Ash/Tephra Fall

Several hazards will likely accompany a future eruption of Lassen volcano.

Volcanic ash travels with the wind, and ashfall can impact areas near to and far from the eruption site.

On May 22, 1915, an explosive eruption at Lassen Peak, California, the southernmost active volcano in the Cascade Range, devastated nearby areas and rained volcanic ash as far away as 300 km (about 200 mi) to the east. This explosion was the most powerful in a 1914-17 series of eruptions that were the last to occur in the Cascades before the 1980 eruption of Mount St. Helens.