Passage Three
The recent wildfire in Alberta, Canada, has already burned through 600 square miles of land, and 20% of houses in the city of Fort McMurray; all its 88,000 residents have left their homes. But how do you put out fires this big and intense?
Wind, fuel and the slope (坡度) of the land are three vital factors. You can’t do very much about the first one. The firefighters will be paying attention to weather conditions. In an ideal world, the wind would force the flames back on to ground that has already been burned.
Fuel—mainly the trees—can be managed in several ways, such as bulldozing (铲除) it out of the way or starting controlled fires to burn it off so it can’t feed the main fire.
The slope of the land can also help. Fires burn much more aggressively going uphill than they do downhill. You don’t try to fight a fire going uphill. The firefighters will be looking very carefully how they arrange their personnel and equipment on a downhill side of a slope. In a fire that is relatively small and moving downhill, you can launch a direct attack, physically beating the flames out with special tools. You would come in behind the fire, so you’re not face to face with flames coming towards you.
In addition, fire can spread a large distance away from the fire-front by burning embers (余火) carried on the wind, which then start other fires elsewhere. You can actively work on preventing parts of the fire going in certain directions. But this requires resources, such as water-bombers—planes thatdumpvast quantities of water. They aren’t just flying over the top of the fire and releasing water. They usually wet the fuel ahead of the fire or along its sides to stop the spread of the fire.
Which factor is mainly talked about in Paragraph 2?