1.
Summit
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A summit is a point on a surface that is higher in elevation than all points immediately adjacent to it. Mathematically, a summit is a maximum in elevation. The topographic terms acme, apex, peak, and zenith are synonymous, the UIAA definition is that a summit is independent if it has a prominence of 30 metres or more, it is a mountain if it has a prominence of at least 300 metres. This can be summarised as follows, A pyramidal peak is an exaggerated form produced by ice erosion of a mountain top, Summit may also refer to the highest point along a line, trail, or route. In many parts of the western United States, the term refers to the highest point along a road, highway. For example, the highest point along Interstate 80 in California is referred to as Donner Summit while the highest point on Interstate 5 is Siskiyou Mountain Summit, geoid Hill List of highest mountains Maxima and minima Nadir Summit accordance Peak finder
2.
Cook Inlet
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Cook Inlet stretches 180 miles from the Gulf of Alaska to Anchorage in south-central Alaska. Cook Inlet branches into the Knik Arm and Turnagain Arm at its northern end, on its south end merges with Shelikof Strait, Stevenson Entrance, Kennedy Entrance and Chugach Passage. The watershed includes the areas of Denali. Within the watershed there are national parks and the active volcano Mount Redoubt. Cook Inlet provides navigable access to the port of Anchorage at the northern end, before the growth of Anchorage, Knik was the destination for most marine traffic in upper Cook Inlet. Approximately 400,000 people live within the Cook Inlet watershed, the Cook Inlet region contains active volcanoes, including Augustine Volcano and Mount Redoubt. Volcanic eruptions in the region have been associated with earthquakes and tsunamis, there was an earthquake of the magnitude of 7.1 on December 31,1901 generated by an eruption that caused several tsunamis. In 2009 a lahar from Mt. Redoubt threatened the Drift River oil terminal, the inlet was first explored and settled by Denaina people. In the 18th century, Russian fur hunters were among the first European visitors, the Lebedev Lastochkin Company leader Stepan Zaikov established a post at the mouth of the Kenai River, Fort Nikolaev, in 1786. Other Europeans to visit Cook Inlet include the 1778 expedition of James Cook, its namesake, the inlet was named after Cook in 1794 by George Vancouver, who had served under Cook in 1778. Turnagain Arm was named by William Bligh of HMS Bounty fame, Bligh served as Cooks Sailing Master on his 3rd and final voyage, the aim of which was discovery of the Northwest Passage. Upon reaching the head of Cook Inlet, Bligh was of the opinion that both Knik Arm and Turnagain Arm were the mouths of rivers and not the opening to the Northwest Passage. Under Cooks orders Bligh organized a party to travel up Knik Arm, afterwards a second party was dispatched up Turnagain Arm and it too returned to report only a river lay ahead. As a result of this frustration the second body of water was given the disingenuous name Turn Again, early maps label Turnagain Arm as the Turnagain River. The S. S. Farallon was a wooden Alaskan Steamship Company liner that struck Black Reef in the Cook Inlet on January 5,1910, all thirty-eight men on board survived, and were rescued twenty-nine days later. Few white people visited upper Cook Inlet until construction of the Alaska Railroad along the shores of Turnagain Arm. The natives of the Eklutna village are the descendants of the residents of eight villages around upper Cook Inlet. During the 1964 Alaska earthquake, areas around the head of Turnagain Arm near Girdwood and Portage dropped as much as 8 feet by subsidence, Girdwood was later relocated inland and Portage was abandoned
3.
