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100-552: Philippsthal lies between the outliers of the Rhön and the Thuringian Forest (ranges) on the river Werra . The river Ulster empties into the Werra between the main centre and the outlying centre of Röhrigshof. The nearest major towns are Bad Hersfeld (some 25 km; 15 miles to the west) and Eisenach (some 29 km; 18 miles to the northeast). Philippsthal borders in the north on

200-476: 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

300-663: A border adjustment that put the whole property in West Germany. The municipal election held on 26 March 2006 yielded the following results: The community's executive ( Gemeindevorstand ) is made up of ten members, with four seats allotted to the SPD, two to the CDU and four to the FWG. The mayoral election on 16 September 2007 brought Ralf Orth (SPD) into office with 55.1% of the vote. Since 1 January 2008 he has been Hartwig Klotzbach's (FWG) successor after

400-437: 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,

500-526: A new greater community of Philippsthal (Werra) within the framework of municipal reform on 1 August 1972. The title "market community" ( Marktgemeinde ) was granted the community on 30 May 2001. In 1191, Philippsthal had its first documentary mention in a Schutzbrief ("protection letter") from Pope Celestine III to the Hersfeld Abbey . In this year, the Abbey founded a Benedictine convent and named it after

600-536: A palatial residence built in 1685, which he named Schloss Philippsthal . By the late 18th century, this had become the local placename. After mining began at the Hattorf potash works in 1905, the craft and weaving village became an industrial community. During the time of Germany's division, the former Hoßfeld printing shop building earned some fame as the border between East Germany and West Germany ran straight through it. Only in 1976 did East and West Germany agree to

700-443: 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

800-506: A rich cultural landscape. Compared with other low mountain regions, the Rhön is particularly rich in plant varieties. Its natural vegetation would probably be dominated by beech woods with scattered groups of other trees, but today beech trees are very much in decline. A few of these ancient woods were identified as core elements of the Rhön biosphere reserve. The higher beech woods are a habitat for rare, sometimes isolated, species of plant such as

900-632: 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

1000-555: 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

1100-465: 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

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1200-727: 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

1300-412: 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

1400-554: 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

1500-567: 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

1600-555: Is often thought to derive from the Celtic word raino (=hilly), but numerous other interpretations are also possible. Records of the monks at Fulda Abbey from the Middle Ages describe the area around Fulda as well as more distant parts of the Rhön as Buchonia , the land of ancient beech woods. In the Middle Ages beech was an important raw material. Large scale wood clearing resulted in

1700-524: 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

1800-536: Is the alpine shrew . Birds occurring here include the black grouse , the capercaillie , the black stork , the eagle owl , the corncrake , the red-backed shrike and the wryneck . There are also two species endemic to the Rhön: the rove beetle and a local snail, the Rhönquellschnecke ( Bythinella compressa ). The Dachmarke Rhön project (Rhön umbrella brand project) is run by the Rhön working group and its aim

1900-458: Is to promote a common identity for the Rhön region and to present a unified view of the area to the outside world and to harmonise the marketing measures of the three participating federal states. These mountains are a popular tourist destination. Hikers come for the nearly 6,000 km (3,700 mi) of trails, and gliding enthusiasts have been drawn to the area since the early 20th century. More recently, farm holidays have been flourishing in

2000-466: 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

2100-502: The Alpine blue-sow-thistle , giant bellflower and annual honesty . The vegetation of the lower-lying beech woods has a mix of mountain and other varieties. In addition to common wildflowers like the martagon lily , lily of the valley , wild chervil and wild garlic , various orchids also flourish here including Cephalanthera orchids, the yellow coralroot , bird's-nest orchid , lady's slipper and lady orchid . Only small areas of

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2200-774: The Brend valley near Bischofsheim forms the boundary with another mountain group of the High Rhön, the Kreuzberg Group, which contains the Arnsberg (843.1 m (2,766 ft)) and the Kreuzberg (927.8 m (3,044 ft)). In between these two mountains lies the source of the Sinn . This river, which forms a wide and deep valley head flanked by the Dammersfeld ridge, flows to the southwest. On

2300-600: 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

2400-571: The Dammersfeldkuppe (927.9 m (3,044 ft)), the ridge being clearly narrower than the Long Rhön and its basalt layer being interrupted several times. The Großer (808.6 m (2,653 ft)) and Kleiner Auersberg (about 808 m (2,651 ft)), separated by the valley of the Schmale Sinn , are also part of this natural region. South of Heidelstein and Hoher Hölle the narrow head of

