Fire behavior is so complex that sometimes it might help visualizing it in a different way. Some fire experts describe wildfires according to the location of the fuels. These types are ground fires, surface fires, and the spectacular crown fires of the type that swept through Yellowstone Park in 1988, advancing along three-hundred-year-old trees and burning tens of thousands of acres.

In ground fires, the fuel is the layer of organic material that accumulates directly under the ground level, beneath the surface covered with leaves, needles, and twigs. Ground fires do not produce flames, they smolder or burn like glowing embers. Ground fires occur, for example, after the firefighters have extinguished the flames burning a group of bushes. Even though the flames are no longer a threat, there are usually layers of organic matter smoldering under the ground beneath...