Alaska
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Alaska is a U. S. state located in the northwest extremity of North America. To the north are the Chukchi and Beaufort seas–the southern parts of the Arctic Ocean, the Pacific Ocean lies to the south and southwest. Alaska is the largest state in the United States by area, the 3rd least populous, approximately half of Alaskas residents live within the Anchorage metropolitan area. Alaskas economy is dominated by the fishing, natural gas, military bases and tourism are also a significant part of the economy. The United States purchased Alaska from the Russian Empire on March 30,1867, the area went through several administrative changes before becoming organized as a territory on May 11,1912. It was admitted as the 49th state of the U. S. on January 3,1959, the name Alaska was introduced in the Russian colonial period when it was used to refer to the peninsula. It was derived from an Aleut, or Unangam idiom, which refers to the mainland of Alaska. Literally, it means object to which the action of the sea is directed, Alaska is the northernmost and westernmost state in the United States and has the most easterly longitude in the United States because the Aleutian Islands extend into the Eastern Hemisphere. Alaska is the only non-contiguous U. S. state on continental North America and it is technically part of the continental U. S. but is sometimes not included in colloquial use, Alaska is not part of the contiguous U. S. often called the Lower 48. The capital city, Juneau, is situated on the mainland of the North American continent but is not connected by road to the rest of the North American highway system. Alaskas territorial waters touch Russias territorial waters in the Bering Strait, as the Russian Big Diomede Island, Alaska has a longer coastline than all the other U. S. states combined. Alaska is the largest state in the United States by total area at 663,268 square miles, over twice the size of Texas, Alaska is larger than all but 18 sovereign countries. Counting territorial waters, Alaska is larger than the area of the next three largest states, Texas, California, and Montana. It is also larger than the area of the 22 smallest U. S. states. Also referred to as the Panhandle or Inside Passage, this is the region of Alaska closest to the rest of the United States, as such, this was where most of the initial non-indigenous settlement occurred in the years following the Alaska Purchase. The region is dominated by the Alexander Archipelago as well as the Tongass National Forest and it contains the state capital Juneau, the former capital Sitka, and Ketchikan, at one time Alaskas largest city. The Alaska Marine Highway provides a vital transportation link throughout the area. The Interior is the largest region of Alaska, much of it is uninhabited wilderness, Fairbanks is the only large city in the region
4.
United States Geological Survey
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The United States Geological Survey is a scientific agency of the United States government. The scientists of the USGS study the landscape of the United States, its resources. The organization has four science disciplines, concerning biology, geography, geology. The USGS is a research organization with no regulatory responsibility. The USGS is a bureau of the United States Department of the Interior, the USGS employs approximately 8,670 people and is headquartered in Reston, Virginia. The USGS also has major offices near Lakewood, Colorado, at the Denver Federal Center, the current motto of the USGS, in use since August 1997, is science for a changing world. The agencys previous slogan, adopted on the occasion of its anniversary, was Earth Science in the Public Service. Prompted by a report from the National Academy of Sciences, the USGS was created, by a last-minute amendment and it was charged with the classification of the public lands, and examination of the geological structure, mineral resources, and products of the national domain. This task was driven by the need to inventory the vast lands added to the United States by the Louisiana Purchase in 1803, the legislation also provided that the Hayden, Powell, and Wheeler surveys be discontinued as of June 30,1879. Clarence King, the first director of USGS, assembled the new organization from disparate regional survey agencies, after a short tenure, King was succeeded in the directors chair by John Wesley Powell. Administratively, it is divided into a Headquarters unit and six Regional Units, Other specific programs include, Earthquake Hazards Program monitors earthquake activity worldwide. The National Earthquake Information Center in Golden, Colorado on the campus of the Colorado School of Mines detects the location, the USGS also runs or supports several regional monitoring networks in the United States under the umbrella of the Advanced National Seismic System. The USGS informs authorities, emergency responders, the media, and it also maintains long-term archives of earthquake data for scientific and engineering research. It also conducts and supports research on long-term seismic hazards, USGS has released the UCERF California earthquake forecast. The USGS National Geomagnetism Program monitors the magnetic field at magnetic observatories and distributes magnetometer data in real time, the USGS operates the streamgaging network for the United States, with over 7400 streamgages. Real-time streamflow data are available online, since 1962, the Astrogeology Research Program has been involved in global, lunar, and planetary exploration and mapping. USGS operates a number of related programs, notably the National Streamflow Information Program. USGS Water data is available from their National Water Information System database
5.
Lava dome
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In volcanology, a lava dome or volcanic dome is a roughly circular mound-shaped protrusion resulting from the slow extrusion of viscous lava from a volcano. The geochemistry of lava domes can vary from basalt to rhyolite although most preserved domes tend to have high silica content, the characteristic dome shape is attributed to high viscosity that prevents the lava from flowing very far. This high viscosity can be obtained in two ways, by high levels of silica in the magma, or by degassing of fluid magma. Since viscous basaltic and andesitic domes weather fast and easily break apart by further input of fluid lava, most of the domes have high silica content. Existence of lava domes has been suggested for some domed structures on the Martian surface in the part of Arcadia Planitia. Lava domes evolve unpredictably, due to non-linear dynamics caused by crystallization, domes undergo various processes such as growth, collapse, solidification and erosion. Lava domes grow by endogenic dome growth or exogenic dome growth, the former implies dome interior expansion to accommodate new lava and the latter refers to superficial piling up of lava. It is the viscosity of the lava that prevents it from flowing far from the vent from which it extrudes. Domes may reach heights of several hundred meters, and can grow slowly and steadily for months, years, the sides of these structures are composed of unstable rock debris. Due to the intermittent buildup of gas pressure, erupting domes can often experience episodes of explosive eruption over time, if part of a lava dome collapses while it is still molten, it can produce pyroclastic flows, one of the most lethal forms of volcanic event. Other hazards associated with domes are the destruction of property, forest fires. Lava domes are one of the structural features of many stratovolcanoes worldwide. Lava domes are prone to unusually dangerous explosions since they contain rhyolitic silica-rich lava, characteristics of lava dome eruptions include shallow, long-period and hybrid seismicity, which is attributed to excess fluid pressures in the contributing vent chamber. Other characteristics of lava domes include their hemispherical shape, cycles of dome growth over long periods. The average rate of growth may be used as a rough indicator of magma supply. A cryptodome is a structure created by accumulation of viscous magma at a shallow depth. Coulées are lava domes that have experienced some flow away from their original position, the worlds largest known dacite flow is the Chao dacite dome complex, a huge coulée flow-dome between two volcanoes in northern Chile. This flow is over 14 kilometres long, has obvious flow features like pressure ridges, there is another prominent coulée flow on the flank of Llullaillaco volcano, in Argentina, and other examples in the Andes
6.
