Fulgurite

Fulgurite
Stereo image
Right frame 
Two Type I (arenaceous) fulgurites: a common tube fulgurite and a more irregular specimen.
Stereo image
Right frame 
Two small Type I Saharan Desert fulgurites. 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.
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Fulgurites (from the Latin fulgur, meaning "lightning") are classified generically as a variety of the mineraloid lechatelierite, although their absolute chemical composition is dependent on the physical and chemical properties of target material affected by the discharge of cloud-ground lightning. They are commonly hollow and/or branching assemblages of glassy, protocrystalline, and heterogeneously-microcrystalline tubes, crusts, slags, vesicular masses, and clusters of refractory materials that often form during the discharge phase of lightning strikes propagating into silica-rich quartzose sand, mixed soil, clay, caliche and other carbonate-rich sediments.[1][2] Colloquially, they have been referred to as petrified lightning.[3] 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.[4][5]

Description

Fulgurites are formed when lightning with a temperature of at least 1,800 °C (3,270 °F) melts silica or other common conductive and semiconductive minerals and substrates, fusing, vitrifying, oxidizing and reducing mineral grains and organic compounds;[6] the fulgurite mass is the rapidly-quenched end-product.[7] The temperature peak within a lightning channel, however, is known to exceed 30,000 K, with sufficient pressure to produce planar deformation features, or "shock lamellae" in SiO2 polymorphs.[8][9][10] It is assumed that the process of forming a fulgurite occurs over a timespan of the order of a single second,[11] following the termination of the return stroke sequence, and leaves direct evidence of the dissipation path and its dispersion over the surface or into the earth.[12] Artificial fulgurites can also be produced when the controlled arcing of electricity into a fusable medium. This has been documented in cases of downed high voltage power lines; current was discharged into the ground, producing blue fulgurite-like lechatelierites, colored by copper from the power line.[13]

The color of fulgurites varies widely, depending on composition and chemical impurities. It can range from black or tan, to green, blue, metallic blue-grey, or a translucent white. More colorful variants are usually synthetic and reflect incorporation of synthetic materials. The interior of Type I (sand) fulgurites normally is very smooth or lined with fine bubbles, while other types are often both vesicular and dense or porous and scoria-like; their exteriors generally can be coated with rough sedimentary particles and can be porous, smooth, or structurally-complex. Fulgurites display some degree of self-similarity and structural scale invariance as a macroscopic or microscopic network of root-like branches. Fulgurites formed in sand or loose soil are mechanically fragile, making the field collection of large specimens difficult.

The primary SiO2 phase in fulgurites is lechatelierite, a silica glass. Because their groundmass is generally amorphous in structure, fulgurites are classified as mineraloids.

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, but may form directly on appropriate sedimentary surfaces.[14] 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.[15] 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).[16][17] 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).[2][18]

Classification

Fulgurites have been classified by Pasek et al. (2012)[19] into five types related to the type of sediment in which the fulgurite formed, as follows:

Place in planetary processes and the geologic record

Many observations have been made in fulgurites of high-pressure, high-temperature materials more commonly assumed to be the exclusive to meteoritic sources, products of asteroid impacts, comet airbursts, or cosmic dust influx. Such materials - as a suite - formerly considered to be unique to hypervelocity impacts, have been identified in fulgurites, including highly reduced silicon-metal alloys (silicides), the fullerene allotropes C60 (buckminsterfullerene) and C70, as well as high-pressure polymorphs of SiO2, in fulgurites.[2][8][18][21][22][23][24][25][26][27][28][29][30]

Reduced phosphorus as phosphides and phosphites have 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) - terrestrially extremely rare, but common on meteorites, comets, interplanetary dust, and some planetary bodies - and TiP, which is unique to fulgurites.[2][31][32]

Fulgurites are, with the analysis of paleomagnetic (LIRM, or Lightning-induced remanent magnetism) anomaly, primary sources for environmental information produced by the study of paleolightning in paleoclimatology and atmospheric sciences.[33] For instance, the fact that fulgurites are abundant in the central Sahara Desert, where thunderstorm activity is very rare, demonstrates that thunderstorms were once more frequent in that region, and as such, their spatial distributions guide reconstruction of convection and precipitation patterns, while their pores enclose and preserve samples of the ancient atmosphere in which they formed.[34][35]

Fulgurites in material culture

A fulgurite was found within the contents of the ash altar at the temple (hieron) of Lykaian Zeus at Mt. Lykaion in Greece, and may be associated with ritual activity performed there.[36][37][38]

Fulgurites are appreciated by many for their scientific value as permanent tangible evidence of transient lightning strikes.[39] Fulgurites also are popular among hobbyists and collectors of natural specimens.[40]

