Akutan reported activity

Event Name : Akutan Cascade Bight Valley Young Lahar

Start: 100

Years BP Tephrochronology

Lahar, debris-flow, or mudflow:

Description: From Waythomas (1999): "A second, younger noncohesive lahar deposit is present at sections 74, 56, 57, 41, and 41a (Fig. 10 [in original text]). This deposit is similar to the basal gray lahar except that it is deformed and reworked. Folded strata, hummocky surface morphology (Fig. 11 [in original text]), and a prominent headscarp in the upper part of the valley indicate that, after deposition, approximately 3 km 2 of the lahar (70-80% of the total area) was remobilized and flowed a short distance downstream. This may have been caused by ground motion associated with local earthquakes, which are common in this region. The lack of a tephra mantle or soil on the upper lahar in Cascade Bight valley also indicates that the lahar is young, possibly 100 years old or less."