A mathematical model is presented for the cooling of an active flow with two separate thermal components. One component is a crust that cools by radiation and generally thickens with time. The other component is an inner core that is vertically isothermal and partially exposed at the top surface, where heat is lost by radiation. This model provides a more realistic description of active lava flows than the existing models that assume thermal homogeneity in each vertical cross section perpendicular to the direction of flow advance. Characteristic time scales for heat loss from the core are comparable to typical durations for the emplacement of single‐lobed basaltic flows. The two‐component model predicts fractional areas of exposed core between 0.001 and 0.1, consistent with several types of observations of lava flows. Predicted temperature changes for the crust and core, as a function of distance from the vent, also comparable favorably to the limited observations available for active flows. Depending on eruption duration, fraction of exposed core, flow thickness, and initial eruption temperature, the thermal interaction between the crust and the core can have a significant effect on the core temperature, the growth of the crust, and various averages of thermal losses by radiation. This analysis suggests that flow dimensions may be strongly influenced by thermal dynamics in the core if emplacement duration is long, the fraction of exposed core is maintained at a high level, or the initial eruption temperature is low.
Abstract. Contrary to assumptions often made in the literature, explosive volcanic eruptions are capable of transporting significant amounts of water into the stratosphere. In addition to the magmatic water component, atmospheric water vapor is entrained by the column at lower levels. A theoretical model for the conservation of mass, momentum, and thermal energy of four separate components (dry air, water vapor, liquid condensates, and solid particles) is used to determine the extent of atmospheric water redistribution. We examine the effects of water vapor condensation on dynamical characteristics and ambient water vapor transport. A simple technique is presented for deriving canonical forms for the complex system of ordinary differential equations governing the column components. Solutions of this model are presented that show the influence of different volcanic boundary conditions and a range of ambient water vapor distributions on transport of the buoyant column. We show that the water component (vapor + liquid) of small eruption columns rising through a wet atmosphere is dominated by entrained water, whereas larger columns are dominated by the magmatic water. This is due, in part, to the proportionately smaller entrainment surface area in relation to the control volume for the larger columns.We also show that a maintained column with an initial mass flux of 2.7 x 108 kg s -• erupted into a wet atmosphere would inject 96 Mt of water vapor into the stratosphere over 24 hours, comparable to the annual input from methane oxidation or 100 midlatitude thunderstorms. This increase may accelerate the conversion of simultaneously erupted volcanic SO 2 into sulfuric acid.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.