|
Hayes Volcano
Hayes Volcano is a stratovolcano in southwestern Matanuska-Susitna Borough, Alaska, 135 km northwest of Anchorage, that was not discovered until 1975. It is responsible for a series of six major tephra layers in the Cook Inlet region of Alaska. Hayes was mostly destroyed by at least six catastrophic eruptions between 3,400 and 3,800 years ago, and the average volume of these eruptions was 2.4 cubic km. In comparison, the volume of the May 18, 1980 eruption of Mount St. Helens was about 1 cubic km. The eruptions of Hayes Volcano during that time were the most voluminous Holocene eruptions to have occurred in the Cook Inlet region. There is currently no fumarolic activity present. The last eruption of Hayes Volcano occurred roughly 1,200 years ago. It is named after the adjacent Hayes Glacier. Physical setting Hayes Volcano is an ice-shrouded, glacially scoured eruptive center of Quaternary age composed of pyroclastic deposits, volcanic breccia, and lava domes. Although the ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Mount Hayes
Mount Hayes is the highest mountain in the eastern Alaska Range, in the U.S. state of Alaska. Despite not being a fourteener, it is one of the largest peaks in the United States in terms of rise above local terrain. For example, the Northeast Face rises 8,000 feet (2,440 m) in approximately 2 miles (3.2 km). This large vertical relief contributes to Mount Hayes being the 51st most topographically prominent peak in the world. The mountain was named in 1898 by W. J. Peters and A. H. Brooks of the U.S. Geological Survey for Charles Willard Hayes (1858–1916), a geologist with the Survey from 1887 through 1911. Mount Hayes was first climbed on August 1, 1941, by Bradford Washburn, Barbara Washburn, Benjamin Ferris, Sterling Hendricks, Henry Hall, and William Shand. Today's standard climbing route is the East Ridge (Alaska Grade 2+). Mount Hayes is not frequently climbed due to its remoteness and the resulting access difficulties. Climate Based on the Köppen climate cl ... [...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] |
Stratovolcanoes Of The United States
A stratovolcano, also known as a composite volcano, is a conical volcano built up by many layers (strata) of hardened lava and tephra. Unlike shield volcanoes, stratovolcanoes are characterized by a steep profile with a summit crater and periodic intervals of explosive eruptions and effusive eruptions, although some have collapsed summit craters called calderas. The lava flowing from stratovolcanoes typically cools and hardens before spreading far, due to high viscosity. The magma forming this lava is often felsic, having high-to-intermediate levels of silica (as in rhyolite, dacite, or andesite), with lesser amounts of less-viscous mafic magma. Extensive felsic lava flows are uncommon, but have travelled as far as . Stratovolcanoes are sometimes called composite volcanoes because of their composite stratified structure, built up from sequential outpourings of erupted materials. They are among the most common types of volcanoes, in contrast to the less common shield volc ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Mountains Of Alaska
A mountain is an elevated portion of the Earth's crust, generally with steep sides that show significant exposed bedrock. Although definitions vary, a mountain may differ from a plateau in having a limited summit area, and is usually higher than a hill, typically rising at least 300 metres (1,000 feet) above the surrounding land. A few mountains are isolated summits, but most occur in mountain ranges. Mountains are formed through tectonic forces, erosion, or volcanism, which act on time scales of up to tens of millions of years. Once mountain building ceases, mountains are slowly leveled through the action of weathering, through slumping and other forms of mass wasting, as well as through erosion by rivers and glaciers. High elevations on mountains produce colder climates than at sea level at similar latitude. These colder climates strongly affect the ecosystems of mountains: different elevations have different plants and animals. Because of the less hospitable terrain and ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Mountains Of Matanuska-Susitna Borough, Alaska
