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Articles 1231 - 1260 of 1881

Full-Text Articles in Earth Sciences

Geophysical Investigations And Groundwater Modeling Of The Hydrologic Conditions At Masaya Caldera, Nicaragua, Richard Eric Macneil Jul 2006

Geophysical Investigations And Groundwater Modeling Of The Hydrologic Conditions At Masaya Caldera, Nicaragua, Richard Eric Macneil

USF Tampa Graduate Theses and Dissertations

Masaya volcano, Nicaragua, has been the site of tremendous Plinian basaltic eruptions. Two eruptions ~6,500 and 2,250 BP formed the 6 kilometer (km) x 11 km, northwest trending Masaya caldera. The present day active Santiago Crater within the caldera is the site of persistent volcano degassing and occasional phreatic explosions. While the mechanism responsible for these phreatic explosions is unclear, one possible explanation is the interaction of groundwater with the shallow magma chamber beneath Masaya. This interaction with meteoric water is supported by the substantial steam discharge from the vent, which is significantly larger than other similar volcanoes in the …

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Local Infrasound Observations Of Large Ash Explosions At Augustine Volcano, Alaska, During January 11-28, 2006, Tanja Petersen, Silvio De Angelis, Guy Tytgat, Stephen R. Mcnutt Jun 2006

Local Infrasound Observations Of Large Ash Explosions At Augustine Volcano, Alaska, During January 11-28, 2006, Tanja Petersen, Silvio De Angelis, Guy Tytgat, Stephen R. Mcnutt

School of Geosciences Faculty and Staff Publications

We present and interpret acoustic waveforms associated with a sequence of large explosion events that occurred during the initial stages of the 2006 eruption of Augustine Volcano, Alaska. During January 11–28, 2006, 13 large explosion events created ash-rich plumes that reached up to 14 km a.s.l., and generated atmospheric pressure waves that were recorded on scale by a microphone located at a distance of 3.2 km from the active vent. The variety of recorded waveforms included sharp N-shaped waves with durations of a few seconds, impulsive signals followed by complex codas, and extended signals with emergent character and durations up …

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Is There A Northern Lesser Antilles Forearc Block?, A. M. Lopez, S. Stein, Timothy H. Dixon, G. Sella, E. Calais, P. Jansma, J. Weber, P. Lafemina Apr 2006

Is There A Northern Lesser Antilles Forearc Block?, A. M. Lopez, S. Stein, Timothy H. Dixon, G. Sella, E. Calais, P. Jansma, J. Weber, P. Lafemina

School of Geosciences Faculty and Staff Publications

A systematic discrepancy exists between slip vectors of thrust fault earthquakes at the Lesser Antilles trench (LAT) and the predicted direction of North American‐Caribbean convergence. A possibility has been that the discrepancy resulted because neither was well constrained. Estimating Caribbean motion has been challenging owing to the limited data along the plate's complex boundaries. Similarly, earlier studies had few slip vectors because interplate thrust events are infrequent. To address these difficulties, we estimate a new Caribbean‐North America Euler vector using recently available GPS data from sites in the presumably stable interior of the Caribbean, and compare the predicted velocities to …

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Evaluation Of Geophysical And Thermal Methods For Detecting Submarine Groundwater Discharge (Sgd) In The Suwannee River Estuary, Florida, Matthew Weiss Mar 2006

Evaluation Of Geophysical And Thermal Methods For Detecting Submarine Groundwater Discharge (Sgd) In The Suwannee River Estuary, Florida, Matthew Weiss

USF Tampa Graduate Theses and Dissertations

Submarine groundwater discharge (SGD) represents a significant portion of the total discharge from coastal aquifers through diffuse seepage and point source springs, but can be difficult to locate. SGD is important as it can be a source of nutrients to estuaries and other coastal ecosystems. In an effort to evaluate geophysical and thermal methods for detecting SGD on the Florida Gulf coast, a suite of water-borne surveys were run in conjunction with aerial thermal imagery over the lower Suwannee River and estuary in March and September 2005. Thermal imagery exploits temperature differences between discharging groundwater and surface water. Thermal images …

