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102-655: From its headwaters in a heavily glaciated area in British Columbia, south of the lower Iskut River , the Unuk flows west and south for 129 kilometres (80 mi), crossing into Alaska and emptying into Burroughs Bay, an inlet of Behm Canal. In Alaska the river flows through the Misty Fjords National Monument . In Tlingit it is called Joonáx̱ , the meaning of which is obscure but may have to do with dreaming (cf. aawajoon “he dreamed”). It

204-424: 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

306-523: A full dam and reservoir, rather a 7 m (23 ft) high weir diverts about 250 m /s (8,800 cu ft/s) of water from the Iskut into a 3.3 km (2.1 mi) power tunnel, leading to an underground power station containing turbines and generators . A tailrace tunnel returns the water to the Iskut River downstream of the powerhouse. Electricity generated by the project's substation

408-522: 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

510-601: 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

612-411: 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

714-408: 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

816-717: A large contiguous set of protected areas known collectively as the Stikine Country Protected Areas . British Columbia Highway 37 , also called the Stewart–Cassiar Highway, runs along the east side of the upper and part of the middle Iskut River. The Iskut River originates at Kluachon Lake , near the source of the Klastline River, and about 40 km (25 mi) west-northwest of Mount Edziza . A number of small streams feed Kluachon Lake, such as Kluachon Creek. From Kluachon Lake

918-404: 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

1020-460: 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,

1122-467: A maximum depth of 120 m (390 ft). The Iskut exits the south end of the lake and flows into Kinaskan Lake Provincial Park , then enters Natadesleen Lake . After exiting Natadesleen Lake the Iskut River continues south. At the southern end of Kinaskan Lake Provincial Park the Iskut River tumbles down Cascade Falls , a staircase of Jurassic eroded sedimentary rocks , located about 500 m (1,600 ft) below Natadesleen Lake. Cascade Falls

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1224-646: A shared transitional zone between the interior plateau Tahltan and the coastal Tlingit people. In protohistoric times the Tlingit ascended the Stikine River and its tributaries, including the lower Iskut, in large canoes during the summer to dry salmon and berries. They also visited trading camps as far inland as Telegraph Creek and the Tahltan River . In the winter the Tahltan had exclusive use of

1326-488: 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

1428-410: 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

1530-521: A watershed area of 453 km (175 sq mi), about 5% glacier-covered. Much of the lower Little Iskut River is braided. Continuing south the Iskut is joined by Three Mile Creek, then Eastman Creek. Burrage Creek, a significant tributary, joins the Iskut from the southeast, after which the Iskut begins to flow through a constraining canyon in which it is joined by Ball Creek and Durham Creek. The Iskut flows by Iskut River Hot Springs Provincial Park . Extremely hot water, heated by magma of

1632-559: Is a barrier to fish migration , and the Forrest Kerr Project's diversion weir at the head of the canyon is impassable to fish migration. Thus anadromous fish are blocked from the middle and upper Iskut River watershed. There are ongoing studies to assess whether modifications to the river in the canyon and to the Forrest Kerr diversion weir could allow fish migration into the middle Iskut watershed. The canyon marks

1734-541: Is a barrier to fish migration, and the Forrest Kerr Hydroelectric Project at the head of the canyon is impassable to fish migration. Thus anadromous fish are blocked from the middle Iskut River watershed. There are ongoing studies to assess whether modifications to the river in the canyon and the Forrest Kerr diversion weir could allow fish migration into the middle Iskut watershed. Studies have shown that some sockeye and steelhead are keyed to

1836-468: 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

1938-456: 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

2040-407: 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,

2142-619: Is an impassable upstream barrier to fish migration, blocking anadromous fish from reaching the upper Iskut watershed. Cascade Falls also marks the transition between the upper and middle Iskut River drainage basins. Just downstream of Cascade Falls the Little Iskut River joins the Iskut River. Originating in Mount Edziza Provincial Park , the Little Iskut River is a major tributary with

