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Kanaga reported activity

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EVENT SPECIFIC INFORMATION

Start:January 1994 Observed
Stop:December 1995 Observed

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Radial fissure: BibCard BibCard
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Eruption Type:Explosive
Duration: About 2 years BibCard
ColHeight: 7500 m BibCard
MaxVEI: 2 BibCard
Eruption Product: basaltic andesite BibCard
ChemYes
ModalYes
Othermafic

Description: From Miller and others (1998): "The eruption was characterized by steam and ash plumes rising to as high as 7.5 km and drifting a few tens of kilometers downwind, lava extrusion within the summit crater, and minor avalanching of incandescent debris down the north flank reaching the sea in some cases (Neal and others, 1995). Strong sulfur odors were detected on occasion by ground observers in Adak, 33 km to the east."

From Neal and others (1996): "Report of increased steaming by U.S. Navy on 2-17-93 (Note: Neal and others (1995) report the first increased steaming observation incorrectly as April, 1993). Additional pilot reports of increased steaming in April and on 12-29-93; eruption begins in January, 1994.

From Neal and others (1995): "Increased steaming from the summit crater and upper flank fumaroles was first reported to AVO on December 29, 1993. (However, AVO subsequently learned that pilots had noted increased steaming as early as April, 1993). Beginning in early January, 1994, minor ash plumes usually rising < 1 km (3,280 ft) over the summit were reported by pilots and residents of Adak. Photographs of Kanaga Volcano in late January confirmed that a linear vent system extended across the summit crater and part way down the east and west flanks. Ash and steam billowed from discrete segments of the vent and minor debris flow deposits, recognized as dark lobate tongues, extended from the trace of the fissure.

"The eruption continued intermittently at a low level into October, 1994. Sightings of ash plumes were hampered by the frequent poor weather which plagues the Aleutian Islands. Most observed eruptive plumes were relatively dilute, rising to altitudes of < 3 km (9,840 ft) and dropping ash onto the flanks of the volcano. During other times, only white steam plumes were visible rising to altitudes of typically < 1500 m (4,920 ft) above the volcano’s summit. At least two significant ash plumes were recorded over the course of this eruption: the first, to ~7.5 km (24,600 ft) occurred on February 21 and the second on August 18, when an eruption cloud reached ~4.5 km (14,760 ft) [see fig. 13 in original text]. A light dusting of ash fell on the community of Adak on August 20. Air traffic was disrupted on August 22 due to continuing low-level activity and cloudy conditions which prevented visual approaches to the Adak air field.

"Avalanching of incandescent fragmental debris down the north flank into the sea was first reported in April as 'lava flows' by U.S. Navy pilots. On June 20 aboard the USFWS R/V Tiglax just offshore north of the island, Joe Meehan reported that at 1:45 a.m. local time, during a full moon, the crew observed two incandescent streams of fragmental material cascading down the northwest flank from an elevation of approximately 760 m (2490 ft) to near the shoreline. The upper flanks and summit of the volcano were obscured by clouds so the exact origin of the streams could not be determined. The crew could also not confirm whether debris had reached

the ocean. By late July, however, USFWS personnel observed avalanches reaching the ocean and producing powerful littoral explosions. They noted that a new headland had been created.

"Throughout 1994, Adak residents and pilots of aircraft approaching and departing Adak Island reported occasional sulfur smell under westerly wind conditions. AVHRR satellite imagery intermittently detected a hot spot near Kanaga Volcano summit through October 13."

From McGimsey and Neal (1996): "Based on satellite and ground-based observations, the eruption had significantly waned or ceased by late November, 1994. However, weather conditions in the Aleutians typically prevent direct observations for days or weeks at a time, and over the next six months, during breaks in the weather, observers in Adak continued to report minor steam plumes above the summit of Kanaga (Smithsonian Institution, v. 20, n. 4, 1995).

"On June 3-4, 1995, U.S. Fish and Wildlife Service (USFWS) personnel aboard the research vessel Tiglax observed steaming from the summit and from the area covered by 1994 avalanche deposits on the north flank. Two weeks later, on June 19, a pilot reported seeing possible fresh ash or bare ground due to snow-melt on the west flank, and a weak ash plume up to 300 m (1000 ft.) above the summit. An AVHRR satellite image from June 21 showed a steam plume extended north from Kanaga [see fig. 5 in original text].

"The following day, another pilot reported a dirty haze at summit elevation extending 25 km south. AVHRR satellite images recorded a few hours later confirmed a weak thermal anomaly at the summit and a plume extending about 180 km to the north, prompting AVO to issue an information release stating that a small eruption may have occurred at Kanaga. On June 23, the U.S. Navy

Meteorological Office in Adak reported a thin ash cloud at the summit. USCG C-130 pilots observed a dusting of ash on the flank and 3 active steam vents on the south flank (Smithsonian Institution, v. 20, n. 6, 1995). Poor weather prevented observation of the volcano for much of the next 2 months. Occasional observations from Adak confirmed that vigorous fumarolic activity continued high on the southeast flank and minor steaming was still occurring at the summit crater (Smithsonian Institution, v. 20, n. 8, 1995).

"The captain of the USFWS research vessel Tiglax (Kevin Bell) reported in mid-October that on October 1 he observed hot blocks cascading down ravines on the north and northwest flank from near the summit--which was obscured by clouds--to as far as sea level, leaving 'steaming contrails' in their wakes (fig. 6). He noted that the activity was similar to that which he had observed during the documented eruptive period of summer 1994, and that the activity would not have been visible from Adak. However, based on the lack of a corresponding satellite-image anomaly or an ash plume visible from Adak, AVO concluded that Kanaga was probably not erupting at that time; what the Tiglax captain witnessed was most likely the continued avalanching of unstable lava masses that accumulated on the northwest flank during 1993-94.

"No further activity was reported by pilots or ground observers, and no thermal anomalies were visible on satellite imagery for the remainder of 1995. The last 1995 AVO weekly update to include Kanaga was that of August 25 [1995]."

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