The Massif Central ( French pronunciation: [masif sɑ̃tʁal] ) is a highland region in south-central France consisting of mountains and plateaus. It covers about 15% of mainland France.
89-679: Subject to volcanism that has subsided in the last 10,000 years, these central mountains are separated from the Alps by a deep north–south cleft created by the Rhône river and known in French as the sillon rhodanien (literally "Rhône furrow"). The region was a barrier to transport within France until the opening of the A75 motorway , which not only made north–south travel easier but also opened access to
178-578: A barometer to the top of the Puy-de-Dôme . The Université Blaise-Pascal (or Clermont-Ferrand II) was located primarily in the city and is named after him. Clermont-Ferrand also hosts the Clermont-Ferrand International Short Film Festival , the world's first international short film festival, which originated in 1979. This festival, which brings thousands of people every year (137,000 in 2008) to
267-645: A comital one. Clermont became a royal city in 1551, and in 1610, the inseparable property of the French Crown. On 15 April 1630 the Edict of Troyes (the First Edict of Union) joined the two cities of Clermont and Montferrand . This union was confirmed in 1731 by Louis XV with the Second Edict of Union. At this time, Montferrand was no more than a satellite city of Clermont, and it remained so until
356-534: A ghost town ) and Fourpeaked Mountain in Alaska, which, before its September 2006 eruption, had not erupted since before 8000 BCE. Clermont-Ferrand Clermont-Ferrand ( UK : / ˌ k l ɛər m ɒ̃ f ɛ ˈ r ɒ̃ / , US : /- m oʊ n -/ ; French: [klɛʁmɔ̃ fɛʁɑ̃] ) is a city and commune of France , in the Auvergne-Rhône-Alpes region , with
445-886: 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
534-414: 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,
623-423: A TGV stop. Clermont-Ferrand Auvergne Airport serves only a handful of mostly domestic destinations. Clermont-Ferrand was the home of mathematician and philosopher Blaise Pascal , who tested Evangelista Torricelli 's hypothesis concerning the influence of gas pressure on liquid equilibrium. This is the experiment in which a vacuum is created in a mercury tube; Pascal's experiment had his brother-in-law carry
712-437: 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,
801-448: A large concentration of around 450 extinct volcanoes. The Chaîne des Puys (near Clermont-Ferrand ), a range running north to south and less than 160 km (60 sq mi) long, contains 115 of them (monogenic volcanoes only). The Auvergne Volcanoes regional natural park is in the massif. The amusement park of Vulcania near Clermont-Ferrand allows visitors to discover this natural heritage and introduces them to volcanology. In
890-578: A new Romanesque cathedral which was consecrated in 946. It was almost entirely replaced by the current Gothic cathedral, though the crypt survives and the towers were only replaced in the 19th century. Clermont was the starting point of the First Crusade , in which Christendom sought to retake Muslim-ruled Jerusalem . Pope Urban II called for the crusade in 1095 at the Second Council of Clermont . In 1120, following repeated crises between
979-443: 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
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#17327581633621068-467: A population of 147,284 (2020). Its metropolitan area ( aire d'attraction ) had 504,157 inhabitants at the 2018 census. It is the prefecture (capital) of the Puy-de-Dôme département . Olivier Bianchi is its current mayor . Clermont-Ferrand sits on the plain of Limagne in the Massif Central and is surrounded by a major industrial area. The city is known for the chain of volcanoes ,
1157-806: A result of intrigues. In 570, Bishop Avitus ordered the Jews of the city, who numbered over 500, to accept Christian baptism or be expelled. In 848, the city was renamed Clairmont , after the castle Clarus Mons. During this era, it was an episcopal city ruled by its bishop. Clermont was not spared by the Vikings at the time of the weakening of the Carolingian Empire : it was ravaged by the Normans under Hastein in 862 and 864 and, while its bishop Sigon carried out reconstruction work, again in 898 (or 910, according to some sources). Bishop Étienne II built
1246-627: A strong identity. Clermont-Ferrand has an oceanic climate ( Cfb ). The city is in the rain shadow of the Chaîne des Puys, giving it one of the driest climates in metropolitan France, except for a few places around the Mediterranean Sea. The mountains also block most of the oceanic influence of the Atlantic, which creates a much more continental climate than in nearby cities west or north of the mountains, like Limoges and Montluçon . Thus
1335-541: A total student population of over 37,000, along with university faculty and staff. With around 2,700 students, Clermont Auvergne INP is the biggest engineering graduate school in the city. A division of Polytech (an engineering school of Clermont Auvergne INP) located in Clermont-Ferrand made the news when two of its students, Laurent Bonomo and Gabriel Ferez , were murdered in June 2008 while enrolled in
1424-632: 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
1513-555: 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
1602-465: 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
1691-739: 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
