Lava dome in the summit crater of Redoubt Volcano, which grew between April 21 and June 1990. (Photograph by David Wieprecht.)
Lahars generated during the eruption threatened an oil-storage facility located on the banks of Drift River. Oil is pumped from more than a dozen wells in Cook Inlet to the facility and then loaded onto tankers, which dock just offshore. A lahar on January 2 flooded part of the facility with nearly a meter of water, forcing its shutdown until workers could restore power. This and subsequent lahars prompted the Cook Inlet Pipeline Company to temporarily halt oil production from some oil wells and reduce the amount of oil stored at the facility between tanker loadings.
Rock from the lava dome of Redoubt Volcano deposited in a river valley by a lahar during an eruption on January 8, 1990. When found 6 days later, the temperature of the rock was still 145°C. (Photograph by C. Dan Miller.)
Steam plume rises from lava dome atop Augustine Volcano on April 30, 1986. (Photograph by M.E. Yount.)
Augustine Volcano.
One of the most active volcanoes in Cook Inlet is Augustine, whose symmetrical cone rises 1,254 meters above the sea. Since Captain James Cook discovered and named it in 1778, Augustine has erupted in 1812, 1883, 1935, 1963-64, 1976, and 1986. Curiously, the quiet intervals between these eruptions apparently have shortened from 70 to 10 years.
Augustine’s 1986 eruption was similar to the pattern of events observed in 1976. After eight months of earthquake activity beneath the volcano, a violent explosion began on March 26. Billowing ash plumes rose more than 10 kilometers above the vent, pyroclastic flows sped down the volcano’s flanks into the sea, and ash spread throughout Cook Inlet. A second stage began April 23, when lava began erupting near the volcano’s summit and added about 25 meters to the top of the existing lava dome. Small pyroclastic flows accompanied growth of the dome.