|
Ukinrek Maars
The Ukinrek Maars are two volcanic craters on the north side of the Aleutian Range in Alaska that were formed by a phreatomagmatic eruption in 1977. The maars are 1.5 km south of Becharof Lake and 12 km northwest of Peulik Volcano, on a low area of the range, bordering the Bering Sea. The western of the two is elliptical in shape and up to 170 m in diameter and 35 m deep. The other lies 600 m to the east and is circular and up to 300 m in diameter and 70 m deep. The east maar has a 49 m-high lava dome within its crater lake. The eruption occurred in March–April 1977 and lasted for ten days. There was no previous eruption. The magmatic material was olivine basalt from a mantle source. Pyroclastic surge from the eruptions traveled to the northwest. The volume of lava erupted was 9×105 m3 and the volume of tephra expelled was 2.6×107 m3. The Quaternary age Gas Rocks dacite domes some three km to the northeast were the site of a ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Becharof National Wildlife Refuge
Becharof National Wildlife Refuge is a National Wildlife Refuge in the Aleutian Range of the Alaska Peninsula of southwestern Alaska. It is adjacent to Katmai National Park and Preserve. This national wildlife refuge, which covers an area of , was established in 1980 to conserve major grizzly bear, brown bears, salmon, migratory birds, caribou, marine birds, and mammals and to comply with treaty obligations. It lies primarily in the east-central part of Lake and Peninsula Borough, Alaska, Lake and Peninsula Borough, but extends eastward into the mainland portion of Kodiak Island Borough, Alaska, Kodiak Island Borough. The refuge is administered from offices in King Salmon, Alaska, King Salmon. History Jimmy Carter created Becharof National Monument by presidential proclamation on December 1, 1978. The refuge was established on December 2, 1980 by the Alaska National Interest Land Conservation Act (ANILCA). In 1983, the Fish and Wildlife Service undertook the responsibility to mana ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Mantle (geology)
A mantle is a layer inside a planetary body bounded below by a Planetary core, core and above by a Crust (geology), crust. Mantles are made of Rock (geology), rock or Volatiles, ices, and are generally the largest and most massive layer of the planetary body. Mantles are characteristic of planetary bodies that have undergone planetary differentiation, differentiation by density. All Terrestrial planet, terrestrial planets (including Earth), a number of Asteroid, asteroids, and some planetary Natural satellite, moons have mantles. Earth's mantle The Earth's mantle is a layer of Silicate minerals, silicate rock between the Crust (geology), crust and the Earth's outer core, outer core. Its mass of 4.01 × 1024 kg is 67% the mass of the Earth. It has a thickness of making up about 84% of Earth's volume. It is predominantly solid, but in Geologic time scale, geological time it behaves as a Viscosity, viscous fluid. Partial melting of the mantle at mid-ocean ridges produ ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Volcanic Crater Lakes
A volcano is a rupture in the crust of a planetary-mass object, such as Earth, that allows hot lava, volcanic ash, and gases to escape from a magma chamber below the surface. On Earth, volcanoes are most often found where tectonic plates are diverging or converging, and most are found underwater. For example, a mid-ocean ridge, such as the Mid-Atlantic Ridge, has volcanoes caused by divergent tectonic plates whereas the Pacific Ring of Fire has volcanoes caused by convergent tectonic plates. Volcanoes can also form where there is stretching and thinning of the crust's plates, such as in the East African Rift and the Wells Gray-Clearwater volcanic field and Rio Grande rift in North America. Volcanism away from plate boundaries has been postulated to arise from upwelling diapirs from the core–mantle boundary, deep in the Earth. This results in hotspot volcanism, of which the Hawaiian hotspot is an example. Volcanoes are usually not created where two tectonic plates slide pa ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Maars Of Alaska
A maar is a broad, low-relief volcanic crater caused by a phreatomagmatic eruption (an explosion which occurs when groundwater comes into contact with hot lava or magma). A maar characteristically fills with water to form a relatively shallow crater lake which may also be called a maar. The name comes from a Moselle Franconian dialect word used for the circular lakes of the Daun area of Germany. Notes: * According to German Wikipedia's ''"Maar"'' article, in 1544 in his book ''Cosmographia'', Sebastian Münster (1488–1552) first applied the word "maar" (as ''Marh'') to the Ulmener Maar and the Laacher See. See: Sebastian Münster, ''Cosmographia'' (Basel, Switzerland: Heinrich Petri, 1544)p. 341. From p. 341: ''"Item zwen namhafftiger seen seind in der Eyfel / einer bey de schloß Ulmen / und ein ander bey dem Closter züm Laich / die seind sere tieff / habe kein ynflüß aber vil außflüß / die nennet man Marh unnd seind fischreich."'' (Also two noteworthy lakes are ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Active Volcanoes
An active volcano is a volcano which is either erupting or is likely to erupt in the future. An active volcano which is not currently erupting is known as a dormant volcano. Overview Tlocene Epoch. Most volcanoes are situated on the Pacific Ring of Fire. An estimated 500 million people live near active volcanoes. ''Historical time'' (or recorded history) is another timeframe for ''active''. However, the span of recorded history differs from region to region. In China and the Mediterranean, it reaches back nearly 3,000 years, but in the Pacific Northwest of the United States and Canada, it reaches back less than 300 years, and in Hawaii and New Zealand it is only around 200 years. The incomplete ''Catalogue of the Active Volcanoes of the World'', published in parts between 1951 and 1975 by the International Association of Volcanology, uses this definition, by which there are more than 500 active volcanoes. , the Smithsonian Global Volcanism Program recognizes 560 volcanoes with ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
