Search results for "geographical"
showing 10 items of 3355 documents
Intercomparison of SO2 camera systems for imaging volcanic gas plumes
2015
Abstract SO 2 camera systems are increasingly being used to image volcanic gas plumes. The ability to derive SO 2 emission rates directly from the acquired imagery at high time resolution allows volcanic process studies that incorporate other high time-resolution datasets. Though the general principles behind the SO 2 camera have remained the same for a number of years, recent advances in CCD technology and an improved understanding of the physics behind the measurements have driven a continuous evolution of the camera systems. Here we present an intercomparison of seven different SO 2 cameras. In the first part of the experiment, the various technical designs are compared and the advantage…
Laminar Micrite Crusts and Associated Foreslope Processes, Red Sea
1991
ABSTRACT Forereef slopes in the Red Sea of Sudan exhibit a uniform biozonation that is independent from the topography of the slopes. Below - 120 m, ledges protrude horizontally from sleep cliffs of barrier reefs and atolls as well as from patches of in situ lithified slope sediment on inclined fringing reef slopes. Free surfaces and cavities within these ledges are partly covered by laminar micrite crusts of 7-20 mm thickness. The ledges are formed by an organic framework of living azooxanthellate corals, bryozoans, serpulids and fossil red algae. They are affected by repeated episodes of boring, infilling, and cementation which obliterate much of the original fabric. Concomitant cementati…
Using calculated chemical potential relationships to account for coronas around kyanite: an example from the Bohemian Massif
2010
Corona textures around kyanite, involving for example zoned plagioclase separating kyanite from the matrix, reflect the instability of kyanite with the matrix on changing P-T conditions, commonly related to decompression. The chemical potential gradients set up between the kyanite and the matrix as a consequence of slow Al diffusion drive corona development, with the zoning of the plagioclase reflecting the gradients. Calculated mineral equilibria are used to account for corona textures involving plagioclase ± garnet around kyanite, and replacement of kyanite by plagioclase + spinel symplectite, in quartz + plagioclase + K-feldspar + garnet + kyanite granulite facies gneiss from the Blanský…
Trace metal modeling of groundwater–gas–rock interactions in a volcanic aquifer: Mount Vesuvius, Southern Italy
2005
We report a detailed study of trace metals in groundwaters from the Somma-Vesuvius volcanic complex and present a model of the chemical processes that control the fate of these components during gas–water–rock interactions. Trace metal concentrations in Vesuvian groundwaters range from 0.01 to 0.1 Ag/l for ultra-trace elements (Sb, Cs, Co, Cd, and Pb) up to 0.1–10 mg/l for minor elements (Fe and Sr), leading to water–rock ratios from ~0.5 to 10 � 9 when normalized to trace element concentrations in the host rocks. Our results indicate non-isochemical dissolution of local volcanic rocks by groundwaters, during which mobile trace elements (As, Se, Mo, V, Li) are enriched and elements such as …
The viscous-brittle transition of crystal-bearing slilic melt: direct observation of magma rupture and healing
2012
Magmas may fl ow or break depending on their deformation rate. The transition between such viscous and brittle behavior controls the style of volcanic eruptions. While the brittle failure of silicate melts is reasonably well characterized, the effect of crystals on the viscous-brittle transition has not yet been constrained. Here we examine the effect of suspended crystals on the mechanical failure of magmas using torsion experiments performed at temperatures (600‐ 900 °C), strain rates (10 ‐4 ‐10 ‐1 s ‐1 ), and confi ning pressures (200‐300 MPa) relevant for volcanic systems. We present a relationship that predicts the critical stress and associated strain rate at which magmas fail as a fu…
Chemical and isotopic characterization of the gases of Mount Etna (Italy)
1997
Abstract In the period 1990–1995, 43 samples of dissolved gases in groundwaters (wells, springs and drainage galleries) and 64 samples of free gases (fumaroles, bubbling and soil gases) from the Mount Etna area were collected and analysed. Isotopic analyses were also carried out of both the carbon of the CO 2 in free gases and dissolved inorganic carbon (DIC) in the waters. The chemical composition of the gases depends on the relative abundances of three interacting components. These are gases of (1) atmospheric origin enriched in O 2 and N 2 , present almost exclusively in dissolved gases, (2) deep origin enriched in CO 2 , prevalent in the majority of cases, and (3) more superficial origi…
Rapid oxidation of mercury (Hg) at volcanic vents: Insights from high temperature thermodynamic models of Mt Etna's emissions
2011
A major uncertainty regarding the environmental impacts of volcanic Hg is the extent to which Hg is deposited locally or transported globally. An important control on dispersion and deposition is the oxidation state of Hg compounds: Hg(0) is an inert, insoluble gas, while Hg(II) occurs as reactive gases or in particles, which deposit rapidly and proximally, near the volcanic vent. Using a new high temperature thermodynamic model, we show that although Hg in Etna's magmatic gases is almost entirely Hg(0) (i.e., gaseous elemental mercury), significant quantities of Hg(II) are likely formed at Etna's vents as gaseous HgCl2, when magmatic gases are cooled and oxidised by atmospheric gases. Thes…
The effect of the pore structure and zeta potential of porous polymer monoliths on separation performance in ion-exchange mode.
2007
Most often, in bioseparations involving charged macromolecules, the chromatographic systems have low Reynolds and high Peclet numbers. For such systems, an expression is developed and presented in this work for evaluating the throughput in polymeric monoliths where ion-exchange adsorption occurs, as a function of (i) the pressure drop along the length of the monolith, (ii) the functional form and width of the throughpore-size distribution of the monolith, and (iii) the magnitude of the zeta potential on the surface of the throughpores of the monolith. Gaussian and log-normal throughpore-size distributions whose mean throughpore-size and standard deviation values are based on experimentally …
Innovación y TIC en el paisaje sonoro de la música festera a través de la creación de musicomovigramas
2019
Este artículo es parte de un proyecto de investigación sobre el paisaje sonoro, la escucha y la creación y recreación de espacios de educación ambiental y musical. Consiste en una propuesta de creación y utilización de un recurso auditivo-didáctico e interactivo, el musicomovigrama o musicograma en movimiento, para trabajar la escucha y el desarrollo emocional mediante la Fiesta y la música de Moros y Cristianos de Alcoy y su paisaje sonoro. La gran potencialidad de este recurso deriva de su capacidad para ofrecer al alumnado un soporte visual atractivo sincronizado con la progresión de la música que escucha, de tal manera que ambos códigos avancen simultáneamente. El objetivo principal es …
Volcanic SiO2-cristobalite: A natural product of chemical vapor deposition
2020
Abstract Cristobalite is a low-pressure, high-temperature SiO2 polymorph that occurs as a metastable phase in many geologic settings, including as crystals deposited from vapor within the pores of volcanic rocks. Such vapor-phase cristobalite (VPC) has been inferred to result from silica redistribution by acidic volcanic gases but a precise mechanism for its formation has not been established. We address this by investigating the composition and structure of VPC deposited on plagioclase substrates within a rhyolite lava flow, at the micrometer to nanometer scale. The VPC contains impurities of the form [AlO4/Na+]0—coupled substitution of Al3+ charge-balanced by interstitial Na+—which are ty…