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116-413: The landscape of Rupite is dominated by the eminence of Kozhuh ( кожух , "fur coat," taking its name from its shape) to the west. Although it is only 281 m high, it rises prominently from the flat Petrich Plain. The eminence, which is part of the outskirts of an extinct volcano , consists of three small summits, of which the middle one is the highest. Volcanic rocks and rock pyramids can be observed at

232-524: A British Airways Boeing 747-236B ( Flight 9 ) flew through the ash cloud from the eruption of Mount Galunggung , Indonesia resulting in the failure of all four engines. The plane descended 24,000 feet (7,300 m) in 16 minutes before the engines restarted, allowing the aircraft to make an emergency landing. On 15 December 1989, a KLM Boeing 747-400 ( Flight 867 ) also lost power to all four engines after flying into an ash cloud from Mount Redoubt, Alaska . After dropping 14,700 feet (4,500 m) in four minutes,

348-601: A ghost town ) and Fourpeaked Mountain in Alaska, which, before its September 2006 eruption, had not erupted since before 8000 BCE. Volcanic ash Volcanic ash consists of fragments of rock, mineral crystals , and volcanic glass , produced during volcanic eruptions and measuring less than 2 mm (0.079 inches) in diameter. The term volcanic ash is also often loosely used to refer to all explosive eruption products (correctly referred to as tephra ), including particles larger than 2 mm. Volcanic ash

464-886: 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

580-595: A characteristically dark coloured ash containing ~45–55% silica that is generally rich in iron (Fe) and magnesium (Mg). The most explosive rhyolite eruptions produce a felsic ash that is high in silica (>69%) while other types of ash with an intermediate composition (e.g., andesite or dacite ) have a silica content between 55 and 69%. The principal gases released during volcanic activity are water , carbon dioxide , hydrogen , sulfur dioxide , hydrogen sulfide , carbon monoxide and hydrogen chloride . The sulfur and halogen gases and metals are removed from

696-448: A clay matrix. Particle surfaces are often coated with aggregates of zeolite crystals or clay and only relict textures remain to identify pyroclast types. The morphology (shape) of volcanic ash is controlled by a plethora of different eruption and kinematic processes. Eruptions of low-viscosity magmas (e.g., basalt) typically form droplet shaped particles. This droplet shape is, in part, controlled by surface tension , acceleration of

812-856: A few millimeters requires removal before airports can resume full operations. Ash does not disappear (unlike snowfalls) and must be disposed of in a manner that prevents it from being remobilised by wind and aircraft. Ash may disrupt transportation systems over large areas for hours to days, including roads and vehicles, railways and ports and shipping. Falling ash will reduce the visibility which can make driving difficult and dangerous. In addition, fast travelling cars will stir up ash, generating billowing clouds which perpetuate ongoing visibility hazards. Ash accumulations will decrease traction, especially when wet, and cover road markings. Fine-grained ash can infiltrate openings in cars and abrade most surfaces, especially between moving parts. Air and oil filters will become blocked requiring frequent replacement. Rail transport

928-599: A forward-facing surface, that are tuned to detect volcanic ash. This system can detect ash concentrations of <1 mg/m to > 50 mg/m , giving pilots approximately 7–10 minutes warning. The camera was tested by the easyJet airline company, AIRBUS and Nicarnica Aviation (co-founded by Dr Fred Prata). The results showed the system could work to distances of ~60 km and up to 10,000 ft but not any higher without some significant modifications. In addition, ground and satellite based imagery, radar , and lidar can be used to detect ash clouds. This information

1044-413: A good level of removal of suspended particles. Chlorination may have to be increased to ensure adequate disinfection. Many households, and some small communities, rely on rainwater for their drinking water supplies. Roof-fed systems are highly vulnerable to contamination by ashfall, as they have a large surface area relative to the storage tank volume. In these cases, leaching of chemical contaminants from

1160-437: 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,

1276-503: A lack of water for hygiene, sanitation and drinking. Municipal authorities need to monitor and manage this water demand carefully, and may need to advise the public to utilise cleanup methods that do not use water (e.g., cleaning with brooms rather than hoses). Wastewater networks may sustain damage similar to water supply networks. It is very difficult to exclude ash from the sewerage system. Systems with combined storm water/sewer lines are most at risk. Ash will enter sewer lines where there

