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72-558: The municipality lies in the Vulkaneifel , a part of the Eifel known for its volcanic history, geographical and geological features, and even ongoing activity today, including gases that sometimes well up from the earth. The village, which lies somewhat back from the Daun Maars , is actually a typical street village (by some definitions, a “thorpe”). Over the last few decades, particularly since

144-476: A magma chamber below the surface. The process that forms volcanoes is called volcanism . On Earth, volcanoes are most often found where tectonic plates are diverging or converging , and because most of Earth's plate boundaries are underwater, most volcanoes are found underwater. For example, a mid-ocean ridge , such as the Mid-Atlantic Ridge , has volcanoes caused by divergent tectonic plates whereas

216-437: A graduated spectrum, with much overlap between categories, and does not always fit neatly into only one of these three separate categories. The USGS defines a volcano as "erupting" whenever the ejection of magma from any point on the volcano is visible, including visible magma still contained within the walls of the summit crater. While there is no international consensus among volcanologists on how to define an active volcano,

288-443: A paper was published suggesting a new definition for the word 'volcano' that includes processes such as cryovolcanism . It suggested that a volcano be defined as 'an opening on a planet or moon's surface from which magma , as defined for that body, and/or magmatic gas is erupted.' This article mainly covers volcanoes on Earth. See § Volcanoes on other celestial bodies and cryovolcano for more information. The word volcano

360-551: A pile transposed throughout vert charged with three stones of the field, one resting on the other two, dexter a sword palewise gules, the hilt to chief, and sinister a dove of the last. The “pile transposed” (that is, the wedge-shaped charge ) stands for the Steineberger Ley, the 560 m-high volcanic cone that defines the local scenery. On this mountain, the Celts built a defensive wall out of basalt stones and logs that served

432-628: A population of about 200,000. The following volcanoes belong to the Eifel, sorted by height in metres (m) above sea level ( Normalhöhennull , NHN) : Of particular note is the volcanic caldera known as Laacher See , the site of an eruption around 12,900 years ago that had an estimated VEI of 6. The tephras deposited by past eruptions of the Volcanic Eifel are lithological deposits that are radiometrically dateable via argon-argon dating of K-feldspar grains. These have in turn been utilised to ascertain

504-434: A rising magma plume . This activity does not imply an immediate eruptive danger, but might suggest an increase in volcanic and seismic activity in the region. 50°17′N 7°00′E  /  50.283°N 7.000°E  / 50.283; 7.000 Volcano A volcano is a rupture in the crust of a planetary-mass object , such as Earth , that allows hot lava , volcanic ash , and gases to escape from

576-632: A volcano is largely determined by the composition of the lava it erupts. The viscosity (how fluid the lava is) and the amount of dissolved gas are the most important characteristics of magma, and both are largely determined by the amount of silica in the magma. Magma rich in silica is much more viscous than silica-poor magma, and silica-rich magma also tends to contain more dissolved gases. Lava can be broadly classified into four different compositions: Mafic lava flows show two varieties of surface texture: ʻAʻa (pronounced [ˈʔaʔa] ) and pāhoehoe ( [paːˈho.eˈho.e] ), both Hawaiian words. ʻAʻa

648-555: A volcano is of a conical mountain, spewing lava and poisonous gases from a crater at its summit; however, this describes just one of the many types of volcano. The features of volcanoes are varied. The structure and behaviour of volcanoes depend on several factors. Some volcanoes have rugged peaks formed by lava domes rather than a summit crater while others have landscape features such as massive plateaus . Vents that issue volcanic material (including lava and ash ) and gases (mainly steam and magmatic gases) can develop anywhere on

720-465: A volcano that has experienced one or more eruptions that produced over 1,000 cubic kilometres (240 cu mi) of volcanic deposits in a single explosive event. Such eruptions occur when a very large magma chamber full of gas-rich, silicic magma is emptied in a catastrophic caldera -forming eruption. Ash flow tuffs emplaced by such eruptions are the only volcanic product with volumes rivalling those of flood basalts . Supervolcano eruptions, while

