External vs. internal forcing mechanisms in generating maar volcanoes

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Maars are generally thought to result from magma-water interaction. This project aims at testing the hypothesis that expansion of exsolving CO2 is a major force in ascent and fragmentation of highly silicaundersaturated West Eifel magmas, many laden with mantle fragments, resulting in near-surface pyroclast-water interaction. In the less silica-undersaturated and C02-rich East Eifel magmas, environmental conditions (near-surface, permeable overlain by impermeable sediments) favor phreatomagmatic eruptions, deposits differing drastically from those in West Eifel maars. Excellent exposures will allow a detailed stratigraphic analysis of relevant deposits, single particle analysis including X-ray microtomography, scanning electron microscopy, XRF, LA-ICP-MS and electron microprobe. The geochemical and volcanological contrasts between East and West Eifel will allow a thorough evaluation of external versus internal forcing factors triggering and sustaining highly explosive eruptions that generate maars on one hand and unequivocal glass-rich phreatomagmatic deposits on the other. The results will aid assessing volcanic hazards from explosive eruptions.