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Mid-December 1989.-Warnings of a potential eruption were issued by the AVO about 20 hours before the initial explosive event of December 14, 1989. The eruptive activity of December 14 to 19 consisted of numerous vent-clearing and explosive events from the ice-filled summit crater. The largest events occurred on December 15 and sent eruption columns (initial ejection of hot gases) to heights greater than 39,000 feet. Flooding in the Drift River, which drains the north side of the volcano, threatened but only slightly damaged the Drift River Oil Terminal (DROI), a large oil-storage facility (10 million barrels capacity), located 25 miles downstream from the volcano at the mouth of the river.

Airborne ash generated by the numerous explosive events, particularly those of

December 15, was carried east and north
toward the parts of the Cook Inlet region
where approximately 300,000 people reside.
Air traffic was severely disrupted by the can-
cellation of hundreds of flights. A 747 jet air-
liner, carrying 248 passengers and crew, lost
all four engines after encountering an ash
cloud 198 miles northeast of Anchorage. For-
tunately, the engines were restarted and a
crash was averted. Incidents such as this illus-
trate the extreme importance of volcanic
eruption prediction and monitoring.
December 1989 to January 1990.-Growth
of a lava dome began on December 22, 1989,
in the Redoubt summit area. The large (ap-
proximately 1 billion cubic feet), unstable, and
oversteepened dome that eventually formed
was destroyed by two explosive events on the

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evening of January 2, 1990. Voluminous flows of fragmented rocks and hot mud caused extensive melting of glacier ice, and mudflows and floodwaters from melted glaciers filled the 1-mile-wide Drift River valley and carried hot dome rocks 16 feet or more in diameter to the ocean. DROT buildings (which had been evacuated 2 hours earlier following an eruption prediction by the AVO) were flooded, but protective dikes around oil-storage tanks were not broken. On January 12, 1990, USGS Director Dallas Peck informed Alaska Governor Steve Cowper of USGS findings on the current and future eruptive hazards of Redoubt volcano.

February to April 1990.-A new, smaller lava dome began to form in the summit area in late January and was subsequently destroyed in an eruption on February 15. Deposits of an ensuing debris flow—rocks, hot ash, and ice—were less extensive than those of the January 2 eruption. Floodwaters overtopped the protective dike around one DROT tank, but no damage occurred. Following the February 15 eruption, l l domes were emplaced and destroyed during events in February, March, and April. Although these events had little direct effect on DROT, ongoing concern as to the risks of storing oil at the facility resulted in a shutdown in late March and the suspension of oil production in Cook Inlet. Airborne ash continued to impact air traffic and commerce throughout the region, but AVO plume-tracking procedures and close communication with the airline industry kept disruption to a minimum.

As of this writing, Redoubt volcano has not had a major explosive event since April 1990, but further activity is possible. The most recent prior eruptive period, which began in 1966, continued for 3 years. Continued monitoring and close observation will be needed in the coming years until Redoubt volcano has clearly returned to dormancy. AVO scientists have substantially increased monitoring capabilities by enhancing the seismic network and the lightning detection system, by increasing knowledge of the eruptions and products of Redoubt volcano, and by deploying a satellite-based Global Positioning System that may detect the volcanic edifice inflating as molten material rises in the volcano. Changes in Drift River hydrology and drainage were closely monitored, and considerable research was conducted on the large debris flows of January 2 and February 15. Many of the lessons we have learned at Redoubt about debris flows, windborne ash, and other hazards will have wide application at similar volcanoes in Alaska and around the world.

Kilauea Volcano, Hawaii By Thomas L. Wright

r | Whe longest-lived eruption of the east rift zone of Kilauea volcano in this century began in January 1983 and has continued through 1990. In February 1990, lava flows threatened developed property on the east side of the eruption field for the first time since December 1986. By April, lava had entered the Kalapana Gardens Subdivision. By the end of July, all of Kalapana was covered by lava, and flows were moving toward the well-known black sand beach of Kaimu. Between February and June 1990, 168 homes and 7 commercial and recreational structures were destroyed. April 1990. –Personnel from the USGS Hawaiian Volcano Observatory (HVO) worked around the clock to advise the Hawaii County Civil Defense Agency (HCCDA) on the advance of the lava. This information became the basis for HCCDA decisions to close roads and evacuate residents. The USGS gave the HCCDA daily worst-case prognoses of where lava flows might move overnight, in 24 hours, and in 48 hours. The close USGSHCCDA coordination continued, and by August more than 100 homes had been evacuated safely. The success of this crisis management is due to the action taken by the HCCDA, which coordinated all of the numerous State and County agencies, such as the police department, fire department, Department of State Highways, and Department of Land and Natural Resources, in providing for orderly evacuation. Thus the USGS information was delivered to a single source and disseminated consistently to all persons needing the information. The activity of Kilauea during February to April 1990 has led to a greater appreciation of hazard evaluation on the active volcanoes of Hawaii. The timely publication of the USGS general interest booklet Volcanic and Seismic Hazards on the Island of Hawaii put the current eruptive activity in a broader context. May 1990. —The State of Hawaii requested Federal disaster assistance, and the Federal Emergency Management Agency (FEMA) came to Hawaii to evaluate the request. HVO personnel briefed FEMA on the nature of the eruption and associated seismic activity. On the basis of the FEMA investigation, President Bush signed a precedentsetting disaster declaration on May 22. This declaration was unusual because it was retroactive to the beginning of the eruption in 1983 and it was open ended to include areas that the HVO predicted could be affected Over the next few months. FEMA, after