792-727: Is a volcanic field of over 60 cinder cones. Based on satellite images, it has been suggested that cinder cones might occur on other terrestrial bodies in the Solar system too; on the surface of Mars and the Moon. Stratovolcanoes (composite volcanoes) are tall conical mountains composed of lava flows and tephra in alternate layers, the strata that gives rise to the name. They are also known as composite volcanoes because they are created from multiple structures during different kinds of eruptions. Classic examples include Mount Fuji in Japan, Mayon Volcano in

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864-587: Is a region in the Eifel Mountains in Germany that is defined to a large extent by its volcanic geological history. Characteristic of this volcanic field are its typical explosion crater lakes or maars , and numerous other signs of volcanic activity such as volcanic tuffs , lava streams and volcanic craters like the Laacher See . The Volcanic Eifel is still volcanically active today. One sign of this activity

936-597: Is a word often used in the Eifel area, and it means “cliff” or “crag”. Another well known occurrence of this term is in the name Loreley . On 3 October 2003, the Vulcano Infoplattform of the municipality of Steineberg was opened on the Steineberger Ley. The 28 m-tall tower rose with the help of subsidies from the European Union , the state of Rhineland-Palatinate , the Verbandsgemeinde of Daun and

1008-413: Is believed to have stood where two wall ends clearly stand facing each other. Since there have yet to be any archaeological investigations, the complex's age can only be estimated: The size of the area and the wall building method using dry stonework (likely with a wooden truss) would seem to suggest a Celtic castle from the time between 500 and 100 BC. In those times, similar castles arose throughout

1080-412: Is characterized by a rough, clinkery surface and is the typical texture of cooler basalt lava flows. Pāhoehoe is characterized by its smooth and often ropey or wrinkly surface and is generally formed from more fluid lava flows. Pāhoehoe flows are sometimes observed to transition to ʻaʻa flows as they move away from the vent, but never the reverse. More silicic lava flows take the form of block lava, where

1152-554: Is derived from the name of Vulcano , a volcanic island in the Aeolian Islands of Italy whose name in turn comes from Vulcan , the god of fire in Roman mythology . The study of volcanoes is called volcanology , sometimes spelled vulcanology . According to the theory of plate tectonics, Earth's lithosphere , its rigid outer shell, is broken into sixteen larger and several smaller plates. These are in slow motion, due to convection in

1224-559: Is divided into three natural regions: The centre of the Volcanic Eifel is the region around Daun and Manderscheid and the areas within the Mayen-Koblenz district . The landscape of the Volcanic Eifel is dominated by recent volcanism. Volcanic craters, thick pumice and basalt layers and maars create a diverse landscape that clearly witnesses to very recent events in geological terms. The entire Volcanic Eifel covers an area of about 2,000 km (770 sq mi) and as of 2007 has

1296-567: Is expressed using the volcanic explosivity index (VEI), which ranges from 0 for Hawaiian-type eruptions to 8 for supervolcanic eruptions. As of December 2022 , the Smithsonian Institution 's Global Volcanism Program database of volcanic eruptions in the Holocene Epoch (the last 11,700 years) lists 9,901 confirmed eruptions from 859 volcanoes. The database also lists 1,113 uncertain eruptions and 168 discredited eruptions for

1368-524: Is one of the several tuyas in the area of the Tuya River and Tuya Range in northern British Columbia. Tuya Butte was the first such landform analysed and so its name has entered the geological literature for this kind of volcanic formation. The Tuya Mountains Provincial Park was recently established to protect this unusual landscape, which lies north of Tuya Lake and south of the Jennings River near

1440-785: Is the escaping gases in the Laacher See. The Volcanic Eifel stretches from the Rhine to the Wittlich Depression . It is bordered in the south and southwest by the South Eifel , in the west by Luxembourg and Belgian Ardennes and in the north by the North Eifel including the Hohes Venn . To the east the Rhine forms its geographical boundary, with no volcanicity immediately beyond it. The Volcanic Eifel

