Lightning and thunder underground

[Em-caver]

Good evening, yesterday we were in Giants Hole in Derbyshire, we were heading down towards Garlands from Base Camp and heard the rumbling of thunder, or what we thought was thunder. There were a few rumbles over a couple of minutes.

It got us discussing how deep can a strike of lightening travel underground, is there a big risk being that deep or is it just entrances, initial streamways etc... that are most dangerous?

Have tried to do a bit of research online but not finding much other than not to be near entrances.

 

[Slug]

Several members of a BEC expedition to France and the 1970s were struck by lightning, earning one of them, Chris Smart, the nickname of Blitz though I'm not certain whether he was underground at the time.
Apparently caves are known to be lightning "magnets".

Good evening, yesterday we were in Giants Hole in Derbyshire, we were heading down towards Garlands from Base Camp and heard the rumbling of thunder, or what we thought was thunder. There were a few rumbles over a couple of minutes.

It got us discussing how deep can a strike of lightening travel underground, is there a big risk being that deep or is it just entrances, initial streamways etc... that are most dangerous?

Have tried to do a bit of research online but not finding much other than not to be near entrances.

 

[pwhole]

Good evening, yesterday we were in Giants Hole in Derbyshire, we were heading down towards Garlands from Base Camp and heard the rumbling of thunder, or what we thought was thunder. There were a few rumbles over a couple of minutes.

Roughly what time did this happen?

 

[mikem]

This is best advice I could find, from Mammut (all refering to entrance):
"larger caves offer some protection – keep at least six feet from walls and ceiling to avoid indirect lightning strikes. Caves or overhangs are only truly helpful if they provide at least one body length of depth and at least half a body length of clearance above and in front. Skip wet, small, or low caves – they don't provide safe protection and can create additional hazards."

AI had helpfully added keeping 6ft from the floor as well ! But what you are trying to do is avoid being the shortest route between two exposed surfaces, so touching one is fine. Being deep underground is no issue, except in the rare event of the strike causing a rockfall at the entrance.

Some caves / mines are close to roads or railways, so heavy vehicles passing by can sound like thunder.

 

[Em-caver]

Roughly what time did this happen?

It was around 11.45am /12pm

 

[Katie]

As it was day time on a week day it might not have been thunder - but blasting at the nearby quarry you heard.
I have been deep underground in the Peak catchment and heard (and felt!) blasting before.

Although we have had quite a bit of thunder in the Peak recently Tuesday afternoon was very thundery, so it also could have been that. I live about 15 minutes from Giants, and did notice any thunder at all yesterday but it is still far enough away that it could have had thunder when we didn't!

 

[Badlad]

The Blitz story I recall involved lightning tracking down a telephone line and he was on the end of it! There was Jim Eyres concerns about being on the ladder down Proventina in a storm. Also fears that cave entrances attracted lightning due to postitive/negative ions or something like that.

That's all I've got

 

[Leclused]

During one of the early Anialarra expeditions a lighting struck a rope while someone was one. The lighting went through the person, luckily without injuries. So lighting can travel far in a cave when there is a path such as a rope or a wet surface

 

[Babyhagrid]

Jrat got struck at an underground camp whilst using a field telephone I believe

 

[Goydenman]

As a show cave guide in Peak Cavern I got struck by lightning. Saw flashes travelling along the electric wires in the ceiling then it came through the metal rail I was holding and I received a jolt. I was the only one holding the rail at the time the public were shocked to see flashes and then me jump up!

 

[pwhole]

As it was day time on a week day it might not have been thunder - but blasting at the nearby quarry you heard.
I have been deep underground in the Peak catchment and heard (and felt!) blasting before.

That's why I asked - I was at Millstone Edge Quarry around then, and didn't hear or see any storms, so it could have been blasting. That's the furthest detected so far if so - previous record is Blue John Cavern!

 

[grahams]

Here's an interesting summary regarding caves and lightning. I remember reading the Casteret article years ago (maybe in one of his books), but can't find a ref. to it.

https://ackma.org/wp-content/uploads/2025/01/126/ANDYSEZ-63-Lightning-and-caves-Andy-Spate.pdf

 

[Slug]

The Blitz story I recall involved lightning tracking down a telephone line and he was on the end of it! There was Jim Eyres concerns about being on the ladder down Proventina in a storm. Also fears that cave entrances attracted lightning due to postitive/negative ions or something like that.

That's all I've got

Blew up in his hand he told me.

 

[Em-caver]

Thanks everyone, interesting reading everyone's responses and it very well could be the quarry then! Was a few rumbles over a couple of minutes then nothing. Didn't feel anything unusual though. Definitely a healthy respect for lightening needed!

 

[Ad W]

Any chance your noise could have been rockfall? Something settling nearby maybe?

 

[mikem]

Unlikely over an extended period in Giants

 

[Andy Farrant]

I recall hearing that during a storm in Cheddar in which a lightning strike hit a house in the village and caused a fire, some people got an electric shock off the metal railings in Gough's Cave. I do remember the lighting; I was watching the storm from the bedroom window and the thunder was a very loud almost instantaneous bang.

 

[Blitz]

And now a word from the man himself!

Here's the expedition report that describes the lightning strike on the 2km telephone link (or lightning conductor as it is better described) from the Weisberg Haus to the cave entrance, where I was, to J-Rat who was at the bottom of the 50 m ladder pitch.

https://bec-cave.org.uk/bulletin-viewer/?pdf=19320

 

[bagpuss]

Apararently yesterday's storm that passed over Mendip was a supercell, only light rain was originally forecast until it was really close. Anyone get caught in it underground?

 

[alanw]

Apararently yesterday's storm that passed over Mendip was a supercell, only light rain was originally forecast until it was really close. Anyone get caught in it underground?

Dark red is >32mm/h. The red was over Wells from 17:35 until 18:05.