Fulgurite

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Fulgurite
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Two Type I (arenaceous) fulgurites: a common tube fulgurite and a more irregular specimen.
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Two small Type I Saharan Desert fulgurites.[1] In a planar view the specimen on the right has a blade-like morphology, but its tubular nature is dramatically shown in a stereo view.
Dimensions of typical fulgarites

Fulgurites (from the Latin fulgur, meaning "lightning") are natural tubes, clumps, or masses of sintered, vitrified, and/or fused soil, sand, rock, organic debris and other sediments that sometimes form when lightning discharges into ground. Fulgurites are classified as a variety of the mineraloid lechatelierite. Fulgurites have no fixed composition because their chemical composition is determined by the physical and chemical properties of material struck by lightning. When lightning strikes a grounding substrate, upwards of 100 million volts (100 MV) are rapidly discharged into the ground.[2] This charge propagates into and rapidly vaporizes and melts silica-rich quartzose sand, mixed soil, clay, or other sediments.[3] This results in the formation of hollow and/or branching assemblages of glassy, protocrystalline, and heterogeneously microcrystalline tubes, crusts, slags, and vesicular masses.[4] Fulgurites are homologous to Lichtenberg figures, which are the branching patterns produced on surfaces of insulators during dielectric breakdown by high-voltage discharges, such as lightning.[5][6]

Description[edit]

Fulgurites are formed when lightning strikes the ground, fusing and vitrifying mineral grains.[7] The primary SiO2 phase in common tube fulgurites is lechatelierite, an amorphous silica glass. Because their groundmass is generally amorphous in structure, fulgurites are classified as mineraloids.

Material properties (color, surface texture) of fulgurites vary widely, depending on bulk composition, interface dynamics, and trace elements. Most natural fulgurites fall on a spectrum from colorless (transparent), to white, to black. Iron oxide is a common impurity that can result in a deep brownish-green coloration. Lechatelierite similar to fulgurites can also be produced via controlled (or uncontrolled) arcing of artificial electricity into a medium. Downed high voltage power lines have produced lechatelierites, occasionally colored by copper or other materials from the power lines themselves.[8] Brightly-colored lechatelierites resembling fulgurites are usually synthetic and reflect the incorporation of synthetic materials. However, lightning can strike man-made objects, resulting in colored fulgurites.

The interior of Type I (sand) fulgurites normally is smooth or lined with fine bubbles, while their exteriors are coated with rough sedimentary particles or small rocks. Other types or fulgurites are often vesicular, and lack an open central tube; their exteriors can be porous or smooth. Branching fulgurites display fractal-like self-similarity and structural scale invariance as a macroscopic or microscopic network of root-like branches, and can display this texture without central channels or obvious divergence from morphology of context or target (e.g. sheet-like melt, rock fulgurites). Fulgurites formed in sand or loose soil are usually fragile, making the field collection of large specimens difficult.

Fulgurites can exceed tens of centimeters in diameter and can penetrate deep into the subsoil, sometimes occurring as far as 15 m (49 ft) below the surface that was struck. [9] Or they may form directly on sedimentary surfaces.[10] One of the longest fulgurites to have been found in modern times was a little over 4.9 m (16 ft) in length, and was found in northern Florida.[11] The Yale University Peabody Museum of Natural History displays one of the longest known preserved fulgurites, approximately 4 m (13 ft) in length.[12] Charles Darwin in The Voyage of the Beagle recorded that tubes such as these found in Drigg, Cumberland, UK reached a length of 9.1 m (30 ft).[13][14] The Winans Lake fulgurite[s] (Winans Lake, Livingston County, Michigan), extended discontinuously throughout a 30 m range, and arguably includes the largest reported fulgurite mass ever recovered and described: its largest section extending approximately 16 ft (4.88 m) in length by 1 ft in diameter (30 cm).[4][15]

Peak temperatures within a lightning channel exceed 30,000 K, with sufficient pressure to produce planar deformation features in SiO2, a kind of polymorphism. This is also known colloquially as shocked quartz.[16]

Classification[edit]

