Volcanic lightning

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Volcanic lightning
January 2020 eruption of Taal Volcano
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Volcanic lightning is an electrical discharge caused by a

Moist convection currents and ice formation also drive the eruption plume dynamics[6][7] and can trigger volcanic lightning.[8][9] Unlike ordinary thunderstorms, volcanic lightning can also occur when there are no ice crystals in the ash cloud.[10][11]

The earliest recorded observations of volcanic lightning

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."[13] The first studies of volcanic lightning were also conducted at Mount Vesuvius by Luigi Palmieri[14] who observed the eruptions of 1858, 1861, 1868, and 1872 from the Vesuvius Observatory. These eruptions often included lightning activity.[13]

Instances have been reported above Alaska's

Mount Augustine volcano,[15] Iceland's Eyjafjallajökull and Grimsvotn,[16] Mount Etna in Sicily, Italy,[17] Taal Volcano in the Philippines[18][19] and Mount Ruang in Indonesia.[20]

Charging mechanisms

Ice charging

1994 eruption of Mount Rinjani

Ice charging is thought to play an important role in certain types of eruption plumes – particularly those rising above the

hydrometeors.[23] Volcanic plumes can also carry abundant water.[24] This water is sourced from the magma,[25] vaporized from surrounding sources such as lakes and glaciers,[26] and entrained from ambient air as the plume rises through the atmosphere.[6] One study suggested that the water content of volcanic plumes can be greater than that of thunderstorms.[27] 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.[28] Some eruptions even produce volcanic hail.[7][29] Support for the ice-charging hypothesis includes the observation that lightning activity greatly increases once volcanic plumes rise above the freezing level,[30][21] and evidence that ice crystals in the anvil top of the volcanic cloud are effective charge-carriers.[9]

Frictional charging

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.[12] The convective activity causing the plume to rise then separates the different charge regions, ultimately causing electrical breakdown.

Fractoemission

Fractoemission is the generation of charge through break-up of rock particles. It may be a significant source of charge near the erupting vent.[31]

Radioactive charging

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.[32] 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 Eyjafjallajökull plume.[33] However, there was the potential for greater charging near the vent where the particle size is larger.[32] Research continues, and the electrification via radioisotopes, such as radon, may in some instances be significant and at various magnitudes a somewhat common mechanism.[34]

Plume height

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).[30] 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.[35][33]

Lightning-induced volcanic spherules

Experimental studies and investigation of volcanic deposits have shown that volcanic lighting creates a by-product known as "lightning-induced

spherules form during high-temperatures processes such as cloud-to-ground lightning strikes, analogous to fulgurites.[36] The temperature of a bolt of lightning can reach 30,000 °C. When this bolt contacts ash particles within the plume it may do one of two things: (1) completely vaporize the ash particles,[38] or (2) cause them to melt and then quickly solidify as they cool, forming orb shapes.[37] The presence of lightning-induced volcanic spherules may provide geological evidence for volcanic lightning when the lightning itself was not observed directly.[36]

References

  1. ^ Fritz, Angela (2016). "Scientists think they've solved the mystery of how volcanic lightning forms". The Washington Post.
  2. ^ Mulvaney, Kieran (2016). "Mystery of Volcano Lightning Explained". Seeker.
  3. ^ Lipuma, Lauren (2016). "New studies uncover mysterious processes that generate volcanic lightning". American Geophysical Union GeoSpace Blog.
  4. S2CID 92549298
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  6. ^
    doi:10.1029/93JB00718
    .
  7. ^
    PMID 26235052
    .
  8. ^ Williams, Earl R.; McNutt, Stephen R. (2005). "Total water contents in volcanic eruption clouds and implications for electrification and lightning" (PDF). Proceedings of the 2nd International Conference on Volcanic Ash and Aviation Safety: 67–71.
  9. ^
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  10. ISSN 1943-2682
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  11. ISSN 0094-8276
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  12. ^
    S2CID 53140261
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  13. ^ a b "History of Volcanic Lightning | Volcano World | Oregon State University". volcano.oregonstate.edu. 27 May 2010. Retrieved 2018-05-09.
  14. ^ Perrone, Alessio. "A Defiant Volcanologist Survived 5 Eruptions while Living on Mount Vesuvius". Scientific American. Springer Nature. Retrieved 19 April 2024.
  15. ^ Handwerk, Brian (February 22, 2007). "Volcanic Lightning Sparked by "Dirty Thunderstorms"". National Geographic. Archived from the original on February 25, 2007. Retrieved 2009-01-09.
  16. ^ "Iceland Volcano Pictures: Lightning Adds Flash to Ash". National Geographic. April 19, 2010. Archived from the original on April 21, 2010. Retrieved 2010-04-20.
  17. ^ Sample, Ian (3 December 2015). "Sky lights up over Sicily as Mount Etna's Voragine crater erupts". The Guardian. Retrieved 2015-12-03.
  18. ^ DI SANTOLO, ALESSANDRA SCOTTO. "Philippines volcano eruption: Terrifying video of Taal volcano producing lightning strikes". Retrieved 12 January 2020.
  19. ^ Borbon, Christian. "Philippines: Volcano near Manila spews giant ash column". Gulf News. Retrieved 12 January 2020.
  20. ^ "Gunung Ruang Kembali Erupsi, Warga Diimbau Mengungsi". CNN Indonesia. Retrieved 17 April 2024.
  21. ^
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  22. doi:10.1175/1520-0450(1993)032<0642:AROTEP>2.0.CO;2
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  25. ISBN 9780123859389
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  27. S2CID 59522391
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  28. ISSN 0148-0227
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  29. Bibcode:2013EGUGA..15.4797A
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  30. ^
    S2CID 59522391 – via Research Gate.[clarification needed
    ]
  31. ISSN 2156-2202
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  32. ^ a b Alpin, Karen; et al. (2014). "Electronic Charging of Volcanic Ash" (PDF). Electrostatics.org. Retrieved May 8, 2018.
  33. ^
    ISBN 9780081004050
  34. doi:10.1029/2019GL082211
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  35. doi:10.1088/1748-9326/5/4/044013
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  36. ^
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  37. ^ a b Perkins, Sid (March 4, 2015). "Flash glass: Lightning inside volcanic ash plumes create glassy spherules". American Association for the Advancement of Science.
  38. PMID 29138444
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