The Yukon River is a major watercourse of northwestern North America. The river's source is in British Columbia, from which it flows through the Canadian Yukon Territory; the lower half of the river lies in the U. S. state of Alaska. The river empties into the Bering Sea at the Yukon -- Kuskokwim Delta; the average flow is 6,430 m3/s. The total drainage area is 832,700 km2; the total area is more than 25 % larger than Alberta. The longest river in Alaska and Yukon, it was one of the principal means of transportation during the 1896–1903 Klondike Gold Rush. A portion of the river in Yukon—"The Thirty Mile" section, from Lake Laberge to the Teslin River—is a national heritage river and a unit of Klondike Gold Rush International Historical Park. Paddle-wheel riverboats continued to ply the river until the 1950s, when the Klondike Highway was completed. After the purchase of Alaska by the United States in 1867, the Alaska Commercial Company acquired the assets of the Russian-American Company and constructed several posts at various locations on the Yukon River.
The Yukon River has had a history of pollution from military installations, dumps and other sources. However, the Environmental Protection Agency does not list the Yukon River among its impaired watersheds, water quality data from the U. S. Geological Survey shows good levels of turbidity and dissolved oxygen; the Yukon and Mackenzie rivers have much higher suspended sediment concentrations than the great Siberian Arctic rivers. The Yukon River Inter-Tribal Watershed Council, a cooperative effort of 70 First Nations and tribes in Alaska and Canada, has the goal of making the river and its tributaries safe to drink from again by supplementing and scrutinizing government data; the name Yukon, or ųųg han, is a contraction of the words in the Gwich'in phrase chųų gąįį han, which means white water river and refers to "the pale colour" of glacial runoff in the Yukon River. The contraction is Ųųg Han, if the /ųų/ remains nasalized, or Yuk Han, if there is no vowel nasalization. In 1843, the Holikachuks had told the Russian-American Company that their name for the river was Yukkhana and that this name meant big river.
However, Yukkhana does not correspond to a Holikachuk phrase that means big river. Two years the Gwich'ins told the Hudson's Bay Company that their name for the river was Yukon and that the name meant white water river. White water river in fact corresponds to Gwich ` in words; because the Holikachuks had been trading with both the Gwich'ins and the Yup'iks, the Holikachuks had been in a position to borrow the Gwich'in contraction and to conflate its meaning with the meaning of Kuigpak, the Yup'ik name for the same river. For that reason, the documentary evidence reflects that the Holikachuks had borrowed the contraction Ųųg Han from Gwich'in, erroneously assumed that this contraction had the same literal meaning as the corresponding Yup'ik name Kuigpak; the Lewes River is the former name of the upper course of the Yukon, from Marsh Lake to the confluence of the Pelly River at Fort Selkirk. The accepted source of the Yukon River is the Llewellyn Glacier at the southern end of Atlin Lake in British Columbia.
Others suggest. Either way, Atlin Lake flows into Tagish Lake, as does Lake Lindeman after flowing into Bennett Lake. Tagish Lake flows into Marsh Lake; the Yukon River proper starts at the northern end of Marsh Lake, just south of Whitehorse. Some argue that the source of the Yukon River should be Teslin Lake and the Teslin River, which has a larger flow when it reaches the Yukon at Hootalinqua; the upper end of the Yukon River was known as the Lewes River until it was established that it was the Yukon. North of Whitehorse, the Yukon River widens into Lake Laberge, made famous by Robert W. Service's "The Cremation of Sam McGee". Other large lakes that are part of the Yukon River system include Kluane Lake; the river passes through the communities of Whitehorse and Dawson City in Yukon, crossing Alaska into Eagle, Fort Yukon, Stevens Village, Tanana, Galena, Grayling, Holy Cross, Russian Mission, Pilot Station, St. Marys, Mountain Village. After Mountain Village, the main Yukon channel frays into many channels.
