Long Valley Caldera

Potential Tephra Fall Hazards for Small to Moderate-Sized Eruptions in the Long Valley - Mono Lake Area, California

Downwind deposits of ash produced by an explosive eruption could reach thicknesses of at least 20 cm at a distance of 35 km (8 in. at 22 mi), 5 cm at a distance of 85 km (2 in. at 53 mi), and about 1 cm at a distance of 300 km (0.5 in. at 185 mi).

Map shows the potential thickness of tephra on the ground from futu...

Map shows the potential thickness of tephra on the ground from future eruptions in the Long Valley area.

(Credit: Miller, C. D.. Public domain.)

These estimates of potential ash thicknesses are based on deposits of ash from past eruptions at other volcanoes that involved volumes of as much as 1 km3 (0.25 mi3). Only a part of an ash-fall hazard zone would probably be affected by any single ash fall; the part affected would be determined by the wind speed and direction or directions during an eruption.