| Text Description: |
Two-pyroxene andesite and minor two-pyroxene dacite flows erupted from central vent and possibly from local satellitic vents especially along east, southeast, and south flanks of Mount Drum. Flows are 1 to about 20 m thick, have oxidized scoriaceous tops and bottoms, and are locally highly vesicular. Rocks are dark gray to medium brownish gray and are not conspicuously porphyritic. They contain small (1 mm) phenocrysts of plagioclase, hypersthene, augite, olivine, and locally hornblended in variable amounts in an intergranular to intersertal groundmass of feldspar, mafic minerals, and locally minor glass. |