There are a number of communities after the "head of passes," as the channel division is called locally: Nunum Iqua, Alakanuk and Kotlik. Of those delta communities, Emmonak is the largest with 760 people in the 2000 census. Emmonak's gravel airstrip is the regional hub for flights. Navigational obstacles on the Yukon River are the Five Finger Rapids and Rink Rapids downstream from Carmacks. Despite its length, there are only four vehicle-carrying bridges across the river: The Lewes Bridge, north of Marsh Lake on the Alaska Highway. A car ferry crosses the river at Dawson City in the summer. Plans to build a permanent bridge were announced in March 2004, alth
Lake Clark (Alaska)
Lake Clark is a lake in southwest Alaska. It drains through the Newhalen River into Iliamna Lake; the lake is about 8 km wide. Lake Clark was named for John W. Clark, chief of the Nushagak trading post and the first American non-Native to see the lake, when an expedition financed by a weekly magazine reached it in February 1891; the Dena'ina Athabascan name is Qizjeh Vena which means "place where people gather lake". The lake is within Lake Clark National Park and Preserve
Novarupta is a volcano, formed in 1912, located on the Alaska Peninsula in Katmai National Park and Preserve, about 290 miles southwest of Anchorage. Formed during the largest volcanic eruption of the 20th century, Novarupta released 30 times the volume of magma of the 1980 eruption of Mount St. Helens; the 1912 eruption that formed Novarupta was the largest to occur during the 20th century. It began on June 6, 1912, culminated in a series of violent eruptions. Rated a 6 on the Volcanic Explosivity Index, the 60-hour-long eruption expelled 3.1 to 3.6 cubic miles of ash, thirty times as much as the 1980 eruption of Mount St. Helens; the erupted magma of rhyolite and andesite resulted in more than 4.1 cubic miles of air fall tuff and 2.6 cubic miles of pyroclastic ash-flow tuff. During the 20th century, only the 1991 eruption of Mount Pinatubo in the Philippines and the 1902 eruption of Santa María in Guatemala were of comparable magnitude. At least two larger eruptions occurred in the Dutch East Indies during the 19th century: the 1815 eruption of Tambora and the 1883 eruption of Krakatoa.
The Novarupta eruption occurred about 2.5 mi from the peak of Mount Katmai Volcano and 4,000 ft below the post-eruption Mount Katmai summit. During the eruption a large quantity of magma erupted from beneath the Mount Katmai area, resulting in the formation of a 1.2-mile wide, funnel-shaped vent and the collapse of Mount Katmai's summit, creating a 2,000-foot deep, 1.9 by 2.5 mi caldera. The eruption ended with the extrusion of a lava dome of rhyolite; the 295-foot high and 1,180-foot wide dome it created forms what is now referred to as Novarupta. Despite the magnitude of the eruption, no deaths directly resulted. Eye witness accounts from people located downwind in the path of a thick ash cloud describe the gradual lowering of visibility to next to nothing. Ash threatened to contaminate drinking water and decimate food resources, but the native Alaskans were aided in their survival by traditional knowledge passed down through generations from previous eruptions; however the native villages experiencing the heaviest ash falls were abandoned and the inhabitants relocated.
The eruption is said to have had an effect on the level of the Nile. Pyroclastic ash flow from the eruption formed the Valley of Ten Thousand Smokes, named by botanist Robert F. Griggs, who explored the volcano's aftermath for the National Geographic Society in 1916; the eruption forming the Valley of Ten Thousand Smokes is one of the few in recorded history to have produced welded tuff, producing numerous fumaroles that persisted for 15 years. Established as a National Park & Preserve in 1980, Katmai is located on the Alaska Peninsula, across from Kodiak Island, with headquarters in nearby King Salmon, about 290 mi southwest of Anchorage; the area was designated a National Monument in 1918 to protect the area around the 1912 eruption of Novarupta and the 40-square-mile, 100-to-700-foot deep, pyroclastic flow of the Valley of Ten Thousand Smokes. List of volcanoes in the United States Timeline of volcanism on Earth Parícutin, a cinder cone volcano in Mexico whose emergence could be observed.
