Map shows hazard zone for pyroclastic flows and surges around existing explosive vents along the Mono-Inyo Craters volcanic chain.

This hazard zone is based on explosive eruptions from vents located along the chain in the past 10,000 years that are known to have that ejected <1 km³ of magma and generated pryoclastic flows or surges. The zone extends about 15 km (10 mi) from these vents. Along the west and south sides of the chain, the zone is narrower because pyroclastic flows moving in these directions will be blocked by the high Sierra Nevada. Future pryoclastic flows and surges from a single eruption would affect only a part of the total hazard zone shown on the map.

If future monitoring of the Long Valley volcanic unrest suggests magma is moving beneath the Mono-Inyo chain, it may not be possible for scientists to anticipate the exact location of one or more eruptive vents. For example, about 600 years ago eruptions from both the northern and southern part of the chain occurred from vents along zones 6-11 km in length. Thus, scientists will probably not be able to define the pryoclastic-flow and -surge zone (map at left) more precisely when an eruption is expected.