Gallery

See also

References

  1. 1 2 Michael L. Joseph (January 2012). "A Geochemical Analysis of Fulgurites: from the inner glass to the outer crust". Scholarcommons.usf.edu. Retrieved 2015-08-16.
  2. 1 2 3 4 "Fulgurite Classification, Petrology, and Implications for Planetary Processes - The University of Arizona Campus Repository". Arizona.openrepository.com. Retrieved 2015-08-16.
  3. ↑ Peter E. Viemeister (1983). "Petrified Lightning" (PDF). Ira.usf.edu. Retrieved 2015-08-16.
  4. ↑ "SGSMP : Lichtenberg figures". Sgsmp.ch. 2005-07-28. Retrieved 2015-08-16.
  5. ↑ Ouellette, Jennifer (23 July 2013). "Fermilab Physicist Makes "Frozen Lightning" Art with Accelerators". Scientific American blog. Retrieved 11 August 2015.
  6. ↑ "Lightning Strike Fusion: Extreme Reduction and Metal-Silicate Liquid Immiscibility". Sciencemag.org. 1986-10-10. Retrieved 2015-08-16.
  7. ↑ Carl Ege. "What are fulgurites and where can they be found?". geology.utah.gov. Retrieved 2009-03-21.
  8. 1 2 "Lightning-induced shock lamellae in quartz". Ammin.geoscienceworld.org. 2015-07-01. Retrieved 2015-08-16.
  9. ↑
  10. ↑
  11. 1 2 Grapes, R. H. (2006). Pyrometamorphism. Springer. p. 28. ISBN 3-540-29453-8.
  12. ↑ Uman, Martin A. (2008). The Art and Science of Lightning Protection. Cambridge University Press. p. 212. ISBN 0-521-87811-X.
  13. ↑ http://agatelady.blogspot.com/2014/09/more-about-fulgurites.html. Missing or empty |title= (help)
  14. ↑ Ripley, George; Charles Anderson Dana (1859). The New American Cyclopaedia. Appleton. p. 2.
  15. ↑ "New Peabody hall offering high-tech lessons about Earth and space". Yale Bulletin & Calendar (Yale University) 34 (30). June 9, 2006. Retrieved 2013-12-26.
  16. ↑ "Presenting... Fulgurites". Oum.ox.ac.uk. Retrieved 2015-08-16.
  17. ↑ "The popular educator - Books on Google Play". Play.google.com. Retrieved 2015-08-16.
  18. 1 2 "Lightning strike fusion: extreme reduction and metal-silicate liquid immiscibility". Science-AAAS. 1986-10-10. Retrieved 2015-09-07.
  19. ↑ "Fulgurite morphology: a classification scheme and clues to formation - Springer". Link.springer.com. 2012-04-24. Retrieved 2015-08-16.
  20. ↑ "Fulgurite morphology: a classification scheme and clues to formation - Springer". Link.springer.com. 2012-04-24. Retrieved 2015-08-16.
  21. ↑ "Fullerenes from a fulgurite. - PubMed - NCBI". Ncbi.nlm.nih.gov. 2015-04-20. Retrieved 2015-08-16.
  22. ↑ D. Heymann. "Chemistry of Fullerenes on the Earth and in the Solar System : A 1995 Review" (PDF). LPS (Lpi.usra.edu). XXVII. Retrieved 2015-08-16.
  23. ↑ F.A. Macdonald; K. Mitchell; S.E. Cina. "Evidence for a Lightning-Strike Origin of the Edeowie Glass" (PDF). Lunar and Planetry Science (Lpi.usra.edu) XXXV. Retrieved 2015-08-16.
  24. ↑
  25. ↑ "Rapid Raman mapping of a fulgurite. - PubMed - NCBI". Ncbi.nlm.nih.gov. 2015-04-20. Retrieved 2015-08-16.
  26. ↑ "A Raman spectroscopic study of a fulgurite | Philosophical Transactions of the Royal Society of London A: Mathematical, Physical and Engineering Sciences". Rsta.royalsocietypublishing.org. 2010-06-07. Retrieved 2015-08-16.
  27. ↑ Archived September 30, 2009, at the Wayback Machine.
  28. ↑ A.A. Sheffer; M.D. Dyar; E.C. Sklute (2006). "Lightning Strike Glasses as an Analog for Impact Glasses" (PDF). Lunar and Planetry Science (Lpi.usra.edu). XXXVII. Retrieved 2015-08-16.
  29. ↑ G.G. Kochemasov. "Fulgurite" (PDF). Lunar and Planetry Science (Lpi.usra.edu). Retrieved 2015-08-16.
  30. ↑ J. Parnell; S. Thackrey; D. Muirhead; A. Wright. "Transient High-Temperature Processing of Silicates in Fulgurites as Analogues for Meteorite and Impact Melts" (PDF). Lunar and Planetry Science (Lpi.usra.edu). XXXIX. Retrieved 2015-08-16.
  31. ↑ "Lightning-induced reduction of phosphorus oxidation state : Abstract : Nature Geoscience". Nature.com. Retrieved 2015-08-16.
  32. ↑ M.A. Pasek; T.P. Kee; E.A. Carter; M.D. Hargreaves; H.G.M. Edwards; Z.Atlas (2010). "Fried Phospate and Organic Survival : Lightning in Biogeochemical Cycles" (PDF). Astrobiology Sciences Conference (Lpi.usra.edu). Retrieved 2015-08-16.
  33. ↑ 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.
  34. ↑ "Paleoecology reconstruction from trapped gases in a fulgurite from the late Pleistocene of the Libyan Desert" (PDF). Quest.nasa.gov. Retrieved 2015-08-16.
  35. ↑ "Stroke Of Good Fortune: A Wealth Of Data From Petrified Lightning". Freerepublic.com. Retrieved 2015-08-16.
  36. ↑ "Excavating at the Birthplace of Zeus* – Mt. Lykaion Excavation and Survey Project". Lykaionexcavation.org. 2003-07-20. Retrieved 2015-08-20.
  37. ↑ "Geochemical analysis of a Type II fulgurite" (PDF). lpi.usra.edu. Retrieved 2015-08-19.
  38. ↑ "Fulgurite Classification, Petrology, and Implications for Planetary Processes" (abstract, link to PDF full text). arizona.openrepository.com. Retrieved 2015-08-19.
  39. ↑ Chambers's journal By William Chambers, Robert Chambers
  40. ↑ Patti Polk, Collecting Rocks, Gems & Minerals: Easy Identification - Values - Lapidary Uses, Krause, 2010, page 168 ISBN 978-1-4402-0415-9

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