Misplaced Pages

#385614

69-531: The river source is in the Odenwald , in the town of Grasellenbach . It then flows in a westerly direction through a number of communities, including Fürth , Rimbach , Mörlenbach and Birkenau . At Weinheim , the river splits into two branches as it enters the Upper Rhine Plain . The two courses join at Lorsch . It then flows through the communities of Einhausen and Biblis before emptying into

138-886: A mid-ocean ridge , such as the Mid-Atlantic Ridge , has volcanoes caused by divergent tectonic plates whereas the Pacific Ring of Fire has volcanoes caused by convergent tectonic plates. Volcanoes can also form where there is stretching and thinning of the crust's plates, such as in the East African Rift , 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

207-437: 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,

276-443: 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

345-632: 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

414-555: 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

483-465: 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

552-739: 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

621-412: 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

690-489: Is connected with monsters (knight Georg fights against the man-eating lindworm near Frankenstein-castle ) and creatures of nature with magic potency (a water spirit changed into a fox near Niedernhausen, the merwoman in the Meerwiese of Waldürn). Secondly the local legend is connected with the genre of the historic saga: a historic person or an original is portrayed anecdotally (the count of Erbach and Luther, resp.

759-565: 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

SECTION 10

#1732772306386

828-584: 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

897-558: Is known as a leisure destination easily accessible from the urban areas of Mannheim and Frankfurt . It is known for its clean thin air and was once known for its health sanitariums. There are many marked hiking paths through the rural areas. Wild blueberries , strawberries and mushrooms are to be found in the forests. The planned extension to the Odenwaldautobahn , that is, the A ;45 ( Dortmund – Aschaffenburg ),

966-957: Is located between the Upper Rhine Plain with the Bergstraße and the Hessisches Ried (the northeastern section of the Rhine rift) to the west, the Main and the Bauland (a mostly unwooded area with good soils) to the east, the Hanau-Seligenstadt Basin – a subbasin of the Upper Rhine Rift Valley in the Rhine-Main Lowlands – to the north and the Kraichgau to the south. The part south of

1035-537: 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

1104-471: 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

1173-552: The Raubacher Joggel , landgrave Ludwig VIII: of Hesse-Darmstadt, robber Hölzerlips ). Thirdly a local tale explains an etiological or original myth (aetiological saga). For example, there is explained: Beside these legends there are two famous and well-known Odenwaldsagas: In the Nibelungenlied (see also Nibelung ) the dragon slayer Siegfried , on a hunting trip (instead of a failed campaign) leading from

1242-688: The Burgundian city of Worms into the Odenwald, is murdered by Hagen of Tronje . Since no exact spot for this deed has been handed down, countless communities, especially in the Hessian Odenwald are squabbling over the right to call themselves “Siegfried’s Murder Site”, for example a spring near Gras-Ellenbach ( Siegfriedsbrunnen ), Mossautal-Hüttenthal Lindelbrunnen ) or Heppenheim ( Siegfriedbrunnen ). The ruins of Rodenstein (below-mentioned) and Schnellerts near Fränkisch-Crumbach are

1311-617: 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

1380-784: The Main . Parts of the Odenwald now lay in Roman-ruled Germania Superior . About 159, the Limes was shifted about 30 kilometres (19 miles) eastwards to the Miltenberg – Walldürn – Buchen - Osterburken line. In 260, Roman hegemony fell. The Alamanni were also thrusting into the Odenwald and settling the land between the Main and Neckar, after whom came the Franks . In the 5th century, the Franks, under Clovis I , divided

1449-913: The Neckar valley is sometimes called the Kleiner Odenwald ("Little Odenwald"). The northern and western Odenwald belong to southern Hesse, with the south stretching into Baden . In the northeast, a small part lies in Lower Franconia in Bavaria. The Odenwald, along with other parts of the Central German Uplands, belongs to the Variscan , which more than 300 million years ago in the Carboniferous period ran through great parts of Europe . The cause of this orogeny

SECTION 20

#1732772306386

1518-697: The North Sea reached far inland, across the Wetterau Depression into the Rhine Valley. About 2500 BC, there is evidence that the Linear Pottery culture settled along the northern (Gersprenz) and southern (Neckar valley) edges of the Odenwald. About 400 BC, Celts (Gauls) settled throughout southern Germany. Almost all of the Odenwald was covered then with virgin forest , and the outer edges were not settled. Germanic peoples drove

1587-797: The Otzberg , the Daumberg and the Katzenbuckel, all extinct volcanoes in the Odenwald. Furthermore, volcanism with acidic rocks has left a legacy of rhyolites near Dossenheim . At roughly the same time, the Central European plate began to tear apart so that the Upper Rhine Rift developed. Even as the Upper Rhine Rift valley still sinks today by just under a millimetre each year, the Odenwald, relatively to that,

1656-804: The core–mantle boundary , 3,000 kilometres (1,900 mi) deep within Earth. This results in hotspot volcanism , of which 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,