A mountain is an elevated portion of the Earth's crust, generally with steep sides that show significant exposed bedrock. Although definitions vary, a mountain may differ from a plateau in having a limited summit area, and is usually higher than a hill, typically rising at least 300 metres (1,000 feet) above the surrounding land. A few mountains are isolated summits, but most occur in mountain ranges. Mountains are formed through tectonic forces, erosion, or volcanism, which act on time scales of up to tens of millions of years. Once mountain building ceases, mountains are slowly leveled through the action of weathering, through slumping and other forms of mass wasting, as well as through erosion by rivers and glaciers. High elevations on mountains produce colder climates than at sea level at similar latitude. These colder climates strongly affect the ecosystems of mountains: different elevations have different plants and animals. Because of the less hospitable terrain and ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Volcanoes Of Matanuska-Susitna Borough, Alaska
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 ... [...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] |
Mount Spurr
Mount Spurr ( Dena'ina: ''K'idazq'eni'') is a stratovolcano in the Aleutian Arc of Alaska, named after United States Geological Survey geologist and explorer Josiah Edward Spurr, who led an expedition to the area in 1898. The Alaska Volcano Observatory (AVO) currently rates Mount Spurr as Level of Concern Color Code Green. The mountain is known aboriginally by the Dena'ina Athabascan name ''K'idazq'eni'', literally 'that which is burning inside'. Mount Spurr, the highest volcano of the Aleutian Arc, is a large lava dome constructed at the center of a roughly 5 km-wide horseshoe-shaped caldera that is open to the south. The volcano lies 80.87 miles west of Anchorage and NE of Chakachamna Lake. The caldera was formed by a late-Pleistocene or early Holocene debris avalanche and associated pyroclastic flows that destroyed an ancestral Spurr volcano. The debris avalanche traveled more than 15.5 miles to the SE, and the resulting deposit contains blocks as large as 100m in diame ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Igneous Rock
Igneous rock (derived from the Latin word ''ignis'' meaning fire), or magmatic rock, is one of the three main The three types of rocks, rock types, the others being Sedimentary rock, sedimentary and metamorphic rock, metamorphic. Igneous rock is formed through the cooling and solidification of magma or lava. The magma can be derived from Partial melting, partial melts of existing rocks in either a Terrestrial planet, planet's mantle (geology), mantle or crust (geology), crust. Typically, the melting is caused by one or more of three processes: an increase in temperature, a decrease in pressure, or a change in composition. Solidification into rock occurs either below the surface as intrusive rocks or on the surface as extrusive (geology), extrusive rocks. Igneous rock may form with crystallization to form granular, crystalline rocks, or without crystallization to form Volcanic glass, natural glasses. Igneous rocks occur in a wide range of geological settings: shields, platforms ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Intrusion
In geology, an igneous intrusion (or intrusive body or simply intrusion) is a body of intrusive igneous rock that forms by crystallization of magma slowly cooling below the surface of the Earth. Intrusions have a wide variety of forms and compositions, illustrated by examples like the Palisades Sill of New York and New Jersey; the Henry Mountains of Utah; the Bushveld Igneous Complex of South Africa; Shiprock in New Mexico; the Ardnamurchan intrusion in Scotland; and the Sierra Nevada Batholith of California. Because the solid country rock into which magma intrudes is an excellent insulator, cooling of the magma is extremely slow, and intrusive igneous rock is coarse-grained (phaneritic). Intrusive igneous rocks are classified separately from extrusive igneous rocks, generally on the basis of their mineral content. The relative amounts of quartz, alkali feldspar, plagioclase, and feldspathoid is particularly important in classifying intrusive igneous rocks. Intrusions ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Lava Dome
In volcanology, a lava dome is a circular mound-shaped protrusion resulting from the slow extrusion of viscous lava from a volcano. Dome-building eruptions are common, particularly in convergent plate boundary settings. Around 6% of eruptions on Earth are lava dome forming. The geochemistry of lava domes can vary from basalt (e.g. Semeru, 1946) to rhyolite (e.g. Chaiten, 2010) although the majority are of intermediate composition (such as Santiaguito, dacite-andesite, present day) 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 preserved domes have high silica content and consist of rhyolite or dacite. Existence of lava domes has been suggested for some domed structures on the Mo ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
