Emplacement styles of obsidian lavas: an integrated field and laboratory study

Abstract

Previously accepted models of emplacement dynamics of obsidian lavas have recently been called into question by observations made during the effusive eruptions of Chaiten in 2008-2009 and Cordon Caulle in 2011-2012 in Chile. The eruption of Chaiten was characterized by two distinct styles of emplacement, with the transition between the two resulting in hazardous block and ash flows and periods of dome collapse. Cordon Caulle erupted an obsidian coulee that exhibited behaviors typically associated with eruptions of more mafic lavas such as inflation and advancement via break-out lobe development. Lava emplacement styles are controlled by the physical properties of the lava which are a function of composition, temperature, and time. Banco Bonito lava, Valles caldera, NM, and Obsidian Dome, Inyo Craters, Long Valley, CA are like the lavas from Cordon Caulle and Chaiten respectively and were the subject of scientific research drilling in the 1980's, providing spatially well-constrained samples that can be used to measure residual water concentrations, thermal histories, and apparent viscosities. These three datasets are then used to infer emplacement behaviors of Banco Bonito and Obsidian Dome. Thermal histories of obsidian lavas can be constrained experimentally using relaxation geospeedometry. Previous applications of the method used up to five isobaric heat capacity measurements per quantitative cooling rate, requiring multiple days of laboratory work. We present a Monte Carlo inspired numerical solver capable of identifying comparable natural cooling rates using a single experimental measurement.

A Global Sensitivity Analysis Study with More Parameters in Undermoded Reverberation Chambers

“…The nature of the problem made us the choice to a candidate of global SA methods, namely the aforementioned Sobol' indices calculation [18] due to its robustness [15]. A more detailed explanation is included in [14].…”

“…However, there is no unequivocal agreement for the lowest usable frequency (LUF), where the field is wellstirred, the overmoded condition applies, thus the RC is capable of performing certain test [22]. The most common thumb rules considered in this work are listed in [14].…”

“…In [14] paper, three state-of-the-art approaches were examined, out of which the stochastical perspective of the so-called kriging model appeared to be the most suitable resulting from the highly resonant and fluctuating behaviour of the RC. The kriging metamodel [15] constructs the model output as a realization of a Gaussian process, which can be described by the following equation…”

“…A profound inspection of multiple setup parameters such as stirrer position, geometry, antenna position and orientation etc., is still a hot topic [4]- [13]. An extensive literature review can be read in [14]. Some attempts were made to introduce global SA methods [15] to the field of EMC measurements performed in ACs, e.g., [16] [17], in which the powerfulness of these techniques is unquestionable.…”

“…Some attempts were made to introduce global SA methods [15] to the field of EMC measurements performed in ACs, e.g., [16] [17], in which the powerfulness of these techniques is unquestionable. The main contribution of [14] was the extension of the application area of the method of Sobol' indices [18] to RCs. This work considers further parameters, which yields a tool for more profound investigations.…”