EXPLANATION Volcano active during past 2,000 years • Population center 100,000 to 350,000 ALASKA Wrangell Hayes •Anchorage Spurr Redoubt Iliamna Akutan Novarupta Augustine _Cook Inlet_ Trident Bogoslof Ukinrek Martin Mageik Kagamil Chiginagak Ugashik-Peulik Carlisle Emmons Lake Yantami Kiska Cerberus Fisher Dutton Aniakchak Veniaminof Little Sitkin Kasatochi Amukta Pyre Pavlof Isanotski Westdahl Shishaldin Makushin Gareloi Vsevidof Okmok Tanaga Korovin Cleveland Kanaga Great Sitkin Yunaska [Illustration: Redoubt Volcano, Alaska, erupting on December 16, 1989. (_Photograph by National Park Service._)] Redoubt Volcano. Redoubt Volcano erupted for the fourth time this century on December 14, 1989. Following several days of strong explosive activity, a series of lava domes grew in Redoubt’s summit crater during the next four months. Most of the domes were destroyed by explosions or collapsed down the volcano’s north flank. Some of these events triggered small pyroclastic flows that melted snow and ice on the volcano to form lahars in Drift River Valley, which empties into Cook Inlet 35 kilometers away. Ash produced by the eruptions severely affected air traffic enroute to Anchorage, Alaska’s largest city and a major hub of domestic and international commercial air traffic. Many domestic carriers suspended service to Alaska following major explosive events, and several international carriers temporarily rerouted flights around Alaska. On December 15, a jetliner enroute to Japan encountered an ash cloud while descending into Anchorage. The plane quickly lost power in all four engines and lost 4,000 meters in altitude before the pilots were able to restart the engines. The aircraft landed safely in Anchorage, but it sustained more than $80 million in damage. [Illustration: 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. [Illustration: 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._)]