California Department of Forestry and Fire Protection (CAL FIRE) Fire Fighter Practice Exam

Crown fire is characterized by its intense combustion that affects the upper canopy of trees. This type of fire spreads rapidly both vertically and horizontally through the treetops, unlike ground fires which primarily consume fuel at the surface level, such as grasses and underbrush. The ability of crown fire to move through the canopy often leads to devastating impacts on forests, making it harder to control and significantly altering the landscape.

Other phenomena described in the other choices, such as slow ground-level spread or localized burning in brush, pertain more to different types of wildfires. Ground fires typically progress slowly and smolder at the base, while localized burning in brush reflects a more contained fire behavior. Sequential burning of grasslands would refer to fires that spread gradually in grassy areas, rather than the explosive nature associated with crown fires that leap through trees. Thus, the distinct vertical and horizontal movement within the tree canopy defines the crown fire's characteristic feature.