The entire valley, under which the supervolcano is located, stretches 19.8 miles long and 11.2 miles wide.
Long Valley was formed 760,000 years ago when a very large eruption released hot ash that later cooled to form the Bishop tuff that is common to the area. The eruption emptied the magma chamber under the area to the point of collapse.
The second phase of the eruption released pyroclastic flows that burned and buried thousands of square miles. Ash from this eruption blanketed much of the western part of what is now the United States.
USGS seismologists are sure that humanity simply will not survive another eruption.
But earlier it was believed that the seismic activity of the volcano is decreasing. Opposite data began to arrive only at the end of 2015, and it was only now possible to prove the awakening of the supervolcano.
Theoretically, a series of nuclear tests in Nevada could “stir up” Long Valley. From the 1950s to the 1990s, bombs with a capacity of up to 150 kilotons were detonated here.