Fulgurites have been classified by Pasek et al. (2012)[17] into five types related to the type of sediment in which the fulgurite formed, as follows:

  • Type I - sand fulgurites with tubaceous structure; their central axial void may be collapsed
  • Type II - soil fulgurites; these are glass-rich, and form in a wide range of sediment compositions, including clay-rich soils, silt-rich soils, gravel-rich soils, and loessoid; these may be tubaceous, branching, vesicular, irregular/slaggy, or may display a combination of these structures, and can produce exogenic fulgurites (droplet fulgurites)
  • Type III - caliche or calcic sediment fulgurites, having thick, often surficially glazed granular walls with calcium-rich vitreous groundmass with little or no lechatelierite glass; their shapes are variable, with multiple narrow central channels common, and can span the entire range of morphological and structural variation for fulguritic objects
  • Type IV - rock fulgurites, which are either crusts on minimally altered rocks, networks of tunneling within rocks, vesicular outgassed rocks (often glazed by a silicide-rich and/or metal oxide crust), or completely vitrified and dense rock material and masses of these forms with little sedimentary groundmass
  • Type V - [droplet] fulgurites (exogenic fulgurites), which show evidence of ejection (e.g. spheroidal, filamentous, or aerodynamic),[3][18] related by composition to Type II and Type IV fulgurites

Significance[edit]

Paleoenvironmental indicator[edit]

The presence of fulgurites in an area can be used to predict the prevalence of lightning over the particular area over a certain period of time, which in turn can help in understanding past regional climate[s], in the study of paleolightning.[1]

Analysis of LIRM anomaly (see paleomagnetism) and reconstruction of ancient environmental conditions are motivations for the identification and study of fulgurites.[19]

Place in planetary processes and the geologic record[edit]

Many high-pressure, high-temperature materials have been observed in fulgurites. Many of these minerals and compounds are also known to be formed by synthetic or meteoritic sources such as nuclear weapon tests, hypervelocity impacts, and cosmic dust. Shocked quartz was first described in fulgurites in 1980.[20] Other materials, including highly reduced silicon-metal alloys (silicides), the fullerene allotropes C60 (buckminsterfullerene) and C70, as well as high-pressure polymorphs of SiO2, have been identified in fulgurites.[4][16][15][21][22][23][24][25][26][27][28][29][30]

Reduced phosphorus as phosphides and phosphites has been identified through quantitative analyses of a representative sample of 10 fulgurites recovered from most continents, in the form of schreibersite (Fe3P, (Fe,Ni)3P) - otherwise rare on Earth due to its oxidizing surface conditions, but relatively common in meteorites, comets, interplanetary dust, and some planetary bodies - and titanium(III) phosphide (TiP), which is unique to fulgurites, among other unusual compounds resulting from supercritical non-equilibrium.[4][31][32]

In material culture[edit]

In 2008, An object later classified as a fulgurite, but initially believed by archaeologists to be an igneous cinder, was found within the contents of the ritual ash altar at the temple of Lykaian Zeus at Mount Lykaion in Greece. The object was identified and studied by geologist George H. Davis (past president of the Geological Society of America).[33][34][35][36] It may be contemporaneous with ancient site use, and as such potentially associated with ritual activity performed there.

Fulgurites are popular among hobbyists and collectors of natural specimens.[37]

Gallery[edit]

See also[edit]

References[edit]