2500-608: The Gangolfsberg (735.8 m (2,414 ft)) and the Rother Kuppe (710.6 m (2,331 ft)). This landscape bears a clear resemblance to the Kuppen Rhön. The Wildflecken Training Area , which covers an area of 74 km (28.6 sq mi), equivalent to almost a quarter of the High Rhön, is not accessible to the public. The 1,200 square kilometres (460 sq mi) of the "Kuppen Rhön in its narrow sense", to which

2600-843: The Handbook of the Natural Region Divisions of Germany into the following natural regions : The High Rhön ( German : Hohe Rhön or Hochrhön ) is that part of the central Rhön that lies in Hesse , Bavaria , and to a lesser extent in Thuringia ; it covers an area of 344 km (132.8 sq mi) Landscape fact files by the BfN (c.f. section on Natural region division ) and is up to 950.0 m (3,117 ft) and whose highland plateaux with elevations starting at 600 to 700 m (1,969 to 2,297 ft) are covered by solid basalt . Its core area in

2700-618: 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,

2800-712: The Hessian Skittles , a striking regular array of high, gently rounded, basalt cones up to 552.9 m (1,814 ft). North and south of the skittles most of the kuppen in this natural region are also arranged in a row along the watershed between the Werra and the Fulda and between the Ulster and the Haune respectively. To the west they do not quite reach the Haune at the Haune Plateaux ; to

2900-672: The Hochrhön for the protection of its farmers. The Rhön was also home to the Christian Community known as the Bruderhof from 1926 to 1937 when it was dissolved by Nazi persecution . In 1991 UNESCO declared parts of the Rhön a Biosphere Reserve on account of its unique high-altitude ecosystem. As a result of its geography and geology the Rhön is an area with higher-than-average number of different habitats and species . But man, too, has generated valuable secondary habitats by creating

3000-824: 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

3100-460: The "Anterior Rhön", as viewed from Thuringia, forms the foothills (or anterior part) of the mountain region. In this gently rolling landscape numerous individual dome-shaped mountains rise on both sides of the border of Hesse and Thuringia and also, in some places, in Bavaria. These Kuppen are the remnants of ancient volcanos or volcanic activity. The Rhön and its immediate declivities are divided by

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3200-600: The "land of open spaces" ( Land der offenen Fernen ), 30% of which, today, is forested. Lying within the states of Hesse, Bavaria and Thuringia, the Rhön is bounded by the Knüll to the northwest, the Thuringian Forest to the northeast, the Grabfeld to the southeast, Lower Franconia to the south, the Spessart forest to the southwest and the Vogelsberg mountains to the west. Based on

3300-559: The Anterior Rhön also belongs, is the wide outer fringe of markedly different relief, that circles around the High Rhön from the northeast (in Thuringia ) through the northwest (in Hesse ) to the southwest (with small parts in Bavaria ). Numerous dome-shaped isolated mountains and hills rise above the valleys to 500–800 metres (1,640–2,625 ft), whose basalt covering is concentrated around

3400-802: The Feuerberg, Kreuzberg ( monastery ), Oberweißenbrunn, through the Red and Black Moors , over the Ellenbogen and the Emberg via Oberalba, past Baier to Stadtlengsfeld and on to its destination at Bad Salzungen on the Werra River. Other hiking trails are: In addition the following pass through the Rhön: 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

3500-707: The Fulda, is not reached in other parts of the region. To the southwest the area is bounded by the rocky sandstone of the Hoher Kammer (700.0 m (2,297 ft)), as it descends from the heights of the Dammersfeld ridge (up to 927.9 m (3,044 ft)). Separated from the Kammer by the upper reaches of the Döllbach , the Döllau , the Große Haube (658.1 m (2,159 ft)) on

3600-843: 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

3700-612: 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

3800-690: The Rhine-Weser watershed opens the Brückenau Kuppenrhön, whose western half is in Hesse and whose eastern half is in Bavaria. The valleys of the Schmaler and Breiter Sinn running southwestwards, divide the natural region, which is clearly more heterogenous than the other ranges of the Kuppen Rhön, into three segments. In the west, the rugged plateaux of dolerite and basalt transition into the Landrücken , whilst

