Pyroclastic Flows

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).

Possible eruption sequence for the Long Valley-Mono Lake area.

The Bishop Tuff refers to the deposits of ash and pumice ejected during the enormous eruption that created Long Valley Caldera.

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

The resurgent dome is a broad area of the central caldera floor that was pushed upward within 100,000 years or less of the caldera-forming eruption 760,000 years ago.

Since the enormous explosive eruption formed the caldera about 760,000 years ago, hundreds of smaller eruptions have partially filled the initially deep depression.