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Strain Accumulation Across The Carrizo Segment Of The San Andreas Fault, California: Impact Of Laterally Varying Crustal Properties, Gina Schmalzle, Timothy H. Dixon, Rocco Malservisi, Rob Govers Jan 2006

Strain Accumulation Across The Carrizo Segment Of The San Andreas Fault, California: Impact Of Laterally Varying Crustal Properties, Gina Schmalzle, Timothy H. Dixon, Rocco Malservisi, Rob Govers

School of Geosciences Faculty and Staff Publications

Major strike slip faults juxtapose geologically dissimilar terrain which may vary in mechanical properties, leading to an asymmetric pattern of strain accumulation. We present new GPS data on the Carrizo segment of the San Andreas Fault, separating the Salinian block southwest of the fault from Franciscan terrane northeast of the fault, to better quantify asymmetric strain accumulation. We also present a series of finite element models to investigate the possible role of variable elastic layer thickness and material properties of the upper crust. The geodetic data are well fit with a simple model comprising a weak upper crustal zone 10–25 …

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Caves And Speleogenesis At Blomstrandsøya, Kongsfjord, W. Spitsbergen, Stein-Erik Lauritzen Jan 2006

Caves And Speleogenesis At Blomstrandsøya, Kongsfjord, W. Spitsbergen, Stein-Erik Lauritzen

International Journal of Speleology

Blomstrandsøya, at Kongsfjord (78° 57’N), Spitsbergen, is within the high arctic, a completely permafrozen zone. The bedrock consists of Paleozoic marbles and has yielded a surprising amount of karst features. Early phases of hydrothermal, possibly Caledonian, speleogenesis and subsequent Devonian karstification with redbed deposits is well documented. 62 active seacaves, and more than 30 relict karst caves were found in the coastal cliffs and in escarpment faces around the island. All caves have very limited extent; they are either quite short, like most of the active sea caves, or they are soon choked by frozen sediments and ground ice after …

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The Distribution Of Diatom Flora In Ice Caves Of The Northern Yukon Territory, Canada: Relationship To Air Circulation And Freezing, Bernard Lauriol, Clément Prévost, Denis Lacelle Jan 2006

The Distribution Of Diatom Flora In Ice Caves Of The Northern Yukon Territory, Canada: Relationship To Air Circulation And Freezing, Bernard Lauriol, Clément Prévost, Denis Lacelle

International Journal of Speleology

In the late 1980’s and early 1990’s, various media in karst environments in the Northern Yukon Territory were examined for their diatom content. Cryogenic cave calcite powders, grus and various ice formations (ice plugs, ice stalagmites and floor ice) were collected from three freezing caves and one slope cave to make an inventory of the diatom content, and to explain the spatial distribution of the diatoms within the caves. The results show that approximately 20% of diatoms in the caves originate from external biotopes and habitats (e.g., river, lake, stream), with the remaining 80% of local origin (i.e., from subaerial …

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Dry Creek Long Term Watershed Study: Buffer Zone Performance As Viable Amphibian Habitat, Brooke L. Talley, Thomas Crisman Jan 2006

Dry Creek Long Term Watershed Study: Buffer Zone Performance As Viable Amphibian Habitat, Brooke L. Talley, Thomas Crisman

School of Geosciences Faculty and Staff Publications

As bioindicators, amphibians typically require both terrestrial and aquatic habitats to complete their life cycles. Pre- timber-harvest monitoring (December 2002 through September 2003) of salamander and frog (Hylidae) populations was conducted in four watersheds of Decatur County, GA. Post- timber-harvest monitoring (December 2003 through September 2004) continued in the same watersheds (two reference and two treatment watersheds). Coverboards were used to monitor adult salamanders, larval salamanders were surveyed with dipnet sweeps, and frogs were monitored with vertical PVC pipes. Six salamander species (Desmognathus apalachicolae, Eurycea cirrigera, E. guttolineata, Notophthalmus viridescens, Plethodon grobmani, and Pseudotriton ruber) and five frog species (Hyla …

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Dry Creek Long Term Watershed Study: Assessment Of Immediate Response Of Aquatic Macroinvertebrates To Watershed Level Harvesting And Thinning Of Streamside Management Zones, M. W. Griswold, R. T. Winn, Thomas Crisman, W. R. White Jan 2006

