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Stratovolcano

Stratovolcano

.]] A stratovolcano (also composite cone or composite volcano) is a tall, conical mountain (volcano) composed of both hardened lava and volcanic ash. The shape of these volcanoes is characteristically steep in profile because lava flows that formed them were highly viscous, and so cooled and hardened before spreading very far. Such lava tends to be high in silica. At the other end of the spectrum are shield volcanoes (such as Mauna Loa in Hawai'i), which are formed from less viscous lavas, giving them a wide base and more gently sloping profile. Many exceed a height of 2500m. Stratovolcanoes are often created by subduction of tectonic plates. Because all volcanoes of any size have a stratified (layered) structure — that is, are built up from sequential outpourings of eruptive materials — volcanologists prefer to use the term stratovolcano for these mountains. subduction of tectonic plates, eruption that removed much of the top of the mountain]] subduction of tectonic plates] Examples of stratovolcanoes are:
- Ararat, Turkey
- Barren Island (Andaman Islands) - The only active volcano in the Indian subcontinent
- Cotopaxi in Ecuador
- Mount Elbrus Caucasus, Russia
- Mount Erebus in Antarctica
- Mount Fuji in Japan
- Mount Hood in north Oregon state in the United States
- Kazbek, Caucasus, Georgia
- Kollóttadyngja in North-East Iceland
- Mayon Volcano in the Philippines
- El Misti near Southern Peru's city of Arequipa
- Mount Pinatubo in Zambales province in the Philippines
- Mount Rainier in the north-central Washington state in the United States
- Mount Ruapehu in New Zealand's North Island
- Santa Ana near San Blas, El Salvador
- Mount Shasta in northern California state in the United States
- Soufriere Hills volcano on the Caribbean island of Montserrat
- Mount Spurr in Alaska state in the United States
- Mount St. Helens in southern Washington state in the United States
- Mount Tambora Sambawa Island, Indonesia
- Mount Taranaki (formerly Mount Egmont) in New Zealand's North Island
- Mount Usu Located in Hokkaido, Japan
- Teide on Tenerife, Canary Islands, Spain
- Trölladyngja in North-East Iceland
- Mount Vesuvius near Naples, Italy

External link


- [http://vulcan.wr.usgs.gov/Glossary/StratoVolcano/description_composite_volcano.html United States Geological Survey] Category:Volcanology Category:Landforms
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Volcano

:Eruption redirects here. For other meanings of the word eruption, see eruption (disambiguation) A volcano is a geological landform (usually a mountain) where a substance, usually magma (rock of the Earth's interior made molten or liquid by extremely high temperatures along with a reduction in pressure and/or the introduction of water or other volatiles) erupts through the surface of a planet. Although there are numerous volcanoes (some very active) on the solar system's rocky planets and moons, on Earth at least, this phenomenon tends to occur near the boundaries of the continental plates. However, important exceptions exist in hotspot volcanoes. hotspot volcanoes.]] The name "volcano" originates from the name of Vulcan, a god of fire in Roman mythology. The study of volcanoes is called vulcanology (or volcanology in some spellings). Mud volcanoes are formations which are often not associated with known magmatic activity. Active mud volcanoes tend to involve temperatures much lower than those of igneous volcanoes, except when a mud volcano is actually a vent of an igneous volcano. This article describes igneous volcanoes.

Volcano classification

Erupted material

One way of classifying volcanoes is by the type of material erupted, which affects the shape of the volcano. If the erupting magma contains a high percentage (65%) of silica the lava is called felsic or acidic and tends to be highly viscous (not very fluid) and is pushed up in a blob that will solidify relatively quickly. Lassen Peak in California is an example. This type of volcano has a tendency to explode because it retains the volatiles or gases and easily plugs. Mount Pelée on the island of Martinique is another example. If, on the other hand, the magma contains a relatively low percentage of silica, the lava is called mafic or basic and will be very fluid as it erupts, capable of flowing for long distances. Due to the low viscosity the volatiles are able to escape. A good example of a mafic lava flow is the Great flow produced by an eruptive fissure almost in the geographical center of Iceland roughly 8,000 years ago; it flowed to the sea, a distance of 130 kilometers, and covered an area of 800 square km.

Explosivity

The behaviour of volcanoes range from rare collossally explosive events to common cases of long term, gradual and gentle flow of magma. The Volcanic Explosivity Index is an attempt to categorise these into clear types, with low VEI values corresponding to gentle flows and high VEIs indicating a cataclysmic event with severe global consequences.

Shape

Shield volcanoes

Hawaii and Iceland are examples of places where volcanoes extrude huge quantities of lava that gradually build a wide mountain with a shield-like profile. Their lava flows are generally very hot and very fluid, contributing to long flows. The largest lava shield on Earth, Mauna Loa, is 9,000 m tall (it sits on the sea floor), 120 km in diameter and forms part of the Island of Hawai. Olympus Mons is a shield volcano on Mars, and the tallest mountain in the known solar system. Smaller versions of the "lava shield" include the 'lava dome' (tholoid), 'lava cone', and 'lava mound'. Volcanic cones or cinder cones result from eruptions that throw out mostly small pieces of rock that build up around the vent. These can be relatively short-lived eruptions that produce a cone-shaped hill perhaps 30 to 300 m high.

Stratovolcanoes or composite volcanoes

These are tall conical mountains composed of both lava flows and ejected material, which form the strata that give rise to the name. Classic examples include Mt. Fuji in Japan and Mount Mayon in the Philippines. Volcanoes on land often take the form of flat cones, as the expulsions build up over the years, or in short-lived volcanic cones, cinder cones.

Supervolcanoes

Supervolcano is the popular term for large volcanoes that usually have a large caldera and can potentially produce devastation on a continental scale and cause major global weather pattern changes. Potential candidates include Yellowstone National Park and Lake Toba, but are hard to identify given that there is no formal definition of the term.

Submarine volcanoes

Submarine volcanoes are common features on certain zones of the ocean floor. Some are active at the present time and, in shallow water, disclose their presence by blasting steam and rock-debris high above the surface of the sea. Many others lie at such great depths that the tremendous weight of the water above them results in high, confining pressure and prevents the formation and explosive release of steam and gases. Even very large, deepwater eruptions may not disturb the ocean surface. Under water, volcanoes often form rather steep pillars and in due time break the ocean surface in new islands.

Active, Dormant, or Extinct?

Supervolcano Volcanoes are usually situated either at the boundaries between tectonic plates or over geology hotspots. Volcanoes may be either dormant (having no activity) or active (near constant expulsion and occasional eruptions), and change state unpredictably. Surprisingly, there is no consensus among volcanologists on how to define an "active" volcano. The lifespan of a volcano can vary from months to several million years, making such a distinction sometimes meaningless when compared to the lifespans of humans or even civilizations. For example, many of Earth's volcanoes have erupted dozens of times in the past few thousand years but are not currently showing signs of activity. Given the long lifespan of such volcanoes, they are very active. By our lifespans, however, they are not. Complicating the definition are volcanoes that become restless but do not actually erupt. Are these volcanoes active? Scientists usually consider a volcano active if it is currently erupting or showing signs of unrest, such as unusual earthquake activity or significant new gas emissions. Many scientists also consider a volcano active if it has erupted in historic time. It is important to note that the span of recorded history differs from region to region; in the Mediterranean, recorded history reaches back more than 3,000 years but in the Pacific Northwest of the United States, it reaches back less than 300 years, and in Hawaii, little more than 200 years. Dormant volcanoes are those that are not currently active (as defined above), but could become restless or erupt again. Extinct volcanoes are those that scientists consider unlikely to erupt again. Whether a volcano is truly extinct is often difficult to determine. Since calderas have lifespans sometimes measured in millions of years, a caldera that has not produced an eruption in tens of thousands of years is likely to be considered dormant instead of extinct. For example, the Yellowstone Caldera (considered a Supervolcano) in Yellowstone National Park is at least 2 million years old and hasn't erupted violently for approximately 640,000 years — although there has been some minor activity as relatively recent as 70,000 years ago. For this reason, scientists do not consider the Yellowstone Caldera as extinct. In fact, because the caldera has frequent earthquakes, a very active geothermal system (i.e., the entirety of the geothermal activity found in Yellowstone National Park), and rapid rates of ground uplift, many scientists consider it to be a very active volcano.

