# Since California's burning again...\[re: forestfires\] **URL:** \ **Category:** Factual Questions\ **Created:** [August 28, 2009, 3:04pm UTC](https://boards.straightdope.com/t/since-californias-burning-again-re-forestfires/508029 "2009-08-28T15:04:44Z")\ **Posts on this page:** 16\ **Page:** 1
**Author:** ![YogSothoth](https://avatars.discourse-cdn.com/v4/letter/y/8edcca/32.png) [@YogSothoth](https://boards.straightdope.com/u/YogSothoth)\ **Post date:** [August 28, 2009, 3:04pm UTC](https://boards.straightdope.com/t/since-californias-burning-again-re-forestfires/508029/1 "2009-08-28T15:04:44Z")
How does a forest or brush fire start naturally? Humidity’s low out here and temperatures have climbed to over 105 in certain areas, but I find it hard to imagine that a hot piece of wood or dry brush could just spontaneously burst into flames. Doesn’t there need to be some catalyst? We don’t get any thunderstorms in this area at this time of year so that can’t be it at all. Discounting arsons, how does it start? Also, can a piece of metal, say from an empty soda can, left alone amidst dry brush heat up so much in the sun that it causes the surrounding grass to catch fire? ---
**Author:** ![dolphinboy](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/dolphinboy/32/330_2.png) [@dolphinboy](https://boards.straightdope.com/u/dolphinboy)\ **Post date:** [August 28, 2009, 3:12pm UTC](https://boards.straightdope.com/t/since-californias-burning-again-re-forestfires/508029/2 "2009-08-28T15:12:33Z")
Careless campers and dry lightening strikes. In the mountains there can be thunderstorms that produce lightening and high winds and poof, you have a wildfire. And don’t discount kids playing with matches and fireworks. ---
**Author:** ![IAmNotSpartacus](https://avatars.discourse-cdn.com/v4/letter/i/cc9497/32.png) [@IAmNotSpartacus](https://boards.straightdope.com/u/IAmNotSpartacus)\ **Post date:** [August 28, 2009, 3:12pm UTC](https://boards.straightdope.com/t/since-californias-burning-again-re-forestfires/508029/3 "2009-08-28T15:12:39Z")
Many, many ways. The most common is lightning, although that didn’t happen with the fires in SoCal afaik, whose cause have not yet been released (although officials [suspect](http://www.whittierdailynews.com/news/ci_13221098) humans are to blame). Not sure if you are talking about the NorCal or SoCal fires, but in SoCal we get a great deal of monsoons and massive thunderstorms in the late summer months over the San Gabriel Mountains ---
**Author:** ![Duckster](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/duckster/32/1244_2.png) [@Duckster](https://boards.straightdope.com/u/Duckster)\ **Post date:** [August 28, 2009, 3:20pm UTC](https://boards.straightdope.com/t/since-californias-burning-again-re-forestfires/508029/4 "2009-08-28T15:20:35Z")
Wildland fires have two ignition sources, man-made and natural. Duh. You would be surprised by the amount of fires caused by [dry lightning](http://weather.about.com/od/typesofprecipitation/f/dry_storms.htm), with no perceived thunderstorms present. Since lightning can strike as much as 30 miles away from an active thunderstorm, it is conceivable that your location is clear and dry, but a rogue strike from a distant storm is all that it takes. You would be amazed at the tens of thousands of lightning strikes during a single, small storm. Human-caused fires come from many sources. Sparks from passing trains, a tossed cigarette, kids paying with fire, an unattended campfire all come to mind. What is just now making the news, but has been known about for years are the “marihuana gardens” found all over public lands. Illegal camps with illegal fires start many fires. Then there is arson. ---
**Author:** ![suranyi](https://avatars.discourse-cdn.com/v4/letter/s/e36b37/32.png) [@suranyi](https://boards.straightdope.com/u/suranyi)\ **Post date:** [August 28, 2009, 3:27pm UTC](https://boards.straightdope.com/t/since-californias-burning-again-re-forestfires/508029/5 "2009-08-28T15:27:44Z")
> [@YogSosoth](#): > > How does a forest or brush fire start naturally? Humidity’s low out here and temperatures have climbed to over 105 in certain areas, but I find it hard to imagine that a hot piece of wood or dry brush could just spontaneously burst into flames. Doesn’t there need to be some catalyst? We don’t get any thunderstorms in this area at this time of year so that can’t be it at all. Discounting arsons, how does it start? > > Also, can a piece of metal, say from an empty soda can, left alone amidst dry brush heat up so much in the sun that it causes the surrounding grass to catch fire? I was just in the Sierra last weekend and I can tell you from personal experience that we definitely get thunderstorms this time of year. ---
