeper slopes cause a glacier to accelerate. Longitudinal crevasses form semi-parallel to flow where a glacier expands laterally. Marginal crevasses form near the edge of the glacier, caused by the reduction in speed caused by friction of the valley walls. Marginal crevasses are largely transverse to flow. Moving glacier ice can sometimes separate from

15080-411: The idea that meltwater, refreezing inside glaciers, caused the glacier to dilate and extend its length. As it became clear that glaciers behaved to some degree as if the ice were a viscous fluid, it was argued that "regelation", or the melting and refreezing of ice at a temperature lowered by the pressure on the ice inside the glacier, was what allowed the ice to deform and flow. James Forbes came up with

15225-418: The increased pressure can facilitate melting. Most importantly, τ D is increased. These factors will combine to accelerate the glacier. As friction increases with the square of velocity, faster motion will greatly increase frictional heating, with ensuing melting – which causes a positive feedback, increasing ice speed to a faster flow rate still: west Antarctic glaciers are known to reach velocities of up to

15370-423: The infrared OH stretching mode of the water molecule. (Liquid water appears blue for the same reason. The blue of glacier ice is sometimes misattributed to Rayleigh scattering of bubbles in the ice.) A glacier originates at a location called its glacier head and terminates at its glacier foot, snout, or terminus . Glaciers are broken into zones based on surface snowpack and melt conditions. The ablation zone

15515-516: The land well suited for agricultural use, only 1% of tallgrass prairie remains in the U.S. today. Shortgrass prairie is more abundant. Significant preserved areas of prairie include: Virgin prairie refers to prairie land which has never been plowed. Small virgin prairies exist in the American Midwestern states and in Canada. Restored prairie refers to a prairie that has been reseeded after plowing or other disturbance. A prairie garden

15660-481: The landscape. The fourth section, from the Vermilion River to Prince Albert is principally prairie with a few small stretches of timber and secondary forest cover. The valley of the river is much wider, and the river itself spreads out across shallow water and flows over many shifting sand bars . Low-lying, flat areas border the river for much of this section. The final section of the river, from Prince Albert to

15805-420: The largest in terms of run-off and contributed water flow. The glaciers and perpetual snows of the mountain peaks feed the river year-round. Mountains, with little vegetation, experience fast-melting snow cover. The second section of the river comprises the foothills region . The terrain is hilly and rough, with a deeper and more defined valley. This area is well covered with forest and muskeg , and run-off into

15950-446: The level of the lowest outlet of the group. The outflowing streams grew in the same proportion and eroded a broad channel across the height of land and far down stream, while the lake waters built sand reefs or carved shore cliffs along their margin, and laid down sheets of clay on their floors. All of these features are easily recognized in the prairie region. The present site of Chicago was determined by an Indian portage or carry across

16095-500: The low divide between Lake Michigan and the headwaters of the Illinois River . This divide lies on the floor of the former outlet channel of the glacial Lake Michigan. Corresponding outlets are known for Lake Erie , Lake Huron , and Lake Superior . A very large sheet of water, named Lake Agassiz , once overspread a broad till plain in northern Minnesota and North Dakota. The outlet of this glacial lake, called river Warren, eroded

16240-419: The morainic belts are of slight relief in comparison to the great area of the ice. They rise gently from the till plains to 50, 100 or more feet. They may be one, two or three miles (5 km) wide and their hilly surface, dotted over with boulders, contains many small lakes in basins or hollows, instead of streams in valleys. The morainic belts are arranged in groups of concentric loops, convex southward, because

16385-679: The most deformation. Velocity increases inward toward the center line and upward, as the amount of deformation decreases. The highest flow velocities are found at the surface, representing the sum of the velocities of all the layers below. Because ice can flow faster where it is thicker, the rate of glacier-induced erosion is directly proportional to the thickness of overlying ice. Consequently, pre-glacial low hollows will be deepened and pre-existing topography will be amplified by glacial action, while nunataks , which protrude above ice sheets, barely erode at all – erosion has been estimated as 5 m per 1.2 million years. This explains, for example,

