1.
Volcanism
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It includes all phenomena resulting from and causing magma within the crust or mantle of the body, to rise through the crust and form volcanic rocks on the surface. Magma from the mantle or lower crust rises through its crust towards the surface, if magma reaches the surface, its behavior depends on the viscosity of the molten constituent rock. Viscous magma produces volcanoes characterised by explosive eruptions, while non-viscous magma produce volcanoes characterised by effusive eruptions pouring large amounts of lava onto the surface, in some cases, rising magma can cool and solidify without reaching the surface. Instead, the cooled and solidified igneous mass crystallises within the crust to form an igneous intrusion, as magma cools the chemicals in the crystals formed are effectively removed from the main mix of the magma, so the chemical content of the remaining magma evolves as it solidifies slowly. Fresh unevolved magma injections can remobilise more evolved magmas, allowing eruptions from more viscous magmas, movement of molten rock in the mantle, caused by thermal convection currents, coupled with gravitational effects of changes on the earths surface drive plate tectonic motion and ultimately volcanism. Volcanoes are places where magma reaches the earths surface, the type of volcano depends on the location of the eruption and the consistency of the magma. These are formed where magma pushes between existing rock, intrusions can be in the form of batholiths, dikes, sills, earthquakes are generally associated with plate tectonic activity, but some earthquakes are generated as a result of volcanic activity. These are formed where water interacts with volcanism and these include geysers, fumaroles, hotsprings and mudpots, they are often used as a source of geothermal energy. The amount of gas and ash emitted by volcanic eruptions has a significant effect on the Earths climate, large eruptions correlate well with some significant climate change events. When the magma cools it solidifies and forms rocks, the type of rock formed depends on the composition of the magma. Magma that reaches the surface to become lava cools rapidly resulting in rocks with small crystals such as basalt, some of this magma may cool extremely rapidly and will form volcanic glass such as obsidian. Magma that remains trapped below ground in thin intrusions cools slower than magma exposed to the surface, magma that remains trapped in large quantities below ground cools most slowly resulting in rocks with larger crystals - such as granite and gabbro. Existing rocks that come into contact with magma may be melted and assimilated into the magma, other rocks adjacent to the magma may be altered by contact metamorphism or metasomatism as they are affected by the heat and escaping or externally circulating hydrothermal fluids. Volcanism is not confined only to Earth, but is thought to be found on any body having a solid crust, evidence of volcanism should still be found on any body that has had volcanism at some point in its history. It can be surmised that volcanism exists on planets and moons of this type in other systems as well. In 2014, scientists found 70 lava flows which formed on the Moon in the last 100 million years, bimodal volcanism Continental drift Hotspot Volcanic arc Glossary of Volcanic Terms. G. J. Hudak, University of Wisconsin Oshkosh,2001, crumpler, L. S. and Lucas, S. G. Volcanoes of New Mexico, An Abbreviated Guide For Non-Specialists. New Mexico Museum of Natural History and Science Bulletin, archived from the original on 2007-03-21
2.
Mount Cleveland (Alaska)
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Mt. Cleveland is 1,730 m high, and one of the most active of the 75 or more volcanoes in the larger Aleutian Arc. Aleutian natives named the island after their goddess, Chuginadak. In 1894 a team from the U. S. Coast and Geodetic Survey visited the island and gave Mount Cleveland its current name, one of the most active volcanoes in the Aleutian Arc, Cleveland has erupted at least 22 times in the last 230 years. A VEI3 eruption in 1944 produced the only known volcanic fatality. Most recently Mount Cleveland has erupted three times in 2009, twice in 2010, and once in 2011, the volcanos remoteness limits opportunities for its study, and the Alaska Volcano Observatory relies heavily on satellites for monitoring. Mount Cleveland is located 490 km from the end of the Aleutian Arc. Containing over 75 volcanoes, this arc occurs above the subduction zone where the Pacific Plate plunges under the North American plate. As the plate moves deeper into the earth, the increasing pressure results in the loss of volatiles, certain elements and compounds with low boiling points, from various hydrous minerals. One of these compounds is water, its addition to the mantle wedge formed between the subducting and overriding plates lowers the point enough to allow magma to form. The melted material then rises to the surface and forms a volcano—in this case, the native Aleut name for Mount Cleveland is Chuginadak, referring to the Aleut fire goddess, thought to reside in the volcano. The volcanos name is a reference to its constant activity, the Islands of Four Mountains name, the geographic group name for Cleveland and its neighbors, was given to the islands by Russian cartographers in the 19th century. Its current name, Mount Cleveland, was given to it by a U. S. Mount Cleveland is an almost symmetrical andesite stratovolcano in the Islands of Four Mountains, a volcanic group in the Aleutian Arc. Like all stratovolcanoes, Mount Cleveland grew as explosive eruptions, effusive eruptions and it lies southeast of Mount Carlisle and northeast of Herbert Island. Mount Cleveland forms the western half of Chuginadak Island, a broad and uneven bell-shaped landmass, the island is completely uninhabited, the nearest settlement is Nikolski on Umnak Island, about 75 km eastward. Mount Cleveland is 8–8.5 km wide at its base, the volcanos slope increases markedly with height, from 19° at its lower flanks to 35° near its summit. Like many other Aleutian volcanoes, Clevelands flanks are especially rough up to 300 m, covered by multiple overlapping lava flows, lava flows are always built on top of debris flows as a result of the snow melt caused by the emission of heat just before an eruption. The flows are generally short, under 1 km, and thin, less than 10 m thick, although Mount Cleveland is the tallest mountain in the group, it is rarely completely snowed in because of its constant activity disrupts snowfall. A lack of extant erosion shows that Mount Cleveland is likely a Holocene volcano, all known events have occurred at Mount Clevelands summit vent, but there are at least five small andesite to dacite volcanic domes on the lower flanks
3.
Aleutian Islands
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The Aleutian Islands are a chain of 14 large volcanic islands and 55 smaller ones belonging to both the United States and Russia. Crossing longitude 180°, at which point east and west longitude end, the westernmost U. S. island in real terms, however, is Attu Island, west of which runs the International Date Line. The islands, with their 57 volcanoes, are in the part of the Pacific Ring of Fire. Physiographically, they are a section of the larger Pacific Border province. These Islands are most known for the battles and skirmishes occurred there during the Aleutian Islands Campaign of World War II. It was one of two attacks on the United States during that war. The largest islands in the Aleutians are Attu, and Unalaska, Umnak, and Unimak in the Fox Islands. The largest of those is Unimak Island, with an area of 1,571.41 mi², followed by Unalaska Island, the axis of the archipelago near the mainland of Alaska has a southwest trend, but near 179° its direction changes to the northwest. This change of direction corresponds to a curve in the line of fissures that have contributed their products to the building of the islands. Such curved chains are repeated about the Pacific Ocean in the Kuril Islands, the Japanese chain, and in the Philippines. All these island arcs are at the edge of the Pacific Plate and experience much seismic activity, but are still habitable, the general elevation is greatest in the eastern islands and least in the western. The island chain is a continuation of the Aleutian Range on the mainland. The coasts are rocky and surf-worn, and the approaches are exceedingly dangerous and these volcanic islands reach heights of 6,200 feet. Makushin Volcano located on Unalaska Island, is not quite visible from within the town of Unalaska, though the steam rising from its cone is visible on a clear day. Residents of Unalaska need only to one of the smaller hills in the area, such as Pyramid Peak or Mt. Newhall. The volcanic Bogoslof and Fire Islands, which rose from the sea in 1796 and 1883 respectively, in 1906 a new volcanic cone rose between the islets of Bogoslof and Grewingk, near Unalaska, followed by another in 1907. These cones were demolished by an explosive eruption on September 1,1907. Newly found information in 2017, the volcanic cone erupted sending ash, the Aleutians seen from space The climate of the islands is oceanic, with moderate and fairly uniform temperatures and heavy rainfall
4.
Alaska
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Alaska is a U. S. state located in the northwest extremity of North America. To the north are the Chukchi and Beaufort seas–the southern parts of the Arctic Ocean, the Pacific Ocean lies to the south and southwest. Alaska is the largest state in the United States by area, the 3rd least populous, approximately half of Alaskas residents live within the Anchorage metropolitan area. Alaskas economy is dominated by the fishing, natural gas, military bases and tourism are also a significant part of the economy. The United States purchased Alaska from the Russian Empire on March 30,1867, the area went through several administrative changes before becoming organized as a territory on May 11,1912. It was admitted as the 49th state of the U. S. on January 3,1959, the name Alaska was introduced in the Russian colonial period when it was used to refer to the peninsula. It was derived from an Aleut, or Unangam idiom, which refers to the mainland of Alaska. Literally, it means object to which the action of the sea is directed, Alaska is the northernmost and westernmost state in the United States and has the most easterly longitude in the United States because the Aleutian Islands extend into the Eastern Hemisphere. Alaska is the only non-contiguous U. S. state on continental North America and it is technically part of the continental U. S. but is sometimes not included in colloquial use, Alaska is not part of the contiguous U. S. often called the Lower 48. The capital city, Juneau, is situated on the mainland of the North American continent but is not connected by road to the rest of the North American highway system. Alaskas territorial waters touch Russias territorial waters in the Bering Strait, as the Russian Big Diomede Island, Alaska has a longer coastline than all the other U. S. states combined. Alaska is the largest state in the United States by total area at 663,268 square miles, over twice the size of Texas, Alaska is larger than all but 18 sovereign countries. Counting territorial waters, Alaska is larger than the area of the next three largest states, Texas, California, and Montana. It is also larger than the area of the 22 smallest U. S. states. Also referred to as the Panhandle or Inside Passage, this is the region of Alaska closest to the rest of the United States, as such, this was where most of the initial non-indigenous settlement occurred in the years following the Alaska Purchase. The region is dominated by the Alexander Archipelago as well as the Tongass National Forest and it contains the state capital Juneau, the former capital Sitka, and Ketchikan, at one time Alaskas largest city. The Alaska Marine Highway provides a vital transportation link throughout the area. The Interior is the largest region of Alaska, much of it is uninhabited wilderness, Fairbanks is the only large city in the region
5.
International Space Station
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The International Space Station is a space station, or a habitable artificial satellite, in low Earth orbit. Its first component launched into orbit in 1998, and the ISS is now the largest man-made body in space, the ISS consists of pressurised modules, external trusses, solar arrays, and other components. ISS components have been launched by Russian Proton and Soyuz rockets, the ISS serves as a microgravity and space environment research laboratory in which crew members conduct experiments in biology, human biology, physics, astronomy, meteorology, and other fields. The station is suited for the testing of systems and equipment required for missions to the Moon. The ISS maintains an orbit with an altitude of between 330 and 435 km by means of reboost manoeuvres using the engines of the Zvezda module or visiting spacecraft and it completes 15.54 orbits per day. The ISS is the space station to be inhabited by crews, following the Soviet and later Russian Salyut, Almaz. The station has continuously occupied for 16 years and 156 days since the arrival of Expedition 1 on 2 November 2000. This is the longest continuous presence in low Earth orbit. It has been visited by astronauts, cosmonauts and space tourists from 17 different nations, Soyuz has very limited downmass capability. The ISS programme is a joint project among five participating space agencies, NASA, Roscosmos, JAXA, ESA, the ownership and use of the space station is established by intergovernmental treaties and agreements. The station is divided two sections, the Russian Orbital Segment and the United States Orbital Segment, which is shared by many nations. As of January 2014, the American portion of ISS is being funded until 2024, Roscosmos has endorsed the continued operation of ISS through 2024 but has proposed using elements of the Russian Orbital Segment to construct a new Russian space station called OPSEK. On 28 March 2015, Russian sources announced that Roscosmos and NASA had agreed to collaborate on the development of a replacement for the current ISS. NASA later issued a statement expressing thanks for Russias interest in future co-operation in space exploration. According to the original Memorandum of Understanding between NASA and Rosaviakosmos, the International Space Station was intended to be a laboratory, observatory and factory in low Earth orbit. It was also planned to provide transportation, maintenance, and act as a base for possible future missions to the Moon, Mars. In the 2010 United States National Space Policy, the ISS was given roles of serving commercial, diplomatic. The ISS provides a platform to conduct scientific research, the ISS simplifies individual experiments by eliminating the need for separate rocket launches and research staff
6.
Volcanic ash
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Volcanic ash consists of fragments of pulverized rock, minerals and volcanic glass, created during volcanic eruptions and measuring less than 2 mm in diameter. The term volcanic ash is often loosely used to refer to all explosive eruption products. Volcanic ash is formed during volcanic eruptions when dissolved gases in magma expand. The force of the escaping gas shatters the magma and propels it into the atmosphere where it solidifies into fragments of volcanic rock and glass. Ash is also produced when magma comes into contact with water during phreatomagmatic eruptions, once in the air, ash is transported by wind up to thousands of kilometers away. Volcanic ash is formed during volcanic eruptions, phreatomagmatic eruptions. Explosive eruptions occur when magma decompresses as it rises, allowing dissolved volatiles to exsolve into gas bubbles, as more bubbles nucleate a foam is produced, which decreases the density of the magma, accelerating it up the conduit. Fragmentation occurs when bubbles occupy ~70-80 vol% of the erupting mixture, when fragmentation occurs, violently expanding bubbles tear the magma apart into fragments which are ejected into the atmosphere where they solidify into ash particles. Fragmentation is an efficient process of ash formation and is capable of generating very fine ash even without the addition of water. Volcanic ash is produced during phreatomagmatic eruptions. During these eruptions fragmentation occurs when magma comes into contact with bodies of water groundwater, as the magma, which is significantly hotter than the boiling point of water, comes into contact with water an insulating vapor film forms. Eventually this vapor film will collapse leading to direct coupling of the cold water and this increases the heat transfer which leads to the rapid expansion of water and fragmentation of the magma into small particles which are subsequently ejected from the volcanic vent. Fragmentation causes an increase in area between magma and water creating a feedback mechanism, leading to further fragmentation and production of fine ash particles. Pyroclastic density currents can also produce ash particles and these are typically produced by lava dome collapse or collapse of the eruption column. Within pyroclastic density currents particle abrasion occurs as particles interact with each resulting in a reduction in grain size. In addition, ash can be produced during secondary fragmentation of pumice fragments and these processes produce large quantities of very fine grained ash which is removed from pyroclastic density currents in co-ignimbrite ash plumes. Physical and chemical characteristics of volcanic ash are primarily controlled by the style of volcanic eruption, another parameter controlling the amount of ash produced is the duration of the eruption, the longer the eruption is sustained, the more ash will be produced. The types of minerals present in volcanic ash are dependent on the chemistry of the magma from which it erupted, low energy eruptions of basalt produce a characteristically dark coloured ash containing ~45 - 55% silica that is generally rich in iron and magnesium
7.