**Author:** ![Triskadecamus](https://avatars.discourse-cdn.com/v4/letter/t/b19c9b/32.png) [@Triskadecamus](https://boards.straightdope.com/u/Triskadecamus)\ **Post date:** [August 28, 2009, 3:48pm UTC](https://boards.straightdope.com/t/since-californias-burning-again-re-forestfires/508029/6 "2009-08-28T15:48:21Z")
Natural fire sources include the mentioned lightning, probably the most frequent. It also includes spontaneous ignition of decomposing forest detritus under dry windy conditions. Compost warms, significantly as it decays. Keep it at 100 degrees for a while outside, and the inner portions of the heap will approach ignition temperatures. Now blow a nice dry Santa Anna wind through it, funnel it though a decreasing width valley, and it begins to smolder. It sends off sparks, which the wind blows to dry tinder. Now you have a blaze, in a wind tunnel. Tris ---
**Author:** ![YogSothoth](https://avatars.discourse-cdn.com/v4/letter/y/8edcca/32.png) [@YogSothoth](https://boards.straightdope.com/u/YogSothoth)\ **Post date:** [August 28, 2009, 4:23pm UTC](https://boards.straightdope.com/t/since-californias-burning-again-re-forestfires/508029/7 "2009-08-28T16:23:52Z")
I’m located in Southern California and I can definitely tell you that the fires that has been going on here for the past couple of days (up to 4 now!) were not caused by lightning. In fact, we haven’t really had any clouds for a week! > [@Triskadecamus](#): > > Natural fire sources include the mentioned lightning, probably the most frequent. It also includes spontaneous ignition of decomposing forest detritus under dry windy conditions. Compost warms, significantly as it decays. Keep it at 100 degrees for a while outside, and the inner portions of the heap will approach ignition temperatures. Now blow a nice dry Santa Anna wind through it, funnel it though a decreasing width valley, and it begins to smolder. It sends off sparks, which the wind blows to dry tinder. Now you have a blaze, in a wind tunnel. > > Tris Really? That’s kinda scary that temps can reach that high and catch fire so easily. Some of the areas I am talking about is located up in the Angeles National Forest, I’m assuming there are campers up there. They might have caused it a few days ago. So far, the news has been reporting that they are unsure of the cause but think it could have to do with arson but it could equally be caused by nature. ---
**Author:** ![VunderBob](https://avatars.discourse-cdn.com/v4/letter/v/839c29/32.png) [@VunderBob](https://boards.straightdope.com/u/VunderBob)\ **Post date:** [August 28, 2009, 4:28pm UTC](https://boards.straightdope.com/t/since-californias-burning-again-re-forestfires/508029/8 "2009-08-28T16:28:48Z")
I’m in NC, not CA; the two biggest causes of forest fires in my experience are lightning and arson, with accidental causes running third. We also get spontaneous combustion from agricultural sources. ---
**Author:** ![IAmNotSpartacus](https://avatars.discourse-cdn.com/v4/letter/i/cc9497/32.png) [@IAmNotSpartacus](https://boards.straightdope.com/u/IAmNotSpartacus)\ **Post date:** [August 28, 2009, 4:36pm UTC](https://boards.straightdope.com/t/since-californias-burning-again-re-forestfires/508029/9 "2009-08-28T16:36:44Z")
> [@YogSosoth](#): > > I’m located in Southern California and I can definitely tell you that the fires that has been going on here for the past couple of days (up to 4 now!) were not caused by lightning. In fact, we haven’t really had any clouds for a week! Correct, I don’t think any of the fires burning right now have a natural cause of ignition. Interestingly, the US Forest Service reports that the [La Brea Fire](http://www.inciweb.org/incident/1803/) was started by people overseeing an illegal marijuana growing operation. ---
**Author:** ![vivalostwages](https://avatars.discourse-cdn.com/v4/letter/v/d07c76/32.png) [@vivalostwages](https://boards.straightdope.com/u/vivalostwages)\ **Post date:** [August 28, 2009, 8:42pm UTC](https://boards.straightdope.com/t/since-californias-burning-again-re-forestfires/508029/10 "2009-08-28T20:42:34Z")
Other So Cal Dopers: are you curtailing outdoor activities as much as possible? Do you wear a mask if you have to go out? Do you ever think about moving when it gets like this (pretty much every fall)? ---
**Author:** ![silenus](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/silenus/32/166_2.png) [@silenus](https://boards.straightdope.com/u/silenus)\ **Post date:** [August 28, 2009, 8:50pm UTC](https://boards.straightdope.com/t/since-californias-burning-again-re-forestfires/508029/11 "2009-08-28T20:50:51Z")
Not really. The heat is doing more to keep me inside than the smoke is. But it _does_ stink outside. ---
**Author:** ![Shagnasty](https://avatars.discourse-cdn.com/v4/letter/s/9dc877/32.png) [@Shagnasty](https://boards.straightdope.com/u/Shagnasty)\ **Post date:** [August 28, 2009, 9:09pm UTC](https://boards.straightdope.com/t/since-californias-burning-again-re-forestfires/508029/12 "2009-08-28T21:09:40Z")
As a side note, it is almost impossible to start a fire with a cigarette as far as I can tell. I tried it many, many times when I smoked as a teenager and even won all bets by people saying that they could do it. You can flick cigarettes into a bucket of gasoline (literally) all day long and it won’t do anything (don’t try this at home). There has to be a way to start a real fire with a cigarette because there are so many reports of it but I have never figured out what it is. ---
