The study of 'fossilized' lightning

From the UNIVERSITY OF SOUTH FLORIDA (USF INNOVATION)

Study provides a new method to measure the energy of a lightning strike

By investigating ‘fossilized’ sand cylinders made by lightning strikes, sometimes thousands of years old, a University of South Florida professor provides a unique history of lightning and the energy contained in a single strike

TAMPA, Fla. (Aug. 3, 2016) – Florida, often recognized as the “lightning capital of the United States,” is a great place to study the amount of energy released by a lightning strike. Just ask University of South Florida School of Geosciences Associate Professor Matthew Pasek and his colleague Marc Hurst of Independent Geological Sciences, Inc. who have developed a unique method to measure the amount energy expended by a bolt of cloud-to-ground lightning.

According to Pasek, one of the more difficult things to measure is the amount of energy in a lightning strike. While atmospheric physicists can approximate lightning bolt energy by measuring the electrical current and temperature of bolts as they occur, the numbers are usually approximations.

The team of Pasek and Hurst is the first to investigate the energy in lightning strikes by using geology “after-the-fact” research, rather than measuring energy during a strike. By conducting this lightning strike “archaeology,” the researchers were able to measure the energy in a bolt of lightning that struck Florida sand thousands of years ago.

These are fulgurites collected from the field area in Polk County, Florida. Surficial differences likely result from different initial physical conditions (e.g., percent of water in the sand). CREDIT Dr. Matthew Pasek/University of South Florida

These are fulgurites collected from the field area in Polk County, Florida. Surficial differences likely result from different initial physical conditions (e.g., percent of water in the sand). CREDIT Dr. Matthew Pasek/University of South Florida

The results of their analysis were recently published in the journal Scientific Reports.

“When lightning strikes the sand, it may generate a cylindrical tube of glass called a fulgurite, explained Pasek. “The structure of the fulgurite, created by the energy and heat in a lightning strike, can tell us a lot about the nature of the strike, particularly about the amount of energy in a single bolt of lightning.”

The team collected more than 250 fulgurites – both recent and ancient – from sand mines in Polk County, Fla., at a site that is believed to have recorded thousands of years of lightning strikes, providing a way to measure the lightning strike history of what is today called the I-4 Corridor, a region near Tampa and Orlando. They analyzed the properties of the fulgurites, paying particular attention to the length and circumference of the glass cylinders because the amount energy released is revealed by these dimensions.

“Everyone knows there is a lot of energy in a lightning bolt, but how much?” Pasek explained. “Ours is the first attempt at determining lightning energy distribution from fulgurites and is also the first data set to measure lightning’s energy delivery and its potential damage to a solid earth surface.”

According to Pasek, the energy released by lightning is measured in megajoules, also expressed as MJ/m.

“For example a single megajoule is equivalent to about 200 food calories, or the energy from leaving a microwave on for 20 minutes to cook food,” he explains. “It can also be compared to a 60 watt lightbulb’s energy use if left on for about four hours. It’s also the same as the kinetic energy a car has traveling about 60 mph.” Their research found that the energy produced by a lightning strike peaked at greater than 20MJ/m.

The researchers also found a way to separate the “normal” lightning strikes from the “abnormal.”

“While we presented a new method for measuring by using fossilized lightning rocks, we also found – for the first time – that lightning strikes follow something called a ‘lognormal trend,” explained Pasek. “A lognormal trend shows that the most powerful lightning strike happen more often than would be expected if you made a bell curve of strikes. This means that the big lightning strikes are really big.”

According to Pasek, a bolt of lightning can carry extremely high voltage and heat the air temperature around the strike to more 30,000 degrees Kelvin – that’s over 53,000 degrees Fahrenheit. When lightning strikes sand, soil, rock or clay, the current flows through the target and heats the material to above its vaporizing level. Rapid cooling produces the fulgurite.

According to Pasek, who is also an expert in astrobiology, geochemistry and cosmochemistry, lightning strikes the Earth about 45 times per second, with 75 to 90 percent of the strikes over land masses.

“About a quarter of these strikes occur from a cloud to the ground, so the fulgurite-forming potential is great, with up to 10 fulgurites formed per second globally,” said Pasek.

