Which of the following factors increases the potential for fire spread in steep terrain?

Steep terrain presents unique challenges for fire behavior, and certain physical features can markedly influence the potential for fire spread. The presence of chutes and chimneys facilitates the rapid upward movement of fire due to the natural funneling effect they create. These features can enable hot gases and embers to rise quickly, often increasing the intensity of the fire as it moves uphill.

When the fire is channeled into these confined areas, it experiences reduced airflow, leading to faster combustion and greater fire spread. Additionally, as flames move uphill, the heat rises and can preheat the fuels above, making them more susceptible to ignition. Hence, chutes and chimneys dramatically enhance the conditions conducive to fire spread in steep terrain, making this option the correct choice.