Basaltic tephra from monogenetic Marcath Volcano, central Nevada

Abstract

Monogenetic volcanic eruptions are generally assumed to last to tens of years and produce frequent, intermittent explosive activity that creates eruption columns up to ~10km 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. Examining other eruption deposits can help clarify the range of eruption styles and sizes possible from future explosive monogenetic eruptions. The ~38ka Marcath event at Lunar Crater Volcanic Field, Nevada, produced a scoria cone, two tephra fall deposits, and a lava field. We reconstruct the activity that produced the largest tephra fall deposit. Explosive activity produced an eruption column up to ~7km and a volume of about 0.018km3. The Marcath tephra-forming activity was small compared to other characterized scoria cones. Post-eruptive remobilization of the deposit has occurred especially around the margins through both fluvial and eolian processes and has likely removed at least 0.001km3 of fine material from the distal portions of the deposit.