Their research serves not only to provide a way to measure the immense energy in lightning, but also to help raise awareness of the dangers posed by the potentially deadly bolts.

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70 thoughts on “The study of 'fossilized' lightning

  1. Reblogged this on | truthaholics and commented:
    “According to Pasek, the energy released by lightning is measured in megajoules, also expressed as MJ/m.
    “For example a single megajoule is equivalent to about 200 food calories, or the energy from leaving a microwave on for 20 minutes to cook food,” he explains. “It can also be compared to a 60 watt lightbulb’s energy use if left on for about four hours. It’s also the same as the kinetic energy a car has traveling about 60 mph.” Their research found that the energy produced by a lightning strike peaked at greater than 20MJ/m.
    The researchers also found a way to separate the “normal” lightning strikes from the “abnormal.””

    • I did not like the use of ‘abnormal’ in this context. Large/small is a better fit. If a ‘large’ lightening strike happens only once a year but it happens every year, is this abnormal? Uncommon or rare maybe, not abnormal. Leaves the reader to think something has changed (like a cancer cell).

    • MJ is an amount of energy. MJ/m is not a unit of energy. There is some confusion by the author. I don’t care what alternate expressions of energy are used ( kW-hr, tons TNT equivalent, etc.), MJ/m is just wrong!

      • I expect they mean that the amount of energy deposited to form the fulgerite was 20 MJ per meter of fulgurite. Makes perfect sense.

      • I wondered what you could use MJ/m for.
        It could express an energy gradient. It’s not meaningless but, as far as I can google, nobody uses it for anything.

  2. Unless they mention “global warming” they’ll never get funding. As in, this could be a proxy for “climate change” kinda like tree rings?

  3. Better add in a global warming twist or you will be stuck trying to make a living with the fulgurite store on Ebay.

  4. That previous post of lightning obliterating that light pole should be enough warning of the dangers of lightning for anyone.

  5. but also to help raise awareness of the dangers posed by the potentially deadly bolts.
    *********************************
    uhh….does anyone think getting hit by it is safe?

  6. Some interesting statistics here. 10 fulgurites per second globally means about 300,000,000 per year, which adds up to 2 per square kilometer, or two per square meter and million years (of course the majority will be in the tropics). If it wasn’t for weathering the entire surface of the Earth would probably be fulgurites by now….

    • ” If it wasn’t for weathering the entire surface of the Earth would probably be fulgurites by now….”
      and coprolite.

    • You have to figure that a lot of those bolts hit trees, rocks, etc. (and people, e.g., Roy Sullivan, a park ranger in Virginia , was hit by lightning on seven different occasions between 1942 and 1977 and survived all of them).

  7. The VA doctors say that my destroyed heart and spinal nerve problems couldn’t possibly have anything to do with me being struck while on active duty at Fort Dix NJ. Strange that all the civilian doctors have said regarding this issue was “well duh” of course the lightning did this. So I am disabled by social security, but not the VA. This is even though the Neurology specialists on this issue say very plainly that the first two things that lightning does to a body is to screw up the heart and the spine. Strange how the VA treats the veterans isn’t it?

  8. A nice piece of research, but I can’t help being concerned about the claim that 75 to 90 percent of lightning strikes are on the land masses. With 71% of the Earth’s surface covered in water, the idea that lightning preferentially strikes land seems unlikely. When astronauts first orbited the Southern Hemisphere, they were astonished by the amount of lightning striking the Southern Oceans. In point of fact, free chlorine released by lightning strikes on Southern Oceans is a major contributor to the “Ozone Hole”. This is second only to volcanic emissions from the so called “Ring of Fire”.

    • I live on the ocean in south Florida so can contribute some personal observations. Most of the Tstorm lightening over the ocean is cloud to cloud. Most of the lightening over land is cloud to ground. Has been true for the 15 years have been at this location.I think this is because of the way a lightening strike occurs. What you see is actually the counterstroke. There are many more ‘pointy’, sharp, high land objects where the charge leader can form. Waves, much less although not zero.

      • Interesting, since I have personally been almost struck by lightning off the Florida Keys while out in the water. Additionally, after several near misses, I headed for the nearest small Key, beached my boat and cowered among the sparse vegetation until the storm passed. At no time did any land within sight get hit, although several more lightning bolts hit the water.