  1. ^ a b Sponholz, B.; Baumhauer, R.; Felix-Henningsen, P. (27 July 2016). "Fulgurites in the southern Central Sahara, Republic of Niger and their palaeoenvironmental significance". The Holocene. 3 (2): 97–104. CiteSeerX 10.1.1.549.8976. doi:10.1177/095968369300300201.
  2. ^ Ann Cooper, Mary (1980-03-01). "Lightning injuries: Prognostic signs for death". Annals of Emergency Medicine. 9 (3). Retrieved 2019-06-16.
  3. ^ a b Joseph, Michael L. (January 2012). "A Geochemical Analysis of Fulgurites: from the inner glass to the outer crust". Scholarcommons.usf.edu. Retrieved 2015-08-16.
  4. ^ a b c d "Fulgurite Classification, Petrology, and Implications for Planetary Processes - The University of Arizona Campus Repository". Arizona.openrepository.com. Retrieved 2015-08-16.
  5. ^ "SGSMP : Lichtenberg figures". Sgsmp.ch. 2005-07-28. Archived from the original on 2015-08-02. Retrieved 2015-08-16.
  6. ^ Ouellette, Jennifer (23 July 2013). "Fermilab Physicist Makes "Frozen Lightning" Art with Accelerators". Scientific American blog. Retrieved 11 August 2015.
  7. ^ Essene, E. J.; Fisher, D. C. (1986-10-10). "Lightning Strike Fusion: Extreme Reduction and Metal-Silicate Liquid Immiscibility". Science. 234 (4773): 189–193. doi:10.1126/science.234.4773.189. PMID 17746479. Retrieved 2015-08-16.
  8. ^ "The Agatelady: Adventures and Events: More about Fulgurites". 2014-09-18.
  9. ^ W. Wright Jr., Fred (1988-07-01). "Florida's Fantastic Fulgurite Find" (PDF). Weatherwise. 51 (4). Retrieved 2019-06-16.
  10. ^ Ripley, George; Dana, Charles Anderson (1859). The New American Cyclopaedia. Appleton. p. 2.
  11. ^ Grapes, R. H. (2006). Pyrometamorphism. Springer. p. 28. ISBN 978-3-540-29453-5.
  12. ^ "New Peabody hall offering high-tech lessons about Earth and space". Yale Bulletin & Calendar. 34 (30). June 9, 2006. Archived from the original on November 6, 2014. Retrieved 2013-12-26.
  13. ^ "Presenting... Fulgurites". Oum.ox.ac.uk. Retrieved 2015-08-16.
  14. ^ The popular educator - Books on Google Play. 1860. Retrieved 2015-08-16.
  15. ^ a b "Lightning strike fusion: extreme reduction and metal-silicate liquid immiscibility". Science-AAAS. 1986-10-10. doi:10.1126/science.234.4773.189. Retrieved 2015-09-07.
  16. ^ a b Gieré, Reto; Wimmenauer, Wolfhard; Müller-Sigmund, Hiltrud; Wirth, Richard; Lumpkin, Gregory R.; Smith, Katherine L. (2015-07-01). "Lightning-induced shock lamellae in quartz". American Mineralogist. 100 (7): 1645–1648. doi:10.2138/am-2015-5218. Retrieved 2015-08-16.
  17. ^ Pasek, Matthew A.; Block, Kristin; Pasek, Virginia (2012-04-24). "Fulgurite morphology: a classification scheme and clues to formation - Springer". Contributions to Mineralogy and Petrology. 164 (3): 477–492. Bibcode:2012CoMP..164..477P. doi:10.1007/s00410-012-0753-5.
  18. ^ Pasek, Matthew A.; Block, Kristin; Pasek, Virginia (2012-04-24). "Fulgurite morphology: a classification scheme and clues to formation - Springer". Contributions to Mineralogy and Petrology. 164 (3): 477–492. Bibcode:2012CoMP..164..477P. doi:10.1007/s00410-012-0753-5.
  19. ^ Sponholz, B. (January 4–18, 2004). "Fulgurites as paleoclimatic indicators: New approaches on Holocene climatic change in the Sahara". First Joint Meeting of IGCP 490 and ICSU: Environmental Catastrophes in Mauritania, the Desert and the Coast.