USGS collection of descriptions of Novarupta USGS QuickTime video clip on Novarupta geology.com, Novarupta – topographic maps, annotated satellite images Alaska Volcano Observatory: Novarupta USGS Photographic Library – novarupta
Plate tectonics is a scientific theory describing the large-scale motion of seven large plates and the movements of a larger number of smaller plates of the Earth's lithosphere, since tectonic processes began on Earth between 3 and 3.5 billion years ago. The model builds on the concept of continental drift, an idea developed during the first decades of the 20th century; the geoscientific community accepted plate-tectonic theory after seafloor spreading was validated in the late 1950s and early 1960s. The lithosphere, the rigid outermost shell of a planet, is broken into tectonic plates; the Earth's lithosphere is composed of many minor plates. Where the plates meet, their relative motion determines the type of boundary: convergent, divergent, or transform. Earthquakes, volcanic activity, mountain-building, oceanic trench formation occur along these plate boundaries; the relative movement of the plates ranges from zero to 100 mm annually. Tectonic plates are composed of oceanic lithosphere and thicker continental lithosphere, each topped by its own kind of crust.
Along convergent boundaries, subduction, or one plate moving under another, carries the lower one down into the mantle. In this way, the total surface of the lithosphere remains the same; this prediction of plate tectonics is referred to as the conveyor belt principle. Earlier theories, since disproven, proposed gradual expansion of the globe. Tectonic plates are able to move because the Earth's lithosphere has greater mechanical strength than the underlying asthenosphere. Lateral density variations in the mantle result in convection. Plate movement is thought to be driven by a combination of the motion of the seafloor away from spreading ridges due to variations in topography and density changes in the crust. At subduction zones the cold, dense crust is "pulled" or sinks down into the mantle over the downward convecting limb of a mantle cell. Another explanation lies in the different forces generated by tidal forces of the Moon; the relative importance of each of these factors and their relationship to each other is unclear, still the subject of much debate.
The outer layers of the Earth are divided into the asthenosphere. The division is based on differences in mechanical properties and in the method for the transfer of heat; the lithosphere is more rigid, while the asthenosphere is hotter and flows more easily. In terms of heat transfer, the lithosphere loses heat by conduction, whereas the asthenosphere transfers heat by convection and has a nearly adiabatic temperature gradient; this division should not be confused with the chemical subdivision of these same layers into the mantle and the crust: a given piece of mantle may be part of the lithosphere or the asthenosphere at different times depending on its temperature and pressure. The key principle of plate tectonics is that the lithosphere exists as separate and distinct tectonic plates, which ride on the fluid-like asthenosphere. Plate motions range up to a typical 10–40 mm/year, to about 160 mm/year; the driving mechanism behind this movement is described below. Tectonic lithosphere plates consist of lithospheric mantle overlain by one or two types of crustal material: oceanic crust and continental crust.
Average oceanic lithosphere is 100 km thick. Because it is formed at mid-ocean ridges and spreads outwards, its thickness is therefore a function of its distance from the mid-ocean ridge where it was formed. For a typical distance that oceanic lithosphere must travel before being subducted, the thickness varies from about 6 km thick at mid-ocean ridges to greater than 100 km at subduction zones. Continental lithosphere is about 200 km thick, though this varies between basins, mountain ranges, stable cratonic interiors of continents; the location where two plates meet is called a plate boundary. Plate boundaries are associated with geological events such as earthquakes and the creation of topographic features such as mountains, mid-ocean ridges, oceanic trenches; the majority of the world's active volcanoes occur along plate boundaries, with the Pacific Plate's Ring of Fire being the most active and known today. These boundaries are discussed in further detail below; some volcanoes occur in the interiors of plates, these have been variously attributed to internal plate deformation and to mantle plumes.
As explained above, tectonic plates may include continental crust or oceanic crust, most plates contain both. For example, the African Plate includes the continent and parts of the floor of the Atlantic and Indian Oceans; the distinction between oceanic crust and continental crust is based on their modes of formation. Oceanic crust is fo
The Alaska Range is a narrow, 650-km-long mountain range in the southcentral region of the U. S. state of Alaska, from Lake Clark at its southwest end to the White River in Canada's Yukon Territory in the southeast. The highest mountain in North America, Denali, is in the Alaska Range, it is part of the American Cordillera. The range is the highest in the world outside Asia and the Andes; the range forms a east-west arc with its northernmost part in the center, from there trending southwest towards the Alaska Peninsula and the Aleutians, trending southeast into the Pacific Coast Ranges. The mountains act as a high barrier to the flow of moist air from the Gulf of Alaska northwards, thus has some of the harshest weather in the world; the heavy snowfall contributes to a number of large glaciers, including the Canwell, Black Rapids, Yanert, Eldridge, Ruth and Kahiltna Glaciers. Four major rivers cross the Range, including the Delta River, Nenana River in the center of the range and the Nabesna and Chisana Rivers to the east.