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1392-462: A legend, Vanga lost her sight during a storm in her early childhood, but during the accident she had a vision, which gave her clairvoyance abilities. In the last years of her life, Vanga lived in a small house in Rupite, because according to her relatives she considered the area an "energy source" from which she collected her powers.According to the statistics of Vasil Kanchov in 1900, Shirbanovo (as it

1508-901: A minor role in the determination of grain shape in phreatomagmatic eruptions. In this sort of eruption, the rising magma is quickly cooled on contact with ground or surface water. Stresses within the "quenched" magma cause fragmentation into five dominant pyroclast shape-types: (1) blocky and equant; (2) vesicular and irregular with smooth surfaces; (3) moss-like and convoluted; (4) spherical or drop-like; and (5) plate-like. The density of individual particles varies with different eruptions. The density of volcanic ash varies between 700 and 1200 kg/m for pumice, 2350–2450 kg/m for glass shards, 2700–3300 kg/m for crystals, and 2600–3200 kg/m for lithic particles. Since coarser and denser particles are deposited close to source, fine glass and pumice shards are relatively enriched in ash fall deposits at distal locations. The high density and hardness (~5 on

1624-443: 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

1740-605: A place of worship for many people and a renowned tourist attraction. The icons were created by artist Svetlin Rusev and were not generally approved by the Holy Synod of the Bulgarian Orthodox Church for being too realistic and not conforming to the canons. The house of Vanga can be seen nearby, and a new monastery is currently under construction. Rupite Glacier on Smith Island , South Shetland Islands

1856-838: A range of different pyroclasts dependent on the eruptive process. For example, ash collected from Hawaiian lava fountains consists of sideromelane (light brown basaltic glass) pyroclasts which contain microlites (small quench crystals, not to be confused with the rare mineral microlite ) and phenocrysts . Slightly more viscous eruptions of basalt (e.g., Strombolian) form a variety of pyroclasts from irregular sideromelane droplets to blocky tachylite (black to dark brown microcrystalline pyroclasts). In contrast, most high-silica ash (e.g. rhyolite) consists of pulverised products of pumice (vitric shards), individual phenocrysts (crystal fraction) and some lithic fragments ( xenoliths ). Ash generated during phreatic eruptions primarily consists of hydrothermally altered lithic and mineral fragments, commonly in

1972-417: A sequential leaching experiment on ash from the 1980 eruption of Mount St. Helens , chloride salts were found to be the most readily soluble, followed by sulfate salts Fluoride compounds are in general only sparingly soluble (e.g., CaF 2 , MgF 2 ), with the exception of fluoride salts of alkali metals and compounds such as calcium hexafluorosilicate (CaSiF 6 ). The pH of fresh ash leachates

2088-403: A significant health risk to those without pre-existing respiratory conditions . The health effects of volcanic ash depend on the grain size, mineralogical composition and chemical coatings on the surface of the ash particles. Additional factors related to potential respiratory symptoms are the frequency and duration of exposure, the concentration of ash in the air and the respirable ash fraction;

2204-632: 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

2320-555: 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

2436-465: 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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2552-739: 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

2668-464: Is a proclaimed natural landmark since 1962. A 0.4-hectare protected area is located about 2 km from the village of Rupite at the eastern foot of Kozhuh. Rupite is also famous for its healing mineral springs with a temperature of 71-78 °C and an average discharge of 35  L / s . Remains of an ancient town were discovered at the southwestern foot of Kozhuh. In 2002, a Latin inscription dated 308 CE and consisting of an imperial appeal addressed to

2784-412: 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

2900-511: Is classified as a human carcinogen by the International Agency for Research on Cancer . Guideline values have been created for exposure, but with unclear rationale; UK guidelines for particulates in air (PM10) are 50 μg/m and USA guidelines for exposure to crystalline silica are 50 μg/m . It is thought that the guidelines on exposure levels could be exceeded for short periods of time without significant health effects on

3016-565: 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

3132-584: 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

3248-401: Is formed during explosive volcanic eruptions and phreatomagmatic eruptions, and may also be formed during transport in pyroclastic density currents . Explosive eruptions occur when magma decompresses as it rises, allowing dissolved volatiles (dominantly water and carbon dioxide ) to exsolve into gas bubbles. As more bubbles nucleate a foam is produced, which decreases the density of

