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Iliamna reported activity

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EVENT SPECIFIC INFORMATION

Event Name : Iliamna 2400 yBP

This is a questionable event.

Start: 2400 Years BP C-14 (raw)
Stop: 1300 Years BP C-14 (raw)

Debris-avalanche, volcanic avalanche, or landslide: BibCard
Lahar, debris-flow, or mudflow: BibCard
Eruption Type:Not an eruption.
Other""

Description: From Wathomas and others (2000): "The upper lahar deposit in West Glacier Creek Valley (L2, Fig. 15 [in original text]) contrasts markedly with the underlying lahar deposit L1, because hydrothermally altered rocks make up more than 80 percent of the clasts in L2 and impart a distinctive yellow-brown color (10YR4/6) to the deposit. Lahar deposit L2 is also a massive, matrix-supported diamict, and about 90 percent of the clasts are angular and subangular. The matrix of lahar deposit L2 is slightly sticky and plastic when wet or moist, indicating the presence of clay. However, the one sample analyzed for particle-size distribution contained only about 1 percent clay and 2 percent silt (Table 4 [in original text]) and we do not believe that this sample is truly representative of the matrix texture. Soil organic matter from a soil developed on top of lahar deposit L2 yielded a radiocarbon age of 1390+/-75 yr BP (Table 3 [in original text]) and this is also a mini- mum-limiting age for the lahar deposit.

"Because of its slightly cohesive texture and clast composition, deposit L2 could be a cohesive lahar that evolved from a debris avalanche on the southwest fank of Iliamna Volcano 1300-2400 yr BP. We are uncertain if L2 is related to an eruption of Iliamna Volcano."

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Page modified: March 30, 2017 14:36
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