Notable Volcanoes

Volcanoes on Earth

:Main article: List of volcanoes List of volcanoes
- Mount Baker (Washington, USA)
- Cold Bay Volcano (Alaska, USA)
- El Chichon/El Chichonal, (Chiapas, Mexico)
- Citlaltépetl/Pico de Orizaba, (Veracruz/Puebla, Mexico)
- Cotopaxi (Ecuador)
- Mount Fuji (Honshu, Japan)
- Mount Hood (Oregon, USA)
- Mount Erebus (Ross Island, Antarctica)
- Etna (Sicily, Italy)
- Krafla (Iceland)
- Hekla (Iceland)
- Kick-'em-Jenny, (Grenada)
- Kilauea (Hawaii, USA)
- Kluchevskaya (Kamchatka, Russia)
- Krakatoa (Rakata, Indonesia)
- Mauna Kea (Hawaii, USA)
- Mauna Loa (Hawaii, USA)
- El Misti (Arequipa, Peru)
- Novarupta (Alaska, USA)
- Paricutín (Michoacán, Mexico)
- Mount Pinatubo (Luzon Island, Philippines)
- Popocatépetl (Mexico-Puebla state line, Mexico)
- Santorini (Santorini islands, Greece)
- Soufriere Hills volcano, (Montserrat)
- Stromboli (Aeolian Islands, Italy)
- Mount Rainier (Washington, USA)
- Mount Shasta (California, USA)
- Mount St. Helens (Washington, USA)
- Surtsey (Iceland)
- Tambora (Sumbawa, Indonesia)
- Teide (Tenerife, Canary Islands, Spain)
- White Island (Bay of Plenty, New Zealand)
- Mount Vesuvius (Bay of Naples, Italy)

Volcanoes elsewhere in the solar system

Italy, "Mount Olympus") is the tallest known mountain in our solar system, located on the planet Mars.]] The Earth's Moon has no large volcanoes, but does have many volcanic features such as rilles and domes. The planet Venus is believed to be volcanically active, and its surface is 90% basalt, indicating that volcanism plays a major role in shaping its surface. Lava flows are widespread and many of its surface features are attributed to exotic forms of volcanism not present on Earth. Other Venusian phenomena, such as changes in the planet's atmosphere and observations of lightning, have been attributed to ongoing volcanic eruptions. There are several extinct volcanoes on Mars, four of which are vast shield volcanoes far bigger than any on Earth:
- Arsia Mons
- Ascraeus Mons
- Hecates Tholus
- Olympus Mons
- Pavonis Mons These volcanoes have been extinct for many millions of years, but the European Mars Express spacecraft has found evidence that volcanic activity may have occurred on Mars in the recent past as well. Jupiter's moon Io is the most volcanic object in the solar system, due to tidal interaction with Jupiter. It is covered with volcanoes that erupt sulfur, sulfur dioxide and silicate rock, with the result that the moon is constantly being resurfaced. Its lavas are the hottest known anywhere in the solar system, with temperatures exceeding 1800 K (1500 °C). In February 2001, the largest recorded volcanic eruptions in the solar system occurred on Io [http://www2.keck.hawaii.edu/news/archive/eruption/]. See the list of geological features on Io for a list of named volcanoes on the moon. list of geological features on Io In 1989 the Voyager 2 spacecraft observed ice volcanoes (cryovolcanism) on Triton, a moon of Neptune and in 2005 the Cassini-Huygens probe photographed fountains of frozen particles erupting from Saturn's moon Enceladus. The ejecta are believed to consist of liquid nitrogen, dust, or methane compounds. Cassini-Huygens also found evidence of a methane-spewing cryovolcano on the Saturnian moon Titan, which is believed to be a significant source of the methane found in its atmosphere. [http://www.newscientist.com/article.ns?id=dn7489] It is theorized that cryovolcanism may also be present on the Kuiper Belt Object Quaoar.

Volcanology

Volcano formation

Quaoar Like most of the interior of the earth, the movements and dynamics of magma are poorly understood. However, it is known that an eruption usually follows movement of magma upwards into the solid layer (the earth's crust) beneath a volcano and occupying a magma chamber. Eventually, magma in the chamber is forced upwards and flows out across the planet surface as lava, or the rising magma can heat water in the surrounding landform and cause explosive discharges of steam; either this or escaping gases from the magma can produce forceful ejections of rocks, cinders, volcanic glass, and/or volcanic ash also known as tephra. While always displaying powerful forces, eruptions can vary from effusive to extremely explosive. Most volcanoes on the land are formed at destructive plate margins: where oceanic crust is forced below the continental crust because oceanic crust is denser than continental crust. Friction between these moving plates will cause the oceanic crust to melt, and reduced density will force the newly formed magma to rise. As the magma rises through weak areas in the continental crust it may eventually erupt as one or more volcanoes. For example, Mount St. Helens is found inland from the margin between the oceanic Juan de Fuca Plate and the continental North American Plate. North American Plate A volcano generally presents itself to the imagination as a mountain sending forth from its summit great clouds of smoke with vast sheets of flame. The truth is that a volcano seldom emits either smoke or flame, although various combinations of hydrogen, carbon, oxygen, and sulfur do sometimes ignite. What is mistaken for smoke consists of vast volumes of fine dust, mingled with steam and other vapors, chiefly sulfurous. Most of what appears to be flames is the glare from the erupting materials, glowing because of their high temperature; this glare reflects off the clouds of dust and steam, resembling fire. Perhaps the most conspicuous part of a volcano is the crater, a basin of a roughly circular form within which occurs a vent (or vents) from which magma erupts as gases, lava, and ejecta. A crater can be of large dimensions, and sometimes of vast depth. Very large features of this sort are termed calderas. Some volcanoes consist of a crater alone, with scarcely any mountain at all; but in the majority of cases the crater is situated on top of a mountain (the volcano), which can tower to an enormous height. Volcanoes that terminate in a principal crater are usually of a conical form. Volcanic cones are usually smaller features composed of loose ash and cinder, with occasional masses of stone which have been tossed violently into the air by the eruptive forces (and are thus called ejecta). Within the crater of a volcano there may be numerous cones from which vapours are continually issuing, with occasional volleys of ashes and stones. In some volcanoes these cones form lower down the mountain, along rift zones or fractures. When the cone is eroded these rifts or lava filled fractures remain as radial near vertical dikes of volcanic rock. For example the radiating dikes at Shiprock in NW New Mexico.

Tectonic environments of volcanoes

Volcanoes can principally be found in three tectonic environments. New Mexico
Constructive plate margins
These are by far the most common volcanoes on the Earth. They are also the least frequently seen, because most of their activity takes place beneath the surface of the oceans. Along the whole of the oceanic ridge system are irregularly spaced surface eruptions, and more frequent sub-surface intrusions without surface expression. The large majority of these are only known about at surface because of earthquakes as part of the eruptions/ intrusions, or occasionally if passing shipping happens to notice unusually high water temperatures or chemical precipitates in the seawater. In a few places oceanic ridge activity has lead to the volcanoes coming up to the surface - Saint Helena and Tristan da Cunha in the Atlantic Ocean; the Galapagos Islands in the Pacific Ocean, allowing them to be studied in some detail. But most activity takes place in considerable water depths. Iceland is also on a ridge, but has different characteristics than a simple volcano. It could be argued that the volcanoes of the Great Rift Valley system of East Africa are modified constructive margin volcanoes. However the modifications caused by the presence of thick continental crust are very substantial, and the magmas produced are very different from the typically very homogenous MORB (Mid-Ocean Ridge Basalt) that makes up the huge majority of constructive margin volcanoes.
Destructive plate margins
These are the most visible and well-known types of volcanoes on earth, forming above the subduction zones where (oceanic) plates dive into the Earth to their destruction. Their magmas are typically "calc-alkaline" as a result of their origins in the upper parts of altered ocean plate materials, mixed with sediments, and processed through variable thicknesses of more-or-less continental crust. The heavier plate sinks under the lighter one and the friction from the melting plate causes magma to force it's way out through a crack in the crust. Unsurprisingly, their compositions are much more varied than at constructive margins.
Hotspot situations
subduction zones, Iceland]] Hotspots were originally a catch-all for volcanoes that didn't fit into one of the above two categories, but these days this refers to a more specific circumstance - where an isolated plume of hot mantle material intersects the underside of crust (oceanic or continental), leading to a volcanic center that is not obviously connected with a plate margin. The classic example is the Hawaiian chain of volcanoes and seamounts; Yellowstone is cited as another classic example, in this case the intersection is with the underside of continental crust. Iceland is sometimes cited as yet a third classical example, but complicated by the coincidence of a hotspot intersecting an oceanic ridge constructive margin. There are debates about the simple "hotspot" concept, since theorists cannot agree on whether the "hot mantle plumes" originate in the upper mantle or in the lower mantle. Meanwhile, field geologists and petrologists see considerable variation in the detailed chemistry of one hotspot's magmas versus a second hotspot's magmas. On the third hand, high-resolution seismology of different hotspots is yielding different pictures of the deep sub-structure of Hawaii versus Iceland. There is no detailed consensus about how to interpret these varied results, and it seems plausible that eventually several different sub-types of hotspots will be identified.