3900-645: The Rhön Mountains or flow by or through them (length given in brackets) : The name Rhön is believed to be of Celtic origin. A regional Celtic presence is well established, with an important Celtic town at Milseburg . Furthermore, there are circular embankments that could be both of Celtic and of Germanic origin in the Kuppenrhön on the Stallberg and the Kleinberg mountains. Many names of places, mountains and meadows in

4000-597: The Rhön landscape are essentially open: the raised bogs ( Hochmoore ), the rock outcrops and the stone runs . These habitats are home to highly specialised species. The raised bogs of the Long Rhön - the Red Moor ( Rotes Moor ) and the Black Moor ( Schwarzes Moor ) are floristically important links between the northern and Alpine raised bogs. Here, for example, can be found sundews , crowberry and cottongrass . Growing amongst

4100-407: The Rhön likely have their origins in Celtic root words. Up to the 10th century parts of the Rhön belonged to Altgau Buchonia . This term was coined by the Romans in Late Antiquity and described an ancient beech forest in the Rhön and the neighbouring low mountain ranges of the Spessart and Vogelsberg . Expansive stands of beech still exist today in the area. Due to the far reaching view from

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4200-400: The Rhön mountains, they became sites for hilltop castles in the Middle Ages . One example is Hauneck Castle ( Burg Hauneck ) on the Stoppelsberg , the ruins of which can still be seen. It served to oversee and protect traffic on the ancient road, the Antsanvia , as well as protecting the villages in the Haune valley. In the Middle Ages the Würzburg Defences ( landwehr ) were erected on

4300-416: The Rhön's highest summit, the Wasserkuppe (950.0 m (3,117 ft)), whose basalt likewise covers a wide area, but is broken in places by bunter sandstone and muschelkalk – in particular the basalt kuppen of the Weiherberg (785.7 m (2,578 ft), northwest) and Ehrenberg (816.5 m (2,679 ft) northeast) are slightly separated from the rest. Between the northeastern end of

4400-562: 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

4500-491: The Wasserkuppen Rhön at the Ehrenberg and the plateau of the Long Rhön from the Heidelstein to just beyond the Stirnberg is the Upper Ulster valley , which cuts into the bunter sandstone by up to about 300 m (984 ft) and divides the Plattenrhön in two. The Long Rhön runs southwest along the main watershed to the Dammersfeld ridge which continues along the watershed via the Hohe Hölle (893.8 m (2,932 ft)) and Eierhauckberg (909.9 m (2,985 ft)) to

4600-451: The aforementioned ridges is the eastern slope of the Long Rhön , which forms the transition zone from the High Rhön to the muschelkalk region of the Mellrichstadt Gäu ( Mellrichstädter Gäu ), the eastern part of the Werra Gäu Plateaux . Individual domes rise from the descending Triassic beds east of the solid basalt covering of the Long Rhön in the interfluvials of the tributaries of the Franconian Saale between Brend and Streu , notably

4700-402: The basalt and phonolite cones sit directly on the sandstones of the Middle Bunter. Cutting deeply into the sandstone, the rivers of the Haune and the Fulda flow westwards. The phonolitic cone of the Milseburg (835.2 m (2,740 ft)) is the only mountain in the Kuppen Rhön that exceeds the 800-metre-mark. Even the height of the Großer Nallenberg (768.3 m (2,521 ft)) south of

4800-446: 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

4900-402: 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

5000-446: The centuries also has a great variety of habitats and plants however, today, the extensive grassland areas are amongst the most threatened and heavily cultivated habitats. It is on the semi-arid grasslands and juniper heaths that the silver thistle , symbol of the Rhön region, grows, alongside gentians , pasque flowers and wood anemones , as well as orchids like the early purple , fragrant and fly orchids . Rarer flowers include

5100-464: The effects of ancient volcanic activity, the Rhön can be divided into the "Anterior Rhön" ( Vorderrhön ), the "Kuppen Rhön" (geographical region 353, Kuppenrhön ) and the "High Rhön" (354, Hohe Rhön ). The terms "Anterior Rhön" ( Vorderrhön ) and "Kuppen Rhön" ( Kuppenrhön or Kuppige Rhön ) are somewhat misleading, since the "Anterior Rhön" also consists mainly of Kuppen or low mountains with dome-shaped summits. The name has genuine historic origins:

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5200-553: 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

