Akutan Flat Bight Valley Lahars

Start: 5420 yBP ± 120 Years [1]

Stop: 1400 yBP [1]

Event Type: Explosive

Event Characteristics:
  • Tephrafall [2]
  • Lahar, debris-flow, or mudflow [1] [2]

Description: From Waythomas and others (1998): "At least three lahar deposits and numerous, coarse-grained, black ash layers in Flat Bight (fig. 3 [in original text]) document an unknown number of minor eruptions from about 6000 years before present to about 1400 years before present."
From Waythomas (1999): "Stratigraphic exposures of unconsolidated voltaniclastic deposits are limited in Flat Bight valley, and only two sections were examined (Fig. 1 [in original text]). In upper Flat Bight valley, stream incision has exposed an 8-m-thick sequence of lahar deposits and tephra (section 81, Fig. 9 [in original text]). At least three thin noncohesive lahar deposits at the base of this section are separated by silty peat beds; the lowest peat bed yielded a radiocarbon age of 5420+/-120 years B.P. (Table 1 [in original text]). The lahar deposits are clast supported and contain a large proportion of rounded cobbles and small boulders that were likely entrained from the stream bed."

References Cited

[1] Stratigraphic framework of Holocene volcaniclastic deposits, Akutan Volcano, east-central Aleutian Islands, Alaska, 1999

Waythomas, C. F., 1999, Stratigraphic framework of Holocene volcaniclastic deposits, Akutan Volcano, east-central Aleutian Islands, Alaska: Bulletin of Volcanology, v. 61, n. 3, p. 141-161.

[2] Preliminary volcano-hazard assessment for Akutan Volcano east-central Aleutian Islands, Alaska, 1998

Waythomas, C. F., Power, J. A., Richter, D. H., and McGimsey, R. G., 1998, Preliminary volcano-hazard assessment for Akutan Volcano east-central Aleutian Islands, Alaska: U.S. Geological Survey Open-File Report 98-0360, 36 p., 1 plate, scale unknown.
full-text PDF 1.68 MB

Complete Eruption References

Stratigraphic framework of Holocene volcaniclastic deposits, Akutan Volcano, east-central Aleutian Islands, Alaska, 1999

Waythomas, C. F., 1999, Stratigraphic framework of Holocene volcaniclastic deposits, Akutan Volcano, east-central Aleutian Islands, Alaska: Bulletin of Volcanology, v. 61, n. 3, p. 141-161.
Hard Copy held by AVO at FBKS - CEC file cabinet

Preliminary volcano-hazard assessment for Akutan Volcano east-central Aleutian Islands, Alaska, 1998

Waythomas, C. F., Power, J. A., Richter, D. H., and McGimsey, R. G., 1998, Preliminary volcano-hazard assessment for Akutan Volcano east-central Aleutian Islands, Alaska: U.S. Geological Survey Open-File Report 98-0360, 36 p., 1 plate, scale unknown.
full-text PDF 1.68 MB
map sheet plate (PDF) 2.62 MB
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