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Atka volcanic complex reported activity





Event Name : Korovin 1998/6

Start:June 30, 1998 ± 1 MonthsObserved
Stop:June 30, 1998 ± 7 DaysObserved

Tephrafall: BibCard
Tephra plume: BibCard BibCard BibCard
Phreatic: BibCard
Eruption Type:Explosive
MaxVEI: 3 BibCard
ColHeight: 10500 m BibCard

Description: From McGimsey and others (2003): "On the morning of June 30, 1998, AVO received a call from the Village Public Safety Officer (VPSO) in the village of Atka with a report of a dark ash cloud rising to 30,000 feet. The VPSO had observed two separate clouds, the first at approximately 07:30 local (Hawaii-Aleutian Time Zone is one hour behind ADT) and the second at approximately 08:30 local. The second cloud was the larger of the two reaching an estimated 30,000 ft and tinted orange 'as if illuminated from within', according to another observer in Atka. At 11:15 local, AVO received a pilot report from a USCG C-130 aircraft in the vicinity who noted an apparent volcanic cloud reaching about 16,000 feet ASL. At 17:20 local, AVO received a United Airlines pilot report of a cloud to 30,000 feet near the volcano. Coincident satellite imagery did not show an obvious volcanic cloud, however a plume-like meteorologic cloud was evident. The Atka VPSO stated further that both events produced dustings of ash in Atka, the first coarser grained than the second. AVO also learned that an individual had observed a dark ash plume over Korovin two days earlier on June 28. In addition, a commercial pilot very familiar with the volcanoes in the Aleutians contacted AVO to report his mid-May observation of the 'southeast slope blackened by ash' during a fly-by on May 10. He had not seen this during the previous week and speculated that it had occurred only a few days prior to May 10 because of weather conditions and wind directions. Thus, the timing of this activity remains poorly constrained; intermittent ash emission may, in fact, have occurred for weeks or prior to June 30.

"AVO conducted a call-down after receiving the initial report from Atka and solicited pilot reports from the FAA. FAA officials issued a Significant Meteorological Information statement (SIGMET), a Temporary Flight Restriction (TFR) around the volcano (20 mi radius from sea level to 25,000 ft) and decided to route aircraft well to the north of Korovin. The Atka Pride Seafood processing plant was closed for the day out of concern for the effects of ash on workers and the quality of fish. Reeve Aleutian Airways had an airplane en route from Dutch Harbor to Adak when the late afternoon pilot report of a cloud to 35,000 feet was received. Based on the report, the Reeve plane returned to Dutch Harbor. The Marine Radio Operator issued an ash advisory to mariners in the vicinity of Atka.

"Over the next several days, poor weather largely precluded any good views of the volcano. One Atka observer reported a 'rusty' cloud estimated to reach 16,000 feet ASL moving southeast from the volcano on the evening of July 2. On July 3, a pilot familiar with the volcano reported profuse steaming from the summit crater, typical of the past few months (cover photo). He noted new ash on the south, southeast, and east flanks. A thin trail of ash extended to the southwest, towards the village of Atka. On July 8, AVO noted minor, weakly ash-bearing clouds over Korovin on Advanced Very High Resolution Radiometer (AVHRR) satellite images. On July 10, Environment Canada contacted AVO to relay a pilot report of a possible ash cloud over the general vicinity of Vancouver Island; a number of SIGMETs and other official notices were released. Several additional pilot reports of possible ash were logged by Canadian aviation authorities who also recorded many aircraft diversions in Canadian airspace. It remains possible that this cloud was related to an undetected Korovin eruption several days prior to the pilot report. A more likely scenario, however, is that smoke from numerous fires in the heavily forested area of western Canada and even Siberia generated a far-traveled haze mistaken for volcanic ash (Little and others, 1999).

"Over the course of this episode of unrest, AVO issued Information Releases on June 30 and July 1, and mentioned Korovin in the Weekly Updates of July 3 and July 10."

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