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Volcanic lightning is an electrical discharge caused by a volcanic eruption rather than from an ordinary thunderstorm. Volcanic lightning arises from colliding, fragmenting particles of volcanic ash (and sometimes ice),which generate static electricity within the volcanic plume, leading to the name dirty thunderstorm. Moist convection and ice formation also drive the eruption plume dynamics and can trigger volcanic lightning. Unlike ordinary thunderstorms, volcanic lightning can also occur before any ice crystals have formed in the ash cloud.
The earliest recorded observations of volcanic lightningare from Pliny the Younger, describing the eruption of Mount Vesuvius in 79 AD, "There was a most intense darkness rendered more appalling by the fitful gleam of torches at intervals obscured by the transient blaze of lightning." The first studies of volcanic lightning were also conducted at Mount Vesuvius by Professor Palmieri who observed the eruptions of 1858, 1861, 1868, and 1872 from the Vesuvius Observatory. These eruptions often included lightning activity.
Instances have been reported above Alaska's Mount Augustine volcano,Iceland's Eyjafjallajökull volcano, Mount Etna in Sicily, Italy, and Taal Volcano in the Philippines.
Ice charging is thought to play an important role in certain types of eruption plumes – particularly those rising above the freezing level or involving magma-water interaction.Ordinary thunderstorms produce lightning through ice charging as water clouds become electrified from colliding ice crystals and other hydrometeors. Volcanic plumes can also carry abundant water. This water is sourced from the magma, vaporized from surrounding sources such as lakes and glaciers, and entrained from ambient air as the plume rises through the atmosphere. One study suggested that the water content of volcanic plumes can be greater than that of thunderstorms. The water is initially transported as a hot vapor, which condenses to liquid in the rising column and ultimately freezes to ice if the plume cools well below freezing. Some eruptions even produce volcanic hail. Support for the ice-charging hypothesis includes the observation that lightning activity greatly increases once volcanic plumes rise above the freezing level, and evidence that ice crystals in the anvil top of the volcanic cloud are effective charge-carriers.
Triboelectric (frictional) charging within the plume of a volcano during eruption is thought to be a major electrical charging mechanism. Electrical charges are generated when rock fragments, ash, and ice particles in a volcanic plume collide and produce static charges, similar to the way that ice particles collide in regular thunderstorms.The convective activity causing the plume to rise then separates the different charge regions, ultimately causing electrical breakdown.
Fractoemission is the generation of charge through break-up of rock particles. It may be a significant source of charge near the erupting vent.
Although it is thought to have a small effect on the overall charging of volcanic plumes, naturally occurring radioisotopes within ejected rock particles may nevertheless influence particle charging.In a study performed on ash particles from the Eyjafjallajökull and Grímsvötn eruptions, scientists found that both samples possessed a natural radioactivity above the background level, but that radioisotopes were an unlikely source of self-charging in the Eyjafjallajö However, there was the potential for greater charging near the vent where the particle size is larger. Research continues, and the electrification via radioisotopes, such as radon, may in some instances be significant and at various magnitudes a somewhat common mechanism.
The height of the ash plume appears to be linked with the mechanism which generates the lightning. In taller ash plumes (7–12 km) large concentrations of water vapor may contribute to lightning activity, while smaller ash plumes (1–4 km) appear to gain more of their electric charge from fragmentation of rocks near the vent of the volcano (fractoemission). The atmospheric temperature also plays a role in the formation of lightning. Colder ambient temperatures promote freezing and ice charging inside the plume, thus leading to more electrical activity.
Experimental studies and investigation of volcanic deposits have shown that volcanic lighting creates a by-product known as "lightning-induced volcanic spherules" (LIVS). °C. When this bolt contacts ash particles within the plume it may do one of two things: (1) completely vaporize the ash particles, or (2) cause them to melt and then quickly solidify as they cool, forming orb shapes. The presence of lightning-induced volcanic spherules may provide geological evidence for volcanic lightning when the lightning itself was not observed directly.These tiny glass spherules form during high-temperatures processes such as cloud-to-ground lightning strikes, analogous to fulgurites. The temperature of a bolt of lightning can reach 30,000
Lightning is a naturally occurring electrostatic discharge during which two electrically charged regions, both in the atmosphere or with one on the ground, temporarily neutralize themselves, causing the instantaneous release of an average of one gigajoule of energy. This discharge may produce a wide range of electromagnetic radiation, from heat created by the rapid movement of electrons, to brilliant flashes of visible light in the form of black-body radiation. Lightning causes thunder, a sound from the shock wave which develops as gases in the vicinity of the discharge experience a sudden increase in pressure. Lightning occurs commonly during thunderstorms as well as other types of energetic weather systems, but volcanic lightning can also occur during volcanic eruptions.
Iceland experiences frequent volcanic activity, due to its location both on the Mid-Atlantic Ridge, a divergent tectonic plate boundary, and over a hot spot. Nearly thirty volcanoes are known to have erupted in the Holocene epoch; these include Eldgjá, source of the largest lava eruption in human history.
Eyjafjallajökull, sometimes referred to by the numeronym E15, is one of the smaller ice caps of Iceland, north of Skógar and west of Mýrdalsjökull. The ice cap covers the caldera of a volcano with a summit elevation of 1,651 metres (5,417 ft). The volcano has erupted relatively frequently since the Last Glacial Period, most recently in 2010, when, although relatively small for a volcanic eruption, it caused enormous disruption to air travel across northern and western Europe for a week.