**Author:** ![Pasta](https://avatars.discourse-cdn.com/v4/letter/p/ecccb3/32.png) [@Pasta](https://boards.straightdope.com/u/Pasta)\ **Post date:** [August 28, 2009, 9:54pm UTC](https://boards.straightdope.com/t/since-californias-burning-again-re-forestfires/508029/13 "2009-08-28T21:54:56Z")
> [@vivalostwages](#): > > Other So Cal Dopers: are you curtailing outdoor activities as much as possible? Do you wear a mask if you have to go out? > Do you ever think about moving when it gets like this (pretty much every fall)? SoCal doper here. While there are always fires, there are not always fires near _you_. So, overall it isn’t that bad. The “Morris” fire in the Angeles National Forest started Tuesday at about 4:15 PM. You could see the smoke clearly in the distance for the rest of the day, but few populated areas were affected at all. By Wednesday morning, the smoke had blown across the basin, making a NE/SW corridor about 20 miles wide that had unpleasant air, and you wouldn’t want to go for a jog or anything in those areas. A 50 mile wide corridor or so had air not quite as bad, but still visibly dirty if you looked across a long way (towards the mountains, say.) Thursday was clearer, and today is also clear for most of the basin, except for regions within 10 miles south-ish from the fire, where the haze is still visually and, to some, respiratorially noticeable. By Monday, if the blaze is well contained, the whole thing will be history even for the people nearby. (It already is for me, about 20 miles WSW.) A newer (Thursday) Rancho Palos Verdes fire is making for more scary headlines because it carries some risk of property damage, but it isn’t affecting the SoCal air quality at all. And for 99.9% (more 9’s?) of the population of SoCal, property damage from fires is never going to happen. Risk is pretty much limited to expensive houses in the mountains and foothills. In summary: For most people in SoCal, the fires are nothing like sitting next to a camp fire, where the smoke almost attacks you. Instead, it is more that there is evidence of fire (dusting of ash on the car windows in the morning, haze when looking at something in the distance) except _maybe_ for one day when it’s worse or unless you happen to be _right there_ at the blaze. ---
**Author:** ![iamthewalrus\_3](https://avatars.discourse-cdn.com/v4/letter/i/258eb7/32.png) [@iamthewalrus\_3](https://boards.straightdope.com/u/iamthewalrus_3)\ **Post date:** [August 28, 2009, 11:41pm UTC](https://boards.straightdope.com/t/since-californias-burning-again-re-forestfires/508029/14 "2009-08-28T23:41:34Z")
> [@Shagnasty](#): > > As a side note, it is almost impossible to start a fire with a cigarette as far as I can tell. I tried it many, many times when I smoked as a teenager and even won all bets by people saying that they could do it. You can flick cigarettes into a bucket of gasoline (literally) all day long and it won’t do anything (don’t try this at home). There has to be a way to start a real fire with a cigarette because there are so many reports of it but I have never figured out what it is. Aren’t there fires started by people falling asleep smoking all the time? I’ll admit I’ve never tried it, but I’d guess I’d be one of those people claiming it’d be pretty easy to start a fire with a cigarette. Off to go try and report back. ---
**Author:** ![vivalostwages](https://avatars.discourse-cdn.com/v4/letter/v/d07c76/32.png) [@vivalostwages](https://boards.straightdope.com/u/vivalostwages)\ **Post date:** [August 29, 2009, 1:54am UTC](https://boards.straightdope.com/t/since-californias-burning-again-re-forestfires/508029/15 "2009-08-29T01:54:11Z")
I’m near the Azusa foothills, so it comes down here sometimes. The other night it smelled like burning hot dogs right outside the window, so I just had to leave all the windows shut all night. ---
**Author:** ![Pasta](https://avatars.discourse-cdn.com/v4/letter/p/ecccb3/32.png) [@Pasta](https://boards.straightdope.com/u/Pasta)\ **Post date:** [August 29, 2009, 2:17am UTC](https://boards.straightdope.com/t/since-californias-burning-again-re-forestfires/508029/16 "2009-08-29T02:17:30Z")
> [@vivalostwages](#): > > I’m near the Azusa foothills, so it comes down here sometimes. The other night it smelled like burning hot dogs right outside the window, so I just had to leave all the windows shut all night. I didn’t notice you were in SoCal also. Yeah, Azusa’s probably the worst place for air quality this week. In Pasadena, the air was a bit crappy Wednesday, but otherwise I haven’t really noticed. (My patio table needs a good wipe, though.)