1780-620: Is booming, taking advantage of the UNESCO heritage classification of the volcanoes of the Chaîne des Puys and the Causses and Cévennes region. The entire economy of the Massif Central has benefited from the opening of roads, particularly the construction of the A75motorway on which is located the famous Millau Viaduct . Volcano A volcano is a rupture in the crust of
1869-412: 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
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#17327581633621958-565: 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
2047-584: 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
2136-537: 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
2225-471: 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
2314-595: The A75 with Montpellier and the A89 with Bordeaux , Lyon and Saint-Étienne ( A72 ). The airport offers flights within France. Recently, Clermont-Ferrand was France's first city to get a new Translohr transit system, the Clermont-Ferrand Tramway , thereby linking the city's north and south neighbourhoods. The TGV will arrive in Auvergne after 2030. It will be one of the last regions not to have
2403-617: 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
2492-484: The Chaîne des Puys , which surround it. This includes the dormant volcano Puy de Dôme , 10 kilometres (6 miles) away, one of the highest in the surrounding area, which is topped by communications towers and visible from the city. Clermont-Ferrand has been listed as a "tectonic hotspot" since July 2018 on the UNESCO World Heritage List . One of the oldest French cities, it was known by Greeks as
2581-575: The Kingdom of the Franks . On 8 November 535 the first Council of Clermont opened at Arvernis (Clermont), with fifteen bishops participating, including Caesarius of Arles , Nizier of Lyons , the Bishop of Trier , and Saint Hilarius , Bishop of Mende . The Council issued 16 decrees. The second canon reiterated the principle that the granting of episcopal dignity must be made according to merit and not as
2670-804: 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,
2759-834: 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
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2848-509: The public square Place de Jaude , in which stands a grand statue of Vercingetorix astride a warhorse and brandishing a sword. The inscription reads in French: J'ai pris les armes pour la liberté de tous , lit. 'I took up arms for the liberty of all'). This statue was sculpted by Frédéric Bartholdi , who also created the Statue of Liberty . Clermont-Ferrand's first name
2937-760: The regions of Auvergne-Rhône-Alpes , Bourgogne-Franche-Comté , Nouvelle-Aquitaine and Occitania . The largest cities in the region are Clermont-Ferrand , Limoges , and Saint-Étienne . In the Massif Central, the industry remains little developed except locally (metallurgy in Saint-Étienne; tires in Clermont-Ferrand , headquarters of Michelin , world leader in the sector; aeronautics industry in Figeac , etc.). The other industries present are linked to agriculture ( Groupe Limagrain ,
3026-473: The sevens version of rugby union, Clermont-Ferrand has hosted the France Women's Sevens , the final event in each season's World Rugby Women's Sevens Series , since 2016 . Education is also an important sector in the economy of Clermont-Ferrand. The University of Clermont Auvergne (formed in 2017 from a merger of Université Blaise Pascal and Université d'Auvergne ) is located in the city and has
3115-440: The 13th and the 19th centuries. Food production and processing as well as engineering are major employers in the area, as are the many research facilities of leading computer software and pharmaceutical companies. The city's industry was for a long time linked to the French tyre manufacturer Michelin , which created the radial tyre and expanded from Clermont-Ferrand to become a worldwide leader in its industry. For most of
3204-734: The 20th century, it had extensive factories throughout the city, employing up to 30,000 workers. While the company has maintained its headquarters in the city, most of the manufacturing is now done in foreign countries. This downsizing took place gradually, allowing the city to court new investment in other industries, thus avoiding the fate of many post-industrial cities and keeping it a very wealthy and prosperous area home to many high-income executives. The main railway station has connections to Paris and several regional destinations: Lyon, Moulins via Vichy , Le Puy-en-Velay , Aurillac , Nîmes , Issoire , Montluçon and Thiers . The A71 motorway connects Clermont-Ferrand with Orléans and Bourges ,
3293-570: The Auvergne region's cultural life is significant in France. One of the city's nicknames is "The Liverpool of France". Groups such as The Elderberries and Cocoon were formed there. Additionally, the city was the subject of the acclaimed documentary The Sorrow and the Pity , which used Clermont-Ferrand as the basis of the film, telling the story of France under Nazi occupation and the Vichy regime of Marshal Pétain . Pierre Laval , Pétain's "handman",
3382-465: The FIBA EuroBasket 1999 . The city was the finish of Tour de France stages in 1951 and 1959, and will host the start of the 2023 Tour de France Femmes . The city is also home to a rugby union club competing at international level, ASM Clermont Auvergne , as well as Clermont Foot Auvergne , a football club that has competed in France's top tier, Ligue 1 , since the 2021/22 season. In
3471-622: 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