      • I don’t blame you for getting to the nearest Key.
        While electric currents in fresh water can kill you, electric currents in salt water can seriously kill you even faster.

      • ‘There are many more ‘pointy’, sharp, high land objects where the charge leader can form…’
        and not enough tall ships on the high seas..
        Good post, great comments and much food for thought. Among them ( thoughts that is) how much NOx is generated by 45 lightning bolts per second and how does that compare with VW’s sins
        of emission… should the EPA be charging (sic!) Juppiter for his thunderbolts by Jove?!

    • The paper gives the sources:

      … Lightning is a ubiquitous phenomenon on Earth, with a global flash rate of about 45 times per second, a majority (75–90%) of which occur over continental landmass8. About a quarter of these strikes occur from a cloud to the ground9, and hence the number of potential fulgurite-forming events is significant,…
      8 Local time variation in land/ocean lightning flash density as measured by the World Wide Lightning Location Network
      Authors Erin H. Lay, Abram R. Jacobson, Robert H. Holzworth, Craig J. Rodger, Richard L. Dowden
      Journal of Geophysical Research, 112, D13111 (2007).
      9 Combined Satellite- and Surface-Based Estimation of the Intracloud–Cloud-to-Ground Lightning Ratio over the Continental United States
      Boccippio, D. J., Cummins, K. L., Christian, H. J. & Goodman, S. J.
      Month. Weath. Rev. 129, 108–122 (2001).

  9. Could we move away from misuse of unit names? It makes us look as if we are unscientific and don’t understand even the basics.
    There is no such thing as “degrees Kelvin”. The unit is a “Kelvin” which is the same “size” as a “degree Celsius”. The difference comes in the zero point. For the Celsius scale “zero” is the triple point of specially purified water (actually 0.01 deg C). For the Kelvin scale it is “Absolute Zero” which is -273.16 degrees Celsius making the numerical difference between the two scale 273,15
    Notice that there is no such thing in science as a “degree Centigrade”. The French (for reasons best known to themselves) use “Centigrade” as one hundredth of a right angle. Celsius (a Swedish astronomer) developed similar scale and the change from degrees Centigrade to degrees Celsius was made 2 generations ago – in 1948!
    There is no such thing as a “degree Kelvin”. The USA may catch up with the rest of the world … (It might even stop calling “aluminium” by the incorrect name, “aluminum” but probably not I’m my lifetime.)

  10. “It can also be compared to a 60 watt lightbulb’s energy use if left on for about four hours. It’s also the same as the kinetic energy a car has traveling about 60 mph.”
    ============
    I’ve got the feeling that if the lightbulb was hit by a car doing 60 mph, it might not think so.
    Anyone care to try explain the above quote to a simpleton ?

    • Reliable sources tell me that when a deer jumps out in front a Ford Bronco with a boat in tow, and realizes its mistake, it lowers its shoulder to take the blow (at 60 mph).
      Apparently what happens is the deer bounces off the bumper like a rubber ball, becomes airborne, and lands in the ditch leaving only some snot on the vehicle.
      I’ve yet to see a lightbulb, no matter how long it has been burning, do that to a deer.

  11. I don’t think the quoted author has much clue about what they are going on about:
    “According to Pasek, the energy released by lightning is measured in megajoules, also expressed as MJ/m.”
    MJ & MJ/m do not have the same dimensions, so to say that the one is “also expressed as” the other is, to use a technical term, bollocks.
    I’d be interested to know the comparison of energy implied by fossil fulgurites (presumably MJ/m * m) verses modern lightning strikes, but we didn’t get that.
    More junk science (or at least junk reporting)?

    • However accurate their measurements and models may be, they are trying to determine energy per length:

      … However, within the ground material in which a fulgurite forms, the energy per unit length is much higher than the energy per unit length in the atmosphere by about a factor of 100–1000. …

  12. Couldn’t be bothered to read. If you can’t be bothered to spell fossilised properly, I can’t be bothered to read the article. And I don’t care about the quotation marks.

    • What a rude set of comments Samuel H W.
      I spell the English English way but this is an American blog so expect American English spelling.