16530-445: The most sensitive indicators of climate change and are a major source of variations in sea level . A large piece of compressed ice, or a glacier, appears blue , as large quantities of water appear blue , because water molecules absorb other colors more efficiently than blue. The other reason for the blue color of glaciers is the lack of air bubbles. Air bubbles, which give a white color to ice, are squeezed out by pressure increasing

16675-406: The nearly imperceptible slopes of the till plains, they determine the course of many streams and rivers, which as a whole are consequent upon the surface form of the glacial deposits. The complexity of the glacial period and its subdivision into several glacial epochs, separated by interglacial epochs of considerable length (certainly longer than the postglacial epoch) has a structural consequence in

16820-416: The north end of Abraham Lake, where the North Saskatchewan emerges to track eastward to Rocky Mountain House . At Rocky Mountain House, the river abruptly turns north again for 100 kilometres (62 mi) where it switches east towards Edmonton, Alberta . In Edmonton, the river passes through the centre of the city in a northeasterly direction and out towards Smoky Lake at which point it quickly changes to

16965-417: The outer side of the morainic belts. Long trains of gravel and sands clog the valleys that lead southward from the glaciated to the non-glaciated area. Later, when the ice retreated further and the unloaded streams returned to their earlier degrading habit, they more or less completely scoured out the valley deposits, the remains of which are now seen in terraces on either side of the present flood plains. When

17110-721: The pooling of meltwater at the base of the glacier  — perhaps delivered from a supraglacial lake  — or the simple accumulation of mass beyond a critical "tipping point". Temporary rates up to 90 m (300 ft) per day have occurred when increased temperature or overlying pressure caused bottom ice to melt and water to accumulate beneath a glacier. In glaciated areas where the glacier moves faster than one km per year, glacial earthquakes occur. These are large scale earthquakes that have seismic magnitudes as high as 6.1. The number of glacial earthquakes in Greenland peaks every year in July, August, and September and increased rapidly in

17255-411: The prairie–parkland divide for much of its course and acted as a natural boundary between plains Blackfoot of the south and woodland Cree of the north for thousands of years. Archaeologists have found evidence and indications of nearly 800 permanent or temporary occupation and quarry sites in the Edmonton region alone, dating back hundreds and sometimes thousands of years. With the westward expansion of

17400-486: The present divides between the drainage basins of Hudson Bay , Lake Superior , and the Gulf of Mexico evidently stand in no very definite relation to the preglacial divides. The course of the Mississippi through Minnesota is largely guided by the form of the drift cover. Several rapids and the Saint Anthony Falls (determining the site of Minneapolis ) are signs of immaturity, resulting from superposition through

17545-410: The pressure of the layers of ice and snow above it, this granular ice fuses into denser firn. Over a period of years, layers of firn undergo further compaction and become glacial ice. Glacier ice is slightly more dense than ice formed from frozen water because glacier ice contains fewer trapped air bubbles. Glacial ice has a distinctive blue tint because it absorbs some red light due to an overtone of

17690-410: The process of prairie formation and the establishment of the diversity of graminoid and forbs species. Fire has the effect on prairies of removing trees , clearing dead plant matter, and changing the availability of certain nutrients in the soil from the ash produced. Fire kills the vascular tissue of trees, but not prairie species, as up to 75% (depending on the species) of the total plant biomass

17835-549: The river is much more constant and stable than in the mountains. From Edmonton to the mouth of the Vermilion River, the North Saskatchewan flows through the plains-parkland divide, with occasional stretches of prairie. The North Saskatchewan River valley parks system ; the largest expanses of urban parkland in Canada. Cutting across Edmonton and the Capital Region . The river runs in a well-defined valley with deep cuts in

17980-460: The rivers and gradually fades away at a distance of ten or more miles (16 or more km) on either side. It contains land shells, and hence cannot be attributed to marine or lacustrine submergence. The best explanation is that, during certain phases of the glacial period, it was carried as dust by the winds from the flood plains of aggrading rivers, and slowly deposited on the neighboring grass-covered plains. The glacial and eolian origin of this sediment

