Redoubt 1989/12

Start: 09:47:00 December 14, 1989 ^[1]

Stop: June 1990 ^[1]

Event Characteristics:

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Impact: From Waythomas and others (1998): "About 23 individual volcanic bursts caused by explosions, dome collapse, or both, occurred during the 1989-90 eruption of Redoubt Volcano. During some of these bursts, vertical clouds or plumes of fine volcanic ash were forcibly expelled into the atmosphere. Ash plumes reached altitudes of 7,000 to more than 12,000 meters above sea level before being dispersed by the prevailing winds. These ash clouds initially drifted to the northeast and east, but eventually moved to the southeast over Canada and into the airspace over the conterminous United States. At least one ash cloud from Redoubt Volcano reached as far west as Texas and the Gulf of Mexico (Casadevall, 1994). Throughout the eruption, clouds of volcanic ash remained a serious threat to aircraft downwind from the volcano and at least seven commercial jet aircraft encountered ash clouds from Redoubt Volcano.
"Volcanic ash from the 1989-90 eruption of Redoubt Volcano is composed of sand-sized and smaller particles of angular pumice, volcanic glass, crystals, and rock fragments. Volcanic ash clouds from Redoubt Volcano occupied a portion of the airspace utilized by jet aircraft and traveled at altitudes ranging from about 4,500 to 12,000 meters (Casadevall, 1994). The ash may interfere with aircraft engine operation and electronic components and its abrasive quality often causes damage to the exterior of jet aircraft, especially the leading edges of wings and cockpit windshields (Casadevall, 1994).
"* * * In addition to the incidents described above, volcanic ash clouds from Redoubt Volcano curtailed activity at two other Anchorage area airports, Merrill Field and Elmendorf Air Force Base. Although no significant amount of ash fallout occurred, ash clouds in the airspace over the Anchorage area and beyond caused numerous flight cancellations, delays, and route changes. During December 1989, more than 90 military cargo flights were diverted from Elmendorf Air Force Base and about 45 flights by military turboprop aircraft were cancelled (Casadevall, 1994). As a result of the 1989-90 eruption, lost revenue at Anchorage International Airport was about $2.6 million (Casadevall, 1994)."
"* * * Ashfall from the 1989-90 eruptions was a serious public health concern for parts of south-central Alaska, especially the Kenai Peninsula. During periods of continuous ash fallout, the public was advised to remain indoors and wear dust masks. Many schools were closed, and some individuals experienced respiratory problems. The municipal airport at Kenai was closed for several days as a result of ash fallout from the January 8, 1990 eruption. Gas-powered turbines at the Beluga power plant, the primary power supply for Anchorage, were shut down in anticipation of the adverse effects of a thick ashfall on February 24, 1990. Only one of the turbines remained in operation for a brief period during the ashfall, but fortunately there were no interruptions in power service."
" * * * During the 1989-90 eruptions of Redoubt Volcano, hot pyroclastic flows melted significant parts of the Drift Glacier and the winter snowpack. Some of the ensuing lahars, lahar-runout flows, and floods completely inundated the Drift River valley, threatened the Drift River Oil Terminal, and eventually flowed into Cook Inlet about 35 kilometers downstream from the volcano. At least six lahars in the Drift River reached Cook Inlet during the 1989-90 eruptions (Dorava and Meyer, 1994). The largest of these occurred on January 2, 1990 and inundated Rust Slough, including parts of the Drift River Oil Terminal. At the oil terminal, muddy sediment about 1 meter thick was deposited by this lahar. As the 1989-90 eruptions progressed, additional sediment was delivered to the lower Drift River, Rust Slough, and Cannery Creek by lahars and lahar-runout flows. This caused the braided channel of the Drift River to change its course repeatedly, temporarily increasing the discharge of tributary streams and accelerating erosion. As a result of this process, increased flow in Montana Bill Creek initiated bank erosion that exposed, but did not rupture, a buried oil pipeline that crosses Montana Bill Creek north of the oil terminal (Dorava and Meyer, 1994).
"The 1989-90 eruption began in December at a time when the amount of snow and ice on the volcano was significantly greater than it would be in March and April. Thus, the initial lahars were greater than those that formed later in the eruption. As the eruption progressed, Drift Glacier became deeply scoured and lesser amounts of snow and ice were available for melting by the hot pyroclastic flows, even though some of those flows were larger but less hot than those that were generated earlier in the eruption. As the amount of snow and ice available for scour and entrainment by the pyroclastic flows decreased, so did the size of the resultant lahars.
