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Chiginagak reported activity



Event Name : Chiginagak 1997/10

Start:October 22, 1997 Observed
Stop:August 21, 1998 Observed

Fumarolic or hydrothermal activity: BibCard BibCard BibCard BibCard BibCard BibCard BibCard
Steam: BibCard BibCard BibCard BibCard BibCard BibCard BibCard
Eruption Type:Not an eruption.
MaxVEI: 1 BibCard
Duration: About 10 months BibCard

Description: From McGimsey and Wallace (1999): "On October 22, 1997, AVO began receiving pilot reports of increased steaming, snowmelt, and sulfur smell at Chiginagak. Residents of Pilot Point and surrounding areas also reported that they began noticing an increase in steam emissions possibly as early as mid-summer 1997. A thermal anomaly was detected on Advanced Very High Resolution Radiometer (AVHRR) imagery analyzed on October 23, 1997 [see fig. 10 in original text]. During a flight around the volcano on October 30, AVO scientists observed an enlarged area of fumarolic activity and new fumaroles at about 6,300 ft (~1,900 m), directly above the previously known fumarole site.

"AVO reported the activity at Chiginagak in the weekly update of October 31, 1997, and in updates through year's end, including GVN (Smithsonian Institution, 1997, v. 23, n. 3). Daily, and later weekly, correspondence was maintained with local residents for observations, and AVO closely monitored satellite imagery for signs of increased activity."

From McGimsey and others (2003): "In October 1997, following pilot reports of increased steaming and the presence of a thermal anomaly on satellite imagery, AVO scientists traveled by fixed-wing aircraft to the volcano and observed an enlarged area of fumarolic activity and new fumaroles on the north flank of the volcano (McGimsey and Wallace, 1999). A second observation flight was conducted on March 11, 1998. Winds were relatively calm but the areas of interest were largely obscured. However, observers noticed an absence of steam emissions from the area where the lower fumaroles had been located. Bulbous white clouds lingered above the area of the new fumaroles. A very strong sulfur smell -- much stronger than that from the fall of 1997 -- was reported, as well as a yellow color to the ice that formed on the plane's windows. AVO received no further reports until August 13, 1998, when USFWS personnel and a resident of Pilot Point [see fig. 1a in original text] observed little clouds of "black smoke" accompanied by a "greenish-yellow gas" rising from two point sources to about 500 to 1,000 ft (~150 to 300 m) above the mountain. A dusting of dark material was observed on fresh snow on the upper flanks of the volcano the next morning. On August 15, AVO detected a 30-km-long (19 mi) plume extending east from the volcano. Although the plume contained no ash signal, this was the first time a plume had been observed in satellite imagery of Chiginagak.

"On September 29, 1998, AVO conducted an airborne ultraviolet correlation spectrometer (COSPEC) flight to Chiginagak and measured between 200-300 tonnes per day of SO2 emanating from the fumarolic field. Observers reported a vigorous fumarole at an estimated 1,980 m (6,500 ft) elevation on the north flank, adjacent discolored ice and snow, and a strong sulphur smell [see fig. 8 in original text]. The weaker, second fumarole reported in October 1997 was no longer present.

"AVO described the activity at Chiginagak in the weekly updates of January 2 and 9, 1998 (continued from 1997), and August 14 and 21, 1998. Although no formal call-downs occurred, AVO shared information informally with the FAA following the August activity. AVO maintained contact with local residents and USFWS personnel throughout the year, and AVO closely monitored satellite imagery for signs of increased activity."

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