The ~38 ka marcath eruption at lunar crater volcanic field, nevada: Characteristics of a monogenetic basaltic tephra fall deposit
Johnson, Peter Jacob
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Monogenetic volcanic eruptions are generally assumed to last up to tens of years and produce numerous, intermittent explosive eruptions that create plumes up to ~10 km in elevation. Although this view fits the historically observed eruptions, few data have been collected about the range of durations and eruption sizes possible from monogenetic events. The few described prehistoric monogenetic eruptions have often had several vents along a fissure and multiple explosive phases. The ~38 ka Marcath eruption at Lunar Crater Volcanic Field (LCVF), Nevada, was focused at a single vent and produced a scoria cone, two tephra fall deposits, and a lava flow. We reconstruct the eruption that produced the largest tephra fall deposit. Explosive activity produced an eruption column up to ~7 km and a volume of about 0.018 km3. The Marcath eruption generally is interpreted as small by the standards of other characterized scoria cones, and the few observed tephra layers and focus on a single vent and extended spatter rampart is simpler than other characterized monogenetic events. Post-eruptive remobilization of the deposit has occurred especially around the margins through both fluvial and eolian processes and has likely removed at least .001 km3 of fine material from the distal portions of the deposit.