1725-834: 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

1794-803: The Celts westwards across the Rhine to what is now France . About AD 100, the older Odenwald line of the Neckar-Odenwald Limes was built under Roman Emperor Trajan (98-117). This stretch of the Empire's border ran from Fort Wimpfen in the Valley ( Kastell Wimpfen im Tal ) northwards by way of the Forts of Neckarburken, the lesser forts of Trienz and Robern near Fahrenbach , Fort Oberscheidental, Fort Schloßau, Fort Hesselbach, Fort Würzberg, Fort Eulbach, Fort Hainhaus and Fort Hesselbach to Fort Wörth on

1863-747: The Mümling- and the Neckar-Valley. Songs have been written about the Odenwald: 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 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,

1932-622: 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

2001-708: The Rhine at the Biblis Nuclear Power Plant . This article related to a river in Baden-Württemberg is a stub . You can help Misplaced Pages by expanding it . This article related to a river in Hesse is a stub . You can help Misplaced Pages by expanding it . Odenwald The Odenwald ( German: [ˈoːdn̩valt] ) is a low mountain range in the German states of Hesse , Bavaria and Baden-Württemberg . The Odenwald

2070-613: 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

2139-510: 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

Weschnitz - Misplaced Pages Continue

2208-402: 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

2277-799: 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

2346-431: 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

2415-610: 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

2484-585: 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

2553-466: 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

2622-492: 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

2691-482: The job of opening the empty woods up by the central Frankish power ( Carolingian ), Lorsch Abbey from the west, Fulda Monastery from the east and Mosbach Monastery from the south. Amorbach Monastery had the greatest importance for ecclesiastical, cultural and economic development in the eastern Odenwald. In the 9th century in the southeastern Odenwald near the now more thickly settled Bauland, settlements were established. The muschelkalk-new red sandstone mineral boundary

2760-461: The land in the Odenwald was uplifted again about 180 million years ago, more than 100 m of the sedimentary layering, in parts, was eroded away down to the bedrock , as can still be seen in the western Odenwald. The bedrock here is composed of a number of different rocks, among them gneiss , granite , diorite , gabbro in the Frankenstein pluton , and so on. In the eastern Odenwald,

2829-434: The land up into districts. In the 7th and 8th centuries came Christianization by Irish - Scottish and Anglo-Saxon monks ( Pirmin , Boniface ). On the muschelkalk lands of today's Bauland, which favoured agriculture , a broad mesh of settlements arose. The parts of the Odenwald farther in from the rivers, though, with their scant New Red Sandstone soils remained uninhabited. Four Benedictine monasteries were assigned

Weschnitz - Misplaced Pages Continue

2898-419: 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

2967-551: 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

3036-415: 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

3105-438: 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

3174-452: 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

3243-876: 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

3312-549: 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

3381-420: 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

3450-471: 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

3519-468: 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

SECTION 50

#1732772306386

3588-425: 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

3657-619: 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

3726-402: The red sandstone is all that is left of the sedimentary mixture. Farther east in the Bauland, the muschelkalk deposits still overlie the Early Triassic layers. Furthermore, in the south near Heidelberg , there is still Zechstein under the Early Triassic deposits. Roughly 50 to 60 million years ago, volcanoes formed along the great geological faults . Still bearing witness to this time are

3795-435: 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

3864-429: 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

3933-421: The setting of an Odenwald ghost story: during the night the knight Rodenstein (the Rodensteiner ) flies with a berserker-cornet through the air to prophesy the beginning of a war ( Wild Hunt motif). Countless streams rise in the Odenwald, the longest of which are the following: There are a few bodies of standing water in the Odenwald, among which are the following: Odenwald is twinned with: The Odenwald

4002-622: 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

4071-406: 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

4140-434: 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

4209-444: 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

SECTION 60

#1732772306386

4278-431: 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

4347-492: 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

4416-424: 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

4485-407: Was crossed. The following are some theories about the origin of the name Odenwald : Linguists who research phonetic changes and the sound shifts reject theories no. 1 to 3 and prefer 4 or 5; some historians favor no. 2. The numerous Odenwald folk legends are mostly connected with historic geographic sites (castle, town, rock, road and so on) They relate: In some stories the local aspect firstly

4554-421: 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

4623-411: Was never realized. Nevertheless, all these Bundesstraßen run through the Odenwald: Furthermore, the Nibelungenstraße and the Siegfriedstraße run through the Odenwald, partly along the roads listed above. The Odenwald is home to many historic castles and palatial residences. In times past the fortresses on the top of the Odenwald mountains controlled Bergstraße and the Weschnitz-, the Gersprenz-,

4692-434: Was the collision of Africa ’s and Europe's forerunner continents. In the Triassic , about 200 million years ago, the land sank again, forming the Germanic Basin in which the metre-thick layers of red sandstone could build up . These were later covered over with layers of muschelkalk from a broad inland sea, then followed by sediments from the Late Triassic (or Keuper). The South German Cuesta Land thus formed. When

4761-420: Was uplifted to the height it has today. Along the faults, the small rivers Gersprenz and Weschnitz have, in part, carved their courses. The Upper Rhine Rift is part of a fracture zone reaching from the Mediterranean Sea to Norway . Right on the edge of the Odenwald, it is roughly 2 500 m deep, but has been filled in to its current height by river and sea sediment, for until about 20 million years ago,

#385614