1512-524: Is the subject of many legends and historical events. It had its beginning in the Eifel ’s once much livelier vulcanism about 35,000,000 years ago in the Tertiary . Steineberg then lay in a north-south band that was characterized by a particularly high level of volcanic activity . As a result of these natural forces, the Steineberger Ley’s bedrock is solid basalt . The second word in the name, Ley ,

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1584-466: Is typically low in silica, shield volcanoes are more common in oceanic than continental settings. The Hawaiian volcanic chain is a series of shield cones, and they are common in Iceland , as well. Lava domes are built by slow eruptions of highly viscous lava. They are sometimes formed within the crater of a previous volcanic eruption, as in the case of Mount St. Helens , but can also form independently, as in

1656-444: The Amt of Daun. The arms have been borne since 15 January 1990. The most prominent point of interest in the municipality is the Steineberger Ley at 557 m above sea level. This mountain on Steineberg's southeast outskirts, which can be seen from afar, and which stretches to the neighbouring municipality of Steiningen , is important to history and tourism. This thickly wooded mountain

1728-600: The Cascade Volcanoes or the Japanese Archipelago , or the eastern islands of Indonesia . Hotspots are volcanic areas thought to be formed by mantle plumes , which are hypothesized to be columns of hot material rising from the core-mantle boundary. As with mid-ocean ridges, the rising mantle rock experiences decompression melting which generates large volumes of magma. Because tectonic plates move across mantle plumes, each volcano becomes inactive as it drifts off

1800-525: The Eifel and the Moselle valleys, and even make out the Nürburgring some 20 km away. The Steineberger Ley's peak bears at its south end an old fortification. Broken-down walls made of mortarless masonry and artificially steepened sides hem a gently sloping inner area of 2.2 ha. At the north end in particular, it is hard to tell natural rubble heaps apart from artificial wall remnants. An old gatehouse

1872-618: The Hawaiian hotspot is an example. Volcanoes are usually not created where two tectonic plates slide past one another. Large eruptions can affect atmospheric temperature as ash and droplets of sulfuric acid obscure the Sun and cool Earth's troposphere . Historically, large volcanic eruptions have been followed by volcanic winters which have caused catastrophic famines. Other planets besides Earth have volcanoes. For example, volcanoes are very numerous on Venus. Mars has significant volcanoes. In 2009,

1944-500: The basalt quarry . The council is made up of 6 council members, who were elected by majority vote at the municipal election held on 7 June 2009, and the honorary mayor as chairman. Steineberg's mayor is Harald Dahlem. The German blazon reads: In Silber eine grüne Spitze, darin 3 silberne Steine, vorne ein rotes Schwert, hinten eine rote Taube. The municipality's arms might in English heraldic language be described thus: Argent

2016-824: The landform and may give rise to smaller cones such as Puʻu ʻŌʻō on a flank of Kīlauea in Hawaii. Volcanic craters are not always at the top of a mountain or hill and may be filled with lakes such as with Lake Taupō in New Zealand. Some volcanoes can be low-relief landform features, with the potential to be hard to recognize as such and be obscured by geological processes. Other types of volcano include cryovolcanoes (or ice volcanoes), particularly on some moons of Jupiter , Saturn , and Neptune ; and mud volcanoes , which are structures often not associated with known magmatic activity. Active mud volcanoes tend to involve temperatures much lower than those of igneous volcanoes except when

2088-589: The 1970s, the village has been growing. New building areas have been opened. Today, along the now four streets, live 240 inhabitants. Steineberg lies south of the High Eifel , some 20 km north of the Moselle valley, near the district seat of Daun . The village's midpoint sits at an elevation of 530 m above sea level . The highest elevation, at 557 m above sea level, is the Steineberger Ley. The municipal area comprises 124 ha of wooded land and 169 ha of cropland and meadows. Steineberg borders in

2160-462: The 19th century, many are still discernible. The castle and the barrows are protected cultural monuments, any digging of or changes to which are therefore forbidden. The municipality itself is characterized by agriculture , even if nowadays only one farm, dealing mainly in dairy , is still being run. Even before the First World War , many Steinebergers worked at a basalt quarry on the edge of