The range is part of the Pacific Ring of Fire, the Denali Fault that runs along the southern edge of the range is responsible for a number of earthquakes. Mount Spurr is a stratovolcano located in the northeastern end of the Aleutian Volcanic Arc of Alaska, USA which has two vents, the summit and nearby Crater Peak. Parts of the range are protected within Wrangell-St. Elias National Park and Preserve, Denali National Park and Preserve, Lake Clark National Park and Preserve; the George Parks Highway from Anchorage to Fairbanks, the Richardson Highway from Valdez to Fairbanks, the Tok Cut-Off from Gulkana Junction to Tok, Alaska pass through low parts of the range. The Alaska Pipeline parallels the Richardson Highway; the name "Alaskan Range" appears to have been first applied to these mountains in 1869 by naturalist W. H. Dall; the name became "Alaska Range" through local use. In 1849 Constantin Grewingk applied the name "Tschigmit" to this mountain range. A map made by the General Land Office in 1869 calls the southwestern part of the Alaska Range the "Chigmit Mountains" and the northeastern part the "Beaver Mountains".
However the Chigmit Mountains are now considered part of the Aleutian Range. Denali Mount Foraker Mount Hunter Mount Hayes Mount Silverthrone Mount Moffit Mount Deborah Mount Huntington Mount Brooks Mount Russell Neacola Mountains Revelation Mountains Teocalli Mountains Kichatna Mountains Central Alaska Range/Denali Massif Eastern Alaska Range/Hayes Range Delta Mountains Mentasta Mountains Nutzotin Mountains Mentasta Lake to Kitchatna Mountains: Scott Woolums, George Beilstein, Steve Eck, Larry Coxen by skis: first traverse. 375 miles in 45 days. Canada to Lake Clark: Roman Dial, Carl Tobin, Paul Adkins by mountain bike and packraft: first full length traverse. 775 miles in 42 days. Tok to Lake Clark: Kevin Armstrong, Doug Woody, Jeff Ottmers by snowshoe and packraft: first foot traverse. 620 miles in 90 days. Lake Clark to Mentasta Lake: Gavin McClurg by paraglider and foot: first vol-biv traverse. 466 miles in 37 days. Summit Lake, Alaska Churkin, M. Jr. and C. Carter.. Stratigraphy and graptolites of an Ordovician and Silurian sequence in the Terra Cotta Mountains, Alaska Range, Alaska.
Washington, D. C.: U. S. Department of the Interior, U. S. Geological Survey
Kodiak Island Borough, Alaska
Kodiak Island Borough is a borough in the U. S. state of Alaska. At the 2010 census, the population was 13,592; the borough seat is Kodiak. The borough has a total area of 12,022 square miles, of which 6,550 square miles is land and 5,472 square miles is water. Most of the land area belongs to Kodiak Island, but a thin strip of coastal area on the western part of the Alaska Peninsula and other nearby islands are in the borough; the waterway between the island and mainland is known as the Shelikof Strait. South of the island are the open waters of the Pacific Ocean, so the site is considered good for launching certain types of satellites; the Kodiak Launch Complex is ideal for putting satellites in polar orbits. Kenai Peninsula Borough, Alaska - north Lake and Peninsula Borough, Alaska - northwest Alaska Maritime National Wildlife Refuge Barren Islands Semidi Wilderness Semidi Islands Trinity Islands Sitkinak Island Tugidak Island Alaska Peninsula National Wildlife Refuge Becharof National Wildlife Refuge Becharof Wilderness Chugach National Forest Katmai National Park and Preserve Katmai Wilderness Kodiak National Wildlife Refuge As of the census of 2000, there were 13,913 people, 4,424 households, 3,256 families residing in the borough.