3364-452: Is formed during explosive volcanic eruptions when dissolved gases in magma expand and escape violently into the atmosphere. The force of the gases shatters the magma and propels it into the atmosphere where it solidifies into fragments of volcanic rock and glass. Ash is also produced when magma comes into contact with water during phreatomagmatic eruptions , causing the water to explosively flash to steam leading to shattering of magma. Once in

3480-416: Is generally controlled by the mechanical properties of the wall rock broken up by spalling or explosive expansion of gases in the magma as it reaches the surface. The morphology of ash particles from phreatomagmatic eruptions is controlled by stresses within the chilled magma which result in fragmentation of the glass to form small blocky or pyramidal glass ash particles. Vesicle shape and density play only

3596-416: Is good evidence that pyroclastic flows produce high proportions of fine ash by communition and it is likely that this process also occurs inside volcanic conduits and would be most efficient when the magma fragmentation surface is well below the summit crater. Ash particles are incorporated into eruption columns as they are ejected from the vent at high velocity. The initial momentum from the eruption propels

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3712-486: Is highly variable, depending on the presence of an acidic gas condensate (primarily as a consequence of the gases SO 2 , HCl and HF in the eruption plume) on the ash surface. The crystalline-solid structure of the salts act more as an insulator than a conductor . However, once the salts are dissolved into a solution by a source of moisture (e.g., fog, mist, light rain, etc.), the ash may become corrosive and electrically conductive. A recent study has shown that

3828-399: Is inflow/infiltration by stormwater through illegal connections (e.g., from roof downpipes), cross connections, around manhole covers or through holes and cracks in sewer pipes. Ash-laden sewage entering a treatment plant is likely to cause failure of mechanical prescreening equipment such as step screens or rotating screens. Ash that penetrates further into the system will settle and reduce

3944-503: Is named after Rupite. 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,

4060-537: 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

4176-626: Is passed between meteorological agencies, volcanic observatories and airline companies through Volcanic Ash Advisory Centers (VAAC) . There is one VAAC for each of the nine regions of the world. VAACs can issue advisories describing the current and future extent of the ash cloud. Volcanic ash not only affects in-flight operations but can affect ground-based airport operations as well. Small accumulations of ash can reduce visibility, produce slippery runways and taxiways, infiltrate communication and electrical systems, interrupt ground services, damage buildings and parked aircraft. Ash accumulation of more than

4292-499: Is physically, socially, and economically disruptive. Volcanic ash can affect both proximal areas and areas many hundreds of kilometres from the source, and causes disruptions and losses in a wide variety of different infrastructure sectors. Impacts are dependent on: ash fall thickness; the grain size and chemistry of the ash; whether the ash is wet or dry; the duration of the ash fall; and any preparedness , management and prevention (mitigation) measures employed to reduce effects from

4408-642: Is removed from pyroclastic density currents in co-ignimbrite ash plumes. Physical and chemical characteristics of volcanic ash are primarily controlled by the style of volcanic eruption. Volcanoes display a range of eruption styles which are controlled by magma chemistry, crystal content, temperature and dissolved gases of the erupting magma and can be classified using the volcanic explosivity index (VEI) . Effusive eruptions (VEI 1) of basaltic composition produce <10 m of ejecta, whereas extremely explosive eruptions (VEI 5+) of rhyolitic and dacitic composition can inject large quantities (>10 m ) of ejecta into

4524-457: Is thought to supply the cations involved in the deposition of sulfate and halide salts . While some 55 ionic species have been reported in fresh ash leachates , the most abundant species usually found are the cations Na , K , Ca and Mg and the anions Cl , F and SO 4 . Molar ratios between ions present in leachates suggest that in many cases these elements are present as simple salts such as NaCl and CaSO 4 . In

4640-471: 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

4756-617: 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

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4872-548: The Mohs Hardness Scale ) together with a high degree of angularity, make some types of volcanic ash (particularly those with a high silica content) very abrasive. Volcanic ash consists of particles (pyroclasts) with diameters less than 2 mm (particles larger than 2 mm are classified as lapilli ), and can be as fine as 1 μm. The overall grain size distribution of ash can vary greatly with different magma compositions. Few attempts have been made to correlate

