A major wildfire has been advancing through the foothills near Los Angeles this week. By Wednesday, the blaze had consumed 140,000 acres and caused the state to spend more than half of its firefighting budget.
Investigators have concluded that the Station fire in Northwest Los Angeles was " caused by someone intending to set a fire," although they have not revealed any details about the evidence. How do you examine a wildfire for signs of arson?
First, figure out where it 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 "puddle" 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. (Read more on how investigators look for signs of arson.
Among the fires now classified as "active incidents" in California, the biggest is the Station fire. Others include the Oak Glen fire, the Big Meadow fire, the Black fire, and the Red Rock 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. (Read more on how a wildfire gets its name.)
Gov. Arnold Schwarzenegger announced on Wednesday morning that the Station fire in Angeles National Forest had been 22 percent contained. 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. (Read more on how wildfires are rated.)
Reporters have described "billows of white and black smoke" in the Los Angeles area, along with a "brownish mushroom cloud … and a gauze of gray smoke." What determines the color of the 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. (Read more on what determines smoke color.)
A pair of firefighters perished Sunday while trying to protect the crew of prison inmates that was assisting them. Why are prison inmates fighting fires?
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. (Read more on prisoners and disaster relief.)
One firefighting inmate says he saw wildfire flames as high as 100 feet. 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. (Read more on how firefighters attack tall flames.)
Officials say the Station fire has already caused millions of dollars in damages. 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 were 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. (Read more on the environmental impact of wildfires.)
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