Embayments in explosive, silicic eruptions : a textural, numerical, and experimental assessment.
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Ruefer, Anna Cameron, 1997-
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I explore the occurrence and formation of embayments in quartz using textural, experimental, and numerical techniques. Embayments are pockets of melt partially trapped inside of volcanic crystals. During eruption these pockets of melt quench to glass. The concentration of water within embayment glass is the foundation for a powerful new technique in volcanology that is thought to record how quickly the magma ascended during an eruption. My goal was to determine how accurately embayments record changes in the magma during ascent. Using a high-pressure, high-temperature system, I performed decompression experiments on natural and synthetic embayments to test their ability to record magmatic conditions. Experimental work is thus far unsuccessful but highlights best practices for researchers going forward. My work on rhyolitic eruptions shows that embayments are common across eruptions. The range in embayment shapes and textures preserves a record of three separate timescales: diffusion speedometry, emptying, and faceting.