Predicting eruptions

Science has not yet been able to predict with absolute certainty when a volcanic eruption will take place, but significant progress in judging when one is probable has been made in recent time. Iceland, 1980 at 8:32 a.m. PDT]] Volcanologists use the following to forecast eruptions.

Seismicity

Seismic activity (small earthquakes and tremors) always occurs as volcanoes awaken and prepare to erupt. Some volcanoes normally have continuing low-level seismic activity, but an increase can signify an eruption. The types of earthquakes that occur and where they start and end are also key signs. Volcanic seismicity has three major forms: short-period earthquakes, long-period earthquakes, and harmonic tremor.
- Short-period earthquakes are like normal fault-related earthquakes. They are related to the fracturing of brittle rock as the magma forces its way upward. These short-period earthquakes signify the growth of a magma body near the surface.
- Long-period earthquakes are believed to indicate increased gas pressure in a volcano's "plumbing system." They are similar to the clanging sometimes heard in your home's plumbing system. These oscillations are the equivalent of acoustic vibrations in a chamber, in the context of magma chambers within the volcanic dome. Patterns of seismicity are complex and often difficult to interpret. However, increasing activity is very worrisome, especially if long-period events become dominant and episodes of harmonic tremor appear. In December 2000, scientists at the National Center for Prevention of Disasters in Mexico City predicted an eruption within two days from Popocatépetl, on the outskirts of Mexico City. Their prediction used research done by Dr. Bernard Chouet, a Swiss vulacanologist working at the United States Geological Survey, into increasing long-period oscillations as an indicator of an imminent eruption. The government evacuated tens of thousands of people. Forty eight hours later, bang on time, the volcano erupted spectacularly. It was Popocatépetl's largest eruption for a thousand years and yet no one was hurt.

Gas emissions

United States Geological Survey As magma nears the surface and its pressure decreases, gases escape. This process is much like what happens when you open a bottle of soda and carbon dioxide escapes. Sulfur dioxide is one of the main components of volcanic gases, and increasing amounts of it herald the arrival of more and more magma near the surface. For example, on May 13, 1991, 500 tonnes of sulfur dioxide were released from Mount Pinatubo in the Philippines. On May 28, just two weeks later, sulfur dioxide emissions had increased to 5,000 tonnes, ten times the earlier amount. Mount Pinatubo erupted on June 12, 1991. On several occasions, such as before the Mount Pinatubo eruption, sulfur dioxide emissions have dropped to low levels prior to eruptions. Most scientists believe that this drop in gas levels is caused by the sealing of gas passages by hardened magma. Such an event leads to increased pressure in the volcano's plumbing system and an increased chance of an explosive eruption.

Ground deformation

Swelling of the volcano signals that magma has accumulated near the surface. Scientists monitoring an active volcano will often measure the tilt of the slope and track changes in the rate of swelling. An increased rate of swelling, especially if accompanied by an increase in sulfur dioxide emissions and harmonic tremors is a high probability sign of an impending event.

Effects of volcanoes

There are many different kinds of volcanic activity and eruptions:
- phreatic eruptions (steam)
- explosive eruption of high-silica lava (e.g., rhyolite)
- effusive eruption of low-silica lava (e.g., basalt)
- pyroclastic flows
- lahars (debris flow)
- carbon dioxide emission All of these activities can pose a hazard to humans. Volcanic activity is often accompanied by earthquakes, hot springs, fumaroles, mud pots and geysers. Low-magnitude earthquakes often precede eruptions. The concentrations of different volcanic gases can vary considerably from one volcano to the next. Water vapor is typically the most abundant volcanic gas, followed by carbon dioxide and sulfur dioxide. Other principal volcanic gases include hydrogen sulfide, hydrogen chloride, and hydrogen fluoride. A large number of minor and trace gases are also found in volcanic emissions, for example: hydrogen, carbon monoxide, and volatile metal chlorides. carbon monoxide carbon monoxide carbon monoxide Large, explosive volcanic eruptions inject water vapor (H2O), carbon dioxide (CO2), sulfur dioxide (SO2), hydrogen chloride (HCl), hydrogen fluoride (HF) and ash (pulverized rock and pumice) into the stratosphere to heights of 10-20 miles above the Earth's surface. The most significant impacts from these injections come from the conversion of sulfur dioxide to sulfuric acid (H2SO4), which condenses rapidly in the stratosphere to form fine sulfate aerosols. The aerosols increase the reflection of radiation from the Sun back into space and thus cool the Earth's lower atmosphere or troposphere; however, they also absorb heat radiated up from the Earth, thereby warming the stratosphere. Several eruptions during the past century have caused a decline in the average temperature at the Earth's surface of up to half a degree (Fahrenheit scale) for periods of one to three years. The sulfate aerosols also promote complex chemical reactions on their surfaces that alter chlorine and nitrogen chemical species in the stratosphere. This effect, together with increased stratospheric chlorine levels from chlorofluorocarbon pollution, generates chlorine monoxide (ClO), which destroys ozone (O3). As the aerosols grow and coagulate, they settle down into the upper troposphere where they serve as nuclei for cirrus clouds and further modify the Earth's radiation balance. Most of the hydrogen chloride (HCl) and hydrogen fluoride (HF) are dissolved in water droplets in the eruption cloud and quickly fall to the ground as acid rain. The injected ash also falls rapidly from the stratosphere; most of it is removed within several days to a few weeks. Finally, explosive volcanic eruptions release the greenhouse gas carbon dioxide and thus provide a deep source of carbon for biogeochemical cycles. Gas emissions from volcanoes are a natural contributor to acid rain. Volcanic activity now releases about 130 to 230 teragrams (145 million to 255 million short tons) of carbon dioxide each year. Volcanic eruptions may inject an aerosol of particles and chemicals in the Earth's atmosphere. Large injections may have visual effects and affect global climate through climate forcing.

Past beliefs

Before it was understood that most of the Earth's interior is molten, various explanations existed for volcano behavior. For decades after awareness that compression and radioactive materials may be heat sources, their contributions were specifically discounted. Volcanic action was often attributed to chemical reactions and a thin layer of molten rock near the surface. Jesuit Athanasius Kircher (1602-1680), witnessed eruptions of Aetna and Stromboli, then visited the crater of Vesuvius and published his view of an Earth with a central fire connected to numerous others caused by the burning of sulfur, bitumen and coal. coal

See also


- Supervolcano
- Iceland hotspot
- Prehistoric volcano
- List of volcanoes
- List of famous volcanic eruption deaths
- Volcanic Explosivity Index
- Black smoker (deep sea vent)
- Magma
- Lava
- Pacific Ring of Fire
- Geomorphology
- Earth science
- Io
- Triton (moon)
- Tsunami
- Top 10 most deadly Volcanic Eruptions
- Haroun Tazieff (famous volcanologist)

References


- Macdonald, Gordon A., and Agatin T. Abbott. (1970). Volcanoes in the Sea. University of Hawaii Press, Honolulu. 441 p.
- Ollier, Cliff. (1988). Volcanoes. Basil Blackwell, Oxford, UK, ISBN 0-631-15664-X (hardback), ISBN 0-631-15977-0 (paperback).