The population density was 2 people per square mile. There were 5,159 housing units at an average density of 1 per square mile; the racial makeup of the borough was 59.69% White, 0.96% Black or African American, 14.58% Native American, 16.04% Asian, 0.79% Pacific Islander, 2.78% from other races, 5.16% from two or more races. 6.10% of the population were Hispanic or Latino of any race. 13.10 % reported speaking Tagalog at a language of the Philippines, while 5.28 % speak Spanish. There were 4,424 households out of which 45.90% had children under the age of 18 living with them, 59.70% were married couples living together, 8.80% had a female householder with no husband present, 26.40% were non-families. 19.90% of all households were made up of individuals and 3.70% had someone living alone, 65 years of age or older. The average household size was 3.07 and the average family size was 3.52. In the borough the population was spread out with 32.40% under the age of 18, 8.30% from 18 to 24, 34.00% from 25 to 44, 20.40% from 45 to 64, 4.80% who were 65 years of age or older.
The median age was 32 years. For every 100 females, there were 112.40 males. For every 100 females age 18 and over, there were 117.40 males. Akhiok Kodiak Larsen Bay Old Harbor Ouzinkie Port Lions Aleneva Chiniak Karluk Kodiak Station Womens Bay List of airports in the Kodiak Island Borough Official website Kodiak Island Public Access Atlas Borough map: Alaska Department of Labor
Lake and Peninsula Borough, Alaska
Lake and Peninsula Borough is a borough in the state of Alaska. As of the 2010 census, the population was 1,631; the borough seat of King Salmon is located in neighboring Bristol Bay Borough, although is not the seat of that borough. The most populous community in the borough is the city of Newhalen. With an average of 0.0296 inhabitants/km2, the Lake and Peninsula Borough is the second least densely populated organized county-equivalent in the United States. The borough has an area of 32,922 square miles, of which 23,652 square miles is land and 9,270 square miles is water; the borough occupies most of the Alaska Peninsula. Its land area is larger than that of San Bernardino County, the largest county in the contiguous Lower 48 states, as large as the state of West Virginia. Bethel Census Area, Alaska – north Kenai Peninsula Borough, Alaska – east Kodiak Island Borough, Alaska – southeast Aleutians East Borough, Alaska – west Bristol Bay Borough, Alaska – west Dillingham Census Area, Alaska – west Alagnak Wild River Alaska Maritime National Wildlife Refuge Sutwik Island Alaska Peninsula National Wildlife Refuge Aniakchak National Monument and Preserve Becharof National Wildlife Refuge Becharof Wilderness Katmai National Park and Preserve Katmai Wilderness Lake Clark National Park and Preserve Lake Clark Wilderness As of the census of 2000, there were 1,823 people, 588 households, 418 families residing in the borough.
The population density was 0.059 people per square mile. There were 1,557 housing units at an average density of 0.05 per square mile. The racial makeup of the borough was 18.76% White, 0.05% Black or African American, 73.51% Native American, 0.22% Asian, 0.16% Pacific Islander, 0.33% from other races, 6.97% from two or more races. 1.15% of the population were Hispanic or Latino of any race. About 5.41% reported speaking a Yupik language at home, while 3.87% speak Alutiiq and 1.23% an Athabaskan language. Some 44.70% of households had children under the age of 18 living with them, 48.50% were married couples living together, 9.70% had a female householder with no husband present, 28.90% were non-families. About 24.70% of all households were made up of individuals, 3.90% consisted of a sole occupant 65 years of age or older. The average household size was 3.10 and the average family size was 3.74. In the borough, the age of the population was spread out with 37.80% under the age of 18, 8.50% from 18 to 24, 28.00% from 25 to 44, 20.20% from 45 to 64, 5.40% who were 65 years of age or older.
The median age was 29 years. For every 100 females, there were 113.50 males. For every 100 females age 18 and over, there were 124.10 males. Chignik Egegik Newhalen Nondalton Pilot Point Port Heiden List of airports in the Lake and Peninsula Borough Official link Media related to Lake and Peninsula Borough, Alaska at Wikimedia Commons Borough map: Alaska Department of Labor