Explosive eruption
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An explosive eruption is a volcanic term to describe a violent, explosive type of eruption. Mount St. Helens in 1980 was an example, such eruptions result when sufficient gas has dissolved under pressure within a viscous magma such that expelled lava violently froths into volcanic ash when pressure is suddenly lowered at the vent. Sometimes a lava plug will block the conduit to the summit, Explosive eruptions can send rocks, dust, gas and pyroclastic material up to 20 km into the atmosphere at rate of up to 100,000 tonnes per second, traveling at several hundred meters per second. This cloud will collapse, creating a pyroclastic flow of hot volcanic matter. An explosive eruption always begins with some form of blockage in the crater of a volcano that prevents the release of trapped in highly viscous andesitic or rhyolitic magma. The high viscosity of these forms of magma prevents the release of trapped gases, when this type of magma flows towards the surface pressure builds, eventually causing the blockage to be blasted out in an explosive eruption. The pressure from the magma and gases are released through the weakest point in the cone, however, in the case of the eruption of Mount St. Helens, pressure was released through the side of the volcano, rather than the crater. The size and duration of the column depends on the volume of magma being released, the eruption column of ash is supported by pressure from the gases being released, and as the gases are depleted, pressure falls and the eruption column begins to collapse. When the column collapses in on itself, ash and rock fall back down to the ground and these flows can travel at up to 80 km per hour, and reach temperatures of 200° to 700° Celsius. The high temperatures can cause combustion of any flammable materials in its path, including wood, vegetation, when snow and ice melt as a part of an eruption, large amounts of water mixed in with the flow can create lahars. The risk of lahars is particularly high on volcanoes such as Mount Rainier near Seattle and Tacoma, the eruption of supervolcanoes is the rarest of volcanic eruptions but also the most destructive. The timescale between these eruptions is generally marked by hundreds or thousands of years and this type of eruption generally causes destruction on a continental scale, and can also result in the lowering of temperatures worldwide. Effusive eruption Volcanic explosivity index Recent Developments in Explosive Volcanism
8.
Mount Pinatubo
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Its eruptive history was unknown to most before the pre-eruption volcanic activities of 1991, just before June. Pinatubo was heavily eroded, inconspicuous and obscured from view and it was covered with dense forests which supported a population of several thousand indigenous Aetas. The volcanos Ultra Plinian eruption on June 15,1991 produced the second-largest terrestrial eruption of the 20th century after the 1912 eruption of Novarupta in the Alaska Peninsula. Complicating the eruption was the arrival of Typhoon Yunya, bringing a lethal mix of ash and rain to towns. Predictions at the onset of the eruption led to the evacuation of tens of thousands of people from the surrounding areas. Surrounding areas were damaged by pyroclastic surges, ash falls. This caused extensive destruction to infrastructure and changed river systems for years after the eruption, the effects of the eruption were felt worldwide. It ejected roughly 10,000,000,000 tonnes or 10 km3 of magma and it injected more particulate into the stratosphere than any eruption since Krakatoa in 1883. Over the following months, the aerosols formed a layer of sulfuric acid haze. Global temperatures dropped by about 0.5 °C in the years 1991–93, the volcano is 87 km northwest of Manila, the capital of the Philippines. Near Mount Pinatubo, the United States maintained two military bases in the region. The U. S. Naval Base Subic Bay was 37 km south of Pinatubo, the volcano is near to about 6 million people. It is part of a chain of volcanoes lie along the western side of the edge of the island of Luzon called the Zambales Mountains. Pinatubo belongs to the Cabusilan sub-range of the Zambales Mountains, which consists of Mt. Cuadrado, Mt. Negron, Mt. Mataba and they are subduction volcanoes, formed by the Eurasian Plate sliding under the Philippine Mobile Belt along the Manila Trench to the west. Mount Pinatubo and the volcanoes on this volcanic belt arise due to magmatic occlusion from this subduction plate boundary. Pinatubo is flanked on the west by the Zambales Ophiolite Complex, the Tarlac Formation north, east and southeast of Pinatubo consists of marine, nonmarine and volcanoclastic sediments formed in the late Miocene and Pliocene. He recognized two life histories of the mountain, which he classified as ancestral and modern Pinatubo, activity of Ancestral Pinatubo seems to have begun about 1.1 million years ago and probably ended tens of thousands of years or more before the birth of Modern Pinatubo. Much of the land around the present volcano consists of remnants of ancestral Pinatubo
9.
Mount Etna
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Mount Etna is an active stratovolcano on the east coast of Sicily, Italy, in the Metropolitan City of Catania, between the cities of Messina and Catania. It lies above the convergent plate margin between the African Plate and the Eurasian Plate and it is the tallest active volcano in Europe, currently 3,329 m high, though this varies with summit eruptions. It is the highest peak in Italy south of the Alps, Etna covers an area of 1,190 km2 with a basal circumference of 140 km. This makes it by far the largest of the three volcanoes in Italy, being about two and a half times the height of the next largest, Mount Vesuvius. Only Mount Teide in Tenerife surpasses it in the whole of the European–North-African region, Mount Etna is one of the most active volcanoes in the world and is in an almost constant state of activity. The fertile volcanic soils support extensive agriculture, with vineyards and orchards spread across the slopes of the mountain. Due to its history of recent activity and nearby population, Mount Etna has been designated a Decade Volcano by the United Nations, in June 2013, it was added to the list of UNESCO World Heritage Sites. According to Adrian Room’s book Place-names of the World, the name Etna originated from the Phoenician word attuna meaning furnace or chimney and he dismisses the hypothesis that Etna is from the Greek αἴθω, meaning I burn, through an iotacist pronunciation. In Classical Greek, it is called Αἴτνη, a name also to Catania and the city originally known as Inessa. In Arabic, it was called جبل النار Jabal al-Nār and it is also known as Mungibeddu in Sicilian and Mongibello or Montebello in Italian. The term is not in use today, although some older people still call it this. According to another hypothesis the term Mongibello comes from the Latin Mulciber, the people of the Etna sometimes use the jargon term a muntagna, simply the mountain par excellence. Nowadays, the term Mongibello indicates the top area of the two central craters encompassing also the craters in the southeast and the northeast of the volcanic cone. Volcanic activity first took place at Etna about 500,000 years ago, about 300,000 years ago, volcanism began occurring to the southwest of the summit then, before activity moved towards the present centre 170,000 years ago. Eruptions at this time built up the first major volcanic edifice, the growth of the mountain was occasionally interrupted by major eruptions, leading to the collapse of the summit to form calderas. From about 35,000 to 15,000 years ago, Etna experienced some highly explosive eruptions, generating pyroclastic flows. Ash from these eruptions has been found as far away as south of Romes border,800 km to the north, the landslide left a large depression in the side of the volcano, known as Valle del Bove. Research published in 2006 suggested this occurred around 8000 years ago, and caused a huge tsunami and it may have been the reason the settlement of Atlit Yam, now below sea level, was suddenly abandoned around that time
10.
Ubinas
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Ubinas is an active 5, 672-metre stratovolcano in the Andes of southern Peru. Until 2006, this stratovolcano had not erupted for about 40 years, Ubinas is located in southern Peru. The upper slopes of the volcano, composed primarily of Pleistocene andesitic lava flows, the steep-walled,1.4 km wide and 150 m deep summit caldera contains an ash cone with a 500 m -wide funnel-shaped vent that is 200 m deep. Debris-avalanche deposits from the collapse of the SE flank of Ubinas extend 10 km from the volcano, the volcano is a composite cone built on a high plateau formed from Oligocene-Miocene ignimbrites and intrusive rocks. Ubinas comprises two edifices that divide two major periods of its eruptive behaviour, the first is the lower volcano under 600 m high, known as Ubinas 1, which collapsed and formed a debris-avalanche deposit as far as 12 km downstream Rio Ubinas. This collapse was followed by an eruption of non-welded ignimbrites, ponding to a thickness of 150 m over 5 km from the summit, Ubinas 1 is overlain by a steeper cone more than 900 m high, known as Ubinas 2. Ubinas 2 formed the caldera, with walls up to 300 m high that consist of hydrothermally altered lava flows and floored by a 20 m thick pile of lapilli. This morphology was created by frequent eruptions in the Late Holocene from the inner crater. The inner crater is under 200 m high and shows pervasive hydrothermal alteration, countless explosive events have taken place inside the summit caldera during the last 9.7 ky, and it has been suggested by Thouret et al. that the caldera be considered gravitationally unstable. Ubinas is located 230 km east of the Peru-Chile trench and about 150 km above the Wadati–Benioff zone, the steep dip angle of the subducting plate can correspond to a thicker wedge of asthenosphere and therefore a greater source of fertile mantle material. Some volcanologists believe that this variation in dip angle along the Nazca Lines is responsible for activity in the Andean volcanic zones, ticsani, Ubinas and Huaynaputina sit on a volcanic lineament slightly oblique to the main volcanic front. There are at least three hundred deposits, reflective of explosive eruptions with more differentiated magmas, the latest such eruption occurred between 1000 and 1160 A. D. producing an andesitic pumice-fall deposit which achieved a thickness of 25 cm over 40 km from the summit. Smaller eruptions since have shown a wide range in composition from mafic to rhyolitic. On April 22,2006, the volcano ended its 40-year hiatus and erupted, producing fumaroles, on April 23,2006, Peru declared a state of emergency in towns near the volcano. On April 28,2014, Despite a recent decline in earthquakes, the Advanced Spaceborne Thermal Emission and Reflection Radiometer collected a false-color view of the volcano on the same day. List of volcanoes in Peru Pirwani Pukasaya NASA Earth Observatory page Instituto Geofísico del Perú Volcán Ubinas, Peru on Peakbagger
11.
Barren Island (Andaman Islands)
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Barren Island is an island located in the Andaman Sea. It is the only confirmed active volcano in South Asia, along with the rest of the Andaman Islands, it is a part of the Indian Union Territory of Andaman and Nicobar Islands, and lies about 138 km northeast of the territorys capital, Port Blair. The first recorded eruption of the dates back to 1787. Since then, the volcano has erupted more than ten times, after the first recorded eruption in 1787, further eruptions were recorded in 1789,1795, 1803–04, and 1852. After nearly one and half century of dormancy, the island had another eruption in 1991 that lasted six months, the 1991 eruption was particularly harmful to the islands fauna. A team from the Geological Survey of India visited Barren Island on 8-9 April 1993 to assess the impact of the eruption on the distribution, habit, the report found that the eruption had reduced the number of bird species and their population. The team only observed 6 of the 16 known species of birds on the island, the Pied Imperial Pigeon was the most abundant among the 6 species observed. In a survey conducted at night, the team spotted one rat species and 51 species of insects from eight orders, the report also noted that the volcano was still emitted gas at the time. There were eruptions in 1994–95 and 2005–07, the considered to be linked to the 2004 Indian Ocean earthquake. A Lighthouse that was established on 1993 was destroyed by the recent eruptions, a team from the National Institute of Oceanography spotted the volcano erupting on 23 January 2017. Abhay Mudholkar, the head of the team, said, The volcano is erupting in small episodes of about five to ten minutes, during the day, only ash clouds were observed. However, after sundown, red lava fountains were spewing from the crater into the atmosphere, all recorded eruptions lie on the low end of the Volcanic Explosivity Index. The 2017 eruption was recorded as a 2 on the index and this volcanic island stands in the midst of a volcanic belt on the edge of the Indian and Burmese tectonic plates. Narcondam Island is a dormant volcano in the area, apart from volcanic seamounts like Alcock, the remnant of the primitive volcanic cone forms a precipitous cliff around the island, with a break towards the west. The highest elevation on the island is 354 m, with most of the volcano underwater. The island is 3 km in diameter, with a surface area of 8.34 km2. True to its name, it is an area uninhabited by humans. Also birds, bats like flying foxes and a few rodent species such as rats are known to survive the harsh conditions, the island is devoid of any significant vegetation
12.
