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Posted at 11:00 AM ET, 05/13/2010

Measuring the thickness of a lightning bolt

By Kevin Ambrose

* Cooler today, summery tomorrow: Full Forecast *

tree_web.jpg
A lightning bolt blew a thin strip of bark from this red oak tree, starting at the top of the tree all the way down to its base. The sap and moisture that was under the tree's bark boiled with the heat of the lightning bolt, causing the bark to literally explode off the tree in long, thin strips. The bark strips were scattered on the ground, up to 50 feet away from the tree.

I was on a golf outing several years ago when my foursome encountered an area below the tee box that was strewn with thin strips of bark. I thought it was very odd for bark to be laying on a recently mowed section of grass and I immediately guessed a nearby tree had been struck by lightning during a thunderstorm the previous night. I persuaded my fellow golfers to help me search for the tree, and it didn't take us long to find the source of the bark.

The tree had indeed been struck by lightning and thin strips of bark had blown off the tree, from the top of the tree to its base, in spiraling patterns. I took out my camera and photographed the scene. I also saved a couple pieces of the bark.

Keep reading for more photos and to find out the thickness of a lightning bolt...

barkandgrass_web.jpg
Strips of bark lay scattered on the ground in all directions from the tree. The bark was blown off the tree by a lightning strike.

I've read that the diameter of a lightning bolt is about the thickness of a pencil up to the diameter of a silver dollar. I wondered how a lightning bolt's diameter was measured, or even estimated. After seeing the result of a tree struck by lightning, I can see how analyzing the burn marks and the damage to the tree and bark is one way to estimate the thickness, or diameter, of a lightning bolt.

After analyzing the tree and bark in my photos, I'd estimate this bolt was less than one inch in diameter. It may have even been less than 0.5", if the burn marks extend past the boundary of the bolt. Regardless of the exact diameter, a lightning bolt is a very thin, but very powerful force of nature.

boltshot_web.jpg
An analysis of the burn marks on the underside of the bark shows the bolt was probably less than an inch in diameter.

tree2_web.jpg
The lightning bolt spiraled around the trunk of the tree from top to bottom, blowing off strips of bark in all directions.

By Kevin Ambrose  | May 13, 2010; 11:00 AM ET
Categories:  Photography  
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Comments

Very cool.

Posted by: Langway4Eva | May 13, 2010 11:07 AM | Report abuse

Most lightning bolts are less than an inch in diameter. The intense white-hot light generated by temperatures hotter than the sun's surface makes them seem much bigger than they really are. Nearby bolts appear purplish due to the intense temperature. Yellow bolts are more distant; the thickness of the atmosphere makes a distant bolt appear yellowish or even reddish, same as the rising or setting sun viewed through a thick layer of atmosphere. The sun's actual color is greenish yellow.

When lightning passes through "green" or wet wood the intense temperature may cause vaporized water to expand with explosive force. This is what accounts for the phenomenon of "exploding trees" due to lightning strikes.

Posted by: Bombo47jea | May 13, 2010 12:19 PM | Report abuse

kevin,
cool story, but i hope you weren't holding up the group behind you... ;-)

Posted by: walter-in-fallschurch | May 13, 2010 3:02 PM | Report abuse

One of the most interesting posts I've read here. I hope your expidition didn't slow down play on the course, though!

Posted by: oldtimehockey | May 13, 2010 4:38 PM | Report abuse

It might be an interesting experiment to see if someone would buy the bark on eBay...

Posted by: spgass1 | May 13, 2010 5:13 PM | Report abuse

I suppose I should note that no golfers were delayed, slowed, or in any way harmed during the shooting of this post. I wish I could say the same regarding my golf game, which is a constant nuisance to the other golfers around me.

Posted by: Kevin-CapitalWeatherGang | May 13, 2010 8:35 PM | Report abuse

kevin,
ok then - as long as no golfers were harmed.... lol.

Posted by: walter-in-fallschurch | May 14, 2010 7:01 AM | Report abuse

The comments to this entry are closed.

 
 
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