Further reading


- Haraldur Sigurðsson, ed. (1999) Encyclopedia of Volcanoes. Academic Press. ISBN 012643140X. This is a reference aimed at geologists, but many articles are accessible to non-professionals.

External links


- [http://volcanoes.usgs.gov/Products/Pglossary/pglossary.html Glossary of Volcanic Terms from USGS]
- [http://volcano.und.nodak.edu/vwdocs/glossary.html Volcanic and Geologic Terms] from [http://volcano.und.nodak.edu/ Volcano World]
- [http://news.bbc.co.uk/1/hi/sci/tech/3183047.stm Television program (BBC) on the prediction of Popocatepetl's 2000 eruption]
- [http://www.volcano.si.edu Smithsonian Global Volcanism Program]
- [http://www.geology.sdsu.edu/how_volcanoes_work Explore the geologic causes of an eruption]
- [http://science.howstuffworks.com/volcano.htm/printable How Volcanoes Work by Tom Harris]
- [http://www.geology.sdsu.edu/how_volcanoes_work/ How Volcanoes Work] - Educational resource on the science and processes behind volcanoes, intended for university students of geology, volcanology and teachers of earth science.
- [http://www.geonet.org.nz/volcanocam.html Volcano Cam Geonet's live pictures of 4 of New Zealand's volcanoes]
- [http://facweb.bhc.edu/academics/science/harwoodr/GEOL101/Labs/VolcanicMaterials/ Volcanic Materials Identification] Category:Landforms Category:Plate tectonics Category:Volcanology
- Category:Geological hazards Category:Climate forcing agents als:Vulkanismus ms:Gunung berapi ja:火山 simple:Volcano th:ภูเขาไฟ

Lava

Look up Lava, ‘A‘a, or Pāhoehoe in Wiktionary, the free dictionary
Lava is molten rock that a volcano expels during an eruption. Lava, when first exuded from a volcanic vent, is a liquid at very high temperature: typically from 700°C to 1200°C (1300°F to 2200°F). Although the viscosity of lava is 100,000 times that of water, the viscous rock can flow many miles before eventually cooling and solidifying. While still below the earth's surface, the molten rock is termed magma. Solidified lava is known as igneous rock, although the term "lava flow" refers to the hardened formation. An "active lava flow" would be one having still molten rock associated with it. The word 'lava' comes from Italian, and is probably ultimately derived from the Latin word labes which means a fall, slide, or sinking in. The first time it was used in connection with extruded magma was apparently in a short account written by Francesco Serao of the eruption of Vesuvius which took place between May 14 and June 4 1737. In this he described "a flow of fiery lava" in analogy to the flow of water and mud down the flanks of the volcano following heavy rain. 1737

Lava flow types

The three main forms taken by flowing of lava are ‘a‘a, pāhoehoe, and pillow lava.

‘A‘a

1737.]] Aa or ‘A‘a (Hawaiian English, from Hawaiian: ‘a‘ā meaning "stoney with rough lava", but also to "burn" or "blaze") is one of three basic types of flow lava. ‘A‘a is characterized by a rough or rubbly surface composed of broken lava blocks called clinker. The loose, broken, and sharp, spiny surface of a solidified ‘a‘a flow makes walking difficult and slow. The clinkery surface actually covers a massive dense core, which was the most active part of the flow. As pasty lava in the core travels downslope, the clinkers are carried along at the surface. At the leading edge of an ‘a‘a flow, however, these cooled fragments tumble down the steep front and are buried by the advancing flow. This produces a layer of lava fragments both at the bottom and top of an ‘a‘a flow. Accretionary lava balls as large as 3 m (10 ft) are common on ‘a‘a flows. ‘A‘a is usually of higher viscosity than pāhoehoe (usually spelled just pahoehoe). Pāhoehoe can turn into ‘a‘a if it becomes turbulent due to meeting impediments or steep slopes.

Pāhoehoe

clinker Volcano in Hawai‘i.]] Pahoehoe or Pāhoehoe (Hawaiian English, from Hawaiian, meaning "smooth, unbroken lava") is basaltic lava that has a smooth, hummocky, or ropy surface. A pāhoehoe flow typically advances as a series of small lobes and toes that continually break out from a cooled crust. The surface texture of pāhoehoe flows varies widely, displaying all kinds of bizarre shapes often referred to as lava sculpture.

Pillow lava

lava Pillow lava is the rock type typically formed when lava emerges from an underwater volcanic vent or a lava flow enters the ocean. The viscous lava gains a solid crust immediately upon contact with the water, and this crust cracks and oozes additional large blobs or "pillows" as more lava emerges from the advancing flow. Since the majority of Earth's surface is covered by water, and most volcanoes are situated near or under it, pillow lava is actually very common.

Lava formations

Lava, being much more viscous than water, tends not to flow as rapidly. Nevertheless, where the slope of the ground is considerable, it can advance with great speed. Even when at its hottest, it is somewhat viscous, like molasses, and this viscosity increases as it cools. Hence, on a level plain, and at some distance from its source, the lava-stream advances at a leisurely pace. In such circumstances the cooling proceeds so quickly that a crust of considerable thickness is soon formed on the top of the current, and persons who are bold enough may cross the stream by means of this natural bridge. Even where a deep interior flow continues, a crust may be formed on the surface; and someone whose curiosity exceeded their prudence could stand on the top of it, bore a hole through the crust, and see the lava flowing underneath their feet! There are few things not made of rock that can resist the progress of flowing lava; trees, houses, everything yields to its massive assault. Trees soon catch fire due to the heat of approaching lava, and when the lava reaches them they emit a hissing noise, almost amounting to a shriek. The trees then plunge into the molten flood and are seen no more. Even the sea cannot stop the lava-stream, but retires on its approach; promontories stretching a considerable distance from the shore are formed in this manner as the molten lava hardens into stone.

Lava cascades and fountains

Earth The eruptions of lava are sometimes attended by peculiarities which impart to them much additional grandeur. Instances have occurred in which the fiery stream has plunged over a sheer precipice of immense height, so as to produce a glowing cascade exceeding in breadth and perpendicular descent of the celebrated Niagara Falls. In other cases, the lava, instead of at once flowing down the sides of the mountain, has been first thrown up into the air as a fiery fountain several hundred feet in height (see Volcanic cone).

Lava lakes

There are only a few sites in the world where permanent lakes of lava exist. These include:
- Mount Erebus, Antarctica
- Kilauea Volcano, Hawai`i
- Erta Ale, Ethiopia
- Nyiragongo, Zaire

Composition of lavas

Zaire The lavas of different mountains, when cooled and hardened, differ much in their appearance and composition. If a rhyolite lava-stream comes into contact with water, for example entering the sea, it can quickly freeze into a black glassy substance called obsidian. (Obsidian may also be formed under many other conditions.) This is particularly common in Iceland and Lipari. It is used for ornamental purposes - it presents a different appearance according to the manner in which it is cut. When cut in one direction it is of a beautiful jetty black; when cut across that direction it is glistering gray. In prehistoric times its hardness and conchoidal fracture properties meant it was widely used to make knives. The lavas of Vesuvius are generally of a brown colour, and are also used in the arts. In them are found the beautiful olive-green crystals of the mineral called olivine, sometimes used by jewellers. But the most useful of all volcanic productions is perhaps sulfur, in which Mount Etna has been very prolific.
- See also: Lava tube

Towns destroyed by lava

Lava tube
- Kaimū, Hawaii (abandoned)
- Kalapana, Hawaii (abandoned)
- Kapoho, Hawaii (abandoned)
- Keawaiki, Hawaii (abandoned)
- Koa‘e, Hawaii (abandoned)
- San Sebastiano al Vesuvio, Italy (rebuilt)

Towns partially destroyed by lava flows


- Catania, Italy, in the eruption Mount Etna in 1669 (rebuilt)
- Goma, Democratic Republic of Congo, in the eruption of Nyiragongo in 2002
- Heimaey, Iceland, in the 1973 Eldfell eruption (rebuilt)
- Royal Gardens, Hawaii, by the eruption of Kilauea in 1986-87 (abandoned)
- Pompeii, Italy (buried)

External links


- [http://volcanoes.usgs.gov/Products/Pglossary/aa.html USGS definition of Aa]
- [http://volcanoes.usgs.gov/Products/Pglossary/pahoehoe.html USGS definition of Pahoehoe] Category:Volcanology ko:용암 ja:溶岩