5300-416: The extreme southeast end of the East Hesse Highlands ( Osthessisches Bergland ), are partly a result of ancient volcanic activity. They are separated from the Vogelsberg Mountains by the river Fulda and its valley. The highest mountain in the Rhön is the Wasserkuppe (950.2 metres or 3,117 feet), which is in Hesse . The Rhön Mountains are a popular tourist destination and walking area. The name Rhön

5400-431: 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

5500-434: 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

5600-445: 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

5700-412: 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

5800-416: The higher slopes. Characteristic plants here include the monkshood , northern wolfsbane , common moonwort , martagon lily , greater butterfly orchid , perennial cornflower and wig knapweed . Bog-bean , grass of Parnassus ' western marsh orchid and lousewort are found in the wet meadows and low marshes; and the extremely rare large brown clover , hairy stonecrop and Pyrenean scurvygrass in

5900-492: 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

6000-403: The last two rocks only surviving where they have been protected by an overlying sheet of basalt . Woods cover less than a third of the area and are largely restricted to the summit regions. Five natural regions may be distinguished: The eastern part of the Kuppen Rhön is the Thuringian Anterior Rhön , which reaches a height of 750.7 m (2,463 ft) at the huge plateau of the Gebaberg in

6100-426: The latter had held the office since 2001. In 2019 Timo Heusner (SPD) was elected mayor. The community's arms might be described thus: Gules a mount of three argent, issuant therefrom a cross of Lorraine pattée of the second, upon the mound an inescutcheon azure a lion rampant barry of nine argent and gules armed and crowned Or. The "double cross" recalls the convent in the community and the Hersfeld Abbey , which

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6200-412: The living knightly family von Cruceburg, after whom the growing community of Kreuzberg was then also named. The convent was destroyed in the German Peasants' War in 1525 and forsaken by the nuns in 1568. All that is still preserved is the former convent church from the 12th century. On the spot where the convent stood, Landgrave Philipp of Hesse-Philippsthal (b. 14 December 1655, d. 18 June 1721) had

6300-430: The main high point on the plateau of the Long Rhön, which runs northeast over the Stirnberg (901.9 m (2,959 ft)) as far as the Ellenbogen (Schnitzersberg) (815.5 m (2,676 ft)) without crossing any significant lower ground. Within the Long Rhön the basalt layer is almost unbroken. At the Heidelstein, another natural region, the Wasserkuppen Rhön , branches off in a north to northwesterly direction to

6400-419: 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

6500-492: 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

6600-415: 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

6700-438: 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

6800-452: 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

6900-769: 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

7000-448: The northeast of the Kleiner Auersberg (c. 808 m (2,651 ft)) leads up to the Dammersfeld ridge. Between the more rugged plateaux and ridges there are gently domed basalt intrusions that rise up, especially in the southeast, left of the Sinn near Bad Brückenau . The Dreistelzberg in the extreme south reaches 660.4 m (2,167 ft). The most well-known peaks in the Rhön Mountains include: The following rivers rise in

7100-417: The northeast used to be called the Plattenrhön . The High Rhön is a natural regional major unit in the East Hesse Highlands; see Natural regions . The High Rhön has five main mountainous regions: At the heart of the Rhön, albeit only the fourth highest summit of these mountains, is the Heidelstein (925.7 m (3,037 ft)) on the border between Bavaria and Hesse on the Rhine-Weser watershed. It forms

7200-541: 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

7300-420: 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

7400-471: 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

7500-462: 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

7600-660: The other side of the Sinn valley, and southwest of the Kreuzberg Group, are the Black Mountains ( German : Schwarze Berge ), which include the Schwarzenberg (Feuerberg, 832.0 m (2,730 ft)) and Totnansberg (839.4 m (2,754 ft)). They are separated from the Kreuzberg Group by the narrow valley of the Premich 's upper reaches, the Kellersbach . Clearly different from

7700-425: 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

7800-648: 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

7900-587: The region, the prominent kuppe of the Baier reaches a height of 713.9 m (2,342 ft), but its northernmost summit is the popular viewing mountain of Oechsen . The western boundary is the Middle Ulster Valley between Hilders in the south and below Buttlar in the north. West of the Ulster valley is the Soisberg Kuppenrhön ( Soisberger Kuppenrhön ), which lies mainly in Hesse, with elements in

8000-586: The region. Towns and larger villages close to the Rhön are: There are well-marked walks and hiking trails in the Rhön which are looked after by the Rhön Club . The Rhön-Höhen-Weg ("Rhön Heights Walk" or RHW) is marked with a horizontal, red teardrop. It is 137 km (85 mi) long and runs from Burgsinn in Main-Spessart district through Roßbach, Dreistelz, Würzburger Haus on the Farnsberg, Kissinger Hütte on