2232-514: The Daun/Vulkaneifel Economic Promotion Organization ( Wirtschaftsförderungsgesellschaft Daun/Vulkaneifel ). The structure was, for ecological reasons built out of 100-year-old, untreated Douglas-fir logs. It has an overall weight of 38 t and supports an observation deck 24 m above the ground. Given its outstanding location above the Steineberger Ley's treetops, visitors can on a clear day see far across

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2304-843: The Pacific Ring of Fire has volcanoes caused by convergent tectonic plates. Volcanoes can also form where there is stretching and thinning of the crust's plates, such as in the East African Rift , the Wells Gray-Clearwater volcanic field , and the Rio Grande rift in North America. Volcanism away from plate boundaries has been postulated to arise from upwelling diapirs from the core–mantle boundary , 3,000 kilometres (1,900 mi) deep within Earth. This results in hotspot volcanism , of which

2376-612: The Philippines, and Mount Vesuvius and Stromboli in Italy. Ash produced by the explosive eruption of stratovolcanoes has historically posed the greatest volcanic hazard to civilizations. The lavas of stratovolcanoes are higher in silica, and therefore much more viscous, than lavas from shield volcanoes. High-silica lavas also tend to contain more dissolved gas. The combination is deadly, promoting explosive eruptions that produce great quantities of ash, as well as pyroclastic surges like

2448-418: The Steineberger Ley. Since this lay right near the historical ringwall on the “Ley”, closure of the quarry was already being considered in the 1950s. It eventually met just this fate in 1967, and beginning in 1976, the quarry became a wetland . In 1983, the Steineberger Ley was officially declared a natural monument, thereby ensuring protection. Today, the overwhelming majority of Steineberg inhabitants work in

2520-609: The USGS defines a volcano as active whenever subterranean indicators, such as earthquake swarms , ground inflation, or unusually high levels of carbon dioxide or sulfur dioxide are present. The USGS defines a dormant volcano as any volcano that is not showing any signs of unrest such as earthquake swarms, ground swelling, or excessive noxious gas emissions, but which shows signs that it could yet become active again. Many dormant volcanoes have not erupted for thousands of years, but have still shown signs that they may be likely to erupt again in

2592-466: The ages of climatic changes such as transitions from glacial to interglacial states during the Pleistocene . There is thought that future eruptions may occur in the Eifel, as: In 2020, Professor Kreemer noted that Eifel was the only region within an area of Europe studied where ground motion happened at significantly higher levels than expected. It is possible that such movements originate from

2664-503: The boundary with the Yukon Territory . Mud volcanoes (mud domes) are formations created by geo-excreted liquids and gases, although several processes may cause such activity. The largest structures are 10 kilometres in diameter and reach 700 meters high. The material that is expelled in a volcanic eruption can be classified into three types: The concentrations of different volcanic gases can vary considerably from one volcano to

2736-402: The case of Lassen Peak . Like stratovolcanoes, they can produce violent, explosive eruptions, but the lava generally does not flow far from the originating vent. Cryptodomes are formed when viscous lava is forced upward causing the surface to bulge. The 1980 eruption of Mount St. Helens was an example; lava beneath the surface of the mountain created an upward bulge, which later collapsed down

2808-772: The enormous area they cover, and subsequent concealment under vegetation and glacial deposits, supervolcanoes can be difficult to identify in the geologic record without careful geologic mapping . Known examples include Yellowstone Caldera in Yellowstone National Park and Valles Caldera in New Mexico (both western United States); Lake Taupō in New Zealand; Lake Toba in Sumatra , Indonesia; and Ngorongoro Crater in Tanzania. Volcanoes that, though large, are not large enough to be called supervolcanoes, may also form calderas in

2880-431: The flow is covered with angular, vesicle-poor blocks. Rhyolitic flows typically consist largely of obsidian . Tephra is made when magma inside the volcano is blown apart by the rapid expansion of hot volcanic gases. Magma commonly explodes as the gas dissolved in it comes out of solution as the pressure decreases when it flows to the surface . These violent explosions produce particles of material that can then fly from

