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Treebeard's Stumper
10 November 2000

Burning Bogs and Exploding Pancakes

An unusual peat bog fire has been burning at nearby Vandenberg Air Force Base for nearly 2 months now, resulting in health concerns and traffic accidents caused by smoke-enhanced fog. How can a wetland burn, despite recent rains and constant watering by fire fighters? Even dry, there's no air to feed it, like trying to burn a thick newspaper. Another unusual kind of fire is a dust or silo explosion. You can demonstrate this by (carefully!) blowing or sifting ordinary flour over a candle flame. I'll have a more impressive demo at the Open House tonight! These different kinds of burning are stumpers by themselves, but they also have an interesting connection. Explain!

I got to talk about this stumper at the Dunn Middle School Open House on Friday night, so I suppose I can say more here.

The Harris Fire started in mid-September in Santa Barbara County in Central California. The big fire was soon extinguished, but not before it spread into the Barka Slough near the mouth of San Antonio Creek on the edge of Vandenberg Air Force Base. The summer-dry wetland caught fire, and it's still smoldering two months later. There's a good record of news reports on the fire in the 30th Space Wing News Flash from Vandenberg AFB. Local newspapers have covered this story, but the best reports have disappeared from their websites. Google still has a few stories in their cache: L.A. Times (23 Sep 2000), Santa Barbara Newspress (20 Sep 2000, 21 Sep 2000, 22 Sep 2000), and Lompoc Record (6 Nov 2000). The best report I read was in the Santa Barbara Newspress (8 Oct 2000), but I can't find it online. A new update (18 Nov 00) is here.

     
One of the four water cannons - hoses with huge nozzles
mounted atop trailors - pouring water around the clock
onto the smoldering bog fire at Barka Slough. We've also
had five inches of rain at my house nearby. This wetland
is critical habitat for the endangered red-legged frog.

     

Smoke from the smoldering bog fire has created unusually
dense fog that has caused traffic accidents on Highway 101.
We haven't seen any sign of the fire at Dunn Middle School
in nearby Los Olivos.

We don't usually think of wheat or dust as an explosive substance, but grain elevators and silos really can explode with deadly results. All it takes is grain dust in the air and a careless spark
     
Historic photo from 1913 shows the Erie Elevator in Buffalo,
New York completely engulfed in flames after an explosion
that killed five men. Photo from Grain Elevators - A History.

     

This photo is from Firefly AB, a site that sells industrial
safety equipment. They point out that "Anything that
has been transformed into finely granulated particles
can explode. Unfortunately, all too often it does."

You can make an impressive fireball with nothing more than ordinary wheat flour, the main ingredient of pancake mix! An easy demo is to blow or sift fine flour or corn starch over a candle. You can make a real explosion by blowing flour or almost any dust over a candle inside a container with a tight lid. This will make a fireball that will blow the the lid into the air! There are directions for this impressive demo on the Web here and here, though my design is slightly different. The DMS Weird Science club had the best results with a 2:1 mix of flour and corn starch, using a two foot high metal popcorn can as the "silo". Be careful kids, this is a real explosion. Don't singe your beard!
Gabe sets off a beautiful flour explosion in the DMS Science room. The
lid is visible hanging flat in the air on the right. I reckon the fireball gets
its classic mushroom shape from pushing up against the lid.

Bog fires and exploding pancakes are stumpers by themselves. They also have an interesting connection. Explain!

Answer


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Copyright © 2000 by Marc Kummel / mkummel@rain.org