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2244-411: 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

2346-406: 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

2448-434: 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

2550-416: 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

2652-529: Is derived from the Tlingit name for the area, Joonáxh (Place of Dreams). 56°04′35″N 131°04′47″W  /  56.07639°N 131.07972°W  / 56.07639; -131.07972 Iskut River The Iskut River , located in the northwest part of the province of British Columbia is the largest tributary of the Stikine River , entering it about 11 km (6.8 mi) above its entry into Alaska . From its source at Kluachon Lake

2754-647: 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

2856-666: Is in the asserted traditional territory of the Tahltan First Nation and Iskut First Nation , of the Tahltan people. The lower Iskut River is also in the traditional territory of the Tlingit , specifically the Shtax'héen Ḵwáan, commonly known as the Stikine River people . The name of the Iskut River possibly comes from a Nisga'a word meaning "stinking", otherwise of unknown origin. The upper Iskut River, defined as

2958-703: Is located near the north end of Eddontenajon Lake, near Iskut. Just south of Eddontenajon Lake the Iskut River enters Tatogga Lake , into which several streams empty, including Jackson Creek, Kimball Creek, and Todagin Creek. Todagin Creek flows through Todagin South Slope Provincial Park , as well as the Todagin Wildlife Management Area . South of Tatogga Lake the Iskut River enters Kinaskan Lake. Kinaskan Lake has an average depth of 57 m (187 ft) and

3060-546: Is occasionally referred to as Oonáx̱ , which is a reduced form. The USGS reports that a 1906 publication said the correct name for the river is “Junuk” or “Junock”, but it is unclear whether the initial sound is supposed to be an affricate [dʒ] or an approximant [j] . The former sound would reflect the full Tlingit name, the latter the English adaptation. The Unuk River supports relatively large runs of salmon , including chinook, coho, pink, chum, and sockeye. The name Unuk

3162-897: 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

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3264-413: 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

3366-402: 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

3468-552: 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

3570-534: Is transmitted to BC Hydro's substation at Bob Quinn Lake via a transmission line built by AltaGas. The Forrest Kerr Project is one of the largest run-of-river hydroelectric projects in North America. AltaGas built two other nearby run-of-river projects, the 66 MW McLymont Creek Hydro Project, and the 16 MW Volcano Creek Project, both of which began producing electricity in 2014. The Forrest Kerr Project's diversion weir blocks fish migration. The canyon below

3672-993: 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

3774-538: The Boundary Ranges of the Coast Mountains . The Iskut River's watershed covers 9,544 km (3,685 sq mi), and its mean annual discharge is 457 m /s (16,100 cu ft/s). The river's watershed's land cover is classified as 34.6% conifer forest , 20.1% barren , 18.2% snow / glacier , 13.4% shrubland , 10.0% herbaceous , and small amounts of other cover. The mouth of

3876-644: 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

3978-760: 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

4080-575: The Nass River watershed, where it follows the Nass tributary, Bell-Irving River . Near Bob Quinn Lake the Iskut is joined by one of its largest tributaries, the Ningunsaw River , flowing from the southeast. The Ningunsaw River's watershed covers an area of 673 km (260 sq mi). The landscape is very mountainous with elevations up to 2,183 m (7,162 ft). About 12% of

4182-800: The Ningunsaw River the Iskut flows southwest through a canyon and is regulated by the Forrest Kerr Hydroelectric Project , a run-of-river hydroelectric project. The lower Iskut flows west through an increasingly braided channel. The upper Iskut is in the Klastline Plateau , a subregion of the Stikine Plateau . The middle Iskut forms the boundary between the Stikine Plateau and the Skeena Mountains . The lower Iskut flows through

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4284-590: The Northern Cordilleran Volcanic Province , weeps out of a rocky embankment and into the Iskut River. Most of the springs are only a few metres from the river during low flows and are submerged during high flows. South of the hot springs the Iskut River is joined by More Creek , which originates in Mount Edziza Provincial Park, then Thomas Creek and Devil Creek. Continuing south the Iskut flows along

