Steam plumes were observed in 1978 and 1987. Photograph of steam and volcanic gas released by active fumaroles on north face of Iliamna by R. McGimsey, U.S. Geological Survey, May 6, 1986. USGS Digitial Data Series 96-040, Neal and McGimsey. Iliamna is made of andesite lava flows and tephra.
Glaciers cover most of the volcano.