April 1977 Events In The United States
April is the fourth month of the year in the Gregorian and Julian calendars. It is the first of four months to have a length of 30 days, and the second of five months to have a length of less than 31 days. April is commonly associated with the season of autumn in parts of the Southern Hemisphere, and spring in parts of the Northern Hemisphere, where it is the seasonal equivalent to October in the Southern Hemisphere and vice versa. History The Romans gave this month the Latin name ''Aprilis''"April" in ''Chambers's Encyclopædia''. London: George Newnes, 1961, Vol. 1, p. 497. but the derivation of this name is uncertain. The traditional etymology is from the verb ''aperire'', "to open", in allusion to its being the season when trees and flowers begin to "open", which is supported by comparison with the modern Greek use of άνοιξη (''ánixi'') (opening) for spring. Since some of the Roman months were named in honor of divinities, and as April was sacre ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
March 1977 Events In The United States
March is the third month of the year in both the Julian and Gregorian calendars. It is the second of seven months to have a length of 31 days. In the Northern Hemisphere, the meteorological beginning of spring occurs on the first day of March. The March equinox on the 20 or 21 marks the astronomical beginning of spring in the Northern Hemisphere and the beginning of autumn in the Southern Hemisphere, where September is the seasonal equivalent of the Northern Hemisphere's March. Origin The name of March comes from '' Martius'', the first month of the earliest Roman calendar. It was named after Mars, the Roman god of war, and an ancestor of the Roman people through his sons Romulus and Remus. His month ''Martius'' was the beginning of the season for warfare, and the festivals held in his honor during the month were mirrored by others in October, when the season for these activities came to a close. ''Martius'' remained the first month of the Roman calendar year perhaps as la ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Map Of Alaska Peninsula Volcanoes
A map is a symbolic depiction emphasizing relationships between elements of some space, such as objects, regions, or themes. Many maps are static, fixed to paper or some other durable medium, while others are dynamic or interactive. Although most commonly used to depict geography, maps may represent any space, real or fictional, without regard to context or scale, such as in brain mapping, DNA mapping, or computer network topology mapping. The space being mapped may be two dimensional, such as the surface of the earth, three dimensional, such as the interior of the earth, or even more abstract spaces of any dimension, such as arise in modeling phenomena having many independent variables. Although the earliest maps known are of the heavens, geographic maps of territory have a very long tradition and exist from ancient times. The word "map" comes from the , wherein ''mappa'' meant 'napkin' or 'cloth' and ''mundi'' 'the world'. Thus, "map" became a shortened term referring to ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Phreatic Eruption
A phreatic eruption, also called a phreatic explosion, ultravulcanian eruption or steam-blast eruption, occurs when magma heats ground water or surface water. The extreme temperature of the magma (anywhere from ) causes near-instantaneous evaporation of water to steam, resulting in an explosion of steam, water, ash, rock, and volcanic bombs. At Mount St. Helens in Washington state, hundreds of steam explosions preceded the 1980 Plinian eruption of the volcano. A less intense geothermal event may result in a mud volcano. Phreatic eruptions typically include steam and rock fragments; the inclusion of liquid lava is unusual. The temperature of the fragments can range from cold to incandescent. If molten magma is included, volcanologists classify the event as a phreatomagmatic eruption. These eruptions occasionally create broad, low-relief craters called '' maars''. Phreatic explosions can be accompanied by carbon dioxide or hydrogen sulfide gas-emissions. Carbon dioxide c ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Quaternary
The Quaternary ( ) is the current and most recent of the three periods of the Cenozoic Era in the geologic time scale of the International Commission on Stratigraphy (ICS). It follows the Neogene Period and spans from 2.58 million years ago to the present. The Quaternary Period is divided into two epochs: the Pleistocene (2.58 million years ago to 11.7 thousand years ago) and the Holocene (11.7 thousand years ago to today, although a third epoch, the Anthropocene, has been proposed but is not yet officially recognised by the ICS). The Quaternary Period is typically defined by the cyclic growth and decay of continental ice sheets related to the Milankovitch cycles and the associated climate and environmental changes that they caused. Research history In 1759 Giovanni Arduino proposed that the geological strata of northern Italy could be divided into four successive formations or "orders" ( it, quattro ordini). The term "quaternary" was introduced by Jules Desnoye ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Tephra
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 into pyroclastic rock or tuff. Tephrochronology is a geochronological technique that uses discrete layers of tephra—volcanic ash from a single eruption—to create a chronological framework in which paleoenvironmental or archaeological records can be placed. When a volcano explodes, it releases a variety of tephra including ash, cinders, and blocks. These layers settle on the land and, over time, sedimentation occurs incorporating these tephra layers into the geologic record. Often, when a volcano explodes, biological organisms are killed and their remains are buried within the tephra layer. These fossils are later dated by scientists to determine the age of the fossil and its place within the geolo ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