2952-592: The formation of a submarine volcano off the coast of Mayotte . Subglacial volcanoes develop underneath ice caps . They are made up of lava plateaus capping extensive pillow lavas and palagonite . These volcanoes are also called table mountains, tuyas , or (in Iceland) mobergs. Very good examples of this type of volcano can be seen in Iceland and in British Columbia . The origin of the term comes from Tuya Butte , which

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3024-568: The future. In an article justifying the re-classification of Alaska's Mount Edgecumbe volcano from "dormant" to "active", volcanologists at the Alaska Volcano Observatory pointed out that the term "dormant" in reference to volcanoes has been deprecated over the past few decades and that "[t]he term "dormant volcano" is so little used and undefined in modern volcanology that the Encyclopedia of Volcanoes (2000) does not contain it in

3096-461: The glossaries or index", however the USGS still widely employs the term. Previously a volcano was often considered to be extinct if there were no written records of its activity. Such a generalization is inconsistent with observation and deeper study, as has occurred recently with the unexpected eruption of the Chaitén volcano in 2008. Modern volcanic activity monitoring techniques, and improvements in

3168-492: The interior of a continent and lead to rifting. Early stages of rifting are characterized by flood basalts and may progress to the point where a tectonic plate is completely split. A divergent plate boundary then develops between the two halves of the split plate. However, rifting often fails to completely split the continental lithosphere (such as in an aulacogen ), and failed rifts are characterized by volcanoes that erupt unusual alkali lava or carbonatites . Examples include

3240-509: The local people as a refuge castle. The stones symbolize this place. They and the mountain are also the origin of the municipality's name ( Steine = stones; Berg = mountain). The sword on the dexter (armsbearer's right, viewer's left) side is meant to stand for the so-called Schwedenschlacht (“Swede Battle”) in the Thirty Years' War , which was supposedly fought near the Steineberger Ley. In this battle, many peasants are said to have died by

3312-435: The low mountain range as rival lords squared off against each other. From late Celtic (1st century BC) and late Roman times (4th century AD) come various finds that have, however, still yielded no conclusions as to the reasons why these peoples frequented the mountain. At its southern foot spreads an early Celtic burying ground with barrows (6th to 3rd centuries BC). Of the roughly 90 barrows, many of which were excavated in

3384-419: The mid-oceanic ridge is above sea level, volcanic islands are formed, such as Iceland . Subduction zones are places where two plates, usually an oceanic plate and a continental plate, collide. The oceanic plate subducts (dives beneath the continental plate), forming a deep ocean trench just offshore. In a process called flux melting , water released from the subducting plate lowers the melting temperature of

3456-545: The modelling of the factors that produce eruptions, have helped the understanding of why volcanoes may remain dormant for a long time, and then become unexpectedly active again. The potential for eruptions, and their style, depend mainly upon the state of the magma storage system under the volcano, the eruption trigger mechanism and its timescale. For example, the Yellowstone volcano has a repose/recharge period of around 700,000 years, and Toba of around 380,000 years. Vesuvius

3528-415: The most dangerous type, are very rare; four are known from the last million years , and about 60 historical VEI 8 eruptions have been identified in the geologic record over millions of years. A supervolcano can produce devastation on a continental scale, and severely cool global temperatures for many years after the eruption due to the huge volumes of sulfur and ash released into the atmosphere. Because of

3600-438: The mud volcano is actually a vent of an igneous volcano. Volcanic fissure vents are flat, linear fractures through which lava emerges. Shield volcanoes, so named for their broad, shield-like profiles, are formed by the eruption of low-viscosity lava that can flow a great distance from a vent. They generally do not explode catastrophically but are characterized by relatively gentle effusive eruptions . Since low-viscosity magma

3672-594: The municipality's southern limit. The nearest railway station is in Gerolstein , more than 20 km away. Steineberg can be reached by bus on route 503 from Daun . Steineberg (Westerwald) is also the name of a constituent community of Malberg in the Westerwald . Vulkan Eifel The Volcanic Eifel or Vulkan Eifel ( German : Vulkaneifel ), also known as the East Eifel Volcanic Field ( EEVF ),