4386-562: 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

4488-535: 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

4590-448: 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

4692-509: The Chiyone (wolf) clan or moiety. The Kartchottee (raven) band of the Tses'Kiya (raven) clan occupied much of the lower Stikine and Iskut Rivers. During the maritime fur trade era of the late 18th and early 19th centuries Tlingit–Tahltan trade intensified as the Tlingit gained local monopolies on trade with Russian, British, and American trading ships. Tlingit Chief Shakes controlled trade up

4794-516: The Craig River is in Alaska. A few kilometres below Caralin Creek the Iskut River empties into the Stikine River just north of the community of Stikine , and south of Fowler , Great Glacier Provincial Park , and Choquette Hot Springs Provincial Park . Most of the Iskut River watershed has been part of the Tahltan peoples homeland since prehistoric times. The lower Iskut is part of

4896-600: The Iskut River flows south about 2 km (1.2 mi) to Eddontenajon Lake , joined along the way by Zetu Creek, flowing southwest from Zechtoo Mountain. The settlement of Iskut , home of the Tahltan Iskut First Nation , is located on Zetu Creek, southeast of Kluachon Lake. The Iskut First Nation's main Indian reserve is "Iskut 6", located at the community of Iskut. The Iskut First Nation administers two other reserves, "Kluachon 1", located at

4998-401: The Iskut River flows south and west for about 248 km (154 mi) to the Stikine River near the border of British Columbia and Alaska. The upper Iskut flows south through a series of lakes: Kluachon Lake, Eddontenajon Lake , Tatogga Lake , Kinaskan Lake , Natadesleen Lake , and others. The middle Iskut encompasses the area between the Little Iskut River and Forrest Kerr Creek . Below

5100-516: The Iskut River is located about 48 km (30 mi) northeast of Wrangell, Alaska , about 140 km (87 mi) northwest of Stewart, British Columbia , and about 133 km (83 mi) south of Telegraph Creek, British Columbia . The Iskut watershed is highly glaciated and is characterized by landscapes shaped by geologically recent glaciers and the Laurentide Ice Sheet as well as volcanism . The Iskut River watershed

5202-478: The Iskut River to the vicinity of the Little Iskut River, where it leaves the Iskut, passes through the Little Iskut River watershed and through Mount Edziza Provincial Park to Telegraph Creek on the Stikine River. After the Ningunsaw confluence the Iskut River turns southwest, flowing through a braided channel and receiving the waters of Estshi Creek. The braided section comes to an end as Volcano Creek joins from

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5304-514: The Iskut watershed, including cutthroat trout , three-spined stickleback , and kokanee salmon . Between Forrest Kerr Creek and Snippaker Creek the Iskut River flows through the Lower Iskut Canyon, about 20 km (12 mi) long, which is carved into basaltic lava flows from Iskut Canyon Cone . Below the canyon the braided portion of the Iskut River begins. The Lower Iskut Canyon, between Snippaker Creek and Forrest Kerr Creek,

5406-675: The Stikine and Iskut Rivers, which largely consisted of Western goods exchanged for furs. Non-indigenous people first visited the middle and upper Iskut River watershed in 1824. In 1825 the Hudson's Bay Company (HBC) and the Russian-American Company (RAC) claimed area for trapping fur-bearing mammals. In 1838 Robert Campbell of the HBC made contact with the Tahltan from the interior, seeking to establish trading relations. But

5508-564: The Tahltan and Tlingit. Socially the Tahltan were divided into two exogamous moieties or clans , Tses'Kiya (raven) and Chiyone (wolf). These were further divided into three groups, sometimes also called clans. Around 1750 Tahltan–Tlingit intermarriage gave rise to a fourth group, the Nanyiee (wolf) family or band. Most of the Iskut River's watershed was inhabited by the Tahltan Tuckclarwaydee (also called "Naskoten") band of