Dry Creek Long Term Watershed Study: Assessment Of Immediate Response Of Aquatic Macroinvertebrates To Watershed Level Harvesting And Thinning Of Streamside Management Zones, M. W. Griswold, R. T. Winn, Thomas Crisman, W. R. White

School of Geosciences Faculty and Staff Publications

Streamside Management Zones (SMZs) are meant to protect riparian habitat and the stream ecosystem. Benthic macroinvertebrates are recognized bioindicators of water quality in streams, typically occupying multiple trophic levels in these systems and providing food for vertebrates. Thus, it is important to understand the effects of harvest within and adjacent to the SMZ on macroinvertebrate assemblages. Benthic macroinvertebrates were sampled pre- and post-harvest from four firstorder streams draining the Dry Creek watershed in southwestern Georgia. A multi-habitat sampling procedure was used. Macroinvertebrates were identified and compared using biotic indices. Comparisons were made between streams within the pre-harvest period and between …

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Thermal Variations In The Hyporheic Zone Of A Karst Stream, Toby Dogwiler, Carol Wicks Jan 2006

Thermal Variations In The Hyporheic Zone Of A Karst Stream, Toby Dogwiler, Carol Wicks

International Journal of Speleology

This investigation quantifies how temperatures in the streambed sediments of a karst stream fluctuate in relation to discharge, seasonal, and diurnal temperature variations as the stream passes through a karst window. Furthermore, the linkages between meteorological processes and temperature variation in the hyporheic zone are delineated. Examination of a high-resolution, three dimensional record of temperature variation in a karst stream substrate provides insight into thermal disturbances in the hyporheic zone. Temperatures in the upper portion of the hyporheic zone are strongly linked to air temperatures via the surface water. The variation is considerably less as depth increases. The annual temperature …

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Unconfined Versus Confined Speleogenetic Settings: Variations Of Solution Porosity, Alexander Klimchouk Jan 2006

Unconfined Versus Confined Speleogenetic Settings: Variations Of Solution Porosity, Alexander Klimchouk

International Journal of Speleology

Speleogenesis in confined settings generates cave morphologies that differ much from those formed in unconfined settings. Caves developed in unconfined settings are characterised by broadly dendritic patterns of channels due to highly competing development. In contrast, caves originated under confined conditions tend to form two- or three-dimensional mazes with densely packed conduits. This paper illustrates variations of solution (channel) porosity resulted from speleogenesis in unconfined and confined settings by the analysis of morphometric parameters of typical cave patterns. Two samples of typical cave systems formed in the respective settings are compared. The sample that represents unconfined speleogenesis consists of solely …

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Tracer-Test Design For Losing Stream–Aquifer Systems, Malcolm S. Field Jan 2006

Tracer-Test Design For Losing Stream–Aquifer Systems, Malcolm S. Field

International Journal of Speleology

Hydrological tracer testing is an effective way for assessing the significance and extent of leakage through the bed of an influent (losing and sinking) stream. In karstic terranes, leakage from losing and sinking streams typically resurge at downstream springs, but flow may be intercepted by production wells. Although sinking streams that disappear into swallow holes and caves are relatively easy to trace, developing a tracer test design for a losing stream that allows slow percolation through its bed is complicated by the lack of basic knowledge regarding leakage rate, leakage locations along its length, and temporal variability. To overcome these …

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Radon In Caves: Clinical Aspects, Stephen A. Craven, Berend J. Smit Jan 2006

Radon In Caves: Clinical Aspects, Stephen A. Craven, Berend J. Smit

International Journal of Speleology

Historical, experimental and clinical evidence is presented to suggest that radon constitutes a relatively small carcinogenic risk for casual visitors to caves. The risk is dependent on radon levels and the smoking of tobacco. Show cave guides, chronically exposed to radon, may be at increased risk for lung cancer due to the effects of radon, especially if they are smokers of tobacco.

