Basaltic ʻaʻā lava field emplacement of the intraplate Marcath volcano (central Nevada) from field and LiDAR data
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Many aspects of basaltic ʻaʻā lava emplacement remain poorly understood, particularly those related to intraplate, monogenetic volcanoes. Using field and high-resolution LiDAR data, lava emplacement of the monogenetic intraplate Marcath volcano (central Nevada) was investigated in terms of surface morphology, rafted cone fragments, and lava parameters. Upon exiting the source crater, lavas are inferred to have initially ponded in an upland saddle between Marcath and an older cone before breaking out to feed three distinct lava lobes that spread out onto a flat valley floor below. As the lobes neared their final extent, pulses in lava flux compressed and brecciated the crust and formed wide arcuate ridges. Levees disappeared with increased distance from the vent and as the flows transitioned from channelized flow to laterally spreading flow. Distributions of over a thousand mapped rafts show that the early stages of the eruption likely produced much of the total raft volume and that rafts were typically deposited as a function of crustal cooling. The missing western sector of the Marcath cone is largely preserved as rafts and the rate of rafting likely kept pace with cone building over the eruption’s duration such that once the cone was breached on one side, it did not heal. Rafts are found to have had an important impact on lava emplacement in certain locations, producing channels, canoes, and even instigating several bifurcations in flow lobes. Investigation into lava parameters yielded a total volume of 6.1 × 10^7 meters cubed, volumetric effusion rates of tens to hundreds of meters cubed per second, emplacement durations of days to weeks, and lava viscosities on the order of 10^6 to 10^7 Pa s. Compared to other documented lavas associated with monogenetic volcanoes, Marcath had a high lava effusion rate, low lava volume, low emplacement duration, and a short maximum flow length.