India
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India, officially the Republic of India, is a country in South Asia. It is the seventh-largest country by area, the second-most populous country, and it is bounded by the Indian Ocean on the south, the Arabian Sea on the southwest, and the Bay of Bengal on the southeast. It shares land borders with Pakistan to the west, China, Nepal, and Bhutan to the northeast, in the Indian Ocean, India is in the vicinity of Sri Lanka and the Maldives. Indias Andaman and Nicobar Islands share a border with Thailand. The Indian subcontinent was home to the urban Indus Valley Civilisation of the 3rd millennium BCE, in the following millennium, the oldest scriptures associated with Hinduism began to be composed. Social stratification, based on caste, emerged in the first millennium BCE, early political consolidations took place under the Maurya and Gupta empires, the later peninsular Middle Kingdoms influenced cultures as far as southeast Asia. In the medieval era, Judaism, Zoroastrianism, Christianity, and Islam arrived, much of the north fell to the Delhi sultanate, the south was united under the Vijayanagara Empire. The economy expanded in the 17th century in the Mughal empire, in the mid-18th century, the subcontinent came under British East India Company rule, and in the mid-19th under British crown rule. A nationalist movement emerged in the late 19th century, which later, under Mahatma Gandhi, was noted for nonviolent resistance, in 2015, the Indian economy was the worlds seventh largest by nominal GDP and third largest by purchasing power parity. Following market-based economic reforms in 1991, India became one of the major economies and is considered a newly industrialised country. However, it continues to face the challenges of poverty, corruption, malnutrition, a nuclear weapons state and regional power, it has the third largest standing army in the world and ranks sixth in military expenditure among nations. India is a constitutional republic governed under a parliamentary system. It is a pluralistic, multilingual and multi-ethnic society and is home to a diversity of wildlife in a variety of protected habitats. The name India is derived from Indus, which originates from the Old Persian word Hindu, the latter term stems from the Sanskrit word Sindhu, which was the historical local appellation for the Indus River. The ancient Greeks referred to the Indians as Indoi, which translates as The people of the Indus, the geographical term Bharat, which is recognised by the Constitution of India as an official name for the country, is used by many Indian languages in its variations. Scholars believe it to be named after the Vedic tribe of Bharatas in the second millennium B. C. E and it is also traditionally associated with the rule of the legendary emperor Bharata. Gaṇarājya is the Sanskrit/Hindi term for republic dating back to the ancient times, hindustan is a Persian name for India dating back to the 3rd century B. C. E. It was introduced into India by the Mughals and widely used since then and its meaning varied, referring to a region that encompassed northern India and Pakistan or India in its entirety
13.
Mount Shasta
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Mount Shasta is a potentially active volcano at the southern end of the Cascade Range in Siskiyou County, California. At an elevation of 14,179 feet, it is the second highest peak in the Cascades, Mount Shasta has an estimated volume of 85 cubic miles, which makes it the most voluminous stratovolcano in the Cascade Volcanic Arc. The mountain and its area are managed by the U. S. Forest Service as part of the Shasta–Trinity National Forest. Mount Shasta is connected to nearby Shastina, and they dominate the northern California landscape and it rises abruptly and stands nearly 10,000 ft above the surrounding terrain. On a clear day, snowy Mount Shasta can be seen from the floor of the Central Valley 140 miles to the south. The mountain has attracted the attention of poets, authors, if Shastina were a separate mountain, it would rank as the fourth-highest peak of the Cascade Range. Mount Shastas surface is free of deep glacial erosion except, paradoxically. This is the largest glacial valley on the volcano, although it not now have a glacier in it. There are seven named glaciers on Mount Shasta, with the four largest radiating down from high on the summit cone to below 10,000 ft primarily on the north. The Whitney Glacier is the longest, and the Hotlum is the most voluminous glacier in the state of California. Three of the smaller named glaciers occupy cirques near and above 11,000 ft on the south and southeast sides, including the Watkins, Konwakiton, and Mud Creek glaciers. The oldest known human habitation in the dates to about 7,000 years ago. The historic eruption of Mount Shasta in 1786 may have been observed by Lapérouse, although perhaps first seen by Spanish explorers, the first reliably reported land sighting of Mount Shasta by a European or American was by Peter Skene Ogden in 1826. In 1827, the name Sasty or Sastise was given to nearby Mount McLoughlin by Ogden, the name was transferred to present-day Mount Shasta in 1841, partly as a result of work by the United States Exploring Expedition. Beginning in the 1820s, Mount Shasta was a prominent landmark along what became known as the Siskiyou Trail, the Siskiyou Trail was on the track of an ancient trade and travel route of Native American footpaths between Californias Central Valley and the Pacific Northwest. The California Gold Rush brought the first Euro-American settlements into the area in the early 1850s, including at Yreka, California, the first recorded ascent of Mount Shasta occurred in 1854, after several earlier failed attempts. In 1856, the first women reached the summit, by the 1860s and 1870s, Mount Shasta was the subject of scientific and literary interest. A book by California pioneer and entrepreneur James Hutchings, titled Scenes of Wonder and Curiosity in California, the summit was achieved by John Muir, Josiah Whitney, Clarence King, and John Wesley Powell
14.
Santa Ana Volcano
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The Santa Ana Volcano or Ilamatepec is a large stratovolcano located in the Santa Ana department of El Salvador. At 2,381 metres above sea level, it is the highest volcano in the country and it is located immediately west of Coatepeque Caldera. The summit of Santa Ana features four nested calderas and volcanic craters, collapse of the summit during the late Pleistocene produced a massive debris avalanche that reached the Pacific Ocean, forming the Acajutla Peninsula. Subsequent eruptions have largely rebuilt the edifice, the San Marcelino vents erupted in 1722 and flowed eastwards for 11 km, destroying the village of San Juan Tecpan. In October,2005, the volcano erupted, killing at least two people, injuring seven people, forcing people to flee their villages. The volcano spat rocks for over 1.5 km with rocks the size of cars, the eruption contributed to the damage from Hurricane Stan. The most recent previous eruption had been in 1904, the climate on the northeast facing slope of the volcano sees substantial rainfall in the summer months. Located at 13.9 N,89.6 W, altitude,1770 m, List of volcanoes in El Salvador List of stratovolcanoes Notes Sources Global Volcanism Program, Santa Ana Sheets P D,2004. Apocalypse then, social science approaches to volcanism, people, and cultures in the Zapotitan Valley, bommer J. J. Lopez D. L. Carr M. J. Major J. J. Natural Hazards in El Salvador. Bolder, Colorado, Geological Society of America Special Paper 375, boulder, Colorado, Geological Society of America Special Paper 375, pp 5–23. BBC news article on recent eruption Nasa Earth Observatory article and image
15.
El Salvador
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El Salvador, officially the Republic of El Salvador, is the smallest and the most densely populated country in Central America. El Salvadors capital and largest city is San Salvador, as of 2015, the country had a population of approximately 6.38 million, consisting largely of Mestizos of European and Indigenous American descent. El Salvador was for centuries inhabited by several Mesoamerican nations, especially the Cuzcatlecs, as well as the Lenca, in the early 16th century, the Spanish Empire conquered the territory, incorporating it into the Viceroyalty of New Spain ruled from Mexico City. In 1821, the country achieved independence from Spain as part of the First Mexican Empire, from the late 19th to the mid-20th century, El Salvador endured chronic political and economic instability characterized by coups, revolts, and a succession of authoritarian rulers. The conflict ended with a settlement that established a multiparty constitutional republic. El Salvador has since reduced its dependence on coffee and embarked on diversifying the economy by opening up trade and financial links, the colón, the official currency of El Salvador since 1892, was replaced by the U. S. dollar in 2001. As of 2010, El Salvador ranks 12th among Latin American countries in terms of the Human Development Index, however, the country continues to struggle with high rates of poverty, inequality, and crime. Conquistador Pedro de Alvarado named the new province for Jesus Christ – El Salvador, the full name was Provincia De Nuestro Señor Jesus Cristo, El Salvador Del Mundo, which was subsequently abbreviated to El Salvador. Tomayate is a site located on the banks of the river of the same name in the municipality of Apopa. The site has produced abundant Salvadoran megafauna fossils belonging to the Pleistocene epoch, at the same time, it is considered the richest vertebrate paleontological site in Central America and one of the largest accumulations of proboscideans in the Americas. Sophisticated civilization in El Salvador dates to its settlement by the indigenous Lenca people, theirs was the first, the Lenca were succeeded by the Olmecs, who eventually also disappeared, leaving their monumental architecture in the form of the pyramids still extant in western El Salvador. The Maya arrived and settled in place of the Olmecs, the Pipil were the last indigenous people to arrive in El Salvador. They called their territory Kuskatan, a Pipil word meaning The Place of Precious Jewels, backformed into Classical Nahuatl Cōzcatlān, the people of El Salvador today are referred to as Salvadoran, while the term Cuzcatleco is commonly used to identify someone of Salvadoran heritage. In pre-Columbian times, the country was inhabited by various other indigenous peoples, including the Lenca. Cuzcatlan was the domain until the Spanish conquest. Since El Salvador resided on the edge of the Maya Civilization. However, it is agreed that Mayas likely occupied the areas around Lago de Guija. Other ruins such as Tazumal, Joya de Cerén and San Andrés may have built by the Pipil or the Maya or possibly both
16.
Rupture (engineering)
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A fracture is the separation of an object or material into two or more pieces under the action of stress. The fracture of a solid usually occurs due to the development of certain displacement discontinuity surfaces within the solid, fracture strength or breaking strength is the stress when a specimen fails or fractures. The word fracture is often applied to bones of living creatures, or to crystalline materials, sometimes, individual crystals fracture without the structure actually separating into two or more pieces. Depending on the substance, a fracture reduces strength or inhibits transmission of waves, a detailed understanding of how fracture occurs in materials may be assisted by the study of fracture mechanics. Fracture strength, also known as breaking strength, is the stress at which a specimen fails via fracture and this is usually determined for a given specimen by a tensile test, which charts the stress-strain curve. The final recorded point is the fracture strength, ductile materials have a fracture strength lower than the ultimate tensile strength, whereas in brittle materials the fracture strength is equivalent to the UTS. If a ductile material reaches its ultimate strength in a load-controlled situation, it will continue to deform, with no additional load application. However, if the loading is displacement-controlled, the deformation of the material may relieve the load, in brittle fracture, no apparent plastic deformation takes place before fracture. In brittle crystalline materials, fracture can occur by cleavage as the result of tensile stress acting normal to crystallographic planes with low bonding. In amorphous solids, by contrast, the lack of a crystalline structure results in a conchoidal fracture, the sinking of RMS Titanic in 1912 from an iceberg collision is widely reported to have been due to brittle fracture of the hulls steel plates. Putting these two together, we get σ f r a c t u r e = E γ ρ4 a r o. Looking closely, we can see that sharp cracks and large defects both lower the strength of the material. Recently, scientists have discovered supersonic fracture, the phenomenon of crack propagation faster than the speed of sound in a material and this phenomenon was recently also verified by experiment of fracture in rubber-like materials. Brittle fracture may be avoided by limiting pressure and temperature within limits, each system has a brittle fracture prevention limit curve defined by the weakest components at given temperatures and pressures allowing for the largest undetected preexisting flaw in each component. In ductile fracture, extensive plastic deformation takes place before fracture, the terms rupture or ductile rupture describe the ultimate failure of ductile materials loaded in tension. Rather than cracking, the material pulls apart, generally leaving a rough surface, in this case there is slow propagation and an absorption of a large amount energy before fracture. The ductility of a material is referred to as toughness. Many ductile metals, especially materials with high purity, can sustain very large deformation of 50–100% or more strain before fracture under favorable loading condition, the strain at which the fracture happens is controlled by the purity of the materials
17.
Crust (geology)
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In geology, the crust is the outermost solid shell of a rocky planet or natural satellite, which is chemically distinct from the underlying mantle. The crust of the Earth is composed of a variety of igneous, metamorphic. The crust is underlain by the mantle, the upper part of the mantle is composed mostly of peridotite, a rock denser than rocks common in the overlying crust. The boundary between the crust and mantle is conventionally placed at the Mohorovičić discontinuity, a boundary defined by a contrast in seismic velocity, the crust occupies less than 1% of Earths volume. The crust of the Earth is of two types, oceanic and continental. The oceanic crust is 5 km to 10 km thick and is composed primarily of basalt, diabase, the continental crust is typically from 30 km to 50 km thick and is mostly composed of slightly less dense rocks than those of the oceanic crust. Some of these less dense rocks, such as granite, are common in the continental crust, both the continental and oceanic crust float on the mantle. Because the continental crust is thicker, it both to greater elevations and greater depth than the oceanic crust. The slightly lower density of continental rock compared to basaltic oceanic rock contributes to the higher relative elevation of the top of the continental crust. As the top of the continental crust reaches elevations higher than that of the oceanic, the temperature of the crust increases with depth, reaching values typically in the range from about 200 °C to 400 °C at the boundary with the underlying mantle. The crust and underlying relatively rigid uppermost mantle make up the lithosphere, because of convection in the underlying plastic upper mantle and asthenosphere, the lithosphere is broken into tectonic plates that move. The temperature increases by as much as 30 °C for every kilometer locally in the part of the crust. Earth has probably always had some form of basaltic crust, in contrast, the bulk of the continental crust is much older. The oldest continental crustal rocks on Earth have ages in the range from about 3.7 to 4, some zircon with age as great as 4.3 billion years has been found in the Narryer Gneiss Terrane. The average age of the current Earths continental crust has been estimated to be about 2.0 billion years, most crustal rocks formed before 2.5 billion years ago are located in cratons. Such old continental crust and the underlying mantle asthenosphere are less dense than elsewhere in Earth, formation of new continental crust is linked to periods of intense orogeny, these periods coincide with the formation of the supercontinents such as Rodinia, Pangaea and Gondwana. The continental crust has a composition similar to that of andesite. The most abundant minerals in Earths continental crust are feldspars, which make up about 41% of the crust by weight, followed by quartz at 12%, Continental crust is enriched in incompatible elements compared to the basaltic ocean crust and much enriched compared to the underlying mantle
18.
