An active crown fire is characterized by which sequence?

An active crown fire is characterized by which sequence?

• A. Aerial fuels burn first, then ground fuels ignite
• B. Only aerial fuels burn
• C. Ground fuels burn, then aerial fuels ignite
• D. Only ground fuels burn

Answer: (C)

An active crown fire starts with a fire in the surface (ground) fuels that heats and dries the vegetation in the overstory through ladder fuels. Once the canopy receives enough heat, the crowns ignite and the fire then propagates through the treetops. So the defining sequence is ground fuels burn first, then aerial fuels ignite. Patterns where only aerial fuels burn or where aerial fuels would ignite before any ground fire don’t reflect how crown fires typically develop, since the canopy ignition relies on heat transferred from the burning ground fuels.

An active crown fire starts with a fire in the surface (ground) fuels that heats and dries the vegetation in the overstory through ladder fuels. Once the canopy receives enough heat, the crowns ignite and the fire then propagates through the treetops. So the defining sequence is ground fuels burn first, then aerial fuels ignite. Patterns where only aerial fuels burn or where aerial fuels would ignite before any ground fire don’t reflect how crown fires typically develop, since the canopy ignition relies on heat transferred from the burning ground fuels.