Hazards

Volcanic unrest through the 1980's to 1990's in the southern part of the Long Valley caldera reminds us that the volcanic system is young. Volcanic activity and related hazards are likely in the future. USGS scientists closely monitor the area and research past activity to better understand what might happen in the future.

Future lava flows in the Long Valley area will be either relatively fluid (basalt lava) or viscous (dacite or rhyolite lava).

During a typical explosive eruption of a Mono-Inyo vent, tephra (volcanic ash and larger rock fragments) may accumulate near the vent to a thickness of tens of meters (yards).

The area of eastern California that includes the Long Valley Caldera and the Mono-Inyo Craters volcanic chain has a long history of geologic activity that includes both earthquakes and volcanic eruptions. This activity is likely to continue long into the future.

Areas as far as 15 km (10 mi) from an explosive eruption could be swept by hot, fast-moving pyroclastic flows and surges.

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).

Since winds above the Long Valley area blow toward an easterly direction more than 80 percent of the time, air routes east of the volcano are likely to be contaminated with volcanic ash during a future eruption.

Future explosive eruptions like those that occurred about 600 years ago from the Mono-Inyo Craters volcanic chain in the Long Valley area would generate eruption columns higher than 18,000 feet above sea level.