Planetary-mass object
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The term planet is ancient, with ties to history, astrology, science, mythology, and religion. Several planets in the Solar System can be seen with the naked eye and these were regarded by many early cultures as divine, or as emissaries of deities. As scientific knowledge advanced, human perception of the planets changed, in 2006, the International Astronomical Union officially adopted a resolution defining planets within the Solar System. This definition is controversial because it excludes many objects of mass based on where or what they orbit. The planets were thought by Ptolemy to orbit Earth in deferent, at about the same time, by careful analysis of pre-telescopic observation data collected by Tycho Brahe, Johannes Kepler found the planets orbits were not circular but elliptical. As observational tools improved, astronomers saw that, like Earth, the planets rotated around tilted axes, and some shared such features as ice caps and seasons. Since the dawn of the Space Age, close observation by space probes has found that Earth and the planets share characteristics such as volcanism, hurricanes, tectonics. Planets are generally divided into two types, large low-density giant planets, and smaller rocky terrestrials. Under IAU definitions, there are eight planets in the Solar System, in order of increasing distance from the Sun, they are the four terrestrials, Mercury, Venus, Earth, and Mars, then the four giant planets, Jupiter, Saturn, Uranus, and Neptune. Six of the planets are orbited by one or more natural satellites, several thousands of planets around other stars have been discovered in the Milky Way. e. in the habitable zone. On December 20,2011, the Kepler Space Telescope team reported the discovery of the first Earth-sized extrasolar planets, Kepler-20e and Kepler-20f, orbiting a Sun-like star, Kepler-20. A2012 study, analyzing gravitational microlensing data, estimates an average of at least 1.6 bound planets for every star in the Milky Way, around one in five Sun-like stars is thought to have an Earth-sized planet in its habitable zone. The idea of planets has evolved over its history, from the lights of antiquity to the earthly objects of the scientific age. The concept has expanded to include not only in the Solar System. The ambiguities inherent in defining planets have led to much scientific controversy, the five classical planets, being visible to the naked eye, have been known since ancient times and have had a significant impact on mythology, religious cosmology, and ancient astronomy. In ancient times, astronomers noted how certain lights moved across the sky, as opposed to the fixed stars, ancient Greeks called these lights πλάνητες ἀστέρες or simply πλανῆται, from which todays word planet was derived. In ancient Greece, China, Babylon, and indeed all pre-modern civilizations, it was almost universally believed that Earth was the center of the Universe and that all the planets circled Earth. The first civilization known to have a theory of the planets were the Babylonians
19.
Earth
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Earth, otherwise known as the World, or the Globe, is the third planet from the Sun and the only object in the Universe known to harbor life. It is the densest planet in the Solar System and the largest of the four terrestrial planets, according to radiometric dating and other sources of evidence, Earth formed about 4.54 billion years ago. Earths gravity interacts with objects in space, especially the Sun. During one orbit around the Sun, Earth rotates about its axis over 365 times, thus, Earths axis of rotation is tilted, producing seasonal variations on the planets surface. The gravitational interaction between the Earth and Moon causes ocean tides, stabilizes the Earths orientation on its axis, Earths lithosphere is divided into several rigid tectonic plates that migrate across the surface over periods of many millions of years. About 71% of Earths surface is covered with water, mostly by its oceans, the remaining 29% is land consisting of continents and islands that together have many lakes, rivers and other sources of water that contribute to the hydrosphere. The majority of Earths polar regions are covered in ice, including the Antarctic ice sheet, Earths interior remains active with a solid iron inner core, a liquid outer core that generates the Earths magnetic field, and a convecting mantle that drives plate tectonics. Within the first billion years of Earths history, life appeared in the oceans and began to affect the Earths atmosphere and surface, some geological evidence indicates that life may have arisen as much as 4.1 billion years ago. Since then, the combination of Earths distance from the Sun, physical properties, in the history of the Earth, biodiversity has gone through long periods of expansion, occasionally punctuated by mass extinction events. Over 99% of all species that lived on Earth are extinct. Estimates of the number of species on Earth today vary widely, over 7.4 billion humans live on Earth and depend on its biosphere and minerals for their survival. Humans have developed diverse societies and cultures, politically, the world has about 200 sovereign states, the modern English word Earth developed from a wide variety of Middle English forms, which derived from an Old English noun most often spelled eorðe. It has cognates in every Germanic language, and their proto-Germanic root has been reconstructed as *erþō, originally, earth was written in lowercase, and from early Middle English, its definite sense as the globe was expressed as the earth. By early Modern English, many nouns were capitalized, and the became the Earth. More recently, the name is simply given as Earth. House styles now vary, Oxford spelling recognizes the lowercase form as the most common, another convention capitalizes Earth when appearing as a name but writes it in lowercase when preceded by the. It almost always appears in lowercase in colloquial expressions such as what on earth are you doing, the oldest material found in the Solar System is dated to 4. 5672±0.0006 billion years ago. By 4. 54±0.04 Gya the primordial Earth had formed, the formation and evolution of Solar System bodies occurred along with the Sun
20.
Lava
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Lava is the molten rock expelled by a volcano during an eruption. The resulting rock after solidification and cooling is called lava. The molten rock is formed in the interior of planets, including Earth. The source of the heat melts the rock within the earth is geothermal energy. When first erupted from a vent, lava is a liquid usually at temperatures from 700 to 1,200 °C. A lava flow is an outpouring of lava, which is created during a non-explosive effusive eruption. When it has stopped moving, lava solidifies to form igneous rock, the term lava flow is commonly shortened to lava. Although lava can be up to 100,000 times more viscous than water, lava can flow great distances before cooling and solidifying because of its thixotropic, explosive eruptions produce a mixture of volcanic ash and other fragments called tephra, rather than lava flows. The word lava comes from Italian, and is derived from the Latin word labes which means a fall or slide. The first use in connection with extruded magma was apparently in an account written by Francesco Serao on the eruption of Vesuvius between May 14 and June 4,1737. Serao described a flow of lava as an analogy to the flow of water. The composition of almost all lava of the Earths crust is dominated by silicate minerals, mostly feldspars, olivine, pyroxenes, amphiboles, micas, igneous rocks, which form lava flows when erupted, can be classified into three chemical types, felsic, intermediate, and mafic. These classes are primarily chemical, however, the chemistry of lava also tends to correlate with the temperature, its viscosity. Felsic or silicic lavas such as rhyolite and dacite typically form lava spines, most silicic lava flows are extremely viscous, and typically fragment as they extrude, producing blocky autobreccias. Felsic magmas can erupt at temperatures as low as 650 to 750 °C, unusually hot rhyolite lavas, however, may flow for distances of many tens of kilometres, such as in the Snake River Plain of the northwestern United States. Intermediate or andesitic lavas are lower in aluminium and silica, and usually somewhat richer in magnesium, intermediate lavas form andesite domes and block lavas, and may occur on steep composite volcanoes, such as in the Andes. Poorer in aluminium and silica than felsic lavas, and also commonly hotter, greater temperatures tend to destroy polymerized bonds within the magma, promoting more fluid behaviour and also a greater tendency to form phenocrysts. Higher iron and magnesium tends to manifest as a darker groundmass, mafic or basaltic lavas are typified by their high ferromagnesian content, and generally erupt at temperatures in excess of 950 °C
21.
Volcanic gas
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Volcanic gases include a variety of substances given off by active volcanoes. The sources of gases on Earth include, primordial and recycled constituents from the Earths mantle, assimilated constituents from the Earths crust, groundwater. Substances that may become gaseous or give off gases when heated are termed volatile substances. The principal components of volcanic gases are water vapor, carbon dioxide, sulfur either as sulfur dioxide or hydrogen sulfide, nitrogen, argon, helium, neon, methane, carbon monoxide and hydrogen. Other compounds detected in volcanic gases are oxygen, hydrogen chloride, hydrogen fluoride, hydrogen bromide, nitrogen oxide, sulfur hexafluoride, carbonyl sulfide, exotic trace compounds include mercury, halocarbons, and halogen oxide radicals. The abundance of gases varies considerably from volcano to volcano, water vapor is consistently the most common volcanic gas, normally comprising more than 60% of total emissions. Carbon dioxide typically accounts for 10 to 40% of emissions, volcanoes located at convergent plate boundaries emit more water vapor and chlorine than volcanoes at hot spots or divergent plate boundaries. This is caused by the addition of seawater into magmas formed at subduction zones, convergent plate boundary volcanoes also have higher H2O/H2, H2O/CO2, CO2/He and N2/He ratios than hot spot or divergent plate boundary volcanoes. Magma contains dissolved volatile components, as described above, the solubilities of the different volatile constituents are dependent on pressure, temperature and the composition of the magma. As magma ascends towards the surface, the ambient pressure decreases, once the solubility decreases below the volatile concentration, the volatiles will tend to come out of solution within the magma and form a separate gas phase. The gas will initially be distributed throughout the magma as small bubbles, as the magma ascends the bubbles grow through a combination of expansion through decompression and growth as the solubility of volatiles in the magma decreases further causing more gas to exsolve. In the former case, the bubbles may rise through the magma and accumulate at a vertical surface, in volcanoes with an open path to the surface, e. g. Stromboli in Italy, the bubbles may reach the surface and as they pop small explosions occur. In the latter case, the gas can flow rapidly through the continuous permeable network towards the surface and this mechanism has been used to explain activity at Santiaguito, Santa Maria volcano, Guatemala and Soufrière Hills Volcano, Montserrat. If the gas cannot escape fast enough from the magma, it will fragment the magma into small particles of ash, the fluidised ash has a much lower resistance to motion than the viscous magma, so accelerates, causing further expansion of the gases and acceleration of the mixture. This sequence of events drives explosive volcanism, whether gas can escape gently or not is determined by the total volatile contents of the initial magma and the viscosity of the magma, which is controlled by its composition. The term closed system degassing refers to the case where gas and its parent magma ascend together, the composition of the emitted gas is in equilibrium with the composition of the magma at the pressure, temperature where the gas leaves the system. In open system degassing, the gas leaves its parent magma, the gas released at the surface has a composition that is a mass-flow average of the magma exsolved at various depths and is not representative of the magma conditions at any one depth. Molten rock near the atmosphere releases high-temperature volcanic gas, in explosive volcanic eruptions, sudden release of gases from magma may cause rapid movements of the molten rock
22.
Magma chamber
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A magma chamber is a large underground pool of liquid rock found beneath the surface of the Earth. The molten rock in such a chamber is under pressure, and given enough time. If it finds a way to the surface, then the result will be a volcanic eruption, magma chambers are hard to detect, and most of the known ones are therefore close to the surface of the Earth, commonly between 1 km and 10 km under the surface. In geological terms, this is close to the surface, although in human terms. Magma rises through cracks from beneath and across the crust because it is less dense than the surrounding rock, when the magma cannot find a path upwards it pools into a magma chamber. Magma chambers are built up incrementally, by successive horizontal or vertical magma injections. Influx of new magma causes reaction of pre-existing crystals and the pressure in the chamber to increase, upon cooling, new mineral phases saturate and the rock type changes, typically forming gabbro, diorite, tonalite and granite or gabbro, diorite, syenite and granite. If magma resides in a chamber for a period, then it can become stratified with lower density components rising to the top. Rocks accumulate in layers, forming a layered intrusion, additionally, the removal of the lower melting point components will tend to make the magma more viscous. If the magma is not vented to the surface in an eruption, it will slowly cool. Often, a volcano may have a deep magma chamber many kilometers down, as a volcano erupts, emptying the magma chamber, the surrounding rock will collapse into it. If a large amount of magma is erupted, causing the chamber to reduce considerably in volume, then this can result in a depression at the surface called a caldera
23.
Plate tectonics
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The theoretical model builds on the concept of continental drift developed during the first few decades of the 20th century. The geoscientific community accepted plate-tectonic theory after seafloor spreading was validated in the late 1950s, the lithosphere, which is the rigid outermost shell of a planet, is broken up into tectonic plates. The Earths lithosphere is composed of seven or eight major plates, where the plates meet, their relative motion determines the type of boundary, convergent, divergent, or transform. Earthquakes, volcanic activity, mountain-building, and oceanic trench formation occur along plate boundaries. The relative movement of the plates typically ranges from zero to 100 mm annually, tectonic plates are composed of oceanic lithosphere and thicker continental lithosphere, each topped by its own kind of crust. Along convergent boundaries, subduction carries plates into the mantle, the material lost is balanced by the formation of new crust along divergent margins by seafloor spreading. In this way, the surface of the lithosphere remains the same. This prediction of plate tectonics is also referred to as the conveyor belt principle, earlier theories, since disproven, proposed gradual shrinking or gradual expansion of the globe. Tectonic plates are able to move because the Earths lithosphere has greater strength than the underlying asthenosphere. Lateral density variations in the result in convection. Plate movement is thought to be driven by a combination of the motion of the seafloor away from the ridge and drag, with downward suction. Another explanation lies in the different forces generated by forces of the Sun. The relative importance of each of these factors and their relationship to other is unclear. The outer layers of the Earth are divided into the lithosphere and asthenosphere and this is based on differences in mechanical properties and in the method for the transfer of heat. Mechanically, the lithosphere is cooler and more rigid, while the asthenosphere is hotter, in terms of heat transfer, the lithosphere loses heat by conduction, whereas the asthenosphere also transfers heat by convection and has a nearly adiabatic temperature gradient. The key principle of plate tectonics is that the lithosphere exists as separate and distinct tectonic plates, Plate motions range up to a typical 10–40 mm/year, to about 160 mm/year. The driving mechanism behind this movement is described below, tectonic lithosphere plates consist of lithospheric mantle overlain by either or both of two types of crustal material, oceanic crust and continental crust. Average oceanic lithosphere is typically 100 km thick, its thickness is a function of its age, as passes, it conductively cools
24.