Silica

The chemical compound silicon dioxide, also known as silica, is the oxide of silicon, chemical formula SiO2. It is found in nature in several forms, including quartz and opal. In fact, silica has 17 crystalline forms (see [http://www.minsocam.org/MSA/collectors_corner/arc/silicanom.htm Nomenclature of Silica]). Also, many forms of life include silica structures, including microorganisms such as diatoms, plants such as horsetail, and animals such as hexactinellid sponges. It is manufactured in several forms including glass (in colorless high purity form called fused silica), synthetic amorphous silica and silica gel (used e.g. as desiccants in brand new clothes and leather goods). Silica, with alumina, is a crucial ingredient in clay and allows for the development of a interlocking crystal matrix after firing in earthenware, stoneware and porcelain ceramic processes. Silica is a major ingredient of Portland cement. The ceramic re-entry heat protection tiles mounted on the bottom side of the Space Shuttles are made mostly of silica, as are the firebricks used in steel processing. The most common constituent of sand in inland continental settings and non-tropical coastal settings is silica, usually in the form of quartz because the considerable hardness of this mineral resists erosion. However, the composition of sand varies according to local rock sources and conditions. Inhaling crystalline silica dust can lead to silicosis. Variants found in high-pressure impacts are coesite and stishovite. Silica is also used as a food additive, primarily as a flow agent in powdered foods, or to absorb water. See the ingredients list for [http://www.bk.com/Food/Nutrition/ingredients.aspx Burger King]. The chemical stability of silicon dioxide and its electrical insulation properties are a major reason why silicon is the dominant material for semiconductor devices. It is used to separate the active regions of devices and to form insulating surfaces.

Chemistry

Silicon dioxide can be formed when silicon is exposed to oxygen (or air) at extremely high temperatures. This can occasionally happen naturally in fires, or in lightning strikes onto sand. Silicon dioxide is attacked by strong acids particularly hydrofluoric acid (HF). HF is used to remove or pattern silicon in the semiconductor industry.

Reference


- R. K. Iler, The Chemistry of Silica (ISBN 047102404X)

External links


- (Tridymite)
- (Quartz)
- (Cristobalite)
- [http://www.cdc.gov/niosh/npg/npgd0552.html NIOSH Pocket Guide to Chemical Hazards] (amorphous)
- [http://www.cdc.gov/niosh/npg/npgd0553.html NIOSH Pocket Guide to Chemical Hazards] (crystalline, as respirable dust) Category:Silicon compounds Category:Oxides Category:Ceramics ja:二酸化ケイ素

Shield volcano

A shield volcano is a wide volcano with shallowly-sloping sides. The name derives from a translation of "Skjaldbreiður", an Icelandic shield volcano whose name means broad shield, from its resemblance to a warrior's shield. Shield volcanoes are formed by lava flows of low viscosity — lava that flows easily. Consequently, a volcanic mountain having a broad profile is built up over time by flow after flow of relatively fluid basaltic lava issuing from vents or fissures on the surface of the volcano. Many of the largest volcanoes on Earth are shield volcanoes. The largest is Mauna Loa on the Big Island of Hawaii; also the rest of the volcanoes in the Hawaiian Islands are shield volcanoes. There are other shield volcanoes, for example in Washington, Oregon, and the Galapagos Islands. The Piton de la Fournaise, on Reunion Island, is one of the more active volcanoes on earth, with one eruption per year on average. The viscosity of magma as it approaches the surface is a function of temperature and composition. Shield volcanoes in the Hawaiian Islands erupt magma as hot as 1,200 °C 2,200 °F, compared with 850 °C 1,560 °F for most continental volcanoes (which are usually composed of acidic lava). Because of the fluidity of the lava, major explosive eruptions do not occur. The most severe explosions occur if water enters a vent, although expanding gases in the magma can produce spectacular fountaining of the low viscosity lava. magma Shield volcanoes are known from other planets. The largest known mountain in the solar system, Olympus Mons on Mars, is thought to be an extinct shield volcano. Shield volcanoes on Mars are higher and much more massive than those on Earth. On Earth, because of plate tectonics, hotspot volcanoes eventually move away from the source of their magma and the volcanoes are individually less massive than might otherwise be the case. Category:Shield volcanoes Category:Volcanology Category:Landforms

Mauna Loa

Mauna Loa is an active shield volcano in the Hawaiian Islands, one of five volcanic peaks that together form the Island of Hawaii. In Hawaiian, mauna loa means "long mountain". The summit caldera of the volcano is called Moku‘āweoweo. Mauna Loa is Earth's largest volcano and is the exposed (subareal) part of an enormous mid-ocean mountain. Indeed, it is the Earth's most massive mountain, with a volume estimated at approximately 18,000 cubic miles (75,000 km³) (Kaye, 2002) and a height—measured from its base some 5,000 m (over 16,000 ft) below the ocean surface to the highest point at 4,170 m (13,680 ft) above sea level—of over 9,000 m (> 30,000 ft). Mauna Loa is about 36 m (120 ft) lower than its neighbor, Mauna Kea. Mauna Loa is part of the Hawaii Volcanoes National Park. There have been some 33 eruptions of Mauna Loa in historical time, the last in March-April, 1984 (Lockwood, 1995).

Scientific observations

1984 The elevation and location of Mauna Loa have made it an important location for atmospheric monitoring by the Global Atmosphere Watch, and other scientific observations. The Mauna Loa Solar Observatory (MLSO), located at 3,400 m (11,155 ft) on the northern slope of the mountain, has long been prominent in observations of the Sun. The NOAA Mauna Loa Observatory (MLO), located close by, monitors the global atmosphere at its location well above local influences. Atmospheric carbon dioxide has been measured regularly since 1958 and shows the steadily increasing trend associated with the "greenhouse effect" and global warming. Mauna Loa is itself observed by the USGS Hawaiian Volcano Observatory, which also monitors other prominent Hawaiian volcanoes such as Kīlauea, Hualālai, Mauna Kea, and Haleakalā.

References

Haleakalā
- Kaye, G. D., Using GIS to estimate the total volume of Mauna Loa Volcano, Hawaii, 98th Annual Meeting, Geological Society of America, (2002).
- Lockwood, J. P., Mauna Loa eruptive history - the preliminary radiocarbon record, Hawai`i, in Rhodes, J.M., and Lockwood, J. P. (eds.), Mauna Loa revealed: structure, composition, history, and hazards: Washington D.C., American Geophysical Union Monograph 92, p. 81-94, (1995).

External links


- [http://wwwhvo.wr.usgs.gov/maunaloa/ Mauna Loa] – USGS website
- [http://www.mlo.noaa.gov/ Mauna Loa Observatory] (MLO) – NOAA
  - [http://www.mlo.noaa.gov/HISTORY/PUBLISH/20th%20anniv/co2.htm History of MLO CO2 measurement] – MLO/NOAA
- [http://mlso.hao.ucar.edu/cgi-bin/mlso_homepage.cgi Mauna Loa Solar Observatory] (MLSO) – operated by the High Altitude Observatory, Boulder, Colorado Category:Volcanoes of the Island of Hawaii Category:Volcanic calderas Category:Hawaii mountains Category:Decade Volcanoes Category:Active volcanoes ja:マウナ・ロア山 simple:Mauna Loa

Ararat

Mount Ararat (Turkish Ağrı Dağı; Kurdish Çîyayê Agirî;Armenian Արարատ; Persian آرارات; Hebrew אררט, Standard Hebrew Ararat, Tiberian Hebrew ), the tallest peak in modern Turkey, is a snow-capped dormant volcanic cone, located in the far northeast of Turkey, 16 km west of Iran and 32 km south of Armenia. The Book of Genesis identifies this mountain as the resting place of Noah's Ark after the Great Flood described there. A smaller (3896 m) cone, Little Mount Ararat, rises just southeast of the main peak. The lava plateau stretches out between the two pinnacles. Technically, Ararat is a stratovolcano, formed of lava flows and pyroclastic ejecta. The last activity on the mountain was a major earthquake in July 1840 centered around the Ahora Gorge, a northeast trending chasm that drops 1825 metres (6,000 ft) from the top of the mountain.

History

The mountain was the setting for the legend of the ten thousand martyrs of Mount Ararat.