18125-509: The sea, often with an ice tongue , like Mertz Glacier . Tidewater glaciers are glaciers that terminate in the sea, including most glaciers flowing from Greenland, Antarctica, Baffin , Devon , and Ellesmere Islands in Canada, Southeast Alaska , and the Northern and Southern Patagonian Ice Fields . As the ice reaches the sea, pieces break off or calve, forming icebergs . Most tidewater glaciers calve above sea level, which often results in

18270-523: The south and the Great Lakes on the north. The prairies are a contribution of the glacial period. They consist of glacial drift deposited unconformably on an underlying rock surface of moderate or small relief. Here, the rocks are an extension of the same stratified Palaeozoic formations already described as occurring in the Appalachian region and around the Great Lakes . They are usually fine-textured limestones and shales lying horizontal. The moderate or small relief they were given by mature preglacial erosion

18415-447: The southeast and then more to the east as it makes its way to the Alberta–Saskatchewan boundary. From the border, the river flows southeast between North Battleford and Battleford and on in the direction of Saskatoon . About 40 kilometres (25 mi) northwest of Saskatoon, near Langham , the river veers to the northeast where it passes through the City of Prince Albert . About 30 kilometres (19 mi) downstream of Prince Albert,

18560-505: The southward slope of the melting ice sheet. When this eastward outlet came to be lower than the south-westward outlet across the height of land to the Ohio or Mississippi river, the discharge of the marginal lakes was changed from the Mississippi system to the Hudson system. Many well-defined channels, cutting across the north-sloping spurs of the plateau in the neighborhood of Syracuse, New York mark

18705-409: The stagnant ice above, forming a bergschrund . Bergschrunds resemble crevasses but are singular features at a glacier's margins. Crevasses make travel over glaciers hazardous, especially when they are hidden by fragile snow bridges . Below the equilibrium line, glacial meltwater is concentrated in stream channels. Meltwater can pool in proglacial lakes on top of a glacier or descend into the depths of

18850-520: The states of Montana , Wyoming , Colorado , New Mexico , Texas in the west, and to the east, Minnesota , Wisconsin , Iowa , Missouri , Illinois , and Indiana . The Palouse of Washington and the Central Valley of California are also prairies. The Canadian Prairies occupy vast areas of Manitoba , Saskatchewan , and Alberta . Prairies may contain various lush flora and fauna , often contain rich soil maintained by biodiversity , with

18995-423: The stress being applied, ice will act as an elastic solid. Ice needs to be at least 30 m (98 ft) thick to even start flowing, but once its thickness exceeds about 50 m (160 ft) (160 ft), stress on the layer above will exceeds the inter-layer binding strength, and then it'll move faster than the layer below. This means that small amounts of stress can result in a large amount of strain, causing

19140-509: The subglacial till was not spread out in a smooth plain, but accumulated in elliptical mounds, 100–200 feet. high and 0.5 to 1 mile (0.80 to 1.61 kilometres) long with axes parallel to the direction of the ice motion as indicated by striae on the underlying rock floor. These hills are known by the Irish name, drumlins , used for similar hills in north-western Ireland . The most remarkable groups of drumlins occur in western New York , where their number

19285-425: The superposition of successive till sheets, alternating with non-glacial deposits. It also has a physiographic consequence in the very different amount of normal postglacial erosion suffered by the different parts of the glacial deposits. The southernmost drift sheets, as in southern Iowa and northern Missouri , have lost their initially plain surface and are now maturely dissected into gracefully rolling forms. Here,

19430-438: The surface snowpack may experience seasonal melting. A subpolar glacier includes both temperate and polar ice, depending on the depth beneath the surface and position along the length of the glacier. In a similar way, the thermal regime of a glacier is often described by its basal temperature. A cold-based glacier is below freezing at the ice-ground interface and is thus frozen to the underlying substrate. A warm-based glacier

