Magmas discharged during individual volcanic eruptions commonly display compositional variations interpreted as new arrivals at shallow depth of more primitive, hotter, volatile-rich magma batches mixing with resident, colder, partially degassed magma. Heterogeneities in eruption products are often interpreted as evidence of short times of order tens of hours from new magma arrival to eruption, raising concerns for emergency planning. We show here, through numerical simulations, that magma convection and mixing in a shallow magma chamber can result in long-lived, dynamically stable configurations with coexistence of magmas from nearly pure to variably mixed end-member compositions. Short mixing time scales may therefore relate to sin-eruptive processes, as heterogeneities found in the eruptive products are not necessarily the fingerprint of new magma arrival shortly preceding or triggering the eruption.
The goal of this study was to evaluate the presence of extrahepatic damage and the uniformity and reversibility of the histological findings in CCl4.induced liver cirrhosis in the rat. To verify these findings rats were sacrificed 2 and 10 weeks after a treatment consisting of ten intragastric doses of CCl4, administered weekly. All treated rats developed an irreversible micronodular cirrhosis with no damage to the brain, kidney and pancreas. Moreover, rats sacrificed 2 weeks after the last CCl4 dose showed a number of functional alterations usually observed in man. In particular, low branched chain/aromatic amino acids (BCAA/AAA) plasma ratio, high ammonia, low zinc and high insulin with normal blood glucose were obtained.
Explosive eruptions are the surface manifestation of dynamics that involve transfer of magma from the underground regions of magma accumulation. Evidence of the involvement of compositionally different magmas from different reservoirs is continuously increasing to countless cases. Yet, models of eruption dynamics consider only the uppermost portion of the plumbing system, neglecting connections to deeper regions of magma storage. Here we show that the extent and efficiency of the interconnections between different magma storage regions largely control the size of the eruptions, their evolution, the causes of their termination, and ultimately their impact on the surrounding environment. Our numerical simulations first reproduce the magnitude-intensity relationship observed for explosive eruptions on Earth and explain the observed variable evolutions of eruption mass flow rates. Because deep magmatic interconnections are largely inaccessible to present-day imaging capabilities, our results motivate the need to better image and characterize extant magma bodies.
The dynamics of magma ascent along volcanic conduits toward the Earth's surface affects eruptive styles and contributes to volcanic hazard. The rheology of ascending magmatic mixtures is known to play a major role on mass flow rate as well as on pressure and exit velocity at the vent, even determining effusive versus explosive eruptive behavior. In this work we explore the effects of bubble‐induced non‐Newtonian rheology on the dynamics of magma flow in volcanic conduits. We develop a quasi 2‐D model of magma ascent that incorporates a rheological constitutive equation describing the strain‐dependent effect of gas bubbles on the viscosity of the multiphase magma. Non‐Newtonian magma flow is investigated through a parametric study where the viscosity of the melt and the water content are varied over natural ranges. Our results show that non‐Newtonian rheology leads to greater exit velocity, mass flow, and density. The pressure distribution along the conduit remains very similar to the Newtonian case, deviating only at the conduit exit. Plug‐like velocity profiles develop approaching the conduit exit, when mixture velocity is high, and are favored by smaller liquid viscosity. Since the mass flow rate, the density and the velocity of the mixture exiting from the conduit are fundamental for quantifying and assessing the transport and emplacement dynamics, neglecting that the non‐Newtonian effect of bubble‐bearing magmas may result in misinterpretation of the deposit and, consequently, eruptive behavior.
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