Symbolism

ten thousand martyrs of Mount AraratEven though the mountain is located in Turkey, Ararat is the national symbol of Armenia, where it is sometimes called Masis (Մասիս), and was once Armenian territory until it fell to the Turks around 1915. Mount Ararat is featured in the center of the Coat of Arms of Armenia. The mountain is clearly visible from most locations in Armenia, including the capital city of Yerevan (from Armenia it is best visible from the Khor Virap monastery, though) and is often depicted by Armenian artists on paintings, obsidian engravings and backgammon boards.

Elevation

An elevation of 5165m for Mount Ararat is given by some authorities, but SRTM data shows that this is less accurate than the elevation given here.

See also


- Ararat anomaly

External links


- [http://www.polosbastards.com/artman/publish/Ararat.shtml Kurds of Ararat]
- [http://www.armgate.com/ararat/index.html Mt. Ararat Pictures from Armenia]
- [http://www.arminco.com/livewebcam.html Mount Ararat live webcam]
- [http://earthobservatory.nasa.gov/Newsroom/NewImages/images.php3?img_id=4996 NASA Earth Observatory page]
- [http://volcano.und.nodak.edu/vwdocs/volc_images/img_ararat.html Space shuttle image and basic details.]
- [http://www.volcano.si.edu/gvp/world/volcano.cfm?vnum=0103-04- Global Volcanism Program, Mount Ararat page].
- [http://www.insightmag.com/media/paper441/news/2000/11/20/CoverStory/Anomaly.Or.Noahs.Ark-208686.shtml Insight article about the Ararat Anomaly]
- [http://eifiles.cn/mn.htm The Mountain of Noah] - Biblical references to Mount Ararat Category:Armenian culture Ararat, Mount Ararat, Mount Ararat, Mount Ararat, Mount ja:アララト山

Barren Island (Andaman Islands)

:For other areas bearing the same name, see the disambiguation page Barren Island Barren Island Barren Island (coordinates :) is located in the Andaman Sea, one of the most easterly of the Andaman Islands. It is the only confirmed active volcano in South Asia. The island along with the rest of the Andamans is part of the Indian union territory of Andaman and Nicobar Islands, and lies some 135 km northeast of the territory's capital, Port Blair. The first recorded eruptions of the volcano dates back to 1787. Since then the volcano has erupted more than 6 times, most recently on May 28, 2005. After the initial eruption in 1787, further eruptions were recorded in 1789, 1795 and the last confirmed one being in 1803-04 (another eruption is also believed to have occurred in 1852). After a gap of nearly 2 centuries, the island became active again in 1991 when it lasted 6 months and caused considerable damage. It reoccurred in 1994-95 before opening up again in 2005. The latest eruption is considered to be linked to the 2004 Indian Ocean Tsunami. After the recent eruptions, the island which still sees the odd tremors is being promoted as a niche tourist destination as the tsunami battered territory seeks to bring in more revenues.

Location

tsunami.]] The volcanic island stands in the midst of a volcanic belt on the edge of the Indian and Burmese tectonic plates. There are other extinct sea and land volcanos in the zone, and Narcondum, a volcano with reported activity. The peak of the volcano (a stratovolcano) rises to an altitude of 354 metres (1,161 ft), but most of the volcano is underwater (standing on the seabed 2250 meters below the surface). The island is 3 km long with a total surface area of 10 km²; the caldera of the volcano is 2 km wide. True to its name, it is a barren area uninhabited by humans with a small population of goats. Also birds, bats and a few rodents like flying fox and rats are known to survive the harsh conditions. rats

External links


- [http://www.gsi.gov.in/barren1.htm Geological Survey of India]
- [http://www.geos.iitb.ac.in/dchandra/biexp/ Department of Earth Sciences, IIT Bombay]
- [http://news.bbc.co.uk/1/hi/world/south_asia/4669921.stm BBC] Category:Andaman and Nicobar Islands Category:Active volcanoes Category:Volcanoes of India Category:Volcanoes of the Indian Ocean Category:Islands

Indian subcontinent

:Southern Asia sometimes refers to all of Asia that was not part of the Soviet Union. Soviet Union Soviet Union as the international border between India and Pakistan, a position that neither party considers acceptable.)]] The term South Asia is considered often as synonymous with the term Indian subcontinent, and includes the following neighboring states:
- India, Pakistan and Bangladesh; constituting the bulk of the subcontinent proper
- the Himalayan States: Nepal and Bhutan
- the Indian Ocean Island States: Sri Lanka, the Maldives All of these countries are members of the South Asian Association for Regional Cooperation (SAARC). The US State Department’s South Asia Bureau is currently planning to include Kazakhstan, Kyrgyzstan, Turkmenistan, Tajikistan and Uzbekistan in its definition of South Asia. These countries, however, are historically considered to belong to the category of Central Asia, along with Chinese Turkestan and Mongolia are not, strictly speaking, a part of South Asia. Geographically, the Indian subcontinent would additionally include some disputed territory currently controlled by China, and Myanmar and exclude most of western and northern Pakistan and Kashmir where the Indian plate and Eurasian plate meet and collide. Politically (as in the SAARC member-states), the region covers about 4,480,000 km² (1,729,738 sq. mi.), or 10% of the Asian continent. However, its population accounts for about 40% of Asia. Some or all of Afghanistan is sometimes considered part of the region of South Asia since, due to its geographic proximity, it has shared many historical currents with the region. Recently, Afghanistan has been admitted to the SAARC as a member.

Nomenclature

The term "South Asia"' is a common contemporary term for what in times before 1947, the end of the British Raj and the beginning of the First Indo-Pakistani War, was simply known as "India" and has subsequently been referred to as "British India," though prior to Independence that term referred to those portions of the country that were directly administered by the British, as opposed to the princely states. Historically, South Asia and South-East Asia together constitute what is known as the East Indies, with the first being defined as Hither India or India Citerior and Further India or India Ulterior. These terms, however, have ceased to be current and have become arcane and largely used, if at all, by academics, with only the "East Indies" still retaining some current usage.

Geography

India Ulterior Geographically, the region is bound by the Himalaya to the north and east, and the Arabian Sea and the Bay of Bengal to the south. The Hindu Kush mountains that run through Afghanistan and northern Pakistan are usually considered the northwestern edge of the subcontinent. Geologically, most of this region is a subcontinent because it rests on a tectonic plate of its own, the India Plate, separate from the rest of Eurasia and was once a small continent before colliding with the Eurasian Plate and giving birth to the Himalayan range and the Tibetan plateau. Even now the India Plate continues to move northward with the result that the Himalaya are growing taller by a few centimetres each decade. In addition, is also home to an astounding variety of geographical features that are typical of much larger continents, such as glaciers, rainforests, valleys, deserts, and grasslands in an area about half the size of the United States. Further, the peoples of the region possess several distinguishing features that set them apart anthropologically from the rest of Asia; the dominant peoples and cultures are Indo-European and Dravidian, and have a greater affinity with Europe than with most other regions of Asia, excepting the Middle East and the Caucasus. South Asia ranks among the world's most densely-populated regions. About 1.6 billion people live there — about a quarter of all the people in the world. The region's population density of 305 persons per square kilometre is more than seven times the world average. The region has a long history. Ancient civilisations developed in the Indus River Valley. The region was at its most prosperous before the 18th century, when the Mughal Empire held sway in the north; European colonialism led to a new conquering of the region, by Portugal and Holland, and later Britain and to a lesser degree France. Most of the region gained independence from Europe in the late 1940s.