19575-413: The temporary paths of the ice-bordered outlet river. Successive channels are found at lower and lower levels on the plateau slope, indicating the successive courses taken by the lake outlet as the ice melted further and further back. On some of the channels, deep gorges were eroded heading in temporary cataracts which exceeded Niagara in height but not in breadth. The pools excavated by the plunging waters at

19720-704: The toe of the Saskatchewan Glacier in the Columbia Icefield , and flows southeast through Banff National Park alongside the Icefields Parkway . At the junction of the David Thompson Highway (Highway 11), it initially turns northeast for 10 kilometres (6.2 mi) before switching to a more direct eastern flow for about 30 kilometres (19 mi). At this point, it turns north where it eventually arrives at Abraham Lake . Bighorn Dam constricts

19865-546: The uppermost post reached by canoe navigation. The river's importance continued after the amalgamation of the HBC and the NWC. The river was plied by a number of steamboats up to the First World War, although for everyday freight the growing web of railway lines in the western prairies eventually replaced them. The river was used commercially for many years – to carry flatboats of settlers goods and construction materials downstream from Edmonton, to float thousands of logs in

20010-456: The valleys of even the small streams are well opened and graded, and marshes and lakes are rare. These sheets are of early Pleistocene origin. Nearer the Great Lakes, the till sheets are trenched only by the narrow valleys of the large streams. Marshy sloughs still occupy the faint depressions in the till plains and the associated moraines have abundant small lakes in their undrained hollows. These drift sheets are of late Pleistocene origin. When

20155-417: The weight of the ice is supported by the underlying water, and the glacier is afloat. Glaciers may also move by basal sliding , where the base of the glacier is lubricated by the presence of liquid water, reducing basal shear stress and allowing the glacier to slide over the terrain on which it sits. Meltwater may be produced by pressure-induced melting, friction or geothermal heat . The more variable

20300-688: Was built in 1965 by Calgary Power. Though having a higher peak generating capacity than the Bighorn Dam, the hydrology of the Brazeau means that its average annual electricity production is a slightly smaller 397,000 MW⋅h. Tributaries of the North Saskatchewan River: [REDACTED] Media related to North Saskatchewan River at Wikimedia Commons Glacier A glacier ( US : / ˈ ɡ l eɪ ʃ ər / ; UK : / ˈ ɡ l æ s i ər , ˈ ɡ l eɪ s i ər / )

20445-521: Was delivered to the Gulf of Mexico, for the curves of the present river are of distinctly smaller radii than the curves of the valley. Lake Pepin (30 mi [48 km] below St. Paul ), a picturesque expansion of the river across its flood-plain, is due to the aggradation of the valley floor where the Chippewa River , coming from the northeast, brought an overload of fluvio-glacial drift. Hence, even

20590-450: Was distributed during the last glacial advance that began about 110,000 years ago. The glaciers expanding southward scraped the landscape, picking up geologic material and leveling the terrain. As the glaciers retreated about 10,000 years ago, they deposited this material in the form of till . Wind-based loess deposits also form an important parent material for prairie soils. Tallgrass prairie evolved over tens of thousands of years with

20735-477: Was likely to inundate part of the Saddle Lake Indian reserve , and would have flooded a number of oil and natural gas fields in the area. The plan was later shelved in light of economic and environmental concerns. The Bighorn Dam was constructed near Nordegg and created Abraham Lake , one of the largest reservoirs in Alberta. The dam was constructed in 1972 by Calgary Power . The Bighorn Plant has

20880-492: Was one of the most dramatic in the history of Edmonton. On 28 June, the Edmonton Bulletin reported the river had risen "10 feet in as many hours" and ultimately hitting a height of 42 feet over the low water level. A frantic phone call from Rocky Mountain House alerted local authorities to the flood's arrival. The Canadian Northern Railway had parked a number of train cars on the city's Low Level Bridge to protect against

21025-465: Was stronger and cut the roots, making the fertile soils ready for farming. Former grasslands are now among the most productive agricultural lands on Earth. The tallgrass prairie has been converted into one of the most intensive crop producing areas in North America. Less than one tenth of one percent (<0.09%) of the original landcover of the tallgrass prairie biome remains. Much of what persists

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