Author Topic: Lightning Underground  (Read 4363 times)

Offline grahams

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Re: Lightning Underground
« Reply #25 on: September 01, 2021, 08:34:52 am »
Rummaging around at the back end of my memory, I remember reading that Norbert Casteret did a statistical survey regarding lightning strikes at or near cave entrances by looking for lightning damaged trees. I believe that he found a correlation and speculated that ionised air might be the conduit.

The British Caving Library has a reference to Casteret's book The Darkness Under the Earth.
Sceptics wanted!

Offline mikem

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Re: Lightning Underground
« Reply #26 on: September 01, 2021, 09:16:04 am »
This explains the theory (but no test of whether it's true), I'd expect the higher moisture levels of temperate cave air (compared to surrounding) to be a bigger factor:
https://www.irishtimes.com/news/the-effect-of-caves-1.20991%3f
« Last Edit: September 01, 2021, 09:26:27 am by mikem »

Offline Bob Mehew

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Re: Lightning Underground
« Reply #27 on: September 01, 2021, 11:41:29 am »
Why is the air ionised around cave entrances?
radon and its daughter products.  Work on measuring radon levels by BCA's Radon Working Group (see https://british-caving.org.uk/wp-content/uploads/2020/10/Environmental-Sampling-Results-for-BCA.xlsx) shows levels consistently higher than in the open air of between 5 and 10 Bq/m-3 (see https://www.who.int/news-room/fact-sheets/detail/radon-and-health).  So outward venting caves will have higher levels around the entrance than at some distance away.  Whether it is a meaningful difference in respect of a bolt of lightening arising in the cloud many hunderds if not thousands of metres above is another question.

Offline Paul Marvin

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Re: Lightning Underground
« Reply #28 on: September 01, 2021, 11:56:48 am »
Never heard of this issue myself  at all. Probably have a higher chance of seeing Lord Lucan riding Shergar 
I dont know where I am going, but will know where I am when I get there.

Online Speleofish

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Re: Lightning Underground
« Reply #29 on: September 01, 2021, 12:32:56 pm »
I'd always assumed the issue was greater humidity, in the same way that lightning strikes on mountain crags tend to follow wet gullies and groove systems (where presumably radon isn't relevant).

Offline mikem

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Re: Lightning Underground
« Reply #30 on: September 01, 2021, 12:44:58 pm »
Never heard of this issue myself  at all. Probably have a higher chance of seeing Lord Lucan riding Shergar 
Blitz is still around to ask!

Offline Bob Mehew

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Re: Lightning Underground
« Reply #31 on: September 01, 2021, 03:08:23 pm »
I'd always assumed the issue was greater humidity, in the same way that lightning strikes on mountain crags tend to follow wet gullies and groove systems (where presumably radon isn't relevant).
https://www.nonstopsystems.com/radio/pdf-ant/antenna-article-magloop-capa-88059.pdf appears to go along with that idea, though what is the humidity of air in a thunder storm?  Presumably not 100%.

Offline mikem

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Re: Lightning Underground
« Reply #32 on: September 01, 2021, 05:14:45 pm »
The chance of getting struck by lightning generally is not that great (although some people have been hit multiple times), but is it safer to hide in an entrance?

Offline pwhole

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Re: Lightning Underground
« Reply #33 on: September 01, 2021, 05:26:28 pm »
Three of us went to Water Icicle Close Cavern about five weeks ago under threatening skies, and as I hit the base of the shaft, the most enormous clap of thunder erupted - it was amazing. My two companions got down rather quickly and told me there'd been a huge lightning flash directly overhead, and it's pretty exposed up there, with very tall trees about 20m away, so they didn't want to hang around to find out what happened next. It had all gone by the time we got out.

Online Mrs Trellis

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Re: Lightning Underground
« Reply #34 on: September 01, 2021, 07:43:24 pm »
Apologies - duplicate post deleted.
Mrs Trellis
Upper Sheeps Bottom
North Wales

 

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