Divergent boundary
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In plate tectonics, a divergent boundary or divergent plate boundary is a linear feature that exists between two tectonic plates that are moving away from each other. Divergent boundaries within continents initially produce rifts which eventually become rift valleys, most active divergent plate boundaries occur between oceanic plates and exist as mid-oceanic ridges. Divergent boundaries also form volcanic islands which occur when the plates apart to produce gaps which molten lava rises to fill. Current research indicates that complex convection within the Earths mantle allows material to rise to the base of the lithosphere beneath each divergent plate boundary. This supplies the area with vast amounts of heat and a reduction in pressure that melts rock from the asthenosphere beneath the area forming large flood basalt or lava flows. Each eruption occurs in only a part of the boundary at any one time. Over millions of years, tectonic plates may move many hundreds of kilometers away from both sides of a divergent plate boundary, because of this, rocks closest to a boundary are younger than rocks further away on the same plate. At divergent boundaries, two plates move apart from other and the space that this creates is filled with new crustal material sourced from molten magma that forms below. The origin of new divergent boundaries at triple junctions is thought to be associated with the phenomenon known as hotspots. Here, exceedingly large convective cells bring very large quantities of hot asthenospheric material near the surface, the hot spot which may have initiated the Mid-Atlantic Ridge system currently underlies Iceland which is widening at a rate of a few centimeters per year. Divergent boundaries can create massive fault zones in the ridge system. Spreading is generally not uniform, so where spreading rates of adjacent ridge blocks are different and these are the fracture zones, many bearing names, that are a major source of submarine earthquakes. A sea floor map will show a strange pattern of blocky structures that are separated by linear features perpendicular to the ridge axis. If one views the sea floor between the zones as conveyor belts carrying the ridge on each side of the rift away from the spreading center the action becomes clear. Crest depths of the old ridges, parallel to the current spreading center and it is at mid-ocean ridges that one of the key pieces of evidence forcing acceptance of the seafloor spreading hypothesis was found. Airborne geomagnetic surveys showed a pattern of symmetrical magnetic reversals on opposite sides of ridge centers. The pattern was far too regular to be coincidental as the widths of the bands were too closely matched. Scientists had been studying polar reversals and the link was made by Lawrence W. Morley, Frederick John Vine, the magnetic banding directly corresponds with the Earths polar reversals
25.
Convergent boundary
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As a result of pressure, friction, and plate material melting in the mantle, earthquakes and volcanoes are common near convergent boundaries. When two plates move towards one another, they form either a subduction zone or a continental collision and this depends on the nature of the plates involved. In a subduction zone, the plate, which is normally a plate with oceanic crust, moves beneath the other plate. During collisions between two plates, large mountain ranges, such as the Himalayas are formed. The nature of a convergent boundary depends on the type of plates that are colliding, at an oceanic-continental convergent boundary, the oceanic lithosphere will always subduct below the continental lithosphere. This is caused by the density difference between the oceanic and continental lithosphere. This type of boundary is called a subduction zone. At the surface, the expression is commonly an oceanic trench which forms on the oceanic side. On the continental side, a chain of volcanoes forms above the location of the subducting plate, an example of a continental-oceanic subduction zone is the area along the western coast of South America where the oceanic Nazca Plate is being subducted beneath the continental South American Plate. A volcanic arc is formed on the plate, above the location of the downgoing oceanic slab. The volcanic arc is the expression of the magma that is generated by hydrous melting of the mantle above the downgoing slab. The buoyant fluids then rise into the asthenosphere, where they lower the temperature of the mantle. Either action will create extensive mountain ranges and it may have also pushed nearby parts of the Asian continent aside to the east. When two plates with oceanic crust converge, they create an island arc as one plate is subducted below the other. The arc is formed from volcanoes which erupt through the plate as the descending plate melts below it. The arc shape occurs because of the surface of the earth. A deep oceanic trench is located in front of such arcs where the descending slab dips downward, plates may collide at an oblique angle rather than head-on to each other, and this may cause strike-slip faulting along the collision zone, in addition to subduction or compression. Not all plate boundaries are easily defined, some are broad belts whose movements are unclear to scientists
26.
Mid-oceanic ridge
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A mid-ocean ridge is an underwater mountain system formed by plate tectonics. It consists of various mountains linked in chains, typically having a known as a rift running along its spine. This type of mountain ridge is characteristic of what is known as an oceanic spreading center. The production of new results from mantle upwelling in response to plate spreading. The buoyant melt rises as magma at a linear weakness in the oceanic crust, a mid-ocean ridge demarcates the boundary between two tectonic plates, and consequently is termed a divergent plate boundary. Mid-ocean ridges are geologically active, with new magma constantly emerging onto the floor and into the crust at. The crystallized magma forms new crust of basalt and gabbro and they are formed by two oceanic plates moving away from each other. The rocks making up the crust below the seafloor are youngest along the axis of the ridge and age with increasing distance from that axis, new magma of basalt composition emerges at and near the axis because of decompression melting in the underlying Earths mantle. The oceanic crust is made up of much younger than the Earth itself. Most oceanic crust in the basins is less than 200 million years old. The crust is in a constant state of renewal at the ocean ridges, moving away from the mid-ocean ridge, ocean depth progressively increases, the greatest depths are in ocean trenches. As the oceanic crust moves away from the axis, the peridotite in the underlying mantle cools. The crust and the relatively rigid peridotite below it make up the oceanic lithosphere, by contrast, fast spreading ridges like the East Pacific Rise are narrow, sharp incisions surrounded by generally flat topography that slopes away from the ridge over many hundreds of miles. The overall shape of ridges results from Pratt isostacy, close to the ridge there is hot. As the oceanic plates cool, away from the axes, the oceanic mantle lithosphere thickens. Thus older seafloor is underlain by denser material and sits lower, there are two processes, ridge-push and slab pull, thought to be responsible for the spreading seen at mid-ocean ridges, and there is some uncertainty as to which is dominant. Ridge-push occurs when the bulk of the ridge pushes the rest of the tectonic plate away from the ridge. At the subduction zone, slab-pull comes into effect and this is simply the weight of the tectonic plate being subducted below the overlying plate dragging the rest of the plate along behind it
27.
Mid-Atlantic Ridge
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In the North Atlantic, it separates the Eurasian and North American Plates, whereas in the South Atlantic it separates the African and South American Plates. The ridge extends from a junction with the Gakkel Ridge northeast of Greenland southward to the Bouvet Triple Junction in the South Atlantic, although the Mid-Atlantic Ridge is mostly an underwater feature, portions of it have enough elevation to extend above sea level. The section of the ridge that includes the island of Iceland is also known as the Reykjanes Ridge, the ridge has an average spreading rate of about 2.5 cm per year. A ridge under the Atlantic Ocean was first inferred by Matthew Fontaine Maury in 1850, the ridge was discovered during the expedition of HMS Challenger in 1872. A team of scientists on board, led by Charles Wyville Thomson, the existence of such a ridge was confirmed by sonar in 1925 and was found to extend around the Cape of Good Hope into the Indian Ocean by the German Meteor expedition. Ewing, Heezen and Tharp discovered that the ridge is part of a 40, the ridge is central to the breakup of the hypothetical supercontinent of Pangaea that began some 180 million years ago. The Mid-Atlantic Ridge includes a deep valley that runs along the axis of the ridge along nearly its entire length. This rift marks the boundary between adjacent tectonic plates, where magma from the mantle reaches the seafloor, erupting as lava. This trench, however, is not regarded as the boundary between the North and South American Plates, nor the Eurasian and African Plates and this bulge is thought to be caused by upward convective forces in the asthenosphere pushing the oceanic crust and lithosphere. This divergent boundary first formed in the Triassic period, when a series of three-armed grabens coalesced on the supercontinent Pangaea to form the ridge, usually, only two arms of any given three-armed graben become part of a divergent plate boundary. The failed arms are called aulacogens, and the aulacogens of the Mid-Atlantic Ridge eventually became many of the river valleys seen along the Americas. The Fundy Basin on the Atlantic coast of North America between New Brunswick and Nova Scotia in Canada is evidence of the ancestral Mid-Atlantic Ridge, atlantis Massif Central Atlantic Magmatic Province Fifteen-Twenty Fracture Zone Evans, Rachel. Plumbing Depths to Reach New Heights, Marie Tharp Explains Marine Geological Maps, the Library of Congress Information Bulletin. MAR-ECO, a Census of Marine Life project on life along the Mid-Atlantic Ridge
28.
Pacific Ring of Fire
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The Ring of Fire is a major area in the basin of the Pacific Ocean where a large number of earthquakes and volcanic eruptions occur. In a 40,000 km horseshoe shape, it is associated with a continuous series of oceanic trenches, volcanic arcs. The Ring of Fire is sometimes called the circum-Pacific belt, about 90% of the worlds earthquakes and 81% of the worlds largest earthquakes occur along the Ring of Fire. The next most seismically active region is the Alpide belt, which extends from Java to the northern Atlantic Ocean via the Himalayas, all but three of the worlds 25 largest volcanic eruptions of the last 11,700 years occurred at volcanoes in the Ring of Fire. The Ring of Fire is a result of plate tectonics. The eastern section of the ring is the result of the Nazca Plate, the Cocos Plate is being subducted beneath the Caribbean Plate, in Central America. A portion of the Pacific Plate and the small Juan de Fuca Plate are being subducted beneath the North American Plate, along the northern portion, the northwestward-moving Pacific plate is being subducted beneath the Aleutian Islands arc. Farther west, the Pacific plate is being subducted along the Kamchatka Peninsula arcs on south past Japan. Indonesia lies between the Ring of Fire along the islands adjacent to and including New Guinea and the Alpide belt along the south and west from Sumatra, Java, Bali, Flores. The famous and very active San Andreas Fault zone of California is a fault which offsets a portion of the East Pacific Rise under southwestern United States. The motion of the fault generates numerous small earthquakes, at times a day. Bolivia hosts numerous active and extinct volcanoes across its territory, the active volcanoes are located in western Bolivia where they make up the Cordillera Occidental, the western limit of the Altiplano plateau. Many of the volcanoes are international mountains shared with Chile. The Central Volcanic Zone is a major upper Cenozoic volcanic province, apart from Andean volcanoes, the geology of Bolivia hosts the remnants of ancient volcanoes around the Precambrian Guaporé Shield in the eastern part of the country. The volcanoes in Chile are monitored by the National Geology and Mining Service Earthquake activity in Chile is related to subduction of the Nazca Plate to the east, Chile notably holds the record for the largest earthquake ever recorded, the 1960 Valdivia earthquake. Villarrica, one of Chiles most active volcanoes, rises above Villarrica Lake and it is the westernmost of three large stratovolcanoes that trend perpendicular to the Andean chain. A 6-km-wide caldera formed during the late Pleistocene, more than 0.9 million years ago, a 2-km-wide postglacial caldera is located at the base of the presently active, dominantly basaltic-to-andesitic cone at the northwest margin of the Pleistocene caldera. About 25 scoria cones dot Villaricas flanks, lahars from the glacier-covered volcanoes have damaged towns on its flanks
29.
East African Rift
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The East African Rift is an active continental rift zone in East Africa. The EAR began developing around the onset of the Miocene, 22–25 million years ago, in the past, it was considered to be part of a larger Great Rift Valley that extended north to Asia Minor. As extension continues, lithospheric rupture will occur within 10 million years, the Somalian plate will break off, a series of distinct rift basins, the East African Rift System extends over thousands of kilometers. The EAR consists of two main branches, the Eastern Rift Valley includes the Main Ethiopian Rift, running eastward from the Afar Triple Junction, which continues south as the Kenyan Rift Valley. The Western Rift Valley includes the Albertine Rift, and farther south, to the north of the Afar Triple Junction, the rift follows one of two paths, west to the Red Sea Rift or east to the Aden Ridge in the Gulf of Aden. The EAR runs from the Afar Triple Junction in the Afar Triangle of Ethiopia through eastern Africa, the EAR transects through Ethiopia, Kenya, Uganda, Rwanda, Burundi, Zambia, Tanzania, Malawi and Mozambique. The Davie Ridge ranges between 30–120 km wide, with a west facing scarp along the half of its length that rises up to 2300 m above the sea floor. Its movement is concurrent with the EAR, over time, many theories have tried to clarify the evolution of the East African Rift. In 1972 it was proposed that the EAR was not caused by tectonic activity, others proposed an African superplume causing mantle deformation. However, the varying geochemical signatures of a suite of Ethiopian lavas suggest multiple plume sources, at least one of deep mantle origin, additionally, the subject of deep-rooted mantle plumes is still a matter of controversy, and therefore cannot be confirmed. The most recent and accepted view is the theory put forth in 2009, at that time it was suggested that lithospheric thinning generated volcanic activity, further increasing the magmatic processes at play such as intrusions and numerous small plumes. These processes further thin the lithosphere in saturated areas, forcing the thinning lithosphere to behave like a mid-ocean ridge, prior to rifting, enormous continental flood basalts erupted on the surface and uplift of the Ethiopian, Somalian, and East African plateaus occurred. The first stage of rifting of the EAR is characterized by rift localization, periods of extension alternated with times of relative inactivity. There was also the reactivation of a weakness in the crust, a suture zone of multiple cratons, displacement along large boundary faults. The second stage of rifting is characterized by the deactivation of large boundary faults, the development of internal fault segments, today, the narrow rift segments of the East African Rift system form zones of localized strain. These rifts are the result of the actions of numerous faults which are typical of all tectonic rift zones. The African continental crust is generally cool and strong, many cratons are found throughout the EAR, such as the Tanzania and Kaapvaal cratons. The cratons are thick, and have survived for billions of years with little tectonic activity and they are characterized by greenstone belts, tonalites, and other high-grade metamorphic lithologies
30.