3560-644: The Roman assault at the Battle of Gergovia in 52 BC. After the Roman conquest, the city became known as Augustonemetum . The city became the seat of a bishop in the 5th century, at the time of the bishop Namatius , who built a cathedral here described by Gregory of Tours . Clermont went through a dark period after the disappearance of the Roman Empire and during the High Middle Ages was pillaged by
3649-613: 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
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3738-470: The beginning of the 20th century. Wishing to retain its independence, Montferrand made three demands for independence, in 1789, 1848, and 1863. The Hôtel de Ville (City Hall) was completed in 1844. In the 20th century, the construction of the Michelin factories and of city gardens, which shaped modern Clermont-Ferrand, united the two cities, although two distinct downtowns survive and Montferrand retains
3827-510: 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
3916-672: The capital of the Arvernie tribe before developing in the Gallo-Roman era under the name of Augustonemetum in the 1st century BC. The forum of the Roman city was located on the top of the Clermont mound, on the site of the present cathedral. During the decline of the Western Roman Empire it was subjected to repeated looting by the peoples who invaded Gaul , including Vandals , Alans , Visigoths and Franks . It
4005-402: 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
4094-469: The city has comparatively cold winters and hot summers. From November to March, frost is very frequent, and the city, being at the bottom of a valley, is frequently subject to temperature inversion , in which the mountains are sunny and warm, and the plain is freezing cold and cloudy. Snow is quite common, although usually short-lived and light. Summer temperatures often exceed 35 °C (95 °F), with sometimes violent thunderstorms. The highest temperature
4183-637: The city, is the second French film Festival after Cannes in terms of visitors, but ranks first for spectators (in Cannes, visitors are not allowed in theatres, only professionals). This festival has revealed many young talented directors who are now well known in France and internationally, such as Mathieu Kassovitz , Cédric Klapisch and Éric Zonka. Beside the short film festival, Clermont-Ferrand hosts more than twenty music, film, dance, theatre and video and digital art festivals every year. With more than 800 artistic groups from dance to music, Clermont-Ferrand and
4272-451: The counts of Auvergne and the bishops of Clermont and in order to counteract the clergy's power, the counts founded the rival city of Montferrand on a mound next to the fortifications of Clermont, on the model of the new cities of the Midi that appeared in the 12th and 13th centuries. Until the early modern period , the two remained separate cities: Clermont, an episcopal city; Montferrand,
4361-799: 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
4450-731: The film. Pascal was born in Clermont-Ferrand in 1623. The city also hosts L'Aventure Michelin , the museum dedicated to the history of Michelin group. A racing circuit close to the city, the Charade Circuit , using closed-off public roads , held the French Grand Prix in 1965 , 1969 , 1970 and 1972 . It was a daunting circuit, with such harsh elevation changes that some drivers became ill as they drove. Winners included Jim Clark , Jackie Stewart (twice), and Jochen Rindt . Clermont-Ferrand has some experience in hosting major international sports tournaments, including
4539-431: 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
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#17327581633624628-610: 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
4717-585: 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
4806-466: 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
4895-492: 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
4984-613: The massif itself. The Massif Central is an old massif , formed during the Variscan orogeny , consisting mostly of granitic and metamorphic rocks . It was powerfully raised and made to look geologically younger in the eastern section by the uplift of the Alps during the Paleogene period and in the southern section by the uplift of the Pyrenees . The massif thus presents a strongly asymmetrical elevation profile with highlands in
5073-419: 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
5162-551: 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
5251-415: 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
5340-438: 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
5429-465: The name of Clermont-Ferrand. The amalgamation of the two towns was decreed by Louis XIII and confirmed by Louis XV . The old part of Clermont is delimited by the route of the ramparts as they existed at the end of the Middle Ages. Clermont ranks among the oldest cities of France. The first known mention was by the Greek geographer Strabo , who called it the "metropolis of the Arverni " (meaning their oppidum civitas or tribal capital). The city
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#17327581633625518-452: 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
5607-769: 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
5696-444: 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
5785-420: 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
5874-471: 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
5963-409: 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
6052-425: 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
