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Articles 1 - 20 of 20
Full-Text Articles in Entire DC Network
Tectonic Control Of Subsidence And Southward Displacement Of Southeast Louisiana With Respect To Stable North America, Roy K. Dokka, Giovanni F. Sella, Timothy H. Dixon
Tectonic Control Of Subsidence And Southward Displacement Of Southeast Louisiana With Respect To Stable North America, Roy K. Dokka, Giovanni F. Sella, Timothy H. Dixon
School of Geosciences Faculty and Staff Publications
GPS data collected between 1995 and 2006 suggest that southeast Louisiana, including New Orleans and the larger Mississippi Delta, are both subsiding vertically and moving southward with respect to stable North America. Both motions are likely related due to their common tectonic setting. Subsidence in the New Orleans area occurs in part because it is located in the hanging wall of a large listric normal fault system that forms the northern boundary of a 7–10 km thick allochthon that is detached from stable North America. Southward motion of this allochthon relative to stable North America occurs at 2.2 ± 0.6 …
Sinkhole Structure Imaging In Covered Karst Terrain, Sarah E. Kruse, M. Grasmueck, Matthew Weiss, D. Viggiano
Sinkhole Structure Imaging In Covered Karst Terrain, Sarah E. Kruse, M. Grasmueck, Matthew Weiss, D. Viggiano
Geology Faculty Publications
Ground penetrating radar (GPR) and resistivity techniques have been widely used to map the locations of sinkholes in covered karst terrain. To determine whether a sinkhole is a likely preferential conduit for groundwater flow, however, requires higher-resolution imaging than that used in conventional sinkhole mapping surveys. Field observations combined with simulated surveys for a 15-m diameter 3-m deep sinkhole in west-central Florida are used to assess the resolution of GPR and resistivity surveys targeting the semiconfining unit that floors the sinkhole depression. 2D resistivity surveys clearly show the central depression as well as resistivity contrasts between the cover sediments within …
Geophysical Investigations And Groundwater Modeling Of The Hydrologic Conditions At Masaya Caldera, Nicaragua, Richard Eric Macneil
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 …
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
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 …
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
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 …
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 …
Thermal Variations In The Hyporheic Zone Of A Karst Stream, Toby Dogwiler, Carol Wicks
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 …
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
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 …
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
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 …
Dry Creek Long Term Watershed Study: Buffer Zone Performance As Viable Amphibian Habitat, Brooke L. Talley, Thomas Crisman
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 …
Unconfined Versus Confined Speleogenetic Settings: Variations Of Solution Porosity, Alexander Klimchouk
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 …
Salt Ingestion Caves, Charles A. Lundquist, William W. Varnedoe Jr.
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 …
Tracer-Test Design For Losing Stream–Aquifer Systems, Malcolm S. Field
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 …
Caves And Speleogenesis At Blomstrandsøya, Kongsfjord, W. Spitsbergen, Stein-Erik Lauritzen
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 …
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
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 …
Radon In Caves: Clinical Aspects, Stephen A. Craven, Berend J. Smit
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.
Identification Of Cave Minerals By Raman Spectroscopy: New Technology For Non-Destructive Analysis, William B. White
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 …
Relationships Between Deflector Faults, Collapse Dolines And Collector Channel Formation: Some Examples From Slovenia, France Šušteršič
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.
Vashegyite From Gaura Cu Muscă Cave (Locvei Mountains, Romania): A New And Rare Phosphate Occurrence, Bogdan P. Onac, Luminiţa Zaharia, Joe Kearns, Daniel Veres
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) …
Studies Of Condensation/Evaporation Processes In The Glowworm Cave, New Zealand, C. R. De Freitas, A. Schmekal
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 …