Wells Gray-Clearwater volcanic field
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It is situated in the Cariboo Mountains of the Columbia Mountains and on the Quesnel and Shuswap Highlands. As a monogenetic volcanic field, it is a place with numerous small basaltic volcanoes, most of the Wells Gray-Clearwater volcanic field is encompassed within a large wilderness park called Wells Gray Provincial Park. This 5,405 km2 park was established in 1939 to protect Helmcken Falls, five roads enter the park and provide views of some of the fields volcanic features. Short hikes lead to other volcanic features, but some areas are accessible only by aircraft. The emplacement of lava flows spanned at least three periods of glaciation, evidence for which is preserved in the form of tuyas, ice-ponded valley deposits. The few tuyas in the region, such as Gage Hill, Hyalo Ridge, McLeod Hill and Mosquito Mound, were formed when magma intruded into, the partially molten mass cooled as a large block, with gravity flattening its upper surface. The glacial erosion of the tuyas suggests they erupted during the early Pleistocene epoch, at least one explosive subaqueous volcano formed during the Pleistocene epoch. This subaqueous volcano, known as White Horse Bluff, is thought to have formed in three phases and its first phase of activity was involved with water, possibly dammed by glacial ice which filled the Clearwater River valley. The volcano heated glacial water then flooded down the vent, creating violent steam explosions. The volcano ceased erupting soon after breaching the surface of the glacial water, other volcanic events elsewhere interacted with groundwater and magma creating numerous pit craters. Many of these pit craters have been filled with water creating several crater lakes, in some places glacial till and fluvial sands and gravels are maintained under the several lava flows that form the volcanic field. Paleosols are found, but are rare, glaciation has left a thick blanket of till over nearly all of the volcanic deposits and therefore outcrop is largely limited to cliffforming exposures in several valleys. At the end of the last ice age approximately 10,000 years ago, most of these canyons contain rivers such as the Murtle and Clearwater, and waterfalls such as Canim Falls, Moul Falls, Spahats Falls and the 141 m high Helmcken Falls. The faces of the lava flows and waterfalls remain vertical due to the nature of the basaltic lava flows. Basaltic lava shrinks as it cools and forms vertical columns of rock called columnar basalt, More recently, the southern end of the volcanic field has experienced continuous volcanic activity since the end of the last ice age. This volcanic activity occurred in three areas, Spanish Creek, Ray Lake and Kostal Lake which were followed by lava fountain eruptions creating cinder cones, volcanism in the Spanish Creek and Ray Lake areas were synglacial but continued after the glacial ice had melted away. Two cinder cones, known as Flourmill Cone and Pointed Stick Cone, were created in the Spanish Creek area, lava flows from the two cinder cones lie on glaciated bedrock without an intervening paleosol, indicating an early Holocene age. Eruptions near Ray Lake built a cinder cone known as Dragon Cone and this lava flow, known as Dragons Tongue, is at least 15 m thick at the proximal end, but thins to 3 m at the distal end, damming the southern end of Clearwater Lake
31.
Rio Grande Rift
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The Rio Grande Rift is a north-trending continental rift zone. It separates the Colorado Plateau in the west from the interior of the North American craton on the east, the rift extends from central Colorado in the north to the state of Chihuahua, Mexico in the south. The rift zone consists of four basins that have a width of 50 kilometers. The rift can be observed on location at Rio Grande National Forest, White Sands National Monument, Santa Fe National Forest, the Rio Grande Rift has been an important site for humans for a long time, because it provides a north-south route that follows a major river. The Rio Grande follows the course of the rift from southern Colorado to El Paso, important cities, including Albuquerque, Santa Fe, Taos, Española, Las Cruces, El Paso, and Ciudad Juárez lie within the rift. The Rio Grande Rift represents the easternmost manifestation of widespread extension in the western U. S. during the past 35 million years, the rift consists of three major basins and many smaller basins, less than 100 km2. The three major basins are the San Luis, Española, and Albuquerque basins, further south, the rift is defined by a network of smaller, less topographically distinct alternating basins and ranges. The distinction between these basins and those of the Basin and Range Province becomes blurred in northern Mexico. Basin size generally decreases to the north in the rift, where the Española covers approximately 120 km north-south and 40 km east-west, the Albuquerque basin is the largest of the three basins, spanning 160 km north-south and 86 km east-west at its widest points. It is the oldest of the three basins, and contains 7,350 m of Paleogene clastic sediments deposited on Precambrian basement. The southernmost Albuquerque basin contains pre-rift volcanic deposits, while the central, the southernmost Rio Grande Rift broadens, becoming more complex in structure and physiographically indistinguishable from the adjoining Basin and Range province. In cross-section, the geometry of the basins within the rift are asymmetrical half-grabens, with major fault boundaries on one side, which side of the basin has the major fault or the hinge alternates along the rift. The alternation between these half-grabens occurs along transfer faults, which trend across the rift to connect the major basin-bounding faults, flanking mountains are generally taller along the east side of the rift. The thickness of the crust increases to the north beneath the rift, the crustal thickness underneath the rift is on average 30–35 km, thinner by 10–15 km than the Colorado Plateau on the west and the Great Plains to the east. The rift is presently nearly tectonically quiescent, but significant deformation and this extension is associated with very low seismic velocities in the upper mantle above approximately 400 km depth associated with relatively hot mantle and low degrees of partial melting. This intrusion of the asthenosphere into the lithosphere and continental crust is thought to be responsible for all of the volcanism associated with the Rio Grande rift. The sedimentary fill of the basins consists largely of alluvial fan, the most alkalic lavas erupted outside the rift. The sediments that were deposited during rifting are commonly known as the Santa Fe Group and this group contains sandstones, conglomerates, and volcanics
32.
Mantle plume
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A mantle plume is a mechanism proposed in 1971 to explain volcanic regions of the Earth that were not thought to be explicable by the then-new theory of plate tectonics. Some such volcanic regions lie far from plate boundaries, for example. Others represent unusually large-volume volcanism, whether on plate boundaries, e. g. Iceland, a mantle plume is posited to exist where hot rock nucleates at the core-mantle boundary and rises through the Earths mantle becoming a diapir in the Earths crust. The currently active volcanic centers are known as hot spots, the hypothesis of mantle plumes from depth is not universally accepted as explaining all such volcanism. It has required progressive hypothesis-elaboration leading to variant propositions such as mini-plumes, another hypothesis for unusual volcanic regions is the Plate model. In 1971, geophysicist W. Jason Morgan proposed the hypothesis of mantle plumes, in this hypothesis, convection in the mantle transports heat from the core to the Earths surface in thermal diapirs. The latter type of convection is postulated to be independent of plate motions, the sizes and occurrence of mushroom mantle plumes can be predicted easily by transient instability theory developed by Tan and Thorpe. The theory predicts mushroom mantle plumes of about 2000 km diameter with a time of about 830 Myr for a core mantle heat flux of 20 mW/m2. The number of mantle plumes is predicted to be about 17, the plume hypothesis was studied using laboratory experiments conducted in small fluid-filled tanks in the early 1970s. Thermal or compositional fluid-dynamical plumes produced in that way were presented as models for the much larger postulated mantle plumes, the entire structure is considered to resemble a mushroom. The bulbous head of thermal plumes forms because hot material moves upward through the faster than the plume itself rises through its surroundings. In the late 1980s and early 1990s, experiments with thermal models showed that as the bulbous head expands it may entrain some of the adjacent mantle into the head. When a plume head encounters the base of the lithosphere, it is expected to flatten out against this barrier and it may then erupt onto the surface. Numerical modelling predicts that melting and eruption will take place several million years. These eruptions have been linked to flood basalts, although many of those erupt over much shorter time scales, flood basalts in the oceans are known as oceanic plateaus, and include the Ontong Java plateau of the western Pacific Ocean and the Kerguelen Plateau of the Indian Ocean. As the overlying tectonic plate moves over this hot spot, the eruption of magma from the fixed conduit onto the surface is expected to form a chain of volcanoes that parallels plate motion, the Hawaiian Islands chain in the Pacific Ocean is the type example. The eruption of continental flood basalts is often associated with continental rifting and this has led to the hypothesis that mantle plumes contribute to continental rifting and the formation of ocean basins. In the context of the alternative Plate model, continental breakup is an integral to plate tectonics
33.
Hotspot (geology)
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In geology, the places known as hotspots or hot spots are volcanic regions thought to be fed by underlying mantle that is anomalously hot compared with the surrounding mantle. They may be on, near to, or far from plate boundaries. Currently, there are two hypotheses that attempt to explain their origins, one suggests that hotspots are due to mantle plumes that rise as thermal diapirs from the core–mantle boundary. The other hypothesis is that lithospheric extension permits the passive rising of melt from shallow depths and this hypothesis considers the term hotspot to be a misnomer, asserting that the mantle source beneath them is, in fact, not anomalously hot at all. Well known examples include Hawaii, Iceland and Yellowstone and it was later postulated that hotspots are fed by narrow streams of hot mantle rising from the Earths core–mantle boundary in a structure called a mantle plume. Whether or not such mantle plumes exist is currently the subject of a controversy in Earth science. Estimates for the number of hotspots postulated to be fed by mantle plumes has ranged from about 20 to several thousands, over the years, Hawaii, Réunion, Yellowstone, Galápagos, and Iceland are some of the currently most active volcanic regions to which the hypothesis is applied. As a result, they are less explosive than subduction zone volcanoes, where hotspots occur in continental regions, basaltic magma rises through the continental crust, which melts to form rhyolites. These rhyolites can form violent eruptions, for example, the Yellowstone Caldera was formed by some of the most powerful volcanic explosions in geologic history. However, when the rhyolite is completely erupted, it may be followed by eruptions of basaltic magma rising through the same lithospheric fissures, the hotspot hypothesis is now closely linked to the mantle plume hypothesis. Hotspot volcanoes are considered to have a different origin from island arc volcanoes. The latter form over subduction zones, at converging plate boundaries, when one oceanic plate meets another, the denser plate is forced downward into a deep ocean trench. This plate, as it is subducted, releases water into the base of the plate. It is this that fuels a chain of volcanoes, such as the Aleutian Islands, the joint mantle plume/hotspot hypothesis envisages the feeder structures to be fixed relative to one another, with the continents and seafloor drifting overhead. The hypothesis thus predicts that time-progressive chains of volcanoes are developed on the surface, examples are Yellowstone, which lies at the end of a chain of extinct calderas, which become progressively older to the west. Another example is the Hawaiian archipelago, where islands become progressively older, boschi, L. Becker, T. W. Steinberger, B. Mantle plumes, Dynamic models and seismic images, break-up spots, Could the Pacific open as a consequence of plate kinematics. Towards A Better Understanding Of Hot Spot Volcanism, formation of Hotspots Raising Hot Spots Large Igneous Provinces Maria Antretter, PhD Thesis, Moving hotspots – Evidence from paleomagnetism and modeling Do Plumes Exist
34.
Diapir
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A diapir is a type of geologic intrusion in which a more mobile and ductily deformable material is forced into brittle overlying rocks. The term was introduced by the Romanian geologist Ludovic Mrazek, who was the first to understand the principle of salt intrusion and plasticity. The term diapir may be applied to structures, but it is more commonly applied to non-igneous, relatively cold materials, such as salt domes. In addition to Earth-based observations, diapirism is thought to occur on Neptunes moon Triton, Jupiters moon Europa, Saturns moon Enceladus, the density contrast manifests as a force of buoyancy. The process is known as diapirism, the resulting structures are also referred to as piercement structures. In the process, segments of the strata can be disconnected and pushed upwards. While moving higher, they retain much of their properties such as pressure. Such overpressured Floaters pose a significant risk when trying to drill through them, there is an analogy to a Galilean thermometer. Rock types such as evaporitic salt deposits, and gas charged muds are potential sources of diapirs, diapirs also form in the earths mantle when a sufficient mass of hot, less dense magma assembles. Diapirism in the mantle is thought to be associated with the development of large igneous provinces, explosive, hot volatile rich magma or volcanic eruptions are referred to generally as diatremes. Diatremes are not usually associated with diapirs, as they are small-volume magmas which ascend by volatile plumes, diapirs or piercement structures are structures resulting from the penetration of overlaying material. By pushing upward and piercing overlying rock layers, diapirs can form anticlines, salt domes and other structures capable of trapping petroleum, igneous intrusions themselves are typically too hot to allow the preservation of preexisting hydrocarbons. Geyser Granite Granite dome Hydrothermal vent Methods of pluton emplacement Mud volcano Salt tectonics
35.
Jet engine
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A jet engine is a reaction engine discharging a fast-moving jet that generates thrust by jet propulsion. This broad definition includes airbreathing jet engines and non-airbreathing jet engines, in general, jet engines are combustion engines. In common parlance, the jet engine loosely refers to an internal combustion airbreathing jet engine. These typically feature an air compressor powered by a turbine. Jet aircraft use such engines for long-distance travel, early jet aircraft used turbojet engines which were relatively inefficient for subsonic flight. Modern subsonic jet aircraft usually use more complex high-bypass turbofan engines and these engines offer high speed and greater fuel efficiency than piston and propeller aeroengines over long distances. Jet engines date back to the invention of the aeolipile before the first century AD and this device directed steam power through two nozzles to cause a sphere to spin rapidly on its axis. So far as is known, it did not supply mechanical power, instead, it was seen as a curiosity. However, although powerful, at reasonable flight speeds rockets are very inefficient. The earliest attempts at airbreathing jet engines were hybrid designs in which a power source first compressed air. In one such system, called a thermojet by Secondo Campini but more commonly, motorjet, examples of this type of design were the Caproni Campini N.1, and the Japanese Tsu-11 engine intended to power Ohka kamikaze planes towards the end of World War II. None were entirely successful and the N.1 ended up being slower than the design with a traditional engine. If aircraft performance were ever to increase beyond such a barrier and this was the motivation behind the development of the gas turbine engine, commonly called a jet engine. The key to a jet engine was the gas turbine. The gas turbine was not an idea developed in the 1930s, the first gas turbine to successfully run self-sustaining was built in 1903 by Norwegian engineer Ægidius Elling. Limitations in design and practical engineering and metallurgy prevented such engines reaching manufacture, the main problems were safety, reliability, weight and, especially, sustained operation. The first patent for using a gas turbine to power an aircraft was filed in 1921 by Frenchman Maxime Guillaume and his engine was an axial-flow turbojet. Alan Arnold Griffith published An Aerodynamic Theory of Turbine Design in 1926 leading to work at the RAE
36.