Types of volcanic eruptions
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Several types of volcanic eruptions—during which lava, tephra, and assorted gases are expelled from a volcanic vent or fissure—have been distinguished by volcanologists. These are often named after famous volcanoes where that type of behavior has been observed, some volcanoes may exhibit only one characteristic type of eruption during a period of activity, while others may display an entire sequence of types all in one eruptive series. There are three different types of eruptions, the most well-observed are magmatic eruptions, which involve the decompression of gas within magma that propels it forward. Phreatomagmatic eruptions are another type of eruption, driven by the compression of gas within magma. Within these wide-defining eruptive types are several subtypes, the weakest are Hawaiian and submarine, then Strombolian, followed by Vulcanian and Surtseyan. The stronger eruptive types are Pelean eruptions, followed by Plinian eruptions, subglacial and phreatic eruptions are defined by their eruptive mechanism, and vary in strength. An important measure of strength is Volcanic Explosivity Index, an order of magnitude scale ranging from 0 to 8 that often correlates to eruptive types. Explosive eruptions are characterized by gas-driven explosions that propels magma and tephra, effusive eruptions, meanwhile, are characterized by the outpouring of lava without significant explosive eruption. Volcanic eruptions vary widely in strength, on the one extreme there are effusive Hawaiian eruptions, which are characterized by lava fountains and fluid lava flows, which are typically not very dangerous. On the other extreme, Plinian eruptions are large, violent, volcanoes are not bound to one eruptive style, and frequently display many different types, both passive and explosive, even the span of a single eruptive cycle. Volcanoes do not always erupt vertically from a crater near their peak. Some volcanoes exhibit lateral and fissure eruptions, notably, many Hawaiian eruptions start from rift zones, and some of the strongest Surtseyan eruptions develop along fracture zones. Scientists believed that pulses of magma mixed together in the chamber before climbing upward—a process estimated to several thousands of years. But Columbia University volcanologists found that the eruption of Costa Rica’s Irazú Volcano in 1963 was likely triggered by magma that took a route from the mantle over just a few months. The volcanic explosivity index is a scale, from 0 to 8 and it is used by the Smithsonian Institutions Global Volcanism Program in assessing the impact of historic and prehistoric lava flows. It operates in a way similar to the Richter scale for earthquakes, the vast majority of volcanic eruptions are of VEIs between 0 and 2. Volcanic eruptions by VEI index Magmatic eruptions produce juvenile clasts during explosive decompression from gas release, Hawaiian eruptions are a type of volcanic eruption, named after the Hawaiian volcanoes with which this eruptive type is hallmark. Hawaiian eruptions are the calmest types of events, characterized by the effusive eruption of very fluid basalt-type lavas with low gaseous content
7.