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Relationships Between Deflector Faults, Collapse Dolines And Collector Channel Formation: Some Examples From Slovenia, France Šušteršič Jan 2006

Relationships Between Deflector Faults, Collapse Dolines And Collector Channel Formation: Some Examples From Slovenia, France Šušteršič

International Journal of Speleology

In some Slovenian caves collector channels gather sinking underground streams and redirect them for potentially long distances parallel to certain faults. The collector channels formed due to ongoing long-term collapse of cave roofs at the points where passages break through the faults, which function as a kind of screen and are termed deflector faults. The fault trends are marked by collapse within the caves, and by active collapse dolines at the surface.

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Salt Ingestion Caves, Charles A. Lundquist, William W. Varnedoe Jr. Jan 2006

Salt Ingestion Caves, Charles A. Lundquist, William W. Varnedoe Jr.

International Journal of Speleology

Large vertebrate herbivores, when they find a salt-bearing layer of rock, say in a cliff face, can produce sizable voids where, over generations, they have removed and consumed salty rock. The cavities formed by this natural animal process constitute a unique class of caves that can be called salt ingestion caves. Several examples of such caves are described in various publications. An example in Mississippi U.S.A., Rock House Cave, was visited by the authors in 2000. It seems to have been formed by deer or bison. Perhaps the most spectacular example is Kitum Cave in Kenya. This cave has been …

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Vashegyite From Gaura Cu Muscă Cave (Locvei Mountains, Romania): A New And Rare Phosphate Occurrence, Bogdan P. Onac, Luminiţa Zaharia, Joe Kearns, Daniel Veres Jan 2006

Vashegyite From Gaura Cu Muscă Cave (Locvei Mountains, Romania): A New And Rare Phosphate Occurrence, Bogdan P. Onac, Luminiţa Zaharia, Joe Kearns, Daniel Veres

International Journal of Speleology

This study investigated the occurrence of vashegyite from a guano-rich deposit located in the Gaura cu Muscă Cave, Romania. Analytical methods used include optical microscopy, X-ray powder diffraction (XRD), scanning electron-microscopy (SEM), inductively coupled plasma-atomic emission spectrometry (ICP-AES), thermal investigations and Fourier-transform infrared (FT-IR) analyses. Vashegyite occurs as friable, chalky white, irregular nodules of up to 2.5 cm in diameter, within a 15 cm thick sequence of organic and minerogenic sediments. The chemical structural formula is: (Al10.91Fe3+0.06Na0.1Ca0.02Mg0.08)Σ=11.17[(PO4)8.78(SiO4)0.056]Σ=8.83(OH) …

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Studies Of Condensation/Evaporation Processes In The Glowworm Cave, New Zealand, C. R. De Freitas, A. Schmekal Jan 2006

Studies Of Condensation/Evaporation Processes In The Glowworm Cave, New Zealand, C. R. De Freitas, A. Schmekal

International Journal of Speleology

The condensation/evaporation process is important in caves, especially in tourist caves where there is carbon dioxide enriched air caused by visitors. The cycle of condensation and evaporation of condensate is believed to enhance condensation corrosion. The problem is condensation is difficult to measure. This study addresses the problem and reports on a method for measuring and modelling condensation rates in a limestone cave. Electronic sensors for measuring condensation and evaporation of the condensate as part of a single continuous process of water vapour flux are tested and used to collect 12 months of data. The study site is the Glowworm …

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Identification Of Cave Minerals By Raman Spectroscopy: New Technology For Non-Destructive Analysis, William B. White Jan 2006

Identification Of Cave Minerals By Raman Spectroscopy: New Technology For Non-Destructive Analysis, William B. White

International Journal of Speleology

The identification of minerals from caves generally requires that samples be removed from the cave for analysis in the laboratory. The usual tools are X-ray powder diffraction, the optical microscope, and the scanning electron microscope. X-ray diffraction gives a definitive fingerprint by which the mineral can be identified by comparison with a catalog of reference patterns. However, samples must be ground to powder and unstable hydrated minerals may decompose before analysis is complete. Raman spectroscopy also provides a fingerprint useful for mineral identification but with the additional advantage that some a-priori interpretation of the spectra is possible (distinguishing carbonates from …

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Spectral Analysis Of Ground Penetrating Radar Response To Thin Sedimentary Layers, Swagata Guha, Sarah E. Kruse, E. E. Wright, U. E. Kruse Dec 2005

