Observations of a Nuée Ardente from the St. Augustine Volcano

A series of aerial photographs were obtained of a nuée ardente produced by the February 8, 1976 eruption of the St. Augustine volcano, Alaska. The nuée ardente reached a maximum velocity of 50 m s−1 while descending the steeper (∼1∶3) slope of the volcano. It later slowed to a velocity of 6 m s−1 as it traversed the gentler slope (∼1∶25) at the base of the volcano, where it formed a deposit. The nuée ardente appeared to originate with the collapse or penetration of a newly formed dome, rather than the collapse of a vertical eruption column. Fluidization by fine particles in the nuée ardente probably contributed to its mobility.