|Start:||July 6, 1999 ||Observed|
|Debris-avalanche, volcanic avalanche, or landslide: ||
|Eruption Type:||Not an eruption.|
From McGimsey and others (2004): "On July 6, 1999, AVO received a message from the FAA Center Weather Support Unit that a pilot had reported a fresh flow of mud and rock from the upper northeast flank of Iliamna.
"Iliamna is an erosionally dissected ice- and snow-covered stratocone that lies 225 km southweast of Anchorage in the Aleutian Range. No historical eruptive activity has been documented, however, a prominent fumarole field near the summit produces a nearly constant steam plume, which is often mistaken for eruptive activity. The fumaroles high on the south and east-northeast flanks occur where large scars reveal that most of the upper edifice consists of highly altered, unstable rock. The eastern scar has been the source of frequent non-volcanic gravitational collapses that produce mixed avalanches of ice, snow, rock, and mud that typically extend several kilometers down the flank; some are large enough to be visible from the Kenai Peninsula (Neal and others, 1995; McGimsey and Wallace, 1999)."