  20. ^ {{cite journal |title= Petrified Lightning|date=1980-01-01 |pmid=17733026 |doi=10.1080/00357529.1980.11764615 |volume=55 |issue= 1|journal=Rocks & Minerals |pages=13–17 | last1 = Gailliot | first1 = Mary Patricia |
  21. ^ Daly, TK; Buseck, PR; Williams, P; Lewis, CF (2015-04-20). "Fullerenes from a fulgurite". Science. 259 (5101): 1599–601. Bibcode:1993Sci...259.1599D. doi:10.1126/science.259.5101.1599. PMID 17733026.
  22. ^ Heymann, D. "Chemistry of Fullerenes on the Earth and in the Solar System : A 1995 Review" (PDF). LPS. XXVII. Retrieved 2015-08-16.
  23. ^ Macdonald, F.A.; Mitchell, K.; Cina, S.E. "Evidence for a Lightning-Strike Origin of the Edeowie Glass" (PDF). Lunar and Planetary Science. XXXV. Retrieved 2015-08-16.
  24. ^ Pasek, M.A.; Collins, G.S.; Melosh, H.J.; Atlas, Z. "Shocked Quartz in a Fulgurite" (PDF). Meteoritics and Planetary Science. 73. Retrieved 2019-06-16.
  25. ^ Carter, EA; Pasek, MA; Smith, T; Kee, TP; Hines, P; Edwards, HG (2015-04-20). "Rapid Raman mapping of a fulgurite". Anal Bioanal Chem. 397 (7): 2647–58. doi:10.1007/s00216-010-3593-z. PMID 20229006.
  26. ^ Carter, Elizabeth A.; Hargreaves, Michael D.; Kee, Terence P.; Pasek, Matthew A.; Edwards, Howell G. M. (2010-06-07). "A Raman spectroscopic study of a fulgurite | Philosophical Transactions of the Royal Society of London A: Mathematical, Physical and Engineering Sciences". Philosophical Transactions of the Royal Society A: Mathematical, Physical and Engineering Sciences. 368 (1922): 3087–3097. doi:10.1098/rsta.2010.0022. PMID 20529946. Retrieved 2015-08-16.
  27. ^ [1] Archived September 30, 2009, at the Wayback Machine
  28. ^ Sheffer, A.A.; Dyar, M.D.; Sklute, E.C. (2006). "Lightning Strike Glasses as an Analog for Impact Glasses" (PDF). Lunar and Planetary Science. XXXVII. Retrieved 2015-08-16.
  29. ^ Kochemasov, G.G. "Fulgurite" (PDF). Lunar and Planetary Science. Retrieved 2015-08-16.
  30. ^ Parnell, J.; Thackrey, S.; Muirhead, D.; Wright, A. "Transient High-Temperature Processing of Silicates in Fulgurites as Analogues for Meteorite and Impact Melts" (PDF). Lunar and Planetary Science. XXXIX. Retrieved 2015-08-16.
  31. ^ Block, Kristin; Pasek, Matthew (August 2009). "Lightning-induced reduction of phosphorus oxidation state". Nature Geoscience. 2 (8): 553–556. Bibcode:2009NatGe...2..553P. doi:10.1038/ngeo580. Retrieved 2015-08-16.
  32. ^ Pasek, M.A.; Kee, T.P.; Carter, E.A.; Hargreaves, M.D.; H.G.M. Edwards; Z.Atlas (2010). "Fried Phosphate and Organic Survival : Lightning in Biogeochemical Cycles" (PDF). Astrobiology Sciences Conference. Retrieved 2015-08-16.
  33. ^ Romano, D. G. (2014). "Mt. Lykaion Excavation and Survey Project, Part 1: The Upper Sanctuary". Hesperia. 83 (4): 569–652. doi:10.2972/hesperia.83.4.0569.
  34. ^ Romano, D. G. (2015). "Mt. Lykaion Excavation and Survey Project, Part 2: The Lower Sanctuary". Hesperia. 84 (2): 207–276. Text "10.2972/hesperia.84.2.0207" ignored (help)
  35. ^ "Excavating at the Birthplace of Zeus* – Mt. Lykaion Excavation and Survey Project". Lykaionexcavation.org. 2003-07-20. Retrieved 2015-08-20.
  36. ^ "Fulgurite (i.e., petrified lightning) from the Sanctuary of Zeus, Mt. Lykaion, Peloponessos, Greece". The University of Arizona. Retrieved 2019-06-16.
  37. ^ Patti Polk, Collecting Rocks, Gems & Minerals: Easy Identification - Values - Lapidary Uses, Krause, 2010, page 168 ISBN 978-1-4402-0415-9

External links[edit]