Turbine
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A turbine is a rotary mechanical device that extracts energy from a fluid flow and converts it into useful work. The work produced by a turbine can be used for generating power when combined with a generator or producing thrust. A turbine is a turbomachine with at least one moving part called a rotor assembly, moving fluid acts on the blades so that they move and impart rotational energy to the rotor. Early turbine examples are windmills and waterwheels, gas, steam, and water turbines have a casing around the blades that contains and controls the working fluid. Modern steam turbines frequently employ both reaction and impulse in the unit, typically varying the degree of reaction and impulse from the blade root to its periphery. Benoit Fourneyron, a student of Claude Burdin, built the first practical water turbine. A working fluid contains potential energy and kinetic energy, the fluid may be compressible or incompressible. Several physical principles are employed by turbines to collect this energy, the resulting impulse spins the turbine and leaves the fluid flow with diminished kinetic energy. There is no change of the fluid or gas in the turbine blades, as in the case of a steam or gas turbine. Before reaching the turbine, the pressure head is changed to velocity head by accelerating the fluid with a nozzle. Pelton wheels and de Laval turbines use this process exclusively, Impulse turbines do not require a pressure casement around the rotor since the fluid jet is created by the nozzle prior to reaching the blades on the rotor. Newtons second law describes the transfer of energy for impulse turbines, Impulse turbines are most efficient for use in cases where the flow is low and the inlet pressure is high. Reaction turbines develop torque by reacting to the gas or fluids pressure or mass, the pressure of the gas or fluid changes as it passes through the turbine rotor blades. A pressure casement is needed to contain the working fluid as it acts on the stage or the turbine must be fully immersed in the fluid flow. The casing contains and directs the working fluid and, for water turbines, Francis turbines and most steam turbines use this concept. For compressible working fluids, multiple stages are usually used to harness the expanding gas efficiently. Newtons third law describes the transfer of energy for reaction turbines, reaction turbines are better suited to higher flow velocities or applications where the fluid head is low. In practice, modern designs use both reaction and impulse concepts to varying degrees whenever possible
37.
Sulfuric acid
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Sulfuric acid is a highly corrosive strong mineral acid with the molecular formula H2SO4 and molecular weight 98.079 g/mol. It is a pungent-ethereal, colorless to slightly yellow liquid that is soluble in water at all concentrations. Sometimes, it is dyed dark brown during production to alert people to its hazards, the historical name of this acid is oil of vitriol. Sulfuric acid is an acid and shows different properties depending upon its concentration. Its corrosiveness on other materials, like metals, living tissues or even stones, can be ascribed to its strong acidic nature and, if concentrated. It is also hygroscopic, readily absorbing water vapour from the air, Sulfuric acid at a high concentration can cause very serious damage upon contact, since not only does it cause chemical burns via hydrolysis, but also secondary thermal burns through dehydration. It can lead to permanent blindness if splashed onto eyes and irreversible damage if swallowed, Sulfuric acid has a wide range of applications including in domestic acidic drain cleaners, as an electrolyte in lead-acid batteries and in various cleaning agents. It is also a central substance in the chemical industry, principal uses include mineral processing, fertilizer manufacturing, oil refining, wastewater processing, and chemical synthesis. It is widely produced with different methods, such as process, wet sulfuric acid process, lead chamber process. The study of vitriol, a category of glassy minerals from which the acid can be derived, sumerians had a list of types of vitriol that they classified according to the substances color. Some of the earliest discussions on the origin and properties of vitriol is in the works of the Greek physician Dioscorides, galen also discussed its medical use. Ibn Sina focused on its uses and different varieties of vitriol. Sulfuric acid was called oil of vitriol by medieval European alchemists because it was prepared by roasting green vitriol in an iron retort, there are references to it in the works of Vincent of Beauvais and in the Compositum de Compositis ascribed to Saint Albertus Magnus. A passage from Pseudo-Geber´s Summa Perfectionis was long considered to be the first recipe for sulfuric acid, in the seventeenth century, the German-Dutch chemist Johann Glauber prepared sulfuric acid by burning sulfur together with saltpeter, in the presence of steam. As saltpeter decomposes, it oxidizes the sulfur to SO3, in 1736, Joshua Ward, a London pharmacist, used this method to begin the first large-scale production of sulfuric acid. This process allowed the effective industrialization of sulfuric acid production, after several refinements, this method, called the lead chamber process or chamber process, remained the standard for sulfuric acid production for almost two centuries. Sulfuric acid created by John Roebucks process approached a 65% concentration, later refinements to the lead chamber process by French chemist Joseph Louis Gay-Lussac and British chemist John Glover improved concentration to 78%. However, the manufacture of dyes and other chemical processes require a more concentrated product
38.
Sun
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The Sun is the star at the center of the Solar System. It is a perfect sphere of hot plasma, with internal convective motion that generates a magnetic field via a dynamo process. It is by far the most important source of energy for life on Earth. Its diameter is about 109 times that of Earth, and its mass is about 330,000 times that of Earth, accounting for about 99. 86% of the total mass of the Solar System. About three quarters of the Suns mass consists of hydrogen, the rest is mostly helium, with smaller quantities of heavier elements, including oxygen, carbon, neon. The Sun is a G-type main-sequence star based on its spectral class and it formed approximately 4.6 billion years ago from the gravitational collapse of matter within a region of a large molecular cloud. Most of this matter gathered in the center, whereas the rest flattened into a disk that became the Solar System. The central mass became so hot and dense that it eventually initiated nuclear fusion in its core and it is thought that almost all stars form by this process. The Sun is roughly middle-aged, it has not changed dramatically for more than four billion years and it is calculated that the Sun will become sufficiently large enough to engulf the current orbits of Mercury, Venus, and probably Earth. The enormous effect of the Sun on Earth has been recognized since prehistoric times, the synodic rotation of Earth and its orbit around the Sun are the basis of the solar calendar, which is the predominant calendar in use today. The English proper name Sun developed from Old English sunne and may be related to south, all Germanic terms for the Sun stem from Proto-Germanic *sunnōn. The English weekday name Sunday stems from Old English and is ultimately a result of a Germanic interpretation of Latin dies solis, the Latin name for the Sun, Sol, is not common in general English language use, the adjectival form is the related word solar. The term sol is used by planetary astronomers to refer to the duration of a solar day on another planet. A mean Earth solar day is approximately 24 hours, whereas a mean Martian sol is 24 hours,39 minutes, and 35.244 seconds. From at least the 4th Dynasty of Ancient Egypt, the Sun was worshipped as the god Ra, portrayed as a falcon-headed divinity surmounted by the solar disk, and surrounded by a serpent. In the New Empire period, the Sun became identified with the dung beetle, in the form of the Sun disc Aten, the Sun had a brief resurgence during the Amarna Period when it again became the preeminent, if not only, divinity for the Pharaoh Akhenaton. The Sun is viewed as a goddess in Germanic paganism, Sól/Sunna, in ancient Roman culture, Sunday was the day of the Sun god. It was adopted as the Sabbath day by Christians who did not have a Jewish background, the symbol of light was a pagan device adopted by Christians, and perhaps the most important one that did not come from Jewish traditions
39.
Troposphere
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The troposphere is the lowest portion of Earths atmosphere, and is also where nearly all weather takes place. It contains approximately 75% of the mass and 99% of the total mass of water vapor. The average depths of the troposphere are 20 km in the tropics,17 km in the mid latitudes, the lowest part of the troposphere, where friction with the Earths surface influences air flow, is the planetary boundary layer. This layer is typically a few hundred meters to 2 km deep depending on the landform, atop the troposphere is the tropopause, which is the border between the troposphere and stratosphere. The tropopause is a layer, where the air temperature ceases to decrease with height. Most of the phenomena we associate with day-to-day weather occur in the troposphere, by volume, dry air contains 78. 09% nitrogen,20. 95% oxygen,0. 93% argon,0. 04% carbon dioxide, and small amounts of other gases. Air also contains an amount of water vapor. The chemical composition of the troposphere is essentially uniform, with the exception of water vapor. The source of vapor is at the surface through the processes of evaporation. Thus the proportion of water vapor is normally greatest near the surface, the pressure of the atmosphere is maximum at sea level and decreases with altitude. This is because the atmosphere is nearly in hydrostatic equilibrium. The temperature of the troposphere generally decreases as altitude increases, the rate at which the temperature decreases, − d T / d z, is called the environmental lapse rate. The ELR is nothing more than the difference in temperature between the surface and the tropopause divided by the height. The reason for this difference is that the ground absorbs most of the suns energy. Meanwhile, the radiation of heat at the top of the results in the cooling of that part of the atmosphere. The ELR assumes the atmosphere is still, but as air is heated it becomes buoyant, when a parcel of air rises, it expands, because the pressure is lower at higher altitudes. As the air expands, it pushes the surrounding air outward. As energy transfer to a parcel of air by way of heat is very slow, such a process is called an adiabatic process
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Stratosphere
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The stratosphere is the second major layer of Earths atmosphere, just above the troposphere, and below the mesosphere. About 20% of the mass is contained in the stratosphere. The stratosphere is stratified in temperature, with warmer layers higher and cooler layers closer to the Earth, the increase of temperature with altitude is a result of the absorption of the Suns ultraviolet radiation by the ozone. This is in contrast to the troposphere, near the Earths surface, the border between the troposphere and stratosphere, the tropopause, marks where this temperature inversion begins. Near the equator, the starts at 18 km, at mid latitudes, it starts at 10–13 km and ends at 50 km, at the poles. Temperatures vary within the stratosphere with the seasons, in particular with the polar night, the greatest variation of temperature takes place over the poles in the lower stratosphere, those variations are largely steady at lower latitudes and higher altitudes. The mechanism describing the formation of the layer was described by British mathematician Sydney Chapman in 1930. Molecular oxygen absorbs high energy sunlight in the UV-C region, at shorter than about 240 nm. The oxygen atoms produced combine with oxygen to form ozone. Ozone in turn is photolysed much more rapidly than molecular oxygen as it has an absorption that occurs at longer wavelengths. Ozone photolysis produces O and O2, the oxygen atom product combines with atmospheric molecular oxygen to reform O3, releasing heat. The rapid photolysis and reformation of ozone heats the stratosphere resulting in a temperature inversion and this increase of temperature with altitude is characteristic of the stratosphere, its resistance to vertical mixing means that it is stratified. Within the stratosphere temperatures increase with altitude, the top of the stratosphere has a temperature of about 270 K, overall the attenuation of solar UV at wavelengths that damage DNA by the ozone layer allows life to exist on the surface of the planet outside of the ocean. All air entering the stratosphere must pass through the tropopause, the minimum that divides the troposphere and stratosphere. The rising air is literally freeze dried, the stratosphere is a dry place. The top of the stratosphere is called the stratopause, above which the temperature decreases with height and we now know that there are additional ozone loss mechanisms, and that these mechanisms are catalytic meaning that a small amount of the catalyst can destroy a great number of ozone molecules. The first is due to the reaction of hydroxyl radicals OH· with ozone, OH is formed by the reaction of electronically excited oxygen atoms produced by ozone photolysis, with water vapor. While the stratosphere is dry, additional water vapor is produced in situ by the oxidation of methane
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Volcanic winter
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Volcanic stratospheric aerosols cool the surface by reflecting solar radiation and warm the stratosphere by absorbing terrestrial radiation. The volcanic aerosols, resulting from the 1991 Pinatubo eruption and others, have shown to contribute to anthropogenic ozone depletion. The variations in atmospheric warming and cooling results in changes in tropospheric and stratospheric circulation, the effects of volcanic eruptions on recent winters are modest in scale, but historically have been significant. Most recently, the 1991 explosion of Mount Pinatubo, a stratovolcano in the Philippines, in 1883, the explosion of Krakatoa created volcanic winter-like conditions. The four years following the explosion were unusually cold, and the winter of 1887-1888 included powerful blizzards, northern hemisphere temperatures dropped by about 1 °C in the year following the Laki eruption. However Franklins proposal has been questioned, in 1600, the Huaynaputina in Peru erupted. Tree ring studies show that 1601 was cold, russia had its worst famine in 1601-1603. From 1600 to 1602, Switzerland, Latvia and Estonia had exceptionally cold winters, the wine harvest was late in 1601 in France, and in Peru and Germany, wine production collapsed. Peach trees bloomed late in China, and Lake Suwa in Japan froze early, in 1452 or 1453, a cataclysmic eruption of the submarine volcano Kuwae caused worldwide disruptions. The Great Famine of 1315–1317 in Europe may have been precipitated by an event, perhaps that of Mount Tarawera, New Zealand. The extreme weather events of 535–536 are most likely linked to a volcanic eruption, the latest theorised explanation is the Tierra Blanca Joven eruption of the Ilopango caldera in central El Salvador. One proposed volcanic winter occurred around 71, 000–73,000 years ago following the supereruption of Lake Toba on Sumatra island in Indonesia, others argue that the climatic effects of the eruption were too weak and brief to impact early human populations to the degree proposed. This, combined with the occurrence of most human differentiations in that same period, is a probable case of bottleneck linked to volcanic winters. On average, super-eruptions with total eruptive masses of at least 1015 kg occur every 1 million years and this result led the archaeologists to conclude that the largest known volcanic eruption in the history of the human species did not significantly alter the climate of East Africa. Such events may diminish populations to levels low enough for evolutionary changes, with the Toba bottleneck, many species show massive effects of narrowing of the gene pool, and Toba reduced the human population to between 15,000 and 40,000 or even fewer. Global dimming Impact winter Nuclear winter Supervolcano Timeline of volcanism on Earth Year Without a Summer MR Rampino, annual Review of Earth and Planetary Sciences. Limited global change due to the largest known Quaternary eruption, Toba ~~74 Kyr BP
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Famine
