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Pebble Mine
Pebble Mine is the common name of a proposed copper-gold- molybdenum mining project in the Bristol Bay region of Southwest Alaska, near Lake Iliamna and Lake Clark. As of November 2020 the mine developer, Northern Dynasty Minerals, was seeking federal permits from the United States Coast Guard and the Bureau of Safety and Environmental Enforcement. State permitting would then follow, which the developer expected to take up to three years. In November 2020, the developer was denied a U.S. Army Corps of Engineers (USACE) permit for its proposed mine discharge plan. On September 9, 2021, it was reported that the EPA had "asked a federal court to allow for Clean Water Act protections for parts of the bay." Background Geography The Pebble prospect is in a remote, wild, and generally uninhabited part of the Bristol Bay watershed. The nearest communities, about distant, are the villages of Nondalton, Newhalen, and Iliamna. The site is southwest of Anchorage, Alaska. Pebble ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Alaska
Alaska ( ; russian: Аляска, Alyaska; ale, Alax̂sxax̂; ; ems, Alas'kaaq; Yup'ik: ''Alaskaq''; tli, Anáaski) is a state located in the Western United States on the northwest extremity of North America. A semi-exclave of the U.S., it borders the Canadian province of British Columbia and the Yukon territory to the east; it also shares a maritime border with the Russian Federation's Chukotka Autonomous Okrug to the west, just across the Bering Strait. To the north are the Chukchi and Beaufort Seas of the Arctic Ocean, while the Pacific Ocean lies to the south and southwest. Alaska is by far the largest U.S. state by area, comprising more total area than the next three largest states (Texas, California, and Montana) combined. It represents the seventh-largest subnational division in the world. It is the third-least populous and the most sparsely populated state, but by far the continent's most populous territory located mostly north of the 60th parallel, with ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Kvichak River
The Kvichak River (Yup'ik: ''Kuicaraq'') is a large river, about long, in southwestern Alaska in the United States. It flows southwest from Lake Iliamna to Kvichak Bay, an arm of Bristol Bay, on the Alaska Peninsula. The communities of Igiugig and Levelock lie along the Kvichak River. The Kvichak is navigable along its entire length, and is used as a short cut by boats getting between Cook Inlet and Bristol Bay via the Lake Iliamna portage. The Kvichak River is home to the largest red salmon run in the world. Commercial harvests are worth hundreds of millions of U.S. dollars annually. The Kvichak River is part of the watershed downstream of the proposed Pebble Mine. Historically, the river was navigated and subsistence fished by local Alaska Natives. The name of the river means ''from''- or ''up to''- ''great water'', a reference to Iliamna Lake, Alaska's largest freshwater lake. The Kvichak River was a finalist for the 2017 Riverprize Award for being one of the best-manag ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Augustine Volcano
Augustine Volcano (Sugpiaq: ''Utakineq'';https://uafanlc.alaska.edu/Online/G977K1985a/G977K1985a_02.PDF Dena'ina: ''Chu Nula'') is a lava dome volcano in Alaska consisting of a central complex of summit lava domes and flows surrounded by an apron of pyroclastic, lahar, avalanche, and ash deposits. The volcano is frequently active, with major eruptions recorded in 1883, 1935, 1963–64, 1976, 1986, and 2006. Minor eruptive events were reported in 1812, 1885, 1908, 1944, and 1971. The large eruptions are characterized by an explosive onset followed by the quieter effusion of lava. It forms Augustine Island in southwestern Cook Inlet in the Kenai Peninsula Borough of southcentral coastal Alaska, southwest of Anchorage. Augustine Island has a land area of , while West Island, just off Augustine's western shores, has . The irregular coastline of Augustine Island is due to the repeated catastrophic collapse of the summit dome, forming debris avalanches down the flanks and into Co ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Good Friday Earthquake
The 1964 Alaskan earthquake, also known as the Great Alaskan earthquake and Good Friday earthquake, occurred at 5:36 PM AKST on Good Friday, March 27.US Geological Survey report on the earthquake Across south-central , ground fissures, collapsing structures, and s resulting from the earthquake caused about 131 deaths. Lasting four minutes and thirty-eight seconds, the magnitude 9.2 |
Aleutian Trench
The Aleutian Trench (or Aleutian Trough) is an oceanic trench along a convergent plate boundary which runs along the southern coastline of Alaska and the Aleutian islands. The trench extends for from a triple junction in the west with the Ulakhan Fault and the northern end of the Kuril–Kamchatka Trench, to a junction with the northern end of the Queen Charlotte Fault system in the east. It is classified as a "marginal trench" in the east as it runs along the margin of the continent. The subduction along the trench gives rise to the Aleutian Arc, a volcanic island arc, where it runs through the open sea west of the Alaska Peninsula. As a convergent plate boundary, the trench forms part of the boundary between two tectonic plates. Here, the Pacific Plate is being subducted under the North American Plate at a dip angle of nearly 45°. The rate of closure is per year. Trench morphology The north side of the trench slopes 3°–4° and the south side 1°–4°. The deepest part o ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Subduction
Subduction is a geological process in which the oceanic lithosphere is recycled into the Earth's mantle at convergent boundaries. Where the oceanic lithosphere of a tectonic plate converges with the less dense lithosphere of a second plate, the heavier plate dives beneath the second plate and sinks into the mantle. A region where this process occurs is known as a subduction zone, and its surface expression is known as an arc-trench complex. The process of subduction has created most of the Earth's continental crust. Rates of subduction are typically measured in centimeters per year, with the average rate of convergence being approximately two to eight centimeters per year along most plate boundaries. Subduction is possible because the cold oceanic lithosphere is slightly denser than the underlying asthenosphere, the hot, ductile layer in the upper mantle underlying the cold, rigid lithosphere. Once initiated, stable subduction is driven mostly by the negative buoyancy of the de ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Denali Fault