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Topographic map showing the extent of Kilauea lava flows as of July 9 (light shaded area), August 23 (lined pattern), and October 23, 1990 (dark shaded area).

consultation with the HVO, also included damage claims related to a magnitude 6.1 earthquake that occurred on the south flank of Kilauea in June 1989. They agreed in principle to cover claims for lava damage extending beyond the area anticipated in May and to cover damage from future Kilauea south flank earthquakes associated with the ongoing eruption.

Easy access to the flows in Kalapana allowed the study of lava tube development and the varied processes of lava emplacement. Monitoring the inflation and the activity of different lava tubes within the developed area led to more accurate hazard evaluation than could be done without detailed knowledge of the mechanics of the lava emplacement. The eruptive activity at the vent was interrupted repeatedly by 2- to 3-day pauses during which lava tubes drained and partially collapsed. Because the collapsed tubes could not convey renewed flow, breakouts of lava occurred and adjacent land was enveloped. This activity formed the eastward-moving glacier of lava that overwhelmed Kalapana, and, by the end of 1990, lava had filled Kaimu Bay.

Where lava entered the ocean, a new threat was produced; a hydrochloric acid mist (dubbed “laze,” for lava haze, by the HCCDA), formed where the lava boiled seawater. Fortunately, expansion of the lava field at the ocean was consistently into the prevailing northeast trade winds so that laze was carried away from residences, and evacuation due to laze itself was infrequent. Because laze is a greater hazard when wind conditions are reversed, the USGS helped HCCDA prepare a pamphlet informing residents of the hazards inherent in being exposed to laze.

The experience gained during the Kalapana disaster is being used to plan for future eruptions in which risk will be greater because of greater population density in closer proximity to a rift zone, such as the lower east rift zone of Kilauea or in one subdivision adjacent to the southwest rift zone of Mauna Loa, or because of larger eruptions and faster flows that travel rapidly down steep slopes, such as on Mauna Loa's southwest rift zone. The USGS is currently seeking to broaden its cooperative efforts to address these far greater potential hazards.

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1991. The December 14, 1989, eruption of Redoubt volcano produced ash clouds that disrupted air traffic and darkened the skies intermittently for 5 months. Flooding on the Drift River caused by snow and ice melt from the volcanic activity resulted in the closing of the Drift River Oil Terminal, which is the storage and shipping center for oil wells in Cook Inlet. In response to the Exxon Valdez oil spill in Prince William Sound, a joint Federal-State Board of Trustees, formed from land management agencies, was established under the authority of the Comprehensive Environmental Response, Compensation, and Liability Act of 1980. The Board established an Exxon Valdez Oil Spill Damage Assessment Team, which was assigned responsibility for all operations related to the disaster assessment effort. One of the first acts of the team was to establish a Geographic Information and Mapping Technical Group, comprising Federal and State land and resource management agencies as well as the USGS Alaska Field Office in Anchorage. Initially, the group prepared a series of maps that depicted four types of information relevant to the oil spill: (1) shoreline sensitivity information from the NOAA Environmental Sensitivity Index Map Series, (2) oil-impact data from the Alaska Department of Conservation, (3) land ownership information, and (4) coastline information derived from 1:63,360-scale USGS maps. The USGS served as the host site for data base compilation, integration, analysis, and design and production of maps for the damage assessment team. Through the efforts of the USGS and its cooperators, a single integrated map was produced for each of the 180 1:63,360-scale quadrangles covering the 1,500 miles of shoreline affected by the oil spill. Long-term data-base management was assumed by the Alaska Department of Natural Resources. The USGS has retained the original data as backup and for use by other agencies that continue to assess and monitor cleanup activities. During the eruption of Redoubt volcano, digital data from a NOAA weather satellite were used to monitor the distribution of ash in the atmosphere. This information was combined with coastline and elevation information to help scientists monitor the activities of the volcano (see “Redoubt Volcano, Alaska," p. 12). Both the Exxon Valdez oil spill and the Redoubt volcano eruption underscore the value of sound earth science information and scientific cooperation in coping with natural and manmade disasters.

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