In the years between fires, this all builds up and can reach a few metres deep in places. Rain leads to more undergrowth. In times of extended drought, which is what we’ve had here, that all becomes dry. Firefighters euphemistically but accurately refer to it as “fuel”. Where possible, especially when it's close to homes, and despite opposition from environment groups that has seen some national parks "locked up" to controlled burns over the past couple of decades, they try to reduce it through backburning - but they physically can't get everything.
Each summer in Australia, newspapers in every capital city carry the warning that the “state is a tinderbox”. It’s a ready-made cliché, but sadly, it’s often the truth here. Tinderbox really is the perfect way to describe it. The hot offshore westerlies that blow in off the desert on the east coast over summer are fire winds, and carry the smell of the outback: dust, smoke and pollens.
When the fuel burns, the oil-rich eucaplypts burn, and they burn quickly. Embers blow in the direction of the wind and lead to spot fires that can erupt into a firefront ahead of the original one. At the base of a big fire like this in Australia, the temperature can reach 2000C. The tips of the flames will reach 900C, and the heat can kill before the flames do. Changes in air pressure suck in oxygen to fan the flames, and the sound of it roaring across the tree tops sounds like a runaway freight train – which is how survivors and firefighters described Saturday’s inferno. Wind changes can join separate firefronts so that they become one, huge, raging megafire. Kevin Tolhurst, University of Melbourne senior lecturer in fire ecology and management, said the conditions were some of the world's worst. He said temperatures within the fire were so hot it released enough energy to supply Victoria with electricity for at least two years. Up to 80,000kw/m of heat was expelled as fires raged on Saturday. Mr. Tolhurst said this equalled about 500 atomic bombs. He said eyewitness accounts said that they didn't see any evidence of fire and then all of a sudden they felt the area around them was exploding.
Years ago I had a - very short – try-out stint in the old volunteer bush fire brigade, and have covered bushfires as a reporter in my home state, New South Wales, which was also under threat in 40C-plus temperatures on Saturday and Sunday, and have seen “crown fires” where the tops of trees burn and push flames hundreds of metres into the air. The air is so hot nearby it feels like it's pulling the breath from your lungs, and the fires are so intense, they can jump across roads and even wide areas of cleared land. And the smell of burning eucalypt is distinctive and choking.