Wall of fire!

Fifty-two smokejumpers and helitackers--elite fire-fighters who rush into fiery forests by parachute and chopper--faced their worst nightmare last July. As they battled what they thought was a typical blaze on Colorado's Storm King Mountain, the weather suddenly turned against them. A mass of cold air blew into the region. It whipped up winds and fed the flames. Within seconds, towering walls of fire surrounded the crew.

Some firefighters managed to outpace the explosive "blow-up" of flames, which charged uphill at 30 meters (98 feet) per minute. Others tried to hide in fold-out fire shelters. Fourteen firefighters--10 men and 4 women--perished in the blaze.

Firefighters will remember Storm King as one of the most tragic fires of the 1994 fire season, which lasts from May to November. By September, 58,626 fires had torched more than 3.5 million acres of land in Western states. Some 25,000 firefighters were spread so thin that the Army and Marines sent in troops to help fight the flames.

BUSTING OUT

"When this year's fire season started, we got the feeling that things were going to bust out all over," says Mike Brown, a fire information officer at the Interagency Fire Center in Boise, Idaho. The West's warm, dry climate, the weather pattern that repeats there year after year, sets up conditions that are especially welcoming to wildfires.

"In the West there is less rain [than in the East]," says Dave Imy, a meteorologist at the National Weather Service. As moist air from the Pacific travels eastward over the Sierra Nevada and Cascade mountains, he explains, the moisture turns to rain and snow. But by the time the air has passed over the mountains, it has dried out. Result: Little rain falls over the inland states.

In 1993, however, more rain fell than usual. Trees and other plants flourished. Then, 1994 was particularly dry--and warm. Colorado, for example, experienced more than days over 32[degrees]C (90[degrees]F). The heat dried out last year's growth, leaving a buildup of parched brush, grasses, and pine needles--perfect fuel for a fire. One year's worth of growth on one acre of forest contains the energy equivalent of 1,100 liters (300 gallons) of gasoline, according to the U.S. Forest Service. All that's needed to release that pent-up energy, says meteorologist Imy, is a single fiery spark.

The weather often provides such sparks in the form of lightning, Imy says. At Storm King, for example, a dry thunderstorm--a lightning storm without rain--hovered over the mountaintops. When lightning zapped a parched tree, the 30,000[degrees]C 54,000'F) spark set off a dangerous chemical reaction--combustion, or burning. The reactants--molecules of fuel in the brush and oxygen in the air--quickly combined to give off enormous amounts of energy in the forms of heat and light.

FANNING THE FLAMES

Weather not only sparks the flames, says Imy. It can fan them out of control. Cold air masses, like the one that swept over Storm King, are "every firefighter's nightmare," says fire expert John Chandler.

The reason: As warm air within the fire rises, the cold air rushes in to replace it, whipping up fierce winds. Because of the rising heat, "huge fires can even create their own [winds]," says meteorologist Imy. At Storm King, the 80km per hour (50mph) winds blew the tame fire into an inferno.

The fire "sounded like a tornado," says firefighter Brad Haugh, one of the 38 Storm King survivors. "Without warning it just exploded."

The winds feed the flames by constantly removing the products of combustion, smoke and ash (spent fuel), and bringing in a fresh supply of oxygen. Strong winds also set off a fire-starting chain reaction, Imy says. They blow glowing embers into nearby clumps of trees and brush, he explains. The hot embers, combined with plenty of oxygen and abundant fuel, set off the combustion reaction again. Result: more raging fires that are nearly impossible to contain.

A few of this past summer's fires were ignited not by weather, but by people "dropping cigarettes or leaving camp fires [smoldering]," says fire information officer Mike Brown. A huge fire in Oregon ignited when a truck with faulty brakes sprayed sparks into a stretch of parched roadside woods. Some fires--for example, one that burned 42,000 acres in central California last August--were set by arsonists, people who start fires intentionally (a felony).

Regardless of a forest fire's cause, firefighters use similar methods to break the fire chain. One technique: They dig wide ditches in the path of the fire's approach to create a gap in the fuel supply. Ideally, these fire lines prevent the fire from spreading. Firefighters also spray foam and fire-retardant chemicals from planes to smother the fire by cutting off its oxygen supply. Helicopters dump thousands of liters of water to cool and snuff out the embers. Yet using all these techniques, a fire the size of Storm King's can still take weeks to put out.

What most firefighters hope for is a helping hand from the forces of nature: heavy rains to squelch the flames--and rejuvenate the forest.

RELATED ARTICLE: To burn or not to burn?

Maybe you've heard the expression, "You can't fight fire with fire." Well, that's what many scientists believe we should be doing. Intentionally setting small fires in controlled areas, they argue, would burn up some of the available fuel--trees, grass, pine needles, and brush. Some people also argue that setting these prescribed fires helps rejuvenate forest ecosystems by clearing space and by releasing nutrients into the soil.

About 20 years ago, the U.S. government adopted policies in favor of prescribed burning on public lands, says fire historian Stephen Pyne. But this policy has been carried out only on a very small scale because it raises other concerns. These include:

* Air pollution Billowing smoke from a fire is a form of air pollution. On many public lands in the West, the government is required to keep the air pristinely clean, says Pyne. "If people light a fire [for prescribed burning] and it creates air pollution, it's difficult to argue in favor of it," he says.

* Wildlife threat Many fire-prone lands are home to countless species of plants and animals. Some species--for example, sand pine trees, which release seeds only when burned--benefit from fire. But Americans raised on Smokey the Bear are more likely to identify with those species that are harmed by fire: deer, birds, wolves, fish, and others.

* Property damage Even though prescribed fires are set where they're least likely to spread, they sometimes burn out of control, says Pyne. If a prescribed fire destroys homes, residents might sue for damages.

* What do you think? Should the prescribed-burning policy be enforced? Debate and decide.