Sunday, October 25, 2009

The Fire Down Under

This New Yorker article (subscription required) about the Black Saturday wildfires in Australia, which occurred on February 7 of this year, was amazing.

A couple particularly intense passages:

[Ackerman] rushed back north to Marysville against a stream of traffic coming the other way. By the time he was a few miles from Marysville, he could see a colossal firewall coming toward him from the southwest. It was three hundred feet high. He raced it all the way back to the town, driving on the wrong side of the road to get through blocked intersections and dodging cars that sped toward him in their effort to flee. The fire behind Ackerman emitted a roar like a jet engine and threw embers and fireballs out ahead of him. Huge patches of trees and grass ignited around the car as he drove....

Strange cataclysmic phenomena occur in a huge wildfire. Kevin Tollhurst, a fire ecologist in Melbourne, told me that fires as hot as the one at Marysville—which is thought to have reached a temperature of twenty-two hundred degrees—can produce their own weather. Fires generate convection columns of gas, which may rise as much as forty thousand feet and form pyrocumulus clouds. The clouds can create lightning, which may then start more fires downwind of the original fire. The sound of the gas—like a twig popping in a fireplace, but exponentially louder—creates a wildfire's distinctive roar. The Marysville fire was so hot that gas flared out laterally, acting as a wick, along which the fire caught quickly, crossing the ground in sudden, unpredictable pulses. In the face of such a fire, it is possible to be looking at a front more than a thousand feet away and then, in an instant, to be surrounded by flames. Firefighters described the Black Saturday firestorm as "alive," and said that its behavior was completely unprecedented. In some areas it was apparently cyclonic, coming at them from all sides, burning up a road in one direction and then, minutes later, burning in the opposite direction. Tollhurst told the royal commision that the energy from all the fires that day was the equivalent of fifteen hundred Hiroshimas.

Here you can watch some video of the fires.

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