Description: From Waythomas and others (1999): "At least two fine-grained volcanic-ash deposits from Iliamna Volcano have been identified on the Kenai Peninsula. These ash layers are within a vertical sequence of peat and volcanic-ash deposits from other Cook Inlet volcanoes and have been radiocarbon dated and geochemically correlated with a pumiceous lapilli tephra found on the proximal flanks of Iliamna Volcano. A discontinuous mantle of pumiceous lapilli tephra is common on bed-rock pinnacles that extend above modern glaciers northeast of Iliamna Volcano. This tephra deposit is found as much as 50 kilometers northeast of the present summit of Iliamna Volcano. The pumiceous lapilli tephra and fine ash layer on the Kenai Peninsula are evidence for a large plinian eruption of Iliamna Volcano from a vent on the northeast upper flank of the volcano about 4,000 yr B.P."
The Global database on large magnitude explosive volcanic eruptions (LaMEVE; 2017) reports a magnitude of 4.000, bulk eruptive volume of 0.100 cubic km and a dense rock equivalent eruptive volume of 0.040 cubic km for the eruption.