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Wrangell reported activity

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EVENT SPECIFIC INFORMATION

Event Name : Wrangell 2002/8

Start:August 1, 2002 ± 30 MinutesObserved
Stop:August 2, 2002 ± 2 HoursObserved

Fumarolic or hydrothermal activity: BibCard
Eruption Type:Not an eruption.

Description: From Neal and others (2005): "On August 1, 2002, a spectacular, clear day in south-central Alaska, AVO received several calls reporting an eruption of Mount Wrangell. Callers reported a dark cloud drifting downwind from the general summit area and a dark deposit high on the snow-covered flank of the volcano.

"AVO seismologists checked data from the Wrangell seismic network and, based on a lack of correlative seismicity, concluded that no eruption or explosion had occurred. AVO also consulted with Wrangell St. Elias National Park Geologist Danny Rosenkrantz, who suggested that high winds had lofted fine-grained material exposed in the area near the summit fumaroles. On August 4, an AVO geologist traveling in the area verifed that a diffuse, light gray stripe extended a short distance down the flank of the volcano, emanating from the western rim of the caldera.

"Subsequently, AVO received a video from Copper Center resident Brad Henspeter who witnessed the event on August 1. The tape is just a few minutes long and shows the waning portion of the event at approximately 1:15 pm ADT. In a written accompaniment to the videotape, Henspeter added his own commentary and recollections of the most significant portion of activity. Notable excerpts from his words follow: ‘..ash was dark black . . and billowing . . . multiple billows (puffing) coming one after the next, nearly touching each other. The wind where we were standing was still, however at the top of the mountain the wind was directly from the east . . .the billows were not rising above the top of the mountain.' By the time he and his son returned to a good vantage point to film, about 10-12 minutes later, the billowing had stopped and the 'puffs' had 'turned a more grayish color.'

"In the video, there are indeed discrete, light gray 'puffs' that moved downwind and retained their individual.integrity. There are no other weather clouds in the vicinity. A.light gray, relatively motionless and irregular-shaped cloud sits in the vicinity of the caldera rim. There is a good breeze at ground level (indicated by motion in the trees) but at altitude, clouds are not shearing rapidly. High on the snow-covered flank, a gray-colored swath extends from a high point that we identify as the west caldera rim near Mount Wrangell Crater. The end of the video footage shows two distinct dark areas on the rim that is normally snow-covered. Henspeter's son reported a similar but more vigorous event on August 2, 2002 at about the same time of the day, but AVO received no further inquiries or reports.

"AVO concluded that no volcanic process of significance was involved and no formal information releases were issued. However, these observations remain enigmatic: lack of any seismicity would seem to preclude a phreatic or magmatic eruption and yet the pulsatory, 'puffing' nature of the dirty clouds is difficult to reconcile with a wind phenomenon."

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Page modified: March 30, 2017 14:36
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