Explainer’s Wildfire Roundup

Your questions about the disaster, with answers from our archives.

Wildfires In Southern California. Click image to expand.
Wildfires in Southern California

Wildfires raged across Southern California this week, burning 420,424 acres, destroying 1,155 homes, and forcing 881,500 people to flee in what one official described as “probably, the worst fire this county and state has ever seen.”

Among the fires burning in Southern California are the Poomacha Fire, the Ammo Fire, the Magic Fire, and the Witch Fire. Who picks these names?

In general, naming rights go to the group that makes the “initial attack” on a fire, whether it’s a squadron of local firefighters or a team from the U.S. Forest Service. (In contrast, every tropical storm in the Atlantic gets its name from a single organization.) The commander on the scene often uses a nearby geographical feature to describe the fire, but he’s not bound by any official rules. (For more on how a wildfire gets its name, read this Explainer from 2005.)

Officials report a level of “containment” for some, but not all of the 22 fires. What does it mean to contain a fire and how is the percentage calculated?

To prevent a blaze from spreading, firefighters dig a “fire line” around its circumference. If three miles of fire line have been built around a fire that is 10 miles in circumference, then 30 percent of the fire is contained. Once a fire is fully contained, firefighters work on “controlling” it by battling it inside the containment line. A controlled fire is one that has no risk of expanding beyond the fire line. (For more on how wildfires are rated, read this Explainer from 2001.)

According to newspaper reports, 2,300 California prison inmates are helping to put out the blaze.  Why are prisoners fighting wildfires?

In California, some prisoners get transferred to a system of “conservation camps,” where more than 4,000 inmates are housed and trained to fight forest fires. According to the Department of Corrections, “assignment to a conservation camp is a hard-won privilege” and provides the opportunity for prisoners to live without gun towers or security fences and to reduce the duration of their sentences by as much as two-thirds. Spots at the camps are reserved for physically fit offenders with no history of escape attempts, violent crimes, or—naturally—arson. (For more on prisoners and disaster-relief, read this Explainer from 2005.)

A San Diego official says wildfire property damage will top $1 billion.  What about the environmental damage from all the carbon being spewed into the atmosphere?  Do wildfires have a significant impact on global warming?

A lot depends on what the fire destroys, as there is tremendous variation among tree species in terms of carbon storage. If you see a fire sweeping through an expanse of mighty evergreens, the carbon emissions will be much higher than if the conflagration was consuming wispier trees. You’ve also got to factor in the composition of the ravaged soil. The fires that swept across Indonesia in 1997 burned relatively thin tropical trees. But the devastated forests were also covered in carbon-rich peat. As a result, the Indonesian fires were estimated to have released between 13 percent and 40 percent of the world’s annual emissions at the time. (For more on the environmental impact of wildfires, read this article from 2007.)

Fire officials fighting the Orange County fire say it was set deliberately.  How do you investigate a wildfire for signs of arson?

First, figure out where it got started. The place where firefighters first engaged with the blaze is a good place to begin, as are spots where eyewitnesses say they first saw flames or charred ground. Once there, investigators can lay down something like an archaeological grid and start sifting through the debris.  This evidence might include the “puddled” burn patterns caused by an accelerant, or the remains of a cigarette.  Investigators also look for footprints or tire marks, and they sometimes use magnets to find stray bits of metal that might have been part of a time-delayed incendiary device. (For more on how investigators look for signs of arson, read this Explainer from 2006.)

Witnesses have described “thick black smoke” blotting out the sun. Others have seen white plumes. What determines the color of smoke?

The type of fuel and how hot it’s burning.  A wildfire can produce both colors of smoke. First, the hot, flaming combustion of dry underbrush releases little particles of black soot into the atmosphere. But the blaze also produces smoldering combustion—think of the glowing logs at the bottom of a campfire—which don’t burn quite as hot. Big branches or tree trunks that have a lot of moisture are more likely to smolder and release white smoke. (For more on what determines smoke color, read this Explainer from 2006.)

Reports have described wildfire flames as high as 100 feet in some places.  How high can a fire hose shoot?

Between 75 feet and 100 feet straight up, depending on water pressure. In practice, though, firefighters on the ground rarely attempt to reach higher than 40 feet with hoses. (For more on how firefighters attack tall flames, read this Explainer from 2004.)

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