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3744-452: The next. Water vapour is typically the most abundant volcanic gas, followed by carbon dioxide and sulfur dioxide . Other principal volcanic gases include hydrogen sulfide , hydrogen chloride , and hydrogen fluoride . A large number of minor and trace gases are also found in volcanic emissions, for example hydrogen , carbon monoxide , halocarbons , organic compounds, and volatile metal chlorides. The form and style of an eruption of

3816-544: The north on the municipality of Steiningen , in the east on the municipality of Demerath , in the south on the municipality of Ellscheid and in the west on the municipality of Mehren . In prehistoric times, the Celts built a stone refuge castle on the Steineberger Ley. In the Middle Ages , Steineberg belonged to the Electorate of Trier as part of the Amt of Daun. Until 1967, many workers from Steineberg worked at

3888-867: The north side of the mountain. Cinder cones result from eruptions of mostly small pieces of scoria and pyroclastics (both resemble cinders, hence the name of this volcano type) that build up around the vent. These can be relatively short-lived eruptions that produce a cone-shaped hill perhaps 30 to 400 metres (100 to 1,300 ft) high. Most cinder cones erupt only once and some may be found in monogenetic volcanic fields that may include other features that form when magma comes into contact with water such as maar explosion craters and tuff rings . Cinder cones may form as flank vents on larger volcanoes, or occur on their own. Parícutin in Mexico and Sunset Crater in Arizona are examples of cinder cones. In New Mexico , Caja del Rio

3960-541: The ocean surface as new islands or floating pumice rafts . In May and June 2018, a multitude of seismic signals were detected by earthquake monitoring agencies all over the world. They took the form of unusual humming sounds, and some of the signals detected in November of that year had a duration of up to 20 minutes. An oceanographic research campaign in May 2019 showed that the previously mysterious humming noises were caused by

4032-420: The ocean surface, due to the rapid cooling effect and increased buoyancy in water (as compared to air), which often causes volcanic vents to form steep pillars on the ocean floor. Hydrothermal vents are common near these volcanoes, and some support peculiar ecosystems based on chemotrophs feeding on dissolved minerals. Over time, the formations created by submarine volcanoes may become so large that they break

4104-471: The ocean's surface. In the deep ocean basins, the tremendous weight of the water prevents the explosive release of steam and gases; however, submarine eruptions can be detected by hydrophones and by the discoloration of water because of volcanic gases . Pillow lava is a common eruptive product of submarine volcanoes and is characterized by thick sequences of discontinuous pillow-shaped masses which form underwater. Even large submarine eruptions may not disturb

4176-462: The one that destroyed the city of Saint-Pierre in Martinique in 1902. They are also steeper than shield volcanoes, with slopes of 30–35° compared to slopes of generally 5–10°, and their loose tephra are material for dangerous lahars . Large pieces of tephra are called volcanic bombs . Big bombs can measure more than 1.2 metres (4 ft) across and weigh several tons. A supervolcano is defined as

4248-425: The overlying mantle wedge, thus creating magma . This magma tends to be extremely viscous because of its high silica content, so it often does not reach the surface but cools and solidifies at depth . When it does reach the surface, however, a volcano is formed. Thus subduction zones are bordered by chains of volcanoes called volcanic arcs . Typical examples are the volcanoes in the Pacific Ring of Fire , such as

4320-595: The plume, and new volcanoes are created where the plate advances over the plume. The Hawaiian Islands are thought to have been formed in such a manner, as has the Snake River Plain , with the Yellowstone Caldera being part of the North American plate currently above the Yellowstone hotspot . However, the mantle plume hypothesis has been questioned. Sustained upwelling of hot mantle rock can develop under

4392-435: The same time interval. Volcanoes vary greatly in their level of activity, with individual volcanic systems having an eruption recurrence ranging from several times a year to once in tens of thousands of years. Volcanoes are informally described as erupting , active , dormant , or extinct , but the definitions of these terms are not entirely uniform among volcanologists. The level of activity of most volcanoes falls upon

