Projectiles and Lateral Blasts

A directed blast is a large-scale lateral vol-canic explosion caused by a major landslide orslope failure that uncaps the internal vent sys-tem of the volcano. Such an event is rare in thehistory of a volcano. Although geologic evi-dence indicates that Augustine generatesdebris avalanches more frequently than mostvolcanoes, evidence of directed blasts is rare

The lateral blast hazard zone is a bullseye pattern with a 10-km radius centered on Cerro Quemado. The bullseye pattern reflects the likelihood of a lateral blast originating from any flank of the dome. The size of the zone is determined by the extent of lateral blast deposits of the 1150 yr. B.P. eruption, but includes a 3-km safety zone reflecting the possibility of an even larger blast at the dome. Because of its size, the upper flanks of Santa María volcano (above 3100 m) are excluded from the lateral blast hazard zone.