      • Annie, there is no need to concede to SHW. Whether he/she/it likes it or not there are many forms/dialects of “English”. The root is The Queen’s English. Then there is the interesting variant called “American” with its many spelling and linguistic foibles. If he/she/it does not understand that, well that their problem.

      • I also think that some one calling hiself “whitearse” may not care one whit about what he is saying … he may just be messing with the readers.

    • note that it is “grammar” not grammer even a non native English speaker catches you on a real spelling mistake.
      it is fossilized / fossilised (both are correct, depending on the region) just the same way as the word “center” / “centre” (which are also both correct, depending on the region).
      but grammer is not correct it is grammar
      so dear Samuel make sure the next time you nitpick on a spelling that is correct, make sure you spell grammar correctly or you just come over as a rude and arrogant person.
      cheers

  13. The theoretical temperature is determined by extrapolating the ideal gas law; by international agreement, absolute zero is taken as −273.15° on the Celsius scale. (=0 degrees on Kelvin scale)
    The triple point of water is +273.16 Kelvin, being 0.01degrees on the Celsius scale.
    Isn’t that much clearer?
    I think the degrees Kelvin or degrees Celsius is/has a sort of clarity intention, to talk about degrees and then clarify which scale you use.
    Whilst not technically correct or necessary for those technically correct, it is perhaps helpful to others.
    just sayin to help contributor above relieve stress, show a negative to be a positive, lightening the atmosphere here.

  14. I took the ‘MJ/m’ as being the means of determining the energy in the strike. The longer the fulgurite, the more powerful the strike. But what I didn’t see was an account of the diameter of the fulgurite. So I would be more inclined to accept a measure of MJ/cc of fulgurite than ‘MJ/m.’

  15. i find the Mj/m also very confusing is it for the length of the fulgurite? per meter of the lightening bolt?
    Mj/m is even not a correct unity
    it is or Mj/m² or N/m.
    (i even specificly went to look it up in order to understand what the Mj/m was standing for to avoid confusion, thats how i found that it was non existant)

    • Read the article. There is a detailed account under “Calculations” explaining the derivation of the energy required per unit length to form the fulgurite. The following is a cut & paste that loses the equations, but gives enough text to show how it is done:
      http://www.nature.com/articles/srep30586
      >>>>>>>>>>>>>>
      The energy required to vaporize quartz as SiO2 from room temperature is calculated using HSC Chemistry, a thermodynamic equilibrium modeling code that has been previously used to determine the Solar system chemistry of sulfur33, the composition of Europa’s subsurface ocean34, and fulgurite formation processes6. This model determines the energy at one bar of pressure required to promote the reactions:
      [Equations]
      where the vaporization of SiO2 is accompanied by the decomposition of this material to SiO2, SiO and O2 gases. The code determined the vaporization of SiO2 approximately 0.94 MJ per mole (~15.7 MJ/kg,). Correspondingly, the relationship between fulgurite internal diameter and energy per unit length (E) required to vaporize the material to make a fulgurite is equal to:
      [Equations]
      where ρS is the density of sand (here at ~1.65 g/cm3), ΔHvap is the energy required to vaporize SiO2 from room temperature (the above 0.94 MJ/mole), MW is the molecular weight of SiO2 (60.08 g/mole), and d is the internal diameter of the fulgurite in centimeters. We do not consider further energy transfer in the formation of the glass wall (e.g., the melting of the sand to form the fulgurite, and heating of adjacent sand) that may store up to 20% of the energy of a lightning strike, and the heating and ionization of the gas column within the fulgurite is not considered. These data cannot be readily determined from the fulgurites collected. These energy estimates are necessarily minima, and the actual energy transfer may be more than 25% of our calculated values.
      <<<<<<<<<<<<<<

      • Hey! Thanks, Steven Cheesman. That explanation, even sans equations, was sufficient to answer my question about their accounting for the diameter of the fulgurites.
        Much appreciated.

  16. Lightening is dangerous. Zounds!
    Good to know my old alma mater continues to make such valuable contributions to the store of human knowledge.
    One does wonder if the money might be better put to a more fit purpose like cancer research, but I suppose every ricebowl deserves topping up when someone else is paying for it.

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