Spectral Analysis Of Ground Penetrating Radar Response To Thin Sedimentary Layers, Swagata Guha, Sarah E. Kruse, E. E. Wright, U. E. Kruse

Geology Faculty Publications

Ground penetrating radar (GPR) systems utilized in studies of sedimentary deposits generate wavelengths (tens of centimeters) that are commonly much longer than the thickness of bedding (often millimeters to centimeters) within the target strata. Where this is the case, radar profiles represent interference patterns. Simple models of radar response to sequences of thin beds such as those found in coastal deposits show potentially detectable spectral shifts toward higher frequencies in radar returns. Spectral analysis of radar data over barrier beach deposits at Waites Island, South Carolina, shows that returns from packages with heavy mineral laminations are shifted toward higher frequencies …

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Systematic Revision Of The Genus Eupleura H. And A. Adams, 1853 (Gastropoda: Muricidae) In The Neogene To Recent Of Tropical America, Gregory S. Herbert Nov 2005

Systematic Revision Of The Genus Eupleura H. And A. Adams, 1853 (Gastropoda: Muricidae) In The Neogene To Recent Of Tropical America, Gregory S. Herbert

School of Geosciences Faculty and Staff Publications

The systematics of the Neogene to Recent genus Eupleura of tropical America are revised, with descriptions of four new species: Eupleura engerrabunda, from the Late Miocene of Mexico (Atlantic); Eupleura gravidentata, from the Plio-Pleistocene of Colombia (Atlantic); Eupleura paroudia, from the Early or middle Pliocene of Mexico (Atlantic); and Eupleura vokesorum, from the Pliocene of Costa Rica (Pacific) and Ecuador and the Recent tropical eastern Pacific. Two recent taxa, Eupleura plicata and Eupleura limata, are also resurrected, increasing the standing diversity of Eupleura in the eastern Pacific to seven species. Eupleura limata, however, may …

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Geodetic Gps Measurements In South Iceland: Strain Accumulation And Partitioning In A Propagating Ridge System, P. C. Lafemina, Timothy H. Dixon, R. Malservisi, T. Arnadottir, E. Sturkell, F. Sigmundsson, P. Einarsson Nov 2005

Geodetic Gps Measurements In South Iceland: Strain Accumulation And Partitioning In A Propagating Ridge System, P. C. Lafemina, Timothy H. Dixon, R. Malservisi, T. Arnadottir, E. Sturkell, F. Sigmundsson, P. Einarsson

School of Geosciences Faculty and Staff Publications

GPS observations in south Iceland between 1994 and 2003 are compared with two-dimensional elastic half-space and viscoelastic coupling models for two parallel rift zones, representing the Western and Eastern volcanic zones (WVZ, EVZ). GPS data from the Hreppar block, between the WVZ and EVZ, fit a rigid block model within uncertainties. Spreading rates across the WVZ increase from 2.6 ± 0.9 mm/yr in the northeast to 7.0 ± 0.4 mm/yr in the southwest. Conversely, spreading rates in the EVZ decrease from 19.0 ± 2.0 mm/yr in the northeast to 11.0 ± 0.8 mm/yr in the southwest, the direction of ridge …

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The 7 May 2001 Induced Seismic Event In The Ekofisk Oil Field, North Sea, L. Ottemöller, H. H. Nielsen, K. Atakan, Jochen Braunmiller, J. Havskov Oct 2005

The 7 May 2001 Induced Seismic Event In The Ekofisk Oil Field, North Sea, L. Ottemöller, H. H. Nielsen, K. Atakan, Jochen Braunmiller, J. Havskov

School of Geosciences Faculty and Staff Publications

A moderate size seismic event on 7 May 2001 was strongly felt on platforms in the Ekofisk oil field, in the southern North Sea, but did not cause damage to platforms or wells. We combined near- and far-field observations to develop a consistent source model and to determine whether the event was induced. Seismic data placed the epicenter inside the Ekofisk field and suggested a shallow source depth based on spectral and moment tensor analysis. GPS data from the Ekofisk platforms displayed permanent vertical and horizontal movement due to the event. A topographic bulge in the sea bottom, revealed by …

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Modeling Tephra Sedimentation From A Ruapehu Weak Plume Eruption, Costanza Bonadonna, J. C. Phillips, B. F. Houghton Aug 2005

