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Bogoslof reported activity




Event Name : Bogoslof 1992/7

Start:July 6, 1992 Observed
Stop:July 24, 1992 Observed

Lava dome: BibCard BibCard BibCard BibCard BibCard BibCard BibCard
Tephra plume: BibCard BibCard
Phreato-magmatic: BibCard BibCard BibCard
Eruption Type:Explosive
Duration: 19 days BibCard
Eruption Product: basaltic andesite BibCard
MaxVEI: 3 BibCard
ColHeight: 8000 m BibCard

Description: McGimsey and others (1995) summarize this eruption as follows: "The recent eruption began in early July, 1992. At about 3:00 pm ADT on July 6, an eruption cloud rising to 3 km above Bogoslof Island was identified on NOAA satellite imagery. A few hours later pilots visually confirmed the steam and ash plume.

"Satellite imagery showed intermittent small plumes through July 13. Continuous emission occurred during the next two days with the steam and ash plume rising up to 5.5 km and extending 100 km to the SE. At 4:23 pm ADT on July 17 pilots reported a rapidly rising mushroom-shaped plume up to 4.5 km altitude. Inclement weather prevented direct observation of the island. The activity remained intermittent with an episode of vigorous steam and ash emission beginning about 5:00 pm ADT on July 20 that produced a plume as high as 8 km by 1725. A profusely steaming new lava dome at the north end of the island adjacent to the 1927 dome was first sighted on July 21 and confirmed by U.S. Coast Guard observations and photography on July 24. The last report of steaming and minor ash emission was July 24, and except for residual steaming of the dome, activity had subsided by late July, 1992.

"AVO responded to the eruption by compiling pilot reports, monitoring satellite imagery for ash plumes, collecting photographs and video footage of the activity, and disseminating information to government agencies and the media.

"U.S. Fish and Wildlife Service (USFWS) scientists who approached the island by ship several times later in the summer to assess the impact on sea mammals and birds photographed the new dome. During the summer of 1994, an AVO scientist spent a day examining the island and collecting samples of the new lava dome (Harbin, 1994)."

"The dome, measuring 150 m x 275 m across and approximately 150 m high, has a steep-sided central spire surrounded by prismatically jointed, block debris that originally formed more gentle slopes [see figure 11 in original text]. By the summer of 1994, the northern and northwestern sides of the dome had been reduced to sheer sea cliffs. The dome is composed principally of gray to black porphyritic hornblende-andesite (Harbin, 1994)."

Reeder and McGimsey (1995) report an approximate dome volume for this eruption as 1.6x10^6 cubic meters.

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