Event Name : Augustine Pyroclastic Flow West of Augustine Creek
|Start: 1000 (± 100 Years) || Years BP C-14 (raw) || |
|Stop: 710 (± 50 Years) || Years BP C-14 (raw) || |
|Pyroclastic flow, surge, or nuee ardente: ||
|Eruption Type:||Not an eruption.|
From Waitt and Beget (1996): "Between about 1000 and 700 yr B.P. (between tephra layers C and M) pyroclastic flows, pyroclastic surges, and lahars swept the west and south flanks."
"In a coastal gully 300 m west of Augustine Creek, a sandy pumiceous pyroclastic-flow deposit (unit CMp) 0-3 m thick underlies the M(?) tephra and overlies the thick, oxidized pumiceous pyroclastic-flow deposit of "southwest pyroclastic fan" (unit Hcpw). One site reveals two massive deposits-a lower one 13 m thick with gas-escape pipes and an upper one 4 m thick-separated by 20 cm of apparently fluvial deposit lacking a paleosol. These flows probably followed Augustine Creek when and spilled through a western swale. This unit, apparently scarcely eroded, pinches out about 0.5 km west of the creek: its overbank spillage was thus limited to the vicinity of present creek."
"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."