Lava
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Lava is the molten rock expelled by a volcano during an eruption. The resulting rock after solidification and cooling is called lava. The molten rock is formed in the interior of planets, including Earth. The source of the heat melts the rock within the earth is geothermal energy. When first erupted from a vent, lava is a liquid usually at temperatures from 700 to 1,200 °C. A lava flow is an outpouring of lava, which is created during a non-explosive effusive eruption. When it has stopped moving, lava solidifies to form igneous rock, the term lava flow is commonly shortened to lava. Although lava can be up to 100,000 times more viscous than water, lava can flow great distances before cooling and solidifying because of its thixotropic, explosive eruptions produce a mixture of volcanic ash and other fragments called tephra, rather than lava flows. The word lava comes from Italian, and is derived from the Latin word labes which means a fall or slide. The first use in connection with extruded magma was apparently in an account written by Francesco Serao on the eruption of Vesuvius between May 14 and June 4,1737. Serao described a flow of lava as an analogy to the flow of water. The composition of almost all lava of the Earths crust is dominated by silicate minerals, mostly feldspars, olivine, pyroxenes, amphiboles, micas, igneous rocks, which form lava flows when erupted, can be classified into three chemical types, felsic, intermediate, and mafic. These classes are primarily chemical, however, the chemistry of lava also tends to correlate with the temperature, its viscosity. Felsic or silicic lavas such as rhyolite and dacite typically form lava spines, most silicic lava flows are extremely viscous, and typically fragment as they extrude, producing blocky autobreccias. Felsic magmas can erupt at temperatures as low as 650 to 750 °C, unusually hot rhyolite lavas, however, may flow for distances of many tens of kilometres, such as in the Snake River Plain of the northwestern United States. Intermediate or andesitic lavas are lower in aluminium and silica, and usually somewhat richer in magnesium, intermediate lavas form andesite domes and block lavas, and may occur on steep composite volcanoes, such as in the Andes. Poorer in aluminium and silica than felsic lavas, and also commonly hotter, greater temperatures tend to destroy polymerized bonds within the magma, promoting more fluid behaviour and also a greater tendency to form phenocrysts. Higher iron and magnesium tends to manifest as a darker groundmass, mafic or basaltic lavas are typified by their high ferromagnesian content, and generally erupt at temperatures in excess of 950 °C
8.
Tephra
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Tephra is fragmental material produced by a volcanic eruption regardless of composition, fragment size or emplacement mechanism. Volcanologists also refer to airborne fragments as pyroclasts, once clasts have fallen to the ground they remain as tephra unless hot enough to fuse together into pyroclastic rock or tuff. Tephra mixed in with precipitation can also be acidic and cause acid rain, the use of tephra layers, which bear their own unique chemistry and character, as temporal marker horizons in archaeological and geological sites is known as tephrochronology. The word tephra and pyroclast both derive from Greek, τέφρα tephra means ash, while the word pyroclast is derived from the Greek πῦρ, meaning fire, media related to Tephra at Wikimedia Commons How Volcanoes Work Volcanic Materials Identification
9.
Anchorage, Alaska
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Anchorage is a unified home rule municipality in the U. S. state of Alaska. All together, the Anchorage metropolitan area, which combines Anchorage with the neighboring Matanuska-Susitna Borough, had a population of 401,635 in 2016. Anchorage is located in the portion of Alaska at the terminus of the Cook Inlet on a peninsula formed by the Knik Arm to the north. The city limits span 1,961.1 square miles encompass the urban core. Due to its location on the globe, being almost equidistant from New York City, Tokyo, Anchorage has been named an All-America City four times, in 1956,1965, 1984–85, and 2002, by the National Civic League. It has also named by Kiplinger as the most tax-friendly city in the United States. Russian presence in south central Alaska was well established in the 19th century, in 1867, U. S. Secretary of State William H. Seward brokered a deal to purchase Alaska from Imperial Russia for $7.2 million. His political rivals lampooned the deal as Sewards folly, Sewards icebox, by 1888, gold was discovered along Turnagain Arm. Alaska became a United States territory in 1912, Anchorage, unlike every other large town in Alaska south of the Brooks Range, was neither a fishing nor mining camp. The area surrounding Anchorage lacks significant economic metal minerals, a number of Denaina settlements existed along Knik Arm for years. By 1911 the families of J. D. Bud Whitney, jack Brown, and his bride, Nellie, in 1912 to have lived in the Ship Creek valley in the 1910s prior to the large influx of settlers. The city grew from its choice as the site, in 1914, under the direction of Frederick Mears. The area near the mouth of Ship Creek, where the headquarters was located. A town site was mapped out on higher ground to the south of the tent city, greatly noted in the years since for its order and rigidity compared with other Alaska town sites. In 1915, territorial governor John Franklin Alexander Strong encouraged residents to change the name to one that had more significance. In the summer of year, residents held a vote to change the citys name. However, the government ultimately declined to change the citys name. Anchorage was incorporated on November 23,1920, construction of the Alaska Railroad continued until its completion in 1923
10.
