Andesites of the 2009 eruption of Redoubt Volcano, Alaska

► 2009 Redoubt eruption produced andesites with 57-62.5 wt% SiO2. ► Early explosions dominated by low-silica andesite, later effusive activity by high- and intermediate-silica andesites. ► Magmas staged at 4-6 km depth before eruption, but low-silica andesite ascended from lower crust in the ~8 months prior. ► Ascent of low-silica andesite through mushy intrusions mobilized differentiated magma pockets (high-silica andesites).