8100-415: The rocks of the volcanic mountains are rare species such as Cheddar pink , sweet william catchfly , oblong woodsia and fir clubmoss . There are no naturally occurring coniferous forests in the Rhön, but notable species of wild flower such as the lady's slipper orchid , creeping lady's tresses and burning-bush are found in the forests of mixed pine. The cultural landscape formed by humankind over

8200-435: 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

8300-485: 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

8400-622: 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

8500-624: The south and below Dermbach in the north. West of the Felda valley is the Auersberg Kuppenrhön ( Auersberger Kuppenrhön ), which lies mainly in Thuringia, but extends into Hesse in the southwest. This natural region runs from the town of Auersberg in the south, which gives the region its name, to the boundary with the Long Rhön at the Ellenbogen , 756.8 m (2,483 ft). In the northeast of

8600-636: The south the Nüst valley below Obernüst forms a natural boundary. The almost entirely Hessian range of the Milseburg Kuppenrhön ( Milseburger Kuppenrhön ), which bounds the Wasserkuppen Rhön , up to 950.0 m (3,117 ft), south of the Nüst valley and west of the Ulster valley. Again the keuper escarpment is missing and even the muschelkalk only appears in islands around individual domes. The majority of

8700-621: The southeast also extending into Thuringia. This region reaches a height of 629.9 m (2,067 ft) at the Soisberg in the north where the countryside is enclosed by the Seulingswald forest. It reaches even greater elevations in the extreme southeast, where the Habelberg (718.5 m (2,357 ft)) west of Tann stands opposite to and north of the Auersberg. This natural region is well known for

8800-646: The southeast. There is hardly any keuper escarpment there at all. The kuppen and plateaux rest directly on a bedrock of muschelkalk. This natural region runs northeast from the wide, pyramidal Pleß , 645.4 m (2,117 ft), far into the Bunter sandstone of the Stadlengsfeld Hills that descend to the River Werra . In the west the Middle Felda Valley forms a natural boundary between Kaltensundheim in

8900-454: The springwater marshes of the Hohe Rhön . The wildlife in the Rhön mountains is similar to that of other low mountain ranges, but there are also some unusual species. In addition to the more common mammals such as roe deer , fox , badger , hare and wild boar , there are also smaller mammals such as the dormouse , common water shrew and Miller's water shrew . One unusual regional species

9000-423: The summit regions and does not blanket the entire landscape, as it does in the High Rhön. The domes or kuppen are the stumps of heavily weathered former volcanoes or volcanic pipes . Between pointed cones and broad domes lie many small plateaux, especially common in the Anterior Rhön. Over a foundation of Middle Bunter sandstone lie stratigraphic sequences of Upper Bunter ( Röt ), muschelkalk and keuper ,

9100-406: 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

9200-434: 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

9300-444: 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

9400-593: The town of Heringen (in Hersfeld-Rotenburg), in the east on the town of Vacha , in the south on the communities of Unterbreizbach (both in the Wartburgkreis in Thuringia) and Hohenroda and in the west on the community of Friedewald (both in Hersfeld-Rotenburg). The community's Ortsteile are Gethsemane, Harnrode, Heimboldshausen, Philippsthal, Röhrigshof and Unterneurode. All these places were merged into

9500-431: 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

9600-444: The various bee orchids and the military , lady , burnt , green-winged , man , pyramidal , frog and lizard orchids . Along the southern fringes of the Rhön, on the so-called slopes of steppe heathland ( Steppenheidenhängen ) grow warmth-loving plants such as white rock-rose , erect clematis and honewort . Amongst the most valuable habitats in the Rhön are the mountain meadows and fields of mat grass ( Nardetum strictae ) on

9700-492: 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

9800-424: 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

9900-544: Was a definite factor in earlier centuries. The striped lion (Hesse's heraldic beast) stands for the Landgraves of Hesse-Kassel , into whose ownership the community came in the 16th century. Rh%C3%B6n Mountains The Rhön Mountains ( German: [ˈʁøːn] ) are a group of low mountains (or Mittelgebirge ) in central Germany , located around the border area where the states of Hesse , Bavaria and Thuringia come together. These mountains, which are at

10000-421: 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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