Luzon’s Mayon volcano is threatening to erupt again, and authorities have advised residents within a four-mile radius to move to safer areas. Travelers should avoid the volcano and any gullies or rivers that run off the mountain, which can act as conduits for mudflows and other volcanic debris. The risk runs far beyond the central danger zone because flows can run very fast along these natural paths well past the base of the mountain. The most prudent approach is to avoid the volcano entirely.