4988-804: 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,

5104-410: The eruption column . Within pyroclastic density currents particle abrasion occurs as particles violently collide, resulting in a reduction in grain size and production of fine grained ash particles. In addition, ash can be produced during secondary fragmentation of pumice fragments, due to the conservation of heat within the flow. These processes produce large quantities of very fine grained ash which

5220-699: The infrastructure critical to supporting modern societies, particularly in urban areas, where high population densities create high demand for services. Several recent eruptions have illustrated the vulnerability of urban areas that received only a few millimetres or centimetres of volcanic ash. This has been sufficient to cause disruption of transportation, electricity , water , sewage and storm water systems. Costs have been incurred from business disruption, replacement of damaged parts and insured losses. Ash fall impacts on critical infrastructure can also cause multiple knock-on effects, which may disrupt many different sectors and services. Volcanic ash fall

5336-834: 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

5452-622: 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

5568-449: The SiO 2 is not attached to another element to create a new mineral. However, magmas containing less than 58% SiO 2 are thought to be unlikely to contain crystalline silica. The exposure levels to free crystalline silica in the ash are commonly used to characterise the risk of silicosis in occupational studies (for people who work in mining, construction and other industries,) because it

5684-613: 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

5800-481: The addition of water. Volcanic ash is also produced during phreatomagmatic eruptions. During these eruptions fragmentation occurs when magma comes into contact with bodies of water (such as the sea, lakes and marshes) groundwater, snow or ice. As the magma, which is significantly hotter than the boiling point of water, comes into contact with water an insulating vapor film forms ( Leidenfrost effect ). Eventually this vapor film will collapse leading to direct coupling of

5916-459: The air, ash is transported by wind up to thousands of kilometres away. Due to its wide dispersal, ash can have a number of impacts on society, including animal and human health problems, disruption to aviation, disruption to critical infrastructure (e.g., electric power supply systems, telecommunications, water and waste-water networks, transportation), primary industries (e.g., agriculture), and damage to buildings and other structures. Volcanic ash

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6032-439: The area. Via Aristotelis, which passes nearby, is one of the two main bird migration routes through Bulgaria. Some bird species include the olive-tree warbler ( Hippolais olivetorum ), masked shrike ( Lanius nubicus ), and lesser grey shrike ( Lanius minor ). The pygmy cormorant ( Phalacrocorax pygmaeus ) winters in the area. Because of its volcanic origin and the abundance of rare species of both flora and fauna , Kozhuh

6148-516: The ash fall. Different sectors of infrastructure and society are affected in different ways and are vulnerable to a range of impacts or consequences. These are discussed in the following sections. Ash particles of less than 10 μm diameter suspended in the air are known to be inhalable, and people exposed to ash falls have experienced respiratory discomfort, breathing difficulty, eye and skin irritation, and nose and throat symptoms. Most of these effects are short-term and are not considered to pose

6264-457: The ashfall can become a health risk and drinking of water is not recommended. Prior to an ashfall, downpipes should be disconnected so that water in the tank is protected. A further problem is that the surface coating of fresh volcanic ash can be acidic. Unlike most surface waters, rainwater generally has a very low alkalinity (acid-neutralising capacity) and thus ashfall may acidify tank waters. This may lead to problems with plumbosolvency , whereby

6380-442: The atmosphere by processes of chemical reaction, dry and wet deposition, and by adsorption onto the surface of volcanic ash. It has long been recognised that a range of sulfate and halide (primarily chloride and fluoride ) compounds are readily mobilised from fresh volcanic ash. It is considered most likely that these salts are formed as a consequence of rapid acid dissolution of ash particles within eruption plumes , which

6496-414: The atmosphere. The types of minerals present in volcanic ash are dependent on the chemistry of the magma from which it erupted. Considering that the most abundant elements found in silicate magma are silicon and oxygen , the various types of magma (and therefore ash) produced during volcanic eruptions are most commonly explained in terms of their silica content. Low energy eruptions of basalt produce

6612-510: 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

6728-689: The capacity of biological reactors as well as increasing the volume of sludge and changing its composition. The principal damage sustained by aircraft flying into a volcanic ash cloud is abrasion to forward-facing surfaces, such as the windshield and leading edges of the wings, and accumulation of ash into surface openings, including engines. Abrasion of windshields and landing lights will reduce visibility forcing pilots to rely on their instruments. However, some instruments may provide incorrect readings as sensors (e.g., pitot tubes ) can become blocked with ash. Ingestion of ash into engines causes abrasion damage to compressor fan blades. The ash erodes sharp blades in