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4464-485: The same way; they are often described as "caldera volcanoes". Submarine volcanoes are common features of the ocean floor. Volcanic activity during the Holocene Epoch has been documented at only 119 submarine volcanoes, but there may be more than one million geologically young submarine volcanoes on the ocean floor. In shallow water, active volcanoes disclose their presence by blasting steam and rocky debris high above

4536-568: The service and industrial sectors throughout the Eifel , mainly in Daun , Wittlich or Cochem . Long commutes to work and shopping are an everyday reality here. Steineberg lies right near the Autobahnen A ;1 and A 48 , southeast of the Vulkaneifel Autobahn junction. The nearest Autobahn interchange , Daun-Mehren, is only a few kilometres away. Bundesstraße 421 passes by

4608-622: The solidified erupted material that makes up the mantle of a volcano may be stripped away that its inner anatomy becomes apparent. Using the metaphor of biological anatomy , such a process is called "dissection". Cinder Hill , a feature of Mount Bird on Ross Island , Antarctica , is a prominent example of a dissected volcano. Volcanoes that were, on a geological timescale, recently active, such as for example Mount Kaimon in southern Kyūshū , Japan , tend to be undissected. Eruption styles are broadly divided into magmatic, phreatomagmatic, and phreatic eruptions. The intensity of explosive volcanism

4680-406: The surrounding areas, and initially not seismically monitored before its unanticipated and catastrophic eruption of 1991. Two other examples of volcanoes that were once thought to be extinct, before springing back into eruptive activity were the long-dormant Soufrière Hills volcano on the island of Montserrat , thought to be extinct until activity resumed in 1995 (turning its capital Plymouth into

4752-426: The sword. The dove on the sinister (armsbearer's left, viewer's right) side symbolizes Saint Francis of Assisi , the municipality's patron saint, for it is one of his attributes. The tincture vert (green) seen in the pile transposed stands for the village's scenically charming surroundings. The tinctures gules and argent (red and silver) stand for Steineberg's former allegiance to the Electorate of Trier as part of

4824-434: The theory of plate tectonics. For example, some volcanoes are polygenetic with more than one period of activity during their history; other volcanoes that become extinct after erupting exactly once are monogenetic (meaning "one life") and such volcanoes are often grouped together in a geographical region. At the mid-ocean ridges , two tectonic plates diverge from one another as hot mantle rock creeps upwards beneath

4896-444: The thinned oceanic crust . The decrease of pressure in the rising mantle rock leads to adiabatic expansion and the partial melting of the rock, causing volcanism and creating new oceanic crust. Most divergent plate boundaries are at the bottom of the oceans, and so most volcanic activity on Earth is submarine, forming new seafloor . Black smokers (also known as deep sea vents) are evidence of this kind of volcanic activity. Where

4968-431: The underlying ductile mantle , and most volcanic activity on Earth takes place along plate boundaries, where plates are converging (and lithosphere is being destroyed) or are diverging (and new lithosphere is being created). During the development of geological theory, certain concepts that allowed the grouping of volcanoes in time, place, structure and composition have developed that ultimately have had to be explained in

5040-492: The volcano. Solid particles smaller than 2 mm in diameter ( sand-sized or smaller) are called volcanic ash. Tephra and other volcaniclastics (shattered volcanic material) make up more of the volume of many volcanoes than do lava flows. Volcaniclastics may have contributed as much as a third of all sedimentation in the geologic record. The production of large volumes of tephra is characteristic of explosive volcanism. Through natural processes, mainly erosion , so much of

5112-424: The volcanoes of the East African Rift . A volcano needs a reservoir of molten magma (e.g. a magma chamber), a conduit to allow magma to rise through the crust, and a vent to allow the magma to escape above the surface as lava. The erupted volcanic material (lava and tephra) that is deposited around the vent is known as a volcanic edifice , typically a volcanic cone or mountain. The most common perception of

5184-421: Was described by Roman writers as having been covered with gardens and vineyards before its unexpected eruption of 79 CE , which destroyed the towns of Herculaneum and Pompeii . Accordingly, it can sometimes be difficult to distinguish between an extinct volcano and a dormant (inactive) one. Long volcano dormancy is known to decrease awareness. Pinatubo was an inconspicuous volcano, unknown to most people in

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