Other subregions of Asia


- East Asia
- Southeast Asia
- Central Asia
- Southwest Asia or West Asia (One definition of the Middle East is synonymous with Southwest Asia)
- North Asia (Siberia)
- Northern Eurasia (Extends into Europe)
- Central Eurasia (Extends into Europe)

External links


- [http://www.saarc-sec.org/ SAARC Secretariat]
- [http://www.slbc.lk Sri Lanka Broadcasting Corporation]
- [http://www.vernoncorea.info Vernon Corea South Asian Broadcaster] Category:Asia South Asia Category:South Asia. zh-min-nan:Lâm-a ko:남아시아 ms:Asia Selatan ja:南アジア th:เอเชียใต้

Mount Elbrus

:For the Soviet-era computer, see Elbrus (computer). :For the R-300 Elbrus missile, see Scud. Mount Elbrus (meaning twin peaks) is a peak located in the western Caucasus mountains, in Russia, near the border of Georgia. It is the highest mountain in the Caucasus which belongs to Europe (the border between Europe and Asia is located south of Mount Elbrus - at the Kura and Qvirila rivers). Mt Elbrus (west summit) stands at 5,642 m (18,506 ft) and is considered to be the highest mountain in Europe. The east summit is slightly lower: 5,621 m (18,442 ft). Elbrus stands 20 km (12 mi) north of the main range of the Greater Caucasus and 65 km (40 mi) south-southwest of the Russian town of Kislovodsk. Its permanent icecap feeds 22 glaciers which in turn give rise to the Baksan, Kuban, and Malka Rivers. The ancients knew the mountain as Strobilus and believed that Prometheus was chained here. The lower of the two summits was first ascended in 1868 by Douglas Freshfield, A. W. Moore, and C. C. Tucker, and the higher (by about 40 m) in 1874 by a British expedition led by F. Crauford Grove. During the early years of the Soviet Union, mountaineering became a popular sport of the masses, and there was tremendous traffic on the mountain. In the winter of 1936, a very large group of inexperienced Komsomol members attempted the mountain, and ended up suffering many fatalities when they slipped on the ice and fell to their deaths. The Germans briefly occupied the mountain during World War II with 10,000 mountaineer soldiers; a possibly apocryphal story tells of a Soviet pilot being given a medal for bombing the main mountaineering hut, Pruit 11, while it was occupied. He was then later nominated for a medal for not hitting the hut, but instead the fuel supply, leaving the hut standing for future generations. The Soviet Union encouraged ascents of Elbrus, and in 1956 it was climbed en masse by 400 mountaineers to mark the 400th anniversary of the incorporation of Kabardino-Balkaria, the Autonomous Soviet Socialist Republic in which Elbrus was located. From 1959 through 1976, a cable car system was built in stages which can take visitors as high as 3,800 meters. There are a wide variety of routes up the mountain, but the normal route, which is free of crevasses, continues more or less straight up the slope from the end of the cable car system. During the summer, it is not uncommon for 100 people to be attempting the summit via this route each day. The climb is not technically difficult, but it is physically arduous because of the elevations and the frequent strong winds. crevasse Mount Elbrus should not be confused with the Alborz (also called Elburz) mountains in Iran. Parts of this article are from the NASA Earth Observatory; [http://earthobservatory.nasa.gov/Newsroom/NewImages/images.php3?img_id=15340]

Reference


- Anthony Huxley, Standard Encyclopedia of the World's Mountains (New York: Putnam, 1962)

External links


- Computer generated summit panoramas [http://www.viewfinderpanoramas.org/panoramas/ASIA/Elbrus-N.gif North] [http://www.viewfinderpanoramas.org/panoramas/ASIA/Elbrus-S.gif South] [http://www.viewfinderpanoramas.org/panoramas.html index]. There are a few discontinuities due to incomplete data. Politically the Caucasus are in Europe but topographically they are in Asia.
- NASA Earth Observatory pages on Mount Elbrus: [http://earthobservatory.nasa.gov/Newsroom/NewImages/images.php3?img_id=15340], [http://earthobservatory.nasa.gov/Newsroom/NewImages/images.php3?img_id=10817]
- [http://www.elx.ru/web/g2/ Mount Elbrus live webcam] (view from Mount Cheget) Elbrus, Mount Elbrus, Mount Elbrus, Mount Elbrus, Mount ko:엘브루스 산 ja:エルブルス山

Russia

The Russian Federation (, transliteration: Rossiyskaya Federatsiya or Rossijskaja Federacija), or Russia (Russian: Росси́я, transliteration: Rossiya or Rossija), is a country that stretches over a vast expanse of Europe and Asia. With an area of 17,075,200 km² (6,595,600 mi²), it is the largest country in the world (by land mass), covering almost twice the territory of the next-largest country, Canada. It ranks eighth in the world in population. It shares land borders with the following countries (counter-clockwise from NW to SE): Norway, Finland, Estonia, Latvia, Lithuania, Poland (only through Kaliningrad Oblast), Belarus, Ukraine, Georgia, Azerbaijan, Kazakhstan, China, Mongolia and North Korea. It is also close to the United States and Japan across stretches of water: the Diomede Islands (one controlled by Russia, the other by the United States) are just 3 km apart, and Kunashir Island (controlled by Russia but claimed by Japan) is about 20 kilometers from Hokkaido. Formerly the dominant republic of the Union of Soviet Socialist Republics (USSR), Russia is now an independent country, and an influential member of the Commonwealth of Independent States, since the Union's dissolution in December 1991. During the Soviet era, Russia was officially called the Russian Soviet Federated Socialist Republic (RSFSR). Russia is usually considered the Soviet Union's successor state in diplomatic matters. Most of the area, population, and industrial production of the Soviet Union, then one of the world's two superpowers, lay in Russia. After the breakup of the USSR, Russia's global role was greatly diminished, and cannot be compared to that of the former Soviet Union. In October 2005, the federal statistics agency reported that Russia's population has shrunk by more than half a million people dipping to 143 million.

History

Ancient Rus

:This section covers the pre-Russ ancient history of present Russia and its early medieval period, which is historically referred to as Ancient Rus. The vast lands of present Russia were home to disunited tribes who were variously overwhelmed by invading Goths, Huns, and Turkish Avars between the third and sixth centuries C.E. The Iranian Scythians populated the southern steppes, and a Turkic people, the Khazars, ruled the western portion of these lands through the 8th century. They in turn were displaced by a group of Scandinavians, the Varangians, who established a capital at the Slavic city of Novgorod and gradually merged with Slavic ruling classes. The Slavs constituted the bulk of the population from the 8th century onwards and slowly assimilated both the Scandinavians as well as native Finno-Ugric tribes, such as the Merya, the Muromians and the Meshchera. Meshchera The Varangian dynasty lasted several centuries, during which they affiliated with the Byzantine, or Orthodox church and moved the capital to Kiev in 1169 A.D. In this era the term "Rhos", or "Russ", first came to be applied to the Varangians and later also to the Slavs who peopled the region. In the 10th to 11th centuries this state of Kievan Rus became the largest in Europe and was quite prosperous, due to diversified trade with both Europe and Asia. Nomadic Turkic people Kipchaks (Polovtsi) conquered southern Russia at the end of 11th century and founded a nomadic state in the steppes along the Black Sea (Desht-e-Kipchak). In the 13th century the area suffered from internal disputes and was overrun by eastern invaders, the Golden Horde of the pagan Mongols and Muslim Turkic-speaking nomads who pillaged the Russian principalities for over three centuries. Also known as the Tatars, they ruled the southern and central expanses of present-day Russia, while its western zone was largely incorporated into the Grand Duchy of Lithuania and Poland. The political dissolution of Kievan Rus divided the Russian people in the north from the Belarusians and Ukrainians in the west. The northern part of Russia together with Novgorod retained some degree of autonomy during the time of the Mongol yoke and was largely spared the atrocities that affected the rest of the country. Nevertheless it had to fight the Germanic crusaders who attempted to colonize the region. Like in the Balkans and Asia Minor long-lasting nomadic rule retarded the country's economic and social development. Asian autocratic influences degraded many of the country's democratic institutions and affected its culture and economy in a very negative way. In spite of this, unlike its spiritual leader, the Byzantine Empire, Russia was able to revive, and organized its own war of reconquest, finally subjugating its enemies and annexing their territories. After the fall of Constantinople in 1453 Russia remained the only more or less functional Christian state on the Eastern European frontier, allowing it to claim succession to the legacy of the Eastern Roman Empire.