The Denali Fault is a major intracontinental dextral (right lateral) strike-slip fault in western North America, extending from northwestern British Columbia, Canada to the central region of the U.S. state of Alaska. Location The Denali Fault is located in Alaska's Denali National Park and to the east. This National Park includes part of a massive mountain range more than 600 miles long. Along the Denali Fault, lateral and vertical offset movement is taking place. The steep north face of Denali, known as the Wickersham Wall, rises 15,000 feet from its base, and is a result of this relatively recent movement. Effects Alaska's network of faults is a result of tectonic activity; the Pacific Plate is actively subducting (sliding under) the North American Plate, and the Denali Fault is located on the boundary between the two plates. The fault's rate of displacement varies from 1 mm to 35 mm per year. It was the main fault along which the 2002 Denali earthquake occu ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Strike-slip Fault
In geology, a fault is a planar fracture or discontinuity in a volume of rock across which there has been significant displacement as a result of rock-mass movements. Large faults within Earth's crust result from the action of plate tectonic forces, with the largest forming the boundaries between the plates, such as the megathrust faults of subduction zones or transform faults. Energy release associated with rapid movement on active faults is the cause of most earthquakes. Faults may also displace slowly, by aseismic creep. A ''fault plane'' is the plane that represents the fracture surface of a fault. A ''fault trace'' or ''fault line'' is a place where the fault can be seen or mapped on the surface. A fault trace is also the line commonly plotted on geologic maps to represent a fault. A ''fault zone'' is a cluster of parallel faults. However, the term is also used for the zone of crushed rock along a single fault. Prolonged motion along closely spaced faults can blur the ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Andesite
Andesite () is a volcanic rock of intermediate composition. In a general sense, it is the intermediate type between silica-poor basalt and silica-rich rhyolite. It is fine-grained (aphanitic) to porphyritic in texture, and is composed predominantly of sodium-rich plagioclase plus pyroxene or hornblende. Andesite is the extrusive equivalent of plutonic diorite. Characteristic of subduction zones, andesite represents the dominant rock type in island arcs. The average composition of the continental crust is andesitic. Along with basalts, andesites are a component of the Martian crust. The name ''andesite'' is derived from the Andes mountain range, where this rock type is found in abundance. It was first applied by Christian Leopold von Buch in 1826. Description Andesite is an aphanitic (fine-grained) igneous rock that is intermediate in its content of silica and low in alkali metals. It has less than 20% quartz and 10% feldspathoid by volume, with at least 65% of the fe ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Basalt
Basalt (; ) is an aphanite, aphanitic (fine-grained) extrusive igneous rock formed from the rapid cooling of low-viscosity lava rich in magnesium and iron (mafic lava) exposed at or very near the planetary surface, surface of a terrestrial planet, rocky planet or natural satellite, moon. More than 90% of all volcanic rock on Earth is basalt. Rapid-cooling, fine-grained basalt is chemically equivalent to slow-cooling, coarse-grained gabbro. The eruption of basalt lava is observed by geologists at about 20 volcanoes per year. Basalt is also an important rock type on other planetary bodies in the Solar System. For example, the bulk of the plains of volcanism on Venus, Venus, which cover ~80% of the surface, are basaltic; the lunar mare, lunar maria are plains of flood-basaltic lava flows; and basalt is a common rock on the surface of Mars. Molten basalt lava has a low viscosity due to its relatively low silica content (between 45% and 52%), resulting in rapidly moving lava flo ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Late Triassic
The Late Triassic is the third and final epoch (geology), epoch of the Triassic geologic time scale, Period in the geologic time scale, spanning the time between annum, Ma and Ma (million years ago). It is preceded by the Middle Triassic Epoch and followed by the Early Jurassic Epoch. The corresponding series (stratigraphy), series of rock beds is known as the Upper Triassic. The Late Triassic is divided into the Carnian, Norian and Rhaetian Geologic time scale, Ages. Many of the first dinosaurs evolved during the Late Triassic, including ''Plateosaurus'', ''Coelophysis'', and ''Eoraptor''. The Triassic–Jurassic extinction event began during this epoch and is one of the five major mass extinction events of the Earth. Etymology The Triassic was named in 1834 by Friedrich August von Namoh, Friedrich von Alberti, after a succession of three distinct rock layers (Greek meaning 'triad') that are widespread in southern Germany: the lower Buntsandstein (colourful sandstone'')'', t ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Wrangellia
The Wrangellia Terrane (named for the Wrangell Mountains, Alaska) is a crustal fragment (terrane) extending from the south-central part of Alaska and along the Coast of British Columbia in Canada. Some geologists contend that Wrangellia extends southward to Oregon, although this is not generally accepted. Extent and terminology The term Wrangellia is confusingly applied to all of: * The Wrangell(ia) Terrane alone; * A composite terrane (CT) consisting of the Wrangell Terrane, Peninsular Terrane, and other rock units that were not originally part of the North American craton; * A composite terrane which also includes the Alexander Terrane. Earlier geologists sometimes used the term " Talkeetna Superterrane" to describe Wrangellia. Origin There are two conflicting hypotheses about whether the Wrangellia Superterrane originated at polar or equatorial latitudes: # That Wrangellia accreted at a northerly latitude near its current location (when North America, or Laurentia, was ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
