August GEOSPHERE media highlights

Quantitative morphology, recent evolution, and future activity of the Kameni Islands volcano, Santorini, Greece

David M. Pyle (corresponding author), University of Cambridge, Cambridge, UK; and John Elliott, Department of Earth Sciences, University of Oxford, Oxford, UK. Pages 253-268.

Linking quantitative measurements of lava flow surface morphology with historical observations of eruptions is an important, but underexploited, route to understanding eruptions of silicic magma. In this paper, Pyle and Elliott present a new, high-resolution digital elevation model for the intracaldera Kameni Islands, Santorini, Greece, which reveals the potential of high-resolution imaging of lava-flow fields by airborne light detection and ranging laser radar. The new model has an order-of-magnitude better resolution than earlier models, and reveals a wealth of surface morphological information on the dacite lava flows of the Kameni Islands. When combined with a reanalysis of contemporary eruption accounts, these data yield important insights into the behavior of dacite magma during slow effusive eruptions on Santorini and elsewhere and allow the development of forecasts for the style and duration of future eruptions. The author's dome-height model combined with the apparent time-predictable nature of volcanic eruptions of the Kameni Islands allows them to suggest that should an eruption occur during 2006, it will last for more than 2.7 yr and produce a dome ~115–125 m high.


The Oz Machine: A Java applet for interactive instruction in geological log interpretation

Geoffrey C. Bohling (corresponding author) and John H. Doveton, Kansas Geological Survey, Lawrence, KS 66047, USA; and Doveton. Pages 269-274.

Geophysical well logs represent measurements of a variety of properties of the rocks and fluids encountered by a wellbore and are used by petroleum industry analysts to guide decisions regarding further well development and investigation. The Oz Machine is a Java applet (a Web-based computer program accessed through a browser) providing interactive instruction in geological interpretation of these well logs. It employs a statistical technique called Markov chain simulation to generate a synthetic sequence of lithologies (rock types) and then generates a suite of corresponding well logs based on the properties associated with each lithology. The resulting synthetic logs are displayed as a set of curves versus depth and the student paints a geological interpretation of the logs onto the plot, selecting from a palette of lithologies presented next to the log display. The statistical parameters used in the Markov chain simulation are intended to produce lithological sequences similar to real sequences in the U.S. mid-continent. Although the underlying simulation techniques are relatively simple, the generated lithological and log sequences are surprisingly realistic, providing an essentially endless supply of "mirror-world" exercises in geological log interpretation.


Comparison of transport simulations and equivalent dispersion coefficients in heterogeneous media generated by different numerical methods: A genesis model and a simple geostatistical sequential Gaussian simulator

G. de Marsily, University Paris VI, Unité Mixte de Recherche, Sisyphe of Centre National de la Recherche Scientifique, Paris, France; et al. Pages 275-286.

This article presents a genesis method for characterizing heterogeneous media representing alluvial deposits. This method simulates the main steps of the medium genesis for meandering, braided, and incising streams and generates facies, which are then translated into hydraulic conductivities to simulate flow and transport. In order to compare this "genetic" model with other methods commonly used to characterize heterogeneous media, a basic sequential Gaussian indicator method was applied to the same site: a 5200-m-long reach of the Aube River floodplain (France). Ten different geostatistical realizations were generated. An equivalent homogeneous representation was also included. Flow and transport simulations in the different heterogeneous numerical media were conducted with Visual MODFLOW. The results were analyzed and compared in terms of permeability fields, plume spreading, and equivalent longitudinal dispersion. Emphasis is on the ability of the genetic model to represent continuous channels that can serve either as conduits or as barriers to flow.

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Boulder, Colo. -- The August issue of GEOSPHERE, published in electronic format only by the Geological Society of America, is now available online. Research published in GEOSPHERE spans all geology disciplines, with content ranging from comprehensive papers to brief notes, plus data and software contributions from the emerging field of geoinformatics. Contributions from geoscience education also appear in the journal.

View this open-access issue at http://www.gsajournals.org/gsaonline/?request=get-current-toc&issn=1553-040X

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