Alaska Volcano Observatory
Augustine reported activity
EVENT SPECIFIC INFORMATION
Event Name : Augustine Northeast Bench Debris Avalanche or Lahar
|Start: 1725 (± 25 Years) || Years BP C-14 (raw) || |
|Stop: 1470 (± 160 Years) || Years BP C-14 (raw) || |
|Debris-avalanche, volcanic avalanche, or landslide: ||
|Lahar, debris-flow, or mudflow: ||
|Eruption Type:||Not an eruption.|
From Waitt and Beget (1996): "A bouldery gravel diamict (unit JH) containing angular porphyritic andesite stones as large as 4 m lies outside (north of) the levee that delineates the north side of main body of Northeast Point debris-avalancbe deposit (unit IHa). The seaward part of this unit north of the levee is relatively nonhummocky and called here Northeast Bench. By this morphology the unit underlying the bench is interpreted as a lahar deposit (unit IHl). But more than 200 m back from the sea cliff the area outside levee is nearly as hummicky as that south of the levee and this is also mapped with unit IHa. Both map units (units IHl and IHa) are overlain by a tephra sequence with tephra H at its base. The flattish seaward-sloping part of this area delineating the bench may be a laharic phase that issued from the debris avalanche."
"Sandy gravel lacking large blocks underlies H? tephra atop the Pleistocene landslide block *Unit Pl) on south side of island. It may contemporaneous with Northeast Bench lahar (?) deposit."
Page modified: March 30, 2017 14:36
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