6844-402: 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

6960-520: The cold water and hot magma. This increases the heat transfer which leads to the rapid expansion of water and fragmentation of the magma into small particles which are subsequently ejected from the volcanic vent. Fragmentation causes an increase in contact area between magma and water creating a feedback mechanism, leading to further fragmentation and production of fine ash particles. Pyroclastic density currents can also produce ash particles. These are typically produced by lava dome collapse or collapse of

7076-404: The column upwards. As air is drawn into the column, the bulk density decreases and it starts to rise buoyantly into the atmosphere. At a point where the bulk density of the column is the same as the surrounding atmosphere, the column will cease rising and start moving laterally. Lateral dispersion is controlled by prevailing winds and the ash may be deposited hundreds to thousands of kilometres from

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7192-649: The column. Ash fallout is less concentrated during the final stages as the column moves downwind. This results in an ash fall deposit which generally decreases in thickness and grain size exponentially with increasing distance from the volcano. Fine ash particles may remain in the atmosphere for days to weeks and be dispersed by high-altitude winds. These particles can impact on the aviation industry (refer to impacts section) and, combined with gas particles, can affect global climate. Volcanic ash plumes can form above pyroclastic density currents. These are called co-ignimbrite plumes. As pyroclastic density currents travel away from

7308-415: The compressor, reducing its efficiency. The ash melts in the combustion chamber to form molten glass. The ash then solidifies on turbine blades, blocking air flow and causing the engine to stall. The composition of most ash is such that its melting temperature is within the operating temperature (>1000 °C) of modern large jet engines . The degree of impact depends upon the concentration of ash in

7424-425: The droplets after they leave the vent, and air friction. Shapes range from perfect spheres to a variety of twisted, elongate droplets with smooth, fluidal surfaces. The morphology of ash from eruptions of high-viscosity magmas (e.g., rhyolite, dacite, and some andesites) is mostly dependent on the shape of vesicles in the rising magma before disintegration. Vesicles are formed by the expansion of magmatic gas before

7540-412: The effects of an ashfall, but there will not be service interruptions. The final step of drinking water treatment is disinfection to ensure that final drinking water is free from infectious microorganisms. As suspended particles (turbidity) can provide a growth substrate for microorganisms and can protect them from disinfection treatment, it is extremely important that the water treatment process achieves

7656-595: The electrical conductivity of volcanic ash increases with (1) increasing moisture content, (2) increasing soluble salt content, and (3) increasing compaction (bulk density). The ability of volcanic ash to conduct electric current has significant implications for electric power supply systems. Volcanic ash particles erupted during magmatic eruptions are made up of various fractions of vitric (glassy, non-crystalline), crystalline or lithic (non-magmatic) particles. Ash produced during low viscosity magmatic eruptions (e.g., Hawaiian and Strombolian basaltic eruptions) produce

7772-506: The engines were started just 1–2 minutes before impact. Total damage was US$ 80 million and it took 3 months' work to repair the plane. In the 1990s, a further US$ 100 million of damage was sustained by commercial aircraft (some in the air, others on the ground) as a consequence of the 1991 eruption of Mount Pinatubo in the Philippines . In April 2010, airspace all over Europe was affected, with many flights cancelled -which

7888-799: 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

8004-620: The eruption of Puyehue-Cordón Caulle , Chile. Volcanic ash clouds are very difficult to detect from aircraft as no onboard cockpit instruments exist to detect them. However, a new system called Airborne Volcanic Object Infrared Detector (AVOID) has recently been developed by Dr Fred Prata while working at CSIRO Australia and the Norwegian Institute for Air Research , which will allow pilots to detect ash plumes up to 60 km (37 mi) ahead and fly safely around them. The system uses two fast-sampling infrared cameras, mounted on

8120-548: The exception of fluorine . The elements iron , manganese and aluminium are commonly enriched over background levels by volcanic ashfall. These elements may impart a metallic taste to water, and may produce red, brown or black staining of whiteware, but are not considered a health risk. Volcanic ashfalls are not known to have caused problems in water supplies for toxic trace elements such as mercury (Hg) and lead (Pb) which occur at very low levels in ash leachates. Ingesting ash may be harmful to livestock , causing abrasion of