Katla is a large volcano in southern Iceland. It is very active; twenty eruptions have been documented between 930 and 1918, at intervals of 20–90 years. It has not erupted violently for 105 years, although there may have been small eruptions that did not break the ice cover, including ones in 1955, 1999, and 2011.
Eldgjá is a volcano and a canyon in Iceland. Eldgjá is part of the Katla volcano; it is a segment of a 40 kilometres (25 mi) long chain of volcanic craters and fissure vents that extends northeast away from Katla volcano almost to the Vatnajökull ice cap. This fissure experienced a major eruption around 939 CE, which was the largest effusive eruption in recent history. It covered about 780 square kilometres (300 sq mi) of land with 18.6 cubic kilometres (4.5 cu mi) of lava from two major lava flows.
Toney Mountain is an elongated snow-covered shield volcano, 60 km (37 mi) long and rising to 3,595 m (11,795 ft) at Richmond Peak, located 56 km (35 mi) southwest of Kohler Range in Marie Byrd Land, Antarctica.
The Pleiades are a volcanic group in northern Victoria Land of Antarctica. It consists of youthful cones and domes with Mount Atlas/Mount Pleiones, a small stratovolcano formed by three overlapping cones, being the dominant volcano and rising 500 m (1,600 ft) above the Evans Névé plateau. Two other named cones are Alcyone Cone and Taygete Cone, the latter of which has been radiometrically dated to have erupted during the Holocene. A number of tephra layers across Antarctica have been attributed to eruptions of this volcanic group, including several that may have occurred within the last few hundred years.
An eruption column or eruption plume is a cloud of super-heated ash and tephra suspended in gases emitted during an explosive volcanic eruption. The volcanic materials form a vertical column or plume that may rise many kilometers into the air above the vent of the volcano. In the most explosive eruptions, the eruption column may rise over 40 km (25 mi), penetrating the stratosphere. Stratospheric injection of aerosols by volcanoes is a major cause of short-term climate change.
Volcanic gases are gases given off by active volcanoes. These include gases trapped in cavities (vesicles) in volcanic rocks, dissolved or dissociated gases in magma and lava, or gases emanating from lava, from volcanic craters or vents. Volcanic gases can also be emitted through groundwater heated by volcanic action.
Trachyandesite is an extrusive igneous rock with a composition between trachyte and andesite. It has little or no free quartz, but is dominated by sodic plagioclase and alkali feldspar. It is formed from the cooling of lava enriched in alkali metals and with an intermediate content of silica.
The geology of Iceland is unique and of particular interest to geologists. Iceland lies on the divergent boundary between the Eurasian plate and the North American plate. It also lies above a hotspot, the Iceland plume. The plume is believed to have caused the formation of Iceland itself, the island first appearing over the ocean surface about 16 to 18 million years ago. The result is an island characterized by repeated volcanism and geothermal phenomena such as geysers.
The cumulonimbus flammagenitus cloud (CbFg), also known as the pyrocumulonimbus cloud, is a type of cumulonimbus cloud that forms above a source of heat, such as a wildfire or volcanic eruption, and may sometimes even extinguish the fire that formed it. It is the most extreme manifestation of a flammagenitus cloud. According to the American Meteorological Society’s Glossary of Meteorology, a flammagenitus is "a cumulus cloud formed by a rising thermal from a fire, or enhanced by buoyant plume emissions from an industrial combustion process."
Between March and June 2010 a series of volcanic events at Eyjafjallajökull in Iceland caused enormous disruption to air travel across Western Europe.
The 1808 mystery eruption is either a single large volcanic eruption (VEI-6), or a series of volcanic eruptions, conjectured to have taken place in 1808–1809. This eruption is suspected of having contributed to a period of global cooling that lasted several years, analogous to how the 1815 eruption of Mount Tambora (VEI-7) led to the Year Without a Summer in 1816. A VEI-6 eruption is comparable to the 1883 eruption of Krakatoa.
Volcanic ash consists of fragments of rock, mineral crystals, and volcanic glass, created 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, including particles larger than 2 mm. Volcanic ash 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 the air, ash is transported by wind up to thousands of kilometres away.
A multi-component gas analyzer system (Multi-GAS) is an instrument package used to take real-time high-resolution measurements of volcanic gases. A Multi-GAS package includes an infrared spectrometer for CO2, two electrochemical sensors for SO2 and H2S, and pressure–temperature–humidity sensors, all in a weatherproof box. The system can be used for individual surveys or set up as permanent stations connected to radio transmitters for transmission of data from remote locations. The instrument package is portable, and its operation and data analysis are simple enough to be conducted by non-specialists.
Volcanic ash aggregation occurs when particles of volcanic ash collide and stick together during transport. This process modifies the size distribution of airborne particles, which affects both atmospheric dispersal and fallout patterns on the ground. Aggregation also impacts the dynamics of volcanic plumes, pyroclastic density currents, and their associated hazards.
Tamsin Alice Mather is a British Professor of Earth Sciences at the Department of Earth Sciences, University of Oxford and a Fellow of University College, Oxford. She studies volcanic processes and their impacts on the Earth's environment and has appeared on the television and radio.
The 1452/1453 mystery eruption is an unidentified eruption associated to the first of two large sulfate spikes that took place in the 1450s with the second being the 1458 mystery eruption. The eruption caused a severe volcanic winter leading to one of strongest cooling events in Northern Hemisphere. This date also coincides with a substantial intensification of the Little Ice Age.