Modeling Tephra Sedimentation From A Ruapehu Weak Plume Eruption, Costanza Bonadonna, J. C. Phillips, B. F. Houghton

Geology Faculty Publications

We present a two-dimensional model for sedimentation of well-mixed weak plumes, accounting for lateral spreading of the cloud, downwind advection, increase of volumetric flux in the rising stage, and particle transport during fallout. The 17 June 1996 subplinian eruption of Ruapehu produced a bent-over plume that rose to a height of 8.5 km in a wind field with an average velocity of 24 m s−1 and generated a narrow deposit on land extending up to 200 km from vent. The sedimentation from the Ruapehu plume was dominated by coarse ash, with all the blocks and most of the lapilli …

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Degassing And Hydrothermal Activity At Mt. Spurr, Alaska During The Summer Of 2004 Inferred From The Complex Frequencies Of Long-Period Events, S. De Angelis, Stephen R. Mcnutt Jun 2005

Degassing And Hydrothermal Activity At Mt. Spurr, Alaska During The Summer Of 2004 Inferred From The Complex Frequencies Of Long-Period Events, S. De Angelis, Stephen R. Mcnutt

School of Geosciences Faculty and Staff Publications

Results of analyses of unusual long-period earthquakes, recorded between July and September 2004 at Mt. Spurr, Alaska, are presented. The waveforms of these events are characterized by quasi-sinusoidal signatures of long duration (up to 40 sec) with slowly decaying amplitudes; bandwidths of 0.5–4.0 Hz are typical; amplitude spectra are marked by strong and sharp peaks, reflecting the quasi-monochromatic nature of the signal. The temporal variations of the complex frequencies are investigated by use of the Sompi method; the dominant mode is resolved and its Q factor estimated for each available event. Dominant frequencies are found in the band 0.8–2.2 Hz …

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Hydrology Of Vernal Pools At Three Sites, Southern Sacramento Valley, Robert J. Williamson, Graham E. Fogg, Mark C. Rains, Thomas H. Harter Apr 2005

Hydrology Of Vernal Pools At Three Sites, Southern Sacramento Valley, Robert J. Williamson, Graham E. Fogg, Mark C. Rains, Thomas H. Harter

School of Geosciences Faculty and Staff Publications

The subsurface hydrology of vernal pools at three vernal pool complexes was investigated during three wet seasons in 2002-2004. The complexes were at Gridley Ranch, Valensin Ranch, and the Mather Field in northern California. The selected complexes provided variation in soils, landforms and topography. Three vernal pools were chosen in each complex based on variation in pool type, size, and position in the drainage system. The objectives were to describe the subsurface hydrology of vernal pools to refine the conceptual model of vernal pool hydrology and to answer questions about: the size of watershed support for vernal pools, the importance …

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Geochemistry Of Serpentinized Peridotites From The Mariana Forearc Conical Seamount, Odp Leg 125: Implications For The Elemental Recycling At Subduction Zones, Ivan P. Savov, Jeffrey G. Ryan, Massimo D'Antonio, Katherine Kelley, Patrick Mattie Apr 2005

Geochemistry Of Serpentinized Peridotites From The Mariana Forearc Conical Seamount, Odp Leg 125: Implications For The Elemental Recycling At Subduction Zones, Ivan P. Savov, Jeffrey G. Ryan, Massimo D'Antonio, Katherine Kelley, Patrick Mattie

Geology Faculty Publications

Recent examinations of the chemical fluxes through convergent plate margins suggest the existence of significant mass imbalances for many key species: only 20–30% of the to-the-trench inventory of large-ion lithophile elements (LILE) can be accounted for by the magmatic outputs of volcanic arcs. Active serpentinite mud volcanism in the shallow forearc region of the Mariana convergent margin presents a unique opportunity to study a new outflux: the products of shallow-level exchanges between the upper mantle and slab-derived fluids. ODP Leg 125 recovered serpentinized harzburgites and dunites from three sites on the crests and flanks of the active Conical Seamount. These …

