This is a photomicrograph of sample 09RDWES301 - an andesite collected during the Redoubt 2009 eruption. A thin section is created by gluing a small piece of rock on to a glass slide, and then grinding it down to 30 microns (the average human hair is about 100 microns in diameter) thick so that light shines through it when examined under the microscope.
In this image, the brown crystal in the center is amphibole - and measures about 2.2 mm long. The white rectangles are plagioclase. The blue areas are void space (the epoxy holding the slide together is dyed blue for easy identification of empty areas). The fine-grained matrix holding the larger crystals together is mostly glass, plagioclase, and pyroxene microlites. Examining thin sections helps volcanologists better understand magma interactions, storage, and ascent.
Image courtesy of the AVO/ADGGS.
Please cite the photographer and the Alaska Volcano Observatory / Alaska Division of Geological & Geophysical Surveys when using this image.
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