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A famine is a widespread scarcity of food, caused by several factors including crop failure, population imbalance, or government policies. This phenomenon is usually accompanied or followed by regional malnutrition, starvation, epidemic, every inhabited continent in the world has experienced a period of famine throughout history. In the 19th and 20th century, it was generally Eastern Europe, the numbers dying from famine began to fall sharply from the 1970s. Some countries, particularly in sub-Saharan Africa, continue to have cases of famine. Since 2010, Africa has been the most affected continent in the world, as of 2017, the United Nations has warned some 20 million are at risk in South Sudan, Somalia, Nigeria and Yemen. Agricultural conditions have been fluctuating more and more due to variations in weather, most programmes now direct their aid towards Africa. The cyclical occurrence of famine has been a mainstay of societies engaged in agriculture since the dawn of agriculture itself. The frequency and intensity of famine has fluctuated throughout history, depending on changes in demand, such as population growth. Famine was first eliminated in Holland and England during the 17th century, due to the commercialization of agriculture and the implementation of improved techniques to increase crop yields. In the 16th and 17th century, the system began to break down. These capitalist landowners paid their labourers with money, thereby increasing the commercialization of rural society, in the emerging competitive labour market, better techniques for the improvement of labour productivity were increasingly valued and rewarded. It was in the farmers interest to produce as much as possible on their land in order to sell it to areas that demanded that product and they produced guaranteed surpluses of their crop every year if they could. Subsistence peasants were also forced to commercialize their activities because of increasing taxes. Taxes that had to be paid to governments in money forced the peasants to produce crops to sell. Sometimes they produced industrial crops, but they would find ways to increase their production in order to both their subsistence requirements as well as their tax obligations. Peasants also used the new money to purchase manufactured goods, the agricultural and social developments encouraging increased food production were gradually taking place throughout the 16th century, but took off in the early 17th century. By that time, the Netherlands had one of the most commercialized agricultural systems in Europe and they grew many industrial crops such as flax, hemp and hops. Agriculture became increasingly specialized and efficient, the efficiency of Dutch agriculture allowed for much more rapid urbanization in the late sixteenth and early seventeenth centuries than anywhere else in Europe
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Vulcano
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Vulcano is a small volcanic island in the Tyrrhenian Sea, about 25 km north of Sicily and the southernmost of the eight Aeolian Islands. It is 21 km2 in area, rises to 499 m above sea level, the Romans used the island mainly for raw materials, harvesting wood and mining alum and sulfur. This was the activity on the island until the end of the 19th Century. Stevenson lived on Vulcano until the last major eruption on the island, the eruption lasted the better part of two years, by which time Stevenson had sold all of his property to the local populace, and never returned to the island. The volcanic activity in the region is largely the result of the northward-moving African Plate meeting the Eurasian Plate, at the north of the island is Vulcanello, connected to the rest of it by an isthmus which is flooded in bad weather. It emerged from the sea during an eruption in 183 BC as a separate islet, occasional eruptions from its three cones with both pyroclastic flow deposits and lavas occurred from then until 1550, the last eruption creating a narrow isthmus connecting it to Vulcano. Vulcano has been quiet since the eruption of the Fossa cone on 3 August 1888 to 1890 and this eruption of Vulcano was carefully documented at the time by Giuseppe Mercalli. Mercalli described the eruptions as. Explosions sounding like a cannon at irregular intervals, as a result, vulcanian eruptions are based on this description. A typical vulcanian eruption can hurl blocks of solid material several hundreds of metres from the vent, Mercalli reported blocks from the 1888-1890 eruption fell in the sea between Vulcano and Lipari, several were photographed by him or his assistants that had fallen on the island of Vulcano. The Ancient Greeks named the island Therassía and Thérmessa, the island appeared in their myths as the private workshop of the Olympian god Hephaestus, protector of the blacksmiths, he owned another two at Etna and Olympus. Strabo also mentions Thermessa as sacred place of Hephaestus, but it is not clear if it was a name for the island. Similarly the Romans believed that Vulcano was the chimney of the god Vulcans workshop, the island had grown due to his periodic clearing of cinders and ashes from his forge. The earthquakes that either preceded or accompanied the explosions of ash were considered to be due to Vulcan making weapons for Mars, since Vulcano island has volcanic activity, this island is a place where thermophiles and hyperthermophiles are likely to be found. In fact, the hyperthermophilic archaea Pyrococcus furiosus was described for the first time when it was isolated from sediments of this island by Gerhard Fiala and Karl Stetter. Volcanic gas emissions from this volcano are measured by a Multi-Component Gas Analyzer System, list of volcanoes in Italy Vulcan Vulcano a 1950 Italian drama film supposedly set on the island
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Aeolian Islands
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The Aeolian Islands are a volcanic archipelago in the Tyrrhenian Sea north of Sicily, named after the demigod of the winds Aeolus. The islands inhabitants are known as Aeolians, the Aeolian Islands are a popular tourist destination in the summer and attract up to 200,000 visitors annually. The largest island is Lipari and the islands are referred to as the Lipari Islands or Lipari group. The other islands include Vulcano, Salina, Stromboli, Filicudi, Alicudi, Panarea, the present shape of the Aeolian Islands is the result of volcanic activity over a period of 260,000 years. There are two active volcanoes – Stromboli and Vulcano, the volcanic activity of steaming fumaroles and thermal waters are on most of the islands. The volcanic activity has left the islands with very fertile soil that is conductive to the growth of natural flora. Geologically the archipelago is defined as a volcanic arc, the origin of the Aeolian Islands is due to movement of the Earths crust as a result of plate tectonics. The African continental shelf is in constant movement towards Europe, the resulting collision has created a volcanic area with ruptures in the Earths crust with consequent eruptions of lava. The Aeolian Arc extends for more than 140 km, but the area of instability caused by the collision of Africa. It includes Sicily, Calabria, and Campania together with Greece, the complex of the eight Aeolian Islands, covering an area of 1,600 km2, originated in the Tyrrhenian Basin, a great plain at the bottom of the Tyrrhenian Sea. Curbing urban development has been a key to preserving the Aeolian islands in a natural state, existing residences can be bought and restored but must be constructed to resemble its whitewashed houses. Traditional houses consist of modular cubes constructed from indigenous building materials—stone, lava, pumice, almost all houses have a large outdoor terrace, usually shaded by grape-vines and flowering vines. The houses, balconies and terraces are decorated with brightly patterned terra-cotta tiles. The first evidence of Sicilian migration was in Lipari, a manufacture and commerce of obsidian objects was highly developed until the introduction of metals. During the Bronze Age, the Aeolians prospered by means of commerce in an area which extended from Mycenae to the British Isles. Villages on the Aeolian islands flourished on Capo Graziano, Castello, Serro dei Cianfi, Capo Milazzese, all these settlements were destroyed by new Italic invasions in 1250 BC. The Aeolian Islands were occupied by the Ausonians led by Liparus, Liparus was succeeded by Aeolus whose house, according to the Odyssey by Homer, gave hospitality to Odysseus. In 580 BC, Greeks exiled from Rhodes and Knidos landed at Lipari and began a period of Greek domination, there was production of vases and other ceramics
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Vulcan (mythology)
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Vulcan is the god of fire including the fire of volcanoes, metalworking, and the forge in ancient Roman religion and myth. Vulcan is often depicted with a blacksmiths hammer, the Vulcanalia was the annual festival held August 23 in his honor. His Greek counterpart is Hephaestus, the god of fire and smithery, in Etruscan religion, he is identified with Sethlans. The origin of the name is unclear, Roman tradition maintained that it was related to Latin words connected to lightning, which in turn was thought of as related to flames. This interpretation is supported by Walter William Skeat in his dictionary as meaning lustre. It has been supposed that his name was not Latin but related to that of the Cretan god Velchanos, a god of nature, wolfgang Meid has refused this identification as phantastic. More recently this etymology has been taken up by Gérard Capdeville who finds a continuity between Cretan Minoan god Velchanos and Etruscan Velchans, the Minoan gods identity would be that of a young deity, master of fire and companion of the Great Goddess. Christian Guyonvarch has proposed the identification with the Irish name Olcan, vasily Abaev compares it with the Ossetic Wærgon, a variant of the name of Kurdalægon, the smith of the Nart saga. Since the name in its normal form Kurdalægon is stable and has a clear meaning, the Volcanalia sacrifice was offered here to Vulcan, on August 23. Vulcan also had a temple on the Campus Martius, which was in existence by 214 BC, the Romans identified Vulcan with the Greek smith-god Hephaestus. Vulcan became associated like his Greek counterpart with the use of fire in metalworking. A fragment of a Greek pot showing Hephaestus found at the Volcanal has been dated to the 6th century BC, however, Vulcan had a stronger association than Hephaestus with fires destructive capacity, and a major concern of his worshippers was to encourage the god to avert harmful fires. The festival of Vulcan, the Vulcanalia, was celebrated on August 23 each year, during the festival bonfires were created in honour of the god, into which live fish or small animals were thrown as a sacrifice, to be consumed in the place of humans. It is recorded that during the Vulcanalia people used to hang their cloths and this habit might reflect a theological connection between Vulcan and the divinized Sun. Another custom observed on this day required that one should start working by the light of a candle, probably to propitiate a beneficial use of fire by the god. In addition to the Volcanalia of August 23, the date of May 23, a flamen, one of the flamines minores, named flamen Volcanalis was in charge of the cult of the god. The flamen Volcanalis officiated at a sacrifice to the goddess Maia, Vulcan was among the gods placated after the Great Fire of Rome in AD64. In response to the fire, Domitian established a new altar to Vulcan on the Quirinal Hill
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Roman mythology
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Roman mythology is the body of traditional stories pertaining to ancient Romes legendary origins and religious system, as represented in the literature and visual arts of the Romans. Roman mythology may also refer to the study of these representations. The Romans usually treated their traditional narratives as historical, even when these have miraculous or supernatural elements, the stories are often concerned with politics and morality, and how an individuals personal integrity relates to his or her responsibility to the community or Roman state. When the stories illuminate Roman religious practices, they are concerned with ritual, augury. Romes early myths and legends also have a relationship with Etruscan religion. In particular, the versions of Greek myths in Ovids Metamorphoses, written during the reign of Augustus, because ritual played the central role in Roman religion that myth did for the Greeks, it is sometimes doubted that the Romans had much of a native mythology. This perception is a product of Romanticism and the scholarship of the 19th century. From the Renaissance to the 18th century, however, Roman myths were an inspiration particularly for European painting, the Roman tradition is rich in historical myths, or legends, concerning the foundation and rise of the city. These narratives focus on human actors, with only occasional intervention from deities, in Romes earliest period, history and myth have a mutual and complementary relationship. As T. P. Wiseman notes, The Roman stories still matter, as they mattered to Dante in 1300 and Shakespeare in 1600, what does it take to be a free citizen. Can a superpower still be a republic, how does well-meaning authority turn into murderous tyranny. Major sources for Roman myth include the Aeneid of Vergil and the first few books of Livys history as well as Dionysius s Roman Antiquities. Other important sources are the Fasti of Ovid, a six-book poem structured by the Roman religious calendar, scenes from Roman myth also appear in Roman wall painting, coins, and sculpture, particularly reliefs. The Aeneid and Livys early history are the best extant sources for Romes founding myths, material from Greek heroic legend was grafted onto this native stock at an early date. By extension, the Trojans were adopted as the ancestors of the Roman people. Rape of the Sabine women, explaining the importance of the Sabines in the formation of Roman culture, numa Pompilius, the Sabine second king of Rome who consorted with the nymph Egeria and established many of Romes legal and religious institutions. Servius Tullius, the king of Rome, whose mysterious origins were freely mythologized. The Tarpeian Rock, and why it was used for the execution of traitors, lucretia, whose self-sacrifice prompted the overthrow of the early Roman monarchy and led to the establishment of the Republic
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Volcanology
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Volcanology is the study of volcanoes, lava, magma, and related geological, geophysical and geochemical phenomena. The term volcanology is derived from the Latin word vulcan, vulcan was the ancient Roman god of fire. A volcanologist is a geologist who studies the activity and formation of volcanoes. Volcanologists frequently visit volcanoes, especially active ones, to observe volcanic eruptions, collect eruptive products including tephra, rock and lava samples. One major focus of enquiry is the prediction of eruptions, there is no accurate way to do this. In 1841, the first volcanological observatory, the Vesuvius Observatory, was founded in the Kingdom of the Two Sicilies, surface deformation monitoring includes the use of geodetic techniques such as leveling, tilt, strain, angle and distance measurements through tiltmeters, total stations and EDMs. This also includes GNSS observations and InSAR, surface deformation indicates magma upwelling, increased magma supply produces bulges in the volcanic centers surface. Gas emissions may be monitored with equipment including portable ultra-violet spectrometers, increased gas emissions, and more particularly changes in gas compositions, may signal an impending volcanic eruption. Temperature changes are monitored using thermometers and observing changes in properties of volcanic lakes and vents. Satellites are widely used to monitor volcanoes, as they allow an area to be monitored easily. They can measure the spread of an ash plume, such as the one from Eyjafjallajokulls 2010 eruption, InSAR and thermal imaging can monitor large, scarcely populated areas where it would be too expensive to maintain instruments on the ground. Stratigraphic analyses includes analyzing tephra and lava deposits and dating these to give volcano eruption patterns, with estimated cycles of intense activity and size of eruptions. The earliest known recording of an eruption may be on a wall painting dated to about 7,000 BCE found at the Neolithic site at Çatal Höyük in Anatolia. This painting has been interpreted as a depiction of a volcano, with a cluster of houses below shows a twin peaked volcano in eruption. The volcano may be either Hasan Dağ, or its smaller neighbour, the classical world of Greece and the early Roman Empire explained volcanoes as sites of various gods. Greeks considered that Hephaestus, the god of fire, sat below the volcano Etna, the Greek word used to describe volcanoes was etna, or hiera, after Heracles, the son of Zeus. Enceladus brother Mimas was buried beneath Vesuvius by Hephaestus, and the blood of other defeated giants welled up in the Phlegrean Fields surrounding Vesuvius, the Greek philosopher Empedocles saw the world divided into four elemental forces, of Earth, Air, Fire and Water. Volcanoes, Empedocles maintained, were the manifestation of Elemental Fire, plato contended that channels of hot and cold waters flow in inexhaustible quantities through subterranean rivers
Nyiragongo's lava lake
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This article incorporates text from this source, which is in the 
