A(n) passive crown fire is when an individual tree or group catches fire and then runs all the way up the tree.

A(n) passive crown fire is when an individual tree or group catches fire and then runs all the way up the tree.

• A. Active crown fire
• B. Passive crown fire
• C. Ground fire
• D. Surface fire

Answer: (B)

Passive crown fire occurs when heat from a surface fire preheats a tree’s crown until the crown ignites, and the fire then climbs up the tree, torching it from top to bottom. The scenario described—an individual tree or small group catching fire and then running up the trunk—fits this pattern, because the ignition in the crown is driven by the underlying surface fire rather than a self-sustaining canopy flame. In contrast, an active crown fire would spread through the canopy on its own, independent of a surface fire, which isn’t what’s described here. Ground fire stays in the soil and surface fire remains on the ground, so they don’t match the sequence of crown ignition followed by upward spread.

Passive crown fire occurs when heat from a surface fire preheats a tree’s crown until the crown ignites, and the fire then climbs up the tree, torching it from top to bottom. The scenario described—an individual tree or small group catching fire and then running up the trunk—fits this pattern, because the ignition in the crown is driven by the underlying surface fire rather than a self-sustaining canopy flame. In contrast, an active crown fire would spread through the canopy on its own, independent of a surface fire, which isn’t what’s described here. Ground fire stays in the soil and surface fire remains on the ground, so they don’t match the sequence of crown ignition followed by upward spread.