6141-457: The peoples who invaded Gaul. Between 471 and 475, Auvergne was often the target of Visigothic expansion, and the city was frequently besieged, including once by Euric . Although defended by Sidonius Apollinaris , at the head of the diocese from 468 to 486, and the patrician Ecdicius , the city was ceded to the Visigoths by emperor Julius Nepos in 475 and remained part of the Visigothic kingdom until 507. A generation later, it became part of
6230-418: 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
6319-435: 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
6408-492: 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
6497-622: 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
6586-686: The south and in the east ( Cévennes ) dominating the valley of the Rhône and the plains of Languedoc and, by contrast, the less elevated region of Limousin in the northwest. These tectonic movements created faults and may be at the origin of the volcanism in the massif (but the hypothesis is not proved yet). In fact, above the crystalline foundation, one can observe many volcanoes of many different types and ages: volcanic plateaus ( Aubrac , Cézallier ), stratovolcanoes ( Mounts of Cantal , Monts Dore ), and small, very recent monogenic volcanoes ( Chaîne des Puys , Vivarais ). The entire region contains
6675-756: The south, one remarkable region is made up of features called Causses in French and consists of raised limestone plateaus cut by very deep canyons. The most famous of them is the Gorges du Tarn (Tarn Canyon). Mountain ranges, with notable individual mountains, are (roughly north to south): The following departments are generally considered as part of the Massif Central : Allier , Ardèche , Aude , Aveyron , Cantal , Corrèze , Creuse , Gard , Haute-Garonne , Haute-Loire , Haute-Vienne , Hérault , Loire , Lot , Lozère , Puy-de-Dôme , Rhône , Saône-et-Loire , Tarn , and Tarn-et-Garonne ; these form parts of
6764-406: 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
6853-434: 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
6942-444: 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
7031-431: 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
7120-492: 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
7209-424: 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
7298-564: The world's leading festivals for short films . It is also home to the corporate headquarters of Michelin , the global tyre company founded in the city more than 100 years ago. With a quarter of the municipal population being students, and some 6,000 researchers, Clermont-Ferrand is the first city in France to join the UNESCO Learning City Network. Along with its highly distinctive black lava stone Gothic styled Cathedral , Clermont-Ferrand's other famous sites include
7387-497: The world's third-largest seed producer and cheese-producing industries that export to the world such as Cantal and Roquefort ). On the agricultural level, the Limagne plain is dominated by major cereal crops, but in the mountains, it is mainly livestock farming that predominates: cattle farming in the west for meat and milk (Cantal cheese), sheep farming in the south on the limestone plateaus (Roquefort cheese). Finally, tourism
7476-481: Was Augusto nemetum , Latin for " sanctuary for Augustus ", or Civitas Arvernorum (town of the Arverni people). It originated on the central knoll where the cathedral is situated today, overlooking the capital of Gaulish Arvernis [ fr ] . The fortified castle of Clarus Mons gave its name to the whole town in 848, to which the small episcopal town of Montferrand was attached in 1731, together taking
7565-408: Was an Auvergnat . My Night at Maud's ( French : Ma nuit chez Maud ), a 1969 French drama film by Éric Rohmer , was set and filmed in Clermont-Ferrand in and around Christmas Eve. It is the third film (fourth in order of release) in his series of Six Moral Tales . Pascal's wager , a philosophical and theological thought experiment from Blaise Pascal 's Pensées , is a major theme in
7654-502: Was at that time called Nemessos – a Gaulish word for a sacred forest, and was situated on the mound where the cathedral of Clermont-Ferrand stands today. Somewhere in the area around Nemossos, the Arverni chieftain Vercingetorix (later to head a unified Gallic resistance to the Roman invasion led by Julius Caesar ) was born around 72 BC. Nemossos was situated not far from the plateau of Gergovia , where Vercingetorix repulsed
7743-421: 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
7832-654: Was later raided by Vikings as the Carolingian Empire weakened in the early Middle Ages . Growing in importance under the Capetian dynasty , in 1095 it hosted the Council of Clermont , where Pope Urban II called the First Crusade . In 1551, Clermont became a royal town, and was declared an inseparable property of the Crown in 1610. Today Clermont-Ferrand hosts the Clermont-Ferrand International Short Film Festival ( Festival du Court-Métrage de Clermont-Ferrand ), one of
7921-557: Was reached in 2019 of 40.9 °C (105.6 °F) while the lowest was −29.0 °C (−20.2 °F). Clermont-Ferrand has two famous churches. One is Notre-Dame du Port , a Romanesque church which was built during the 11th and 12th centuries (the bell tower was rebuilt during the 19th century). It was nominated as a World Heritage Site by UNESCO in 1998. The other is Clermont-Ferrand Cathedral ( Cathédrale Notre-Dame-de-l'Assomption de Clermont-Ferrand ), built in Gothic style between
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