5610-404: The Tahltan resented the disruption of established trading patterns and Chief Shakes had convinced the Tahltan that traders from the interior were enemies and should be killed. Campbell was forced to retreat from the region. In the late 1830s the HBC and RAC clashed over control of the coastal fur trade in the Stikine River area. In 1839 an agreement was reached in which the HBC leased a section of

5712-412: 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

5814-520: 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

5916-430: 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

6018-713: 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

6120-432: 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

6222-445: 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

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6324-429: The canyon. Three hydroelectric projects have been built in the area: the Forrest Kerr Hydroelectric Project, McLymont Creek Hydroelectric Project, and Volcano Creek Hydroelectric Project, all of which began operating in 2014. The largest is the Forrest Kerr Project, which diverts a portion of the Iskut River into a 3 km (1.9 mi) tunnel leading to an underground hydroelectric powerhouse. The Lower Iskut Canyon

6426-421: The coast and gained access to the Stikine River trade. The HBC acquired an RAC outpost at present Wrangell, Alaska, and named it Fort Stikine . The Tlingit resisted the HBC's attempts to take over the Stikine River trade, forcing the HBC to suspend plans to occupy the interior. During this period of intensified trade many aspects of the Tlingit's coastal culture spread into the interior. Diseases also spread from

6528-402: The coast into the interior, causing a drastic reduction in both Tlingit and Tahltan populations. Several smallpox epidemics devastated the Tahltan people, including one in 1836-38 and the 1862 Pacific Northwest smallpox epidemic . In 1861 prospectors began to search for gold in the Stikine River basin. By 1878 most of the Iskut and Stikine River drainages had been explored by Westerners. In

6630-571: 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

6732-467: 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

6834-483: 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

6936-687: The early 20th century the region became a destination for recreational hunters. Hunting camps were established throughout the region. Local natives were employed as hunting guides. In the 1950s scientists began studying the area's significant wildlife ecosystems, eventually leading to the establishment of Spatsizi Plateau Wilderness Provincial Park in 1975. Many other protected areas have been established since then. The Iskut River supports runs of anadromous salmonid fish species, including bull trout , Chinook salmon , chum salmon , coho salmon , Dolly Varden trout , pink salmon , sockeye salmon , and steelhead trout . Many other fish species are present in

7038-401: The east, then Forrest Kerr Creek joins from the north. Between Forrest Kerr Creek and Snippaker Creek the Iskut River flows through the Lower Iskut Canyon, about 20 km (12 mi) long, which is carved into basaltic lava flows from Iskut Canyon Cone . McLymont Creek, flowing from the north, joins the Iskut in the canyon. Snippaker Creek, flowing from the south, joins at the end of

7140-418: 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

7242-430: The flow chemistry of the Forrest Kerr tailrace sufficiently to enter the power tunnel, which suggests that these fish originated above the canyon. The Iskut River's watershed provides habitat for a large number of animal species. The upper Iskut region supports populations of wolverine, fisher, grizzly bear , Stone sheep , mountain goat , moose , woodland caribou , wolf , and hoary marmot , among many others. Among

7344-475: 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

7446-453: 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

7548-428: 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

7650-510: 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

7752-619: 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

7854-420: 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

7956-556: 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

8058-488: 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

8160-411: 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

8262-418: 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

8364-423: 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

8466-401: The large number of bird species found in the upper Iskut region are northern goshawk , great horned owl , yellow-bellied sapsucker , green-winged teal , blue-listed short-eared owl , and locally endangered Hudsonian godwit . Since 2015 the Iskut River has been regulated by the Forrest Kerr Hydroelectric Project, a 195 MW run-of-river hydroelectric project, located at the head of