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Probabilistic Modeling Of Tephra Dispersal: Hazard Assessment Of A Multiphase Rhyolitic Eruption At Tarawera, New Zealand, Costanza Bonadonna, Charles B. Connor, B. F. Houghton, Laura Connor, Marc A. Byrne, A. Laing, T. K. Hincks Mar 2005

Probabilistic Modeling Of Tephra Dispersal: Hazard Assessment Of A Multiphase Rhyolitic Eruption At Tarawera, New Zealand, Costanza Bonadonna, Charles B. Connor, B. F. Houghton, Laura Connor, Marc A. Byrne, A. Laing, T. K. Hincks

Geology Faculty Publications

The Tarawera Volcanic Complex comprises 11 rhyolite domes formed during five major eruptions between 17,000 B.C. and A.D. 1886, the first four of which were predominantly rhyolitic. The only historical event erupted about 2 km3 of basaltic tephra fall (A.D. 1886). The youngest rhyolitic event erupted a tephra fall volume more than 2 times larger and covered a wider area northwest and southeast of the volcano (∼A.D. 1315 Kaharoa eruption). We have used the Kaharoa scenario to assess the tephra fall hazard from a future rhyolitic eruption at Tarawera of a similar scale. The Plinian phase of this eruption …

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Evidence For Static Stress Changes Triggering The 1999 Eruption Of Cerro Negro Volcano, Nicaragua And Regional Aftershock Sequences, M. Diez, P. C. La Femina, Charles B. Connor, W. Strauch, Tenorio V. Tenorio Feb 2005

Evidence For Static Stress Changes Triggering The 1999 Eruption Of Cerro Negro Volcano, Nicaragua And Regional Aftershock Sequences, M. Diez, P. C. La Femina, Charles B. Connor, W. Strauch, Tenorio V. Tenorio

Geology Faculty Publications

Remarkable evidence of coupling between tectonic and magmatic events emerges from investigation of three tectonic earthquakes, aftershock sequences and eruption of Cerro Negro volcano, Nicaragua in 1999. Here, we explain this coupling through static stress changes following three Mw 5.2 earthquakes. We use focal mechanism solutions to estimate fault system geometry and magnitude of slip from these events, which are then used to calculate the change in minimum horizontal principal stress (σ3) for the region and the change in Coulomb failure stress on optimally oriented fault planes. Results of these simulations indicate that σ3 was reduced by …

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Sedimentological Characteristics And Internal Architecture Of Two Overwash Fans From Hurricanes Ivan And Jeanne, Mark H. Horwitz, Ping Wang Jan 2005

Sedimentological Characteristics And Internal Architecture Of Two Overwash Fans From Hurricanes Ivan And Jeanne, Mark H. Horwitz, Ping Wang

Geology Faculty Publications

Extensive overwash occurred along the Florida coast during the passage of four strong hurricanes in 2004, providing an excellent opportunity to study the spatial patterns and sedimentary architecture of washover deposits. Detailed 3D sedimentological characteristics of two of the overwash fans were studied through coring, trenching, and ground penetration radar surveys. The first washover-fan complex, deposited by hurricanes Frances and Jeanne is located on the Atlantic facing Hutchinson Island in southeastern Florida. The second fan, deposited by hurricane Ivan is located on the Gulf-facing Santa Rosa Island in northwestern Florida. Subsurface imaging using a 250 MHz Ground penetrating radar profiling …

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Numerical Simulation Of Double‐Diffusive Finger Convection, Joseph D. Hughes, Ward E. Sanford, H. L. Vacher Jan 2005

Numerical Simulation Of Double‐Diffusive Finger Convection, Joseph D. Hughes, Ward E. Sanford, H. L. Vacher

School of Geosciences Faculty and Staff Publications

A hybrid finite element, integrated finite difference numerical model is developed for the simulation of double‐diffusive and multicomponent flow in two and three dimensions. The model is based on a multidimensional, density‐dependent, saturated‐unsaturated transport model (SUTRA), which uses one governing equation for fluid flow and another for solute transport. The solute‐transport equation is applied sequentially to each simulated species. Density coupling of the flow and solute‐transport equations is accounted for and handled using a sequential implicit Picard iterative scheme. High‐resolution data from a double‐diffusive Hele‐Shaw experiment, initially in a density‐stable configuration, is used to verify the numerical model. The temporal …

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