Mineralogical and compositional features of rock fulgurites: A record of lightning effects on granite

Elmi, Chiara; Chen, Jiangzhi; Goldsby, D. L.; Gieré, Reto

doi:10.2138/am-2017-5971

Cited by 30 publications

(37 citation statements)

References 42 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Also, near the lightning strike point, the modeled electric field is greater than 10 11 V/m, and dielectric breakdown will occur. However, microstructural observations [ Elmi et al , ] confirm that these processes mainly take place at the rock surface, and the ∼ R −4 decay of temperature and ∼ R −2 decay of the electric field ensure that the material alteration is mostly confined to the close vicinity of the strike point. Our model predicts a radius of the burned region (11.6 cm) that is consistent with observed sizes of burned areas on fulgurite samples from Mottarone [ Elmi et al , ].…”

Section: Discussionmentioning

confidence: 99%

“…However, microstructural observations [ Elmi et al , ] confirm that these processes mainly take place at the rock surface, and the ∼ R −4 decay of temperature and ∼ R −2 decay of the electric field ensure that the material alteration is mostly confined to the close vicinity of the strike point. Our model predicts a radius of the burned region (11.6 cm) that is consistent with observed sizes of burned areas on fulgurite samples from Mottarone [ Elmi et al , ]. Thus, neglecting these variations in thermal and electrical properties with temperature and field strength does not change the overall behavior of our model.…”

Section: Discussionmentioning

confidence: 99%

“…In comparison, the electrical conductivity of granite is 10 −3 S/m, much higher than that of air (∼10 −15 S/m), thus the current is able to pass through the rock and induce significant heating. Without pervasive electrical heating, thermal diffusion is the major mechanism for the formation of the melt tube [ Carter et al , ; Pasek et al , ] with a radius ∼3 cm (Appendix ), consistent with observed sand fulgurite tubes [ Rogers , ; Gailliot , ; Pye , ; Essene and Fisher , ; Navarro‐González et al , ], but much smaller than the fulgurite region on rocks from Les Pradals [ Gieré et al , ] and Mount Mottarone [ Elmi et al , ].…”

Section: Discussionmentioning

confidence: 99%

“…The temperature at the surface as a function of r can be compared with the size of the burned regions observed on fulgurite surfaces. The region within which the granite is expected to be partially melted is obtained by solving T i ( r ) = T g , which gives a radius of ∼9.3 cm for fulgurite presence, and the radius of burned organics is ∼11.6 cm, consistent with observations on Mottarone granite [ Elmi et al , ]. On the other hand, the quartz annealing temperature is reached inside a region of radius ∼8 cm.…”

Section: Modelmentioning

confidence: 93%

“…Rock surfaces are in general somewhat weathered before lightning strikes, with typically higher thermal and electrical conductivities in the weathered part than in the unaltered rocks due to the presence of moisture. However, Elmi et al [] showed that the weathered layer on granite from Mottarone appears to be thinner than 1 mm, whereas the rock itself is tens of centimeters in thickness or larger. We treated the rock as a homogeneous half‐space with uniform thermal and electrical properties.…”

Section: Modelmentioning

confidence: 99%

See 4 more Smart Citations

Generation of shock lamellae and melting in rocks by lightning‐induced shock waves and electrical heating

Chen

Elmi

Goldsby

et al. 2017

Geophysical Research Letters

Self Cite

View full text Add to dashboard Cite

The very rapid energy release from impact events, such as those resulting from lightning strikes or meteorites, can drive a variety of physical and chemical processes which alter rocks and result in the formation of natural glasses (i.e., fulgurites and tektites). Fulgurite is the vitrified soil, sand, or rock resulting from lightning strikes. A thunderbolt is associated with air temperatures of up to 105 K, which can heat rocks to >2000 K within tens of microseconds. The rapid fusing and subsequent quenching of the surface of the rock leaves a distinctive, thin, garbled coating composed of a glassy to fine‐grained porous material. Previous studies on rock fulgurites found planar deformation features in quartz crystals within the target rock substrate, evidence of strong shock waves during fulgurite formation. In this paper, we simulated the shock pressure and temperature caused by an idealized lightning impact on rocks and compared the model results with observations on rock fulgurites from the literature. Our model results indicate that a lightning strike can cause >7 GPa pressure on the rock surface, generate a layer of fulgurite (of radius ∼9 cm), and leave a burned region (of radius ∼11 cm). The fulgurites found on rock surfaces share many features with sand fulgurites, but their spatial distribution is completely different, as sand fulgurites are hollow tube structures. Our study on rock fulgurites provides an indirect constraint on the energy of a lightning event and also demonstrates that the presence of shock features in rocks cannot be taken as unequivocal evidence for impact events.

show abstract

Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

Section: Modelmentioning

confidence: 93%

Section: Modelmentioning

confidence: 99%

See 3 more Smart Citations

Generation of shock lamellae and melting in rocks by lightning‐induced shock waves and electrical heating

Chen

Elmi

Goldsby

et al. 2017

Geophysical Research Letters

Self Cite

View full text Add to dashboard Cite

show abstract

Impact geologists, beware!

Melosh

2017

Geophysical Research Letters

View full text Add to dashboard Cite

Impact geologists have long assumed that shock metamorphic features, such as planar fractures and Planar Deformation Features (PDFs) in quartz are reliable indicators of an extraterrestrial impact. A new paper by Chen et al. (2017, https://doi.org/10.1002/2017GL073843) now shows that such features might arise in terrestrial lightning strikes, thus raising the bar for identification of impact sites.

show abstract

Physico-chemical study of an exogenic fulgurite from a thunderstorm on 10th August 2013 in Dallas, TX

et al. 2021

View full text Add to dashboard Cite

Droplet-like exogenic fulgurites comprise a minor grouplet of natural glasses resulting from powerful lightning strikes. Reports on such type-V fulgurites are scarce in the literature. In this work, a fulgurite specimen from the thunderstorm that took place on 10 th August 2013, in Dallas, TX, USA, has been analyzed using X-ray powder diffraction, X-ray fluorescence, scanning electron microscopy, energy-dispersive X-ray spectroscopy, and infrared and Raman spectroscopy techniques. X-ray diffraction revealed the amorphous nature of the exofulgurite, and X-ray fluorescence showed a high Si, Al and Ca content. Infrared and Raman spectroscopy were key in revealing clear SiO modes related signatures and a very significant presence of water (OH/H2O).A parallel with glassy silicate materials, but also with opal-A, was essential in the understanding of the fulgurite's characteristics. In particular, Raman data evidenced the exofulgurite to have a high degree of depolymerization.

show abstract

Mineralogical and compositional features of rock fulgurites: A record of lightning effects on granite

Cited by 30 publications

References 42 publications

Generation of shock lamellae and melting in rocks by lightning‐induced shock waves and electrical heating

Generation of shock lamellae and melting in rocks by lightning‐induced shock waves and electrical heating

Impact geologists, beware!

Physico-chemical study of an exogenic fulgurite from a thunderstorm on 10th August 2013 in Dallas, TX

Contact Info

Product

Resources

About