Event Name : Augustine Southeast Point Debris Avalanche
|Start: 2160 (± 60 Years) || Years BP C-14 (raw) || |
|Stop: 1830 (± 80 Years) || Years BP C-14 (raw) || |
|Debris-avalanche, volcanic avalanche, or landslide: ||
|Eruption Type:||Not an eruption.|
From Waitt and Beget (1996): "Between about 2100 and 1800 yr B .P. (between tephra layers G and D) two large debris avalanches swept east and southeast to the sea."
"Overlying the Yellow Cliffs diamict and beneath tephra layer I along the coastal cliff 350 m west of Southeast Point lies a diamict at least 8 m thick with in situ boulders as large as 3.5 m, and winnowed ones cm the beach below as large as 7 .5 m. The angular clasts are gray to reddish and scarcely altered, contrasting the underlying Yellow Cliffs diamict. The deposit extends at least 2.5 km northeast along the coastal cliffs to East Point, where it is also overlain by the I tephra and that, in turn, overlain by the Northeast Point debris-avalanche deposit. The surface slope at top of sea cliff, if projected seaward indicates that deposit has been wave eroded back at least 0.5 km. perhaps 1.5 km."
"During this prehistoric period numerous domes must have been emplaced at the summit, repeatedly renewing the source for catastrophic debris avalanches. Remnants of these older domes form the east and south sides of the present summit-dome complex. Below the summit area at least three domes were emplaced on the upper flanks, one on the south (Karnishak dome), two on the northwest (domes "I" and "H"). Another undated and nearly buried dome or lava flow diversifies the upper south flank."