Types of volcanic eruptions
Columbia University volcanologists found that the eruption of Costa Rica's Irazú Volcano in 1963 was likely triggered by magma that took a nonstop route from the mantle over just a few months.It operates in a way similar to the Richter scale for earthquakes, in that each interval in value represents a tenfold increasing in magnitude (it is logarithmic).Central-vent eruptions, meanwhile, often take the form of large lava fountains (both continuous and sporadic), which can reach heights of hundreds of meters or more.The particles from lava fountains usually cool in the air before hitting the ground, resulting in the accumulation of cindery scoria fragments; when the air is especially thick with clasts, they cannot cool off fast enough due to the surrounding heat, and hit the ground still hot, the accumulation of which forms spatter cones.Because of the high gas pressures associated with the lavas, continued activity is generally in the form of episodic explosive eruptions accompanied by the distinctive loud blasts.[15] Strombolian eruptions eject volcanic bombs and lapilli fragments that travel in parabolic paths before landing around their source vent.Unlike Strombolian eruptions, ejected lava fragments are not aerodynamic; this is due to the higher viscosity of Vulcanian magma and the greater incorporation of crystalline material broken off from the former cap.[24] Initial Vulcanian activity is characterized by a series of short-lived explosions, lasting a few minutes to a few hours and typified by the ejection of volcanic bombs and blocks.Thus an early sign of future Vulcanian activity is lava dome growth, and its collapse generates an outpouring of pyroclastic material down the volcano's slope.An early sign of a coming eruption is the growth of a so-called Peléan or lava spine, a bulge in the volcano's summit preempting its total collapse.These landslides make Peléan eruptions one of the most dangerous in the world, capable of tearing through populated areas and causing serious loss of life.The 1902 eruption of Mount Pelée caused tremendous destruction, killing more than 30,000 people and completely destroying St. Pierre, the worst volcanic event in the 20th century.As it reaches higher into the air the plume expands and becomes less dense, convection and thermal expansion of volcanic ash drive it even further up into the stratosphere.[49] Fuel coolant reactions may fragment the volcanic material by propagating stress waves, widening cracks and increasing surface area that ultimately leads to rapid cooling and explosive contraction-driven eruptions.As water is heated by lava, it flashes into steam and expands violently, fragmenting the magma it contacts into fine-grained ash.They can happen on land as well, where rising magma that comes into contact with an aquifer (water-bearing rock formation) at shallow levels under the volcano can cause them.[50] Over time Surtseyan eruptions tend to form maars, broad low-relief volcanic craters dug into the ground, and tuff rings, circular structures built of rapidly quenched lava.Problems detecting deep sea volcanic eruptions meant their details were virtually unknown until advances in the 1990s made it possible to observe them.Volcanoes near plate boundaries and mid-ocean ridges are built by the decompression melting of mantle rock that rises on an upwelling portion of a convection cell to the crustal surface.Each process generates different rock; mid-ocean ridge volcanics are primarily basaltic, whereas subduction flows are mostly calc-alkaline, and more explosive and viscous.The reason for this is that land-based seismometers cannot detect sea-based earthquakes below a magnitude of 4, but acoustic waves travel well in water and over long periods of time.Early accounts described the unusual flat-topped steep-sided volcanoes (called tuyas) in Iceland that were suggested to have formed from eruptions below ice.The first English-language paper on the subject was published in 1947 by William Henry Mathews, describing the Tuya Butte field in northwest British Columbia, Canada.At first the eruptions resemble those that occur in the deep sea, forming piles of pillow lava at the base of the volcanic structure.After a while the ice finally melts into a lake, and the more explosive eruptions of Surtseyan activity begins, building up flanks made up of mostly hyaloclastite.[57] Volcanoes known to have subglacial activity include: Viable microbial communities have been found living in deep (−2800 m) geothermal groundwater at 349 K and pressures >300 bar.[64] The distinguishing feature of phreatic explosions is that they only blast out fragments of pre-existing solid rock from the volcanic conduit; no new magma is erupted.
Eruption (disambiguation)Volcanic Eruption (manga)Volcanic Eruptions (film company)Plinianeruption columnHawaiianStrombolian eruptionvolcanic ventfissurevolcanologistsvolcanoesMagmatic eruptionsPhreatic eruptionssuperheatinggranulationPhreatomagmatic eruptionssubmarineStrombolianVulcanianSurtseyanPelean eruptionsPlinian eruptionsUltra-PlinianSubglacialVolcanic Explosivity Indexorder-of-magnitudeejectaexplosive eruptionseffusive eruptionslava fountainslava flowslateralfissure eruptionsrift zonesmagma chamberColumbia UniversityIrazú VolcanomantleGeorge P. L. WalkerList of largest volcanic eruptionsSmithsonian InstitutionGlobal Volcanism ProgramRichter scaleearthquakeslogarithmicKīlaueaStromboliGalerasNevado del RuizPeléanEyjafjallajökullMount St. HelensMount PinatuboTamboraSupervolcanicLake Toba74 k.y.a.MagmaticjuvenileclastsexplosivedecompressionHawaiieruption columnseruption of Mount Vesuvius in 79 ADPompeiiHawaiian eruptionAsh plumeLava fountainCraterLava lakeFumarolesLava flowStratumHawaiian volcanoesMauna Loaeffusive eruptionbasaltgaseous contentshield volcanofissure ventsfissure ventscoriaPuʻu ʻŌʻōKilauealava lakespahoehoeHawaiʻiviscosityglassyPele's tearsPele's hairreticuliteMount Etnaparasiticcinder coneisland of Hawaiʻifissure-basedList of volcanoes in the Hawaiian – Emperor seamount chainMount MiharaLapilliVolcanic ashVolcanic bombMagma conduitgas slugsair pressuresoap bubblegas pressureseruptive columnsbasalticvolcanic bombscinder conespyroclaststephraHawaiian eruptionsParícutinMexicoMount ErebusAntarcticaMount BatutaraIndonesiaVulcanian eruptionVulcanoGiuseppe Mercalliviscousvesiculate gases