Wildland fires burn in a predictable pattern. A look at the patterns a fire investigator looks for to help determine where a fire started:
V-pattern - Fires generally burn in a V-shape away from the ignition source, with flames spreading wider as winds blow the fire away from the source. Even in the absence of witnesses, the pattern can help narrow the search for the start.
Diagonal burns - As fire advances with the wind, it generally hits trees, brush and grass lower on one side and burns higher out the backside, giving an indication of the direction the fire was moving.
Lateral burns - Even with winds pushing flames in a specific direction, fires also move backward away from the source, creating an even pattern on grasses, tree trunks and other fire fuels.
Combination of diagonal and lateral burns - Near the ignition source, burn patterns will vary, sometime offering conflicting clues about which fire's direction. Fire investigators call it the ``area of confusion'' - or transition. When fire investigators arrive there, they lay out string grids and carefully look at every inch of ground, searching for evidence of the fire start.