Event Name : Akutan Flat Bight Valley Lahars
|Start: 5420 (± 120 Years) || Years BP C-14 (raw) || |
|Stop: 1400 || Years BP Tephrochronology || |
|Lahar, debris-flow, or mudflow: ||
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."