Avalanche
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An avalanche is a rapid flow of snow down a sloping surface. Avalanches are typically triggered in a zone from a mechanical failure in the snowpack when the forces on the snow exceed its strength. After initiation, avalanches usually accelerate rapidly and grow in mass, if the avalanche moves fast enough some of the snow may mix with the air forming a powder snow avalanche, which is a type of gravity current. Slides of rocks or debris, behaving in a way to snow, are also referred to as avalanches. The remainder of this article refers to snow avalanches, the load on the snowpack may be only due to gravity, in which case failure may result either from weakening in the snowpack or increased load due to precipitation. Avalanches that occur in this way are known as spontaneous avalanches, Avalanches can also be triggered by other loads such as skiers, snowmobilers, animals or explosives. Seismic activity may trigger the failure in the snowpack and avalanches. A popular myth is that avalanches can be triggered by loud noise or shouting, Avalanches are not rare or random events and are endemic to any mountain range that accumulates a standing snowpack. Avalanches are most common during winter or spring but glacier movements may cause ice, there is no universally accepted classification of avalanches—different classifications are useful for different purposes. Avalanches can be described by their size, their potential, their initiation mechanism, their composition. Most avalanches occur spontaneously during storms under increased load due to snowfall, the second largest cause of natural avalanches is metamorphic changes in the snowpack such as melting due to solar radiation. Other natural causes include rain, earthquakes, rockfall and icefall, artificial triggers of avalanches include skiers, snowmobiles, and controlled explosive work. Avalanche initiation can start at a point with only an amount of snow moving initially. A snowpack will fail when the load exceeds the strength, the load is straightforward, it is the weight of the snow. However, the strength of the snowpack is much more difficult to determine and is extremely heterogenous and it varies in detail with properties of the snow grains, size, density, morphology, temperature, water content, and the properties of the bonds between the grains. These properties may all metamorphose in time according to the humidity, water vapour flux, temperature. The top of the snowpack is also influenced by incoming radiation. One of the aims of research is to develop and validate computer models that can describe the evolution of the seasonal snowpack over time
11.
Complex volcano
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A complex volcano, also called a compound volcano, is mixed landform consisting of related volcanic centers and their associated lava flows and pyroclastic rock. They may form due to changes in habit or in the location of the principal vent area on a particular volcano. Stratovolcanoes can also form a caldera that gets filled in by a lava dome, or else multiple small cinder cones, lava domes. Although a comparatively unusual type of volcano, they are widespread in the world, metamorphosed ash flow tuffs are widespread in the Precambrian rocks of northern New Mexico, which indicates that caldera complexes have been important for much of Earths history. Yellowstone National Park is on three partly covered caldera complexes, the Bennett Lake Caldera in British Columbia and the Yukon Territory is another example of a Cenozoic caldera complex. Andrew Strait Taal Volcano, Mount Talinis, Three Sisters Te Tatua-a-Riukiuta Tongariro, Valles Caldera Whale Island Yellowstone Caldera Volcanic group
12.
Andesite
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For the extinct cephalopod genus, see Andesites. Andesite is an igneous, volcanic rock, of intermediate composition. In a general sense, it is the type between basalt and dacite, and ranges from 57 to 63% silicon dioxide as illustrated in TAS diagrams. The mineral assemblage is dominated by plagioclase plus pyroxene or hornblende. Magnetite, zircon, apatite, ilmenite, biotite, and garnet are common accessory minerals, alkali feldspar may be present in minor amounts. The quartz-feldspar abundances in andesite and other rocks are illustrated in QAPF diagrams. Classification of andesites may be refined according to the most abundant phenocryst, example, hornblende-phyric andesite, if hornblende is the principal accessory mineral. Andesite can be considered as the 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 they are a component of the Martian crust. The name andesite is derived from the Andes mountain range, magmatism in island arc regions comes from the interplay of the subducting plate and the mantle wedge, the wedge-shaped region between the subducting and overriding plates. During subduction, the oceanic crust is submitted to increasing pressure and temperature. Hydrous minerals such as amphibole, zeolites, chlorite etc. dehydrate as they change to more stable, anhydrous forms, releasing water, fluxing water into the wedge lowers the solidus of the mantle material and causes partial melting. Due to the density of the partially molten material, it rises through the wedge until it reaches the lower boundary of the overriding plate. Basalt thus formed can contribute to the formation of andesite through fractional crystallization, partial melting of crust, or magma mixing, andesite is typically formed at convergent plate margins but may occur in other tectonic settings. Intermediate volcanic rocks are created via several processes, Fractional crystallization of a mafic parent magma and this removal can take place in a variety of ways, but most commonly this occurs by crystal settling. The first minerals to crystallize and be removed from a parent are olivines and amphiboles. These mafic minerals settle out of the magma, forming mafic cumulates, there is geophysical evidence from several arcs that large layers of mafic cumulates lie at the base of the crust