Imperial Russia

While still nominally under the domain of the Mongols, the duchy of Moscow began to assert its influence, and eventually tossed off the control of the invaders late in the 14th century. In the beginning of the 16th century the Russian state set the national goal to return all Russian territories lost as a result of the Mongolian invasion and to protect the borderland against attacks of hordes. The noblemen, receiving a manor from the sovereign, were obliged to serve in the army. The manor system became a basis for the nobiliary horse army. The Russian state persistently battled against Nogai-Horde and Crimean khanat which were successors of the Golden Horde. Russians, captivated by nomads, were on sale on Crimean slave markets. In 1571 Crimean khan Devlet-Girei, with a horde of 120 thousand horsemen, devastated Moscow. Annually thousands of Russians became victims of attacks by nomads. Tens of thousand of soldiers protected the southern borderland--a heavy burden for the state--which slowed its social and economic development. Ivan the Great first took the title Tsar (from the Roman Caesar, also written Czar) of Moscow following his marriage to Sofia, a Byzantine Princess (niece of the last Byzantine Emperor) consolidated surrounding areas under Moscow's dominion. At the end of 16 centuries Russian cossacks established the first settlements in Western Siberia. To the middle of 17th century Russian settlements were in Eastern Siberia, on Chukotka, the river Amur, coast of Pacific ocean. In 1648 Cossack Semyon Dezhnev opened the passage between America and Asia. The Russian Empire was born. Russian Empire] Muscovite control of the nascent nation continued after the Polish intervention 1605-1612 under the subsequent Romanov dynasty, beginning with Tsar Michael Romanov in 1613. Peter the Great, who ruled from 1689 to 1725, succeeded in bringing ideas and culture from Western Europe to a Russia which had been affected by primitive nomadic cultures. Catherine the Great, ruling from 1762 to 1796, enhanced this effort, establishing Russia not just as an Asian power, but on an equal footing with Britain, France, and Germany in Europe. She enlarged the Russian territory by the Partitions of Poland. Russia has taken territories with the ethnic Belarus and Ukrainian population, earlier parts of the medieval Kievan Rus'. As a result of victorious Russian-Turkish wars Russia reached to Black sea and has set as the purpose protection of Balkan Christians against a Turkish yoke. In 1783 Russia and Georgian Kingdom (which was almost totally devastated by Persian and Turkish invasions) have signed the treatise of Georgiev according to which Georgia has received protection of Russia. In 1812, having gathered nearly half a million soldiers from France, as well as from all of its vassal states in Europe, Napoleon entered Russia and was defeated by Russian troops. In 1813 Russian army defeated the French armies in Germany. Russia has won in the War of 1877-1878 and Ottoman Empire recognized the independence of Romania, Serbia and Montenegro and autonomy of Bulgaria. Unrest of the peasants and suppression of the growing Intelligentsia were continuing problems however, and on the eve of World War I, the position of Tsar Nicholas II and his dynasty appeared precarious. Repeated devastating defeats of the Russian army in World War I led to widespread rioting in the major cities of the Russian Empire and to the overthrow in 1917 of the Romanovs. At the close of this Russian Revolution of 1917, a Marxist political faction called the Bolsheviks seized power in St. Petersburg and Moscow under the leadership of Vladimir Lenin. The Bolsheviks changed their name to the Communist Party. A bloody civil war ensued, pitting the Bolsheviks' Red Army against a loose confederation of anti-socialist monarchist and bourgeois forces known as the White Army. The Red Army triumphed, and the Soviet Union was formed in 1922.

Russia as part of Soviet Union

The Soviet Union was to be a transnational worker's state free from nationalism, which Leninism teaches is a ruse used by the bourgeoisie to keep the international working classes from realizing their common exploited position and overthrowing the bourgeois. The concept of Russia as a separate national entity was therefore downplayed in the early Soviet Union. Although Russian institutions and cities certainly remained dominant, many non-Russians participated in the new government at all levels. One of these was a Georgian named Joseph Stalin. A brief power struggle ensued after Lenin's death in 1924. Stalin gradually eroded the various checks and balances which had been designed into the Soviet political system and assumed dictatorial power by the end of the decade. Leon Trotsky and almost all other Old Bolsheviks from the time of the Revolution were killed or exiled. As the 1930s began, Stalin launched the Great Purges, a massive series of political repressions. Millions of people who Stalin suspected of being a threat to his power in some way were executed or exiled to Gulag labor camps in remote areas of Siberia. Stalin forced rapid industrialization of the largely rural country and collectivization of its agriculture. Stalin also strengthened Russian dominance within the Soviet Union as he buttressed his own hold on power. In 1928, Stalin introduced his "First Five-Year Plan" for modernizing the Soviet economy. Most economic output was immediately diverted to establishing heavy industry. Civilian industry was modernized and heavy weapon factories established with German and US assistance. The plan worked, in some sense, as the Soviet Union successfully transformed from an agrarian economy to a major industrial powerhouse in an unbelievably short span of time, but widespread misery and famine ensued for many millions of people as a result of the severe economic upheaval. In 1939 the USSR was in strong opposition to nazi Germany, and supported the republicans in Spain who struggled against German and Italian troops. However, in 1938 Germany and the other major European powers signed the Munich treaty. Germany then divided Czechoslovakia with Poland. The Soviet government, being afraid of a German attack to the USSR, began diplomatic maneuvers. In 1939 Poland refused to participate in any measures of collective safety, so the USSR signed the Molotov-Ribbentrop Pact with Nazi Germany. On September, 17, 1939, when German armies were within 150 kilometers of the Soviet border, the Soviet army invaded eastern portions of Poland, populated by ethnic Ukrainians and Belorussians. The Soviet Union staged an artillery attack it claimed had come from neighboring Finland, and invaded it in an attempt to secure itself against future invasion by Germany (which Finland had good relations with) and to gain control of the country, separating it from Europe, and most importantly, from Germany. This conflict is now known as the Winter War. The invasion was a slight disappointment as only the eastern parts of Finland (Karelia) were occupied. This lead to Finland allying with Germany in order to gain revenge. Germany and its allies (Hungary, Italy, Finland, Romania) invaded the Soviet Union in 1941. Although the Wehrmacht reached the outskirts of Moscow, the Red Army stopped the Nazi offensive at the Battle of Stalingrad in 1943, which became the decisive turning point for Germany's fortunes in the war. The Soviets drove through Eastern Europe and captured Berlin before Germany surrendered in 1945 (see Great Patriotic War). About 10 million Soviet citizens became victims of the oppressive policies and war crimes of Germany and its allies in the occupied territory. Although ravaged by the war, the Soviet Union emerged from the conflict as an acknowledged great power. The Red Army occupied Eastern Europe after the war, including the eastern half of Germany. Stalin installed loyal Communist governments in these satellite states. During the immediate postwar period, the Soviet Union first rebuilt and then expanded its economy, with control always exerted exclusively from Moscow. The Soviets extracted heavy war reparations from the areas of Germany under their control, mostly in the form of machinery and industrial equipment. The Soviet Union consolidated its hold on eastern Europe (see Eastern bloc). The United States helped the western European countries establish democracies, and both countries sought to achieve economic, political, and ideological dominance over the Third World. The ensuing struggle became known as the Cold War, which turned the Soviet Union's wartime allies, the United Kingdom and the United States, into its foes. Stalin died in early 1953 without leaving any instructions for the selection of a successor. His closest associates officially decided to rule the Soviet Union jointly, but secret police chief Lavrenty Beria appeared poised to seize dictatorial control. General Secretary Nikita Khrushchev organized an anti-Beria alliance and staged a coup d'etat. Beria was arrested in June of 1953 and executed later that year; Khrushchev became the undisputed leader of the USSR. Under Khrushchev, the Soviet Union launched the world's first artificial satellite, Sputnik 1, and Soviet cosmonaut Yuri Gagarin became the first person to orbit the earth. Khrushchev's reforms in agriculture and administration, however, were generally unproductive, and foreign policy toward China and the United States suffered reverses, notably the Cuban Missile Crisis, when he began installing nuclear missles in Cuba and nearly provoked a war with the United States. Over the course of several angry outbursts at the United Nations, Khrushchev was increasingly seen by his colleagues as belligerent, boorish, and dangerous. The remainder of the Soviet leadership removed him from power in 1964. Following the ousting of Khrushchev, another period of rule by collective leadership ensued, lasting until Leonid Brezhnev established himself in the early 1970s as the preeminent figure in Soviet political life. Brezhnev is frequently derided by historians for stagnating the development of the Soviet Union. In contrast to the revolutionary spirit that accompanied the birth of the Soviet Union, the prevailing mood of the Soviet leadership at the time of Brezhnev's death in 1982 was one of aversion to change. In the mid and late 19