8568-579: The lower Iskut and Stikine for fishing, hunting, and trapping, as far downriver as the Stikine–Iskut confluence. The fishing village of Saksina was located on the lower Iskut River near the Stikine confluence. The Tahltan traded caribou and moose hides, furs, sinew, babiche , obsidian , snowshoes , and other items to the Tlingit in exchange for fish oils , dentalia and haliotis shells, knives, axes, wooden boxes, woven baskets, Chilkat blankets , and other ceremonial items. Trade and intermarriage linked

8670-559: The lower canyon just above the mouth of Forrest Kerr Creek. Developed by AltaGas , construction began in 2010 and was finished in June 2014 at a cost of CAD $ 725 million. Various contractors were involved in construction, including the Tahltan Nation Development Corporation. AltaGas signed a purchase agreement with BC Hydro to supply electricity to BC Hydro's power grid . The project does not use

8772-679: 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,

8874-445: 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

8976-626: The north, Inhini River , from the south, Johnson River, from the north, and Caralin Creek, from the south. Forrest Kerr Creek, McLymont Creek, the Verrett, Twin, and Hoodoo Rivers all originate from glaciers radiating from the Andrei Icefield , which lies north of the lower Iskut River and east of the lower Stikine River. The upper Craig River flows through the Craig Headwaters Protected Area . The source of

9078-725: 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

9180-581: The portion between its source and Cascade Falls , is nearly surrounded by the Stikine River and its tributaries, including the Stikine River to the north, the Klappan River to the east, and the Klastline River to the west. Much of this region around the upper Iskut watershed is encompassed within protected areas such as Mount Edziza Provincial Park , Stikine River Provincial Park , Spatsizi Plateau Wilderness Provincial Park , and others, in

9282-410: 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

9384-567: 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

9486-401: The southern end of Kluachon Lake, and "Stikine River 7", near Telegraph Creek . From Kluachon Lake the Iskut River flows south into Eddontenajon Lake, where it receives several tributaries such as Coyote Creek, which flows west from Ealue Lake . Eddontenajon Lake has an average depth of 33 m (108 ft) and a maximum depth of 67 m (220 ft). The community of Eddontenajon

9588-409: 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

9690-423: 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

9792-438: 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

9894-572: The three projects are closely linked AltaGas has treated them as separate projects, thus avoiding the Comprehensive Environmental Assessment that would have been required, which has drawn some criticism from politicians such as Doug Donaldson . The main tributaries of the Iskut River, listed hierarchically in upriver order, are: 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 / )

9996-596: The transition from the middle reach of the Iskut River to the lower reach, in which the Iskut flows in a highly braided channel almost directly west through the Coast Mountains. Below Snippaker Creek the Iskut is joined by the Verrett River , flowing from the north, Bronson Creek, from the south, Twin River , from the north, Craig River , from the south, Zippa Creek, from the south, Hoodoo River , from

10098-546: The watershed is covered by glaciers. The lower Ningunsaw is braided and has good salmonid spawning habitats, although anadromous fish are currently unable to reach the Ningunsaw. The Ningunsaw River originates in Ningunsaw Provincial Park , and flows along the edge of Ningunsaw River Ecological Reserve , which is within the river's watershed. The historic Yukon Telegraph Trail passes through Ningunsaw Provincial Park and Ecological Reserve, then runs up

10200-417: 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

10302-404: The weir is a barrier to fish migration as well, so few fish are able to reach the diversion weir. Salmon feasibility studies have assessed the canyon, identifying obstacles that could be modified to allow fish passage, in which case the diversion weir could be modified with a fish passage structure. The Tahltan Nation has approved and participated in the projects, and is a partial owner. Although

10404-594: The west side of the Bob Quinn Plateau and the community of Bob Quinn Lake , on the shore of Bob Quinn Lake. Highway 37 passes through the community of Bob Quinn Lake, which is about halfway between Meziadin Junction and Dease Lake along the highway. From Bob Quinn Lake Highway 37 leaves the Iskut River and follows the Ningunsaw River and its tributary Beaverpond Creek, then crosses a pass into

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