"* * * During the 1989-90 eruptions, pyroclastic flows were formed primarily by repeated collapse of a lava dome (Gardner and others, 1994). Fourteen distinct lava domes formed over the course of the eruption as viscous lava was slowly extruded (Miller, 1994). As the domes were being extruded, they became oversteepened and then failed by gravitational collapse. The collapse caused a sudden release of pressure from the upper part of the magma chamber which explosively propelled hot gas, water vapor, and rock debris down the slope of the volcano. The resultant pyroclastic flows and associated ash clouds were directed down the east side of Drift Glacier and the Drift River valley, traveling about 8 kilometers downstream from the volcano.
"The pyroclastic flows generated by the 1989-90 eruptions melted and scoured large portions of Drift Glacier. Because the glacier was heavily crevassed and steep, the hot pyroclastic flows incised ice canyons through the glacier, some as large as 40 meters deep and 30 meters wide. This led to the development of lahars downstream from Drift Glacier as meltwater mixed with debris deposited at the distal end of Drift Glacier by the pyroclastic flows.
"During the February 15, 1990 eruption of Redoubt Volcano, a pyroclastic surge climbed a ridge 700 meters above the terminus of Drift Glacier and about 10 kilometers from the dome, charring woody vegetation, melting cables to seismic monitoring equipment, and partially burning a ptarmigan."
Tuck and Huskey (1992) estimate the total economic cost of the 1989-90 eruptions to be $159,687,070. ^{[60] [1] [44] [61] [62] [45] [46] [16] [28] [19] [63] [64] [65] [54] [66] [67] [68] [69] [70] [71] [55] [40] [51] [72] [49] [73] [41] [3] [5] [6] [8]}
Aircraft Impact: From Casadevall (1994): "The December 1989-June 1990 eruption of Redoubt Volcano affected commercial and military air operations in the vicinity of Anchorage, Alaska. These effects were due to the direct impact of volcanic ash on jet aircraft, as well as to the rerouting and cancellations of flight operations owing to eruptive activity. Between December and February, five commercial jetliners were damaged from ash encounters. The most serious incident took place on December 15, 1989, when a Boeing 747-400 aircraft temporarily lost power of all four engines after encountering an ash cloud as the airplane descended for a landing in Anchorage. While there were no injuries to passengers, the damage to engines, avionics, and aircraft structure from this encounter is estimated at $80 million. Four additional encounters between jet aircraft and Redoubt ash clouds occurred in the Anchorage area on December 15 and 16, 1989, and February 21, 1990; none resulted in engine failure. Two additional encounters took place on December 17, 1989 when jet airliners encountered the Redoubt cloud over west Texas. At the time of these encounters, the cloud was up to 55 hours old and had traveled in excess of 2,900 nautical miles (5,300 km).
"Following the December 15 encounters, Anchorage International Airport remained open, however, most airline companies cancelled operations for up to several days. As communications between Federal agencies and airlines improved, and as a better understanding of the nature and behavior of ash-rich eruption clouds was achieved, most airlines resumed normal service by early January 1990. The resulting loss of revenue at Anchorage International Airport during several months following the eruption is estimated to total $2.6 million. The impact on general aviation and military operations consisted mostly of cancellation and rerouting of flights. * * * Kenai airport, located on the Kenai peninsula, 43 nautical miles (80 km) east of Redoubt volcano, was shut down by ash fall from the eruption of January 8 and remained closed for several days."
At Elmendorf AFB "* * * Jet fighter operations were limited on December 15-16 and 12 sorties were canceled. During December, about 90 military cargo flights were diverted to either Fairbanks or the Air National Guard base at Anchorage International Airport (AIA). Approximately 45 flights by military turboprop aircraft were canceled in December 1989 due to volcanic activity." ^{[44] [45] [61] [62] [1] [46] [64] [65] [54] [68] [69] [70] [71] [55] [40] [51] [72] [49] [73] [41] [3]}
Other Impacts: From Tuck and Huskey (1992): "The Kenai Peninsula governmental sector lost at least 1,010 days of labor due to closures. Schools closed for three days. These were losses that were not made up for 300 non-teaching personnel. The cities of Soldotna and Homer also sent workers home for periods of time during the eruptions. This accounted for about eighty worker days. Finally the Peninsula Hospital let its non-essential workers go for one-half of one day for a loss of 30 worker days (Johnson, Whelan, Haggerty, and Swarner, personal communications). * * * There were numerous power outages caused by volcanic ash during this period." ^{[55] [54] [40] [1]}

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