8236-431: 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

8352-624: The foot of Kozhuh. The climate in the locality is transitional between continental and Mediterranean , featuring hot, dry summers and relatively mild winters. The natural vegetation consists mainly of white poplar ( Populus alba ), and there are 13 plant species endangered in Bulgaria. Almost all of the snake species observed in the country can be found in Rupite, including the European cat snake ( Telescopus fallax ), as well as four species of tortoises . A total of 201 bird species inhabit

8468-610: 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

8584-585: 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

8700-613: The general population. There have been no documented cases of silicosis developed from exposure to volcanic ash. However, long-term studies necessary to evaluate these effects are lacking. For surface water sources such as lakes and reservoirs, the volume available for dilution of ionic species leached from ash is generally large. The most abundant components of ash leachates (Ca, Na, Mg, K, Cl, F and SO 4 ) occur naturally at significant concentrations in most surface waters and therefore are not affected greatly by inputs from volcanic ashfall, and are also of low concern in drinking water, with

8816-466: 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

8932-439: The grain size characteristics of a deposit with those of the event which produced it, though some predictions can be made. Rhyolitic magmas generally produce finer grained material compared to basaltic magmas, due to the higher viscosity and therefore explosivity. The proportions of fine ash are higher for silicic explosive eruptions, probably because vesicle size in the pre-eruptive magma is smaller than those in mafic magmas. There

9048-492: 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

9164-455: The local urban citizens, suggests that the settlement was Heraclea Sintica . The town likely existed from 4th century BCE to the 6th century CE, and was the main town of the Thracian tribe Sints. Today Rupite is mostly famous as the residence of the late alleged clairvoyant Baba Vanga (Vangeliya Gushterova, 1911 – 1996), who still attracts thousands of worshipers and tourists. According to

9280-513: The magma has solidified. Ash particles can have varying degrees of vesicularity and vesicular particles can have extremely high surface area to volume ratios. Concavities, troughs, and tubes observed on grain surfaces are the result of broken vesicle walls. Vitric ash particles from high-viscosity magma eruptions are typically angular, vesicular pumiceous fragments or thin vesicle-wall fragments while lithic fragments in volcanic ash are typically equant, or angular to subrounded. Lithic morphology in ash

9396-407: The magma, accelerating it up the conduit. Fragmentation occurs when bubbles occupy ~70–80 vol% of the erupting mixture. When fragmentation occurs, violently expanding bubbles tear the magma apart into fragments which are ejected into the atmosphere where they solidify into ash particles. Fragmentation is a very efficient process of ash formation and is capable of generating very fine ash even without

9512-419: 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

9628-551: 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

9744-415: 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

9860-438: 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

9976-452: 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

10092-876: 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

10208-549: 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

10324-420: 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

10440-471: 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

10556-468: 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

10672-425: 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

10788-619: 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

10904-436: The plume, the length of time the aircraft spends within the plume and the actions taken by the pilots. Critically, melting of ash, particularly volcanic glass, can result in accumulation of resolidified ash on turbine nozzle guide vanes, resulting in compressor stall and complete loss of engine thrust. The standard procedure of the engine control system when it detects a possible stall is to increase power which would exacerbate

11020-647: The power delivery process: Groundwater-fed systems are resilient to impacts from ashfall, although airborne ash can interfere with the operation of well-head pumps. Electricity outages caused by ashfall can also disrupt electrically powered pumps if there is no backup generation. The physical impacts of ashfall can affect the operation of water treatment plants. Ash can block intake structures, cause severe abrasion damage to pump impellers and overload pump motors. Ash can enter filtration systems such as open sand filters both by direct fallout and via intake waters. In most cases, increased maintenance will be required to manage

11136-443: The problem. It is recommended that pilots reduce engine power and quickly exit the cloud by performing a descending 180° turn. Volcanic gases, which are present within ash clouds, can also cause damage to engines and acrylic windshields, and can persist in the stratosphere as an almost invisible aerosol for prolonged periods of time. There are many instances of damage to jet aircraft as a result of an ash encounter. On 24 June 1982,

