Event Name : Akutan Reef Bight Ash
|Start: 8500 || Years BP Tephrochronology || |
|Lahar, debris-flow, or mudflow: ||
|Pyroclastic flow, surge, or nuee ardente: ||
From Waythomas and others (1998): "Volcanic ash from Akutan Volcano is typically dark brown or black, and ash of this color first appears in the stratigraphic record about 8500 years ago at Reef Bight...The oldest dated volcanic mudflow (lahar) deposit is exposed at Reef Bight (fig. 3 [in original text]) and is more than 8500 years old. This lahar deposit is the oldest known evidence of Holocene eruptive activity at Akutan Volcano. A younger sequence of deposits at Reef Bight consisting of coarse black ash, pyroclastic flow, and lahar deposits, is evidence for a second eruption or series of eruptions that began soon after 8500 years before present and may be correlative with the formation of the older caldera."
From Waythomas (1999): "Dark-brown or black scoriaceous tephras from Akutan Volcano first appear in the stratigraphic record approximately 8500 years B.P. at Reef Bight...The oldest dated volcaniclastic deposit is a noncohesive lahar at Reef Bight that is >8500 years B.P. and is the first evidence of Holocene eruptive activity at Akutan Volcano. A sequence of scoriaceous lapilli tephra. pyroclastic-flow, and noncohesive lahar deposits also at Reef Bight is evidence for a second early Holocene eruptive period that began soon after 8500 years B.P. An undated, noncohesive lahar at Reef Bight documents a possible third early Holocene eruption. The age and location of deposits at Reef Bight suggest that they were generated during eruptions from the "older" caldera on Akutan Volcano."