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Full-Text Articles in Geology
Morphology, Eruption Rates, And Rheology Of Lava Domes: Insights From Laboratory Models, Jonathan H. Fink, Ross W. Griffiths
Morphology, Eruption Rates, And Rheology Of Lava Domes: Insights From Laboratory Models, Jonathan H. Fink, Ross W. Griffiths
Geology Faculty Publications and Presentations
The growth of lava domes can be either quiescent or violent, with transitions between styles of behavior commonly occurring with little warning. Here we propose that the behavior depends on the eruption rate, the magma rheology, and the thickness ofthe cooling surface. We present a model, based on laboratory simulations, field measurements, and photographic analysis, that relates the morphology and texture of a dome to the thickness of its cooled carapace, and thence to eruption conditions. A sequence of four main types of dome (spiny, lobate, platy, and axisymmetric) is identified in laboratory analog experiments with a Bingham plastic. These …
Mapping The Distribution Of Vesicular Textures On Silicic Lavas Using The Thermal Infrared Multispectral Scanner, Jaime Ondrusek, Philip R. Christensen, Jonathan Fink
Mapping The Distribution Of Vesicular Textures On Silicic Lavas Using The Thermal Infrared Multispectral Scanner, Jaime Ondrusek, Philip R. Christensen, Jonathan Fink
Geology Faculty Publications and Presentations
The Thermal Infrared Multispectral Scanner (TlMS) is a potentially powerful tool for mapping detailed chemical variations in silicic lava flows which in turn could expand knowledge of pre-eruption compositional gradients and mixing processes in silicic magma bodies. However, thermal infrared image data may be greatly influenced by the range of vesicular textures which occur on silicic flows . To investigate the effect of vesicularity on TIMS imagery independent of chemical variations, we studied Little Glass Mountain at the Medicine Lake Volcano of northern California, a large rhyolitic flow of uniform composition but textural heterogeneity. The imagery was recalibrated so that …
Shapes Of Venusian "Pancake" Domes Imply Episodic Emplacement And Silicic Composition, Jonathan H. Fink, Nathan T. Bridges, Robert E. Grimm
Shapes Of Venusian "Pancake" Domes Imply Episodic Emplacement And Silicic Composition, Jonathan H. Fink, Nathan T. Bridges, Robert E. Grimm
Geology Faculty Publications and Presentations
The main evidence available for constraining the composition of the large circular "pancake" domes on Venus is their gross morphology. Laboratory simulations using polyethylene glycol show that the height to diameter (aspect) ratios of domes given total volume depend critically on whether their extrusion was continuous or episodic, with more episodes leading to greater cooling and taller domes. Thus without observations of their emplacement, the compositions of venusian domes cannot be uniquely constrained by their morphology. However, by considering a population of 51 venusian domes to sent a sampling of many stages during the growth of domes with comparable histories, …
Igneous Dikes At Long Valley, Ca: Emplacement Mechanisms And Associated Geologic Structures, David D. Pollard, Jonathan H. Fink, Paul T. Delaney
Igneous Dikes At Long Valley, Ca: Emplacement Mechanisms And Associated Geologic Structures, David D. Pollard, Jonathan H. Fink, Paul T. Delaney
Geology Faculty Publications and Presentations
Two hypotheses for dike emplacement are: (1) magma flows into and dilates pre-existing fractures; or (2) magma flows into and dilates self-generated fractures. In the first case dikes should be parallel to an element of the rock fabric; in the second, they should be perpendicular to the least compressive stress. The two hypotheses suggest different dike intrusion and fissure eruption mechanisms and therefore different strategies for monitoring igneous events at Long Valley. We derive a method to distinguish the two mechanisms, a priori, from in-situ stress measurements and estimates of magma pressure. Estimates of relative dilation and slip across a …