11252-419: The progressive encroachment of urban development into higher risk areas, closer to volcanic centres, increasing the human exposure to volcanic ash fall events. Direct health effects of volcanic ash on humans are usually short-term and mild for persons in normal health, though prolonged exposure potentially poses some risk of silicosis in unprotected workers. Of greater concern is the impact of volcanic ash on

11368-423: The proportion of ash with less than 10 μm diameter, known as PM 10 . The social context may also be important. Chronic health effects from volcanic ash fall are possible, as exposure to free crystalline silica is known to cause silicosis . Minerals associated with this include quartz , cristobalite and tridymite , which may all be present in volcanic ash. These minerals are described as ‘free’ silica as

11484-581: The quality of the fibre. As the usual pastures and plants become covered in volcanic ash during eruption some livestock may resort to eat whatever is available including toxic plants. There are reports of goats and sheep in Chile and Argentina having natural abortions in connection to volcanic eruptions. Volcanic ash can disrupt electric power supply systems at all levels of power generation, transformation, transmission, and distribution. There are four main impacts arising from ash-contamination of apparatus used in

11600-435: 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

11716-492: 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

11832-622: 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

11948-406: 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

12064-580: The teeth, and hypersensibility to pressure in the legs and back. Ash ingestion may also cause gastrointestinal blockages. Sheep that ingested ash from the 1991 Mount Hudson volcanic eruption in Chile, suffered from diarrhoea and weakness. Ash accumulating in the back wool of sheep may add significant weight, leading to fatigue and sheep that can not stand up. Rainfall may result in a significant burden as it adds weight to ash. Pieces of wool may fall away and any remaining wool on sheep may be worthless as poor nutrition associated with volcanic eruptions impacts

12180-633: The teeth, and in cases of high fluorine content, fluorine poisoning (toxic at levels of >100 μg/g) for grazing animals. It is known from the 1783 eruption of Laki in Iceland that fluorine poisoning occurred in humans and livestock as a result of the chemistry of the ash and gas, which contained high levels of hydrogen fluoride . Following the 1995/96 Mount Ruapehu eruptions in New Zealand, two thousand ewes and lambs died after being affected by fluorosis while grazing on land with only 1–3 mm of ash fall. Symptoms of fluorosis among cattle exposed to ash include brown-yellow to green-black mottles in

12296-434: 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

12412-444: 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

12528-431: 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

12644-409: The volcano, depending on eruption column height, particle size of the ash and climatic conditions (especially wind direction and strength and humidity). Ash fallout occurs immediately after the eruption and is controlled by particle density. Initially, coarse particles fall out close to source. This is followed by fallout of accretionary lapilli , which is the result of particle agglomeration within

12760-413: The volcano, smaller particles are removed from the flow by elutriation and form a less dense zone overlying the main flow. This zone then entrains the surrounding air and a buoyant co-ignimbrite plume is formed. These plumes tend to have higher concentrations of fine ash particles compared to magmatic eruption plumes due to the abrasion within the pyroclastic density current. Population growth has caused

12876-492: 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

12992-424: 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

13108-423: The water is more aggressive towards materials that it comes into contact with. This can be a particular problem if there are lead-head nails or lead flashing used on the roof, and for copper pipes and other metallic plumbing fittings. During ashfall events, large demands are commonly placed on water resources for cleanup and shortages can result. Shortages compromise key services such as firefighting and can lead to

13224-421: 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

13340-448: Was known before) was populated by 252 Bulgarian Christians. The village of Rupite had 926 inhabitants at the end of 2019, up from 626 inhabitants in 1934 but down from 1,248 people in 1985. The population is declining since Fall of Communism . Nearly all inhabitants are ethnic Bulgarians (99.6%). The memorial temple "St. Petka of Bulgaria" was sponsored by Baba Vanga and built in 1994 at a site chosen by her in 1992. It has since become

13456-563: Was unprecedented-due to the presence of volcanic ash in the upper atmosphere from the eruption of the Icelandic volcano Eyjafjallajökull . On 15 April 2010, the Finnish Air Force halted training flights when damage was found from volcanic dust ingestion by the engines of one of its Boeing F-18 Hornet fighters. In June 2011, there were similar closures of airspace in Chile, Argentina, Brazil, Australia and New Zealand, following

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