Sarah Kruse | University of South Florida (original) (raw)

Papers by Sarah Kruse

Bulletin of Volcanology, 2013

Scoria cones often grow by the accumulation of individual particles transported ballistically in ... more Scoria cones often grow by the accumulation of individual particles transported ballistically in Strombolian-type eruptions. Alternative models of cone formation suggest that cones are built primarily of fallout from the eruption column in more explosive eruptions, often termed violent Strombolian. Currently, the distinction between normal Strombolian and violent Strombolian is based on direct observations of eruptions or by inference of eruption characteristics from mapping of tephra fall deposits. Unfortunately, medial to distal tephra fall deposits erode rapidly, leaving behind only the near-vent facies of scoria cones which are thicker and less easily eroded. Therefore, a tool that is capable of delineating differences between low-energy Strombolian deposits and higher energy violent Strombolian deposits from investigation of the preserved scoria edifice is necessary. Ground-penetrating radar imaging of Cerro Negro, an active basaltic scoria cone in Nicaragua, has revealed details of cone deposits at depths of up to 12 m. The record of the 1992 eruption, which was observed to be violent Strombolian, shows quantifiable differences from normal Strombolian near-vent facies, including reflections in the downwind profile that are continuous for hundreds of meters and through the slope break. The ability to differentiate between tephra fallout and ballistically emplaced deposits at Cerro Negro suggests ground-penetrating radar imaging may be useful in distinguishing eruptive style in older scoria cones, where the medial to distal tephra deposits are eroded or buried.

Tephra fallout models used to forecast volcanic hazards rely on the advection-diffusion equation ... more Tephra fallout models used to forecast volcanic hazards rely on the advection-diffusion equation to forecast hazards. If the advection-diffusion equation applies, then the thickness of tephra blanket deposits should show Gaussian crosswind profiles and exponential decay with distance from the vent. Complications may arise due to factors such as particle size distributions, particle density, and atmospheric effects not incorporated in

Cinder cones are often assumed to grow via Strombolian activity as described by McGetchin et al (... more Cinder cones are often assumed to grow via Strombolian activity as described by McGetchin et al (1974). Data with which to evaluate this and other models has historically been collected via eyewitness accounts, photography of eruptions, and mapping of exposed deposits. However, the dangerous nature of eruptions often prohibits near vent observations and accessible deposits are rare. Therefore, in order

Beach cusp formation in the active shore zone may be affected by armoring(i.e. seawall, revetment... more Beach cusp formation in the active shore zone may be affected by armoring(i.e. seawall, revetment, etc.) of the shoreline. LIght Detection And Ranging (LIDAR) data allow us to examine beach cusps by using an iterative program to construct beach face slopes from finely-spaced profiles. We examine LIDAR data collected during 2004 along portions of the Atlantic coast of Florida that

Ground penetrating radar is sensitive to the porosity and compositional variations common in coas... more Ground penetrating radar is sensitive to the porosity and compositional variations common in coastal sands, and hence has become a staple tool for coastal stratigraphers. Under the right circumstances, GPR can also provide useful information on surficial aquifer hydrogeology in coastal zones. Here we present examples of the primary uses for GPR in coastal hydrogeology: (1) to identify depth to

In-situ monitoring of infiltration, water flow and retention in the vadose zone currently rely pr... more In-situ monitoring of infiltration, water flow and retention in the vadose zone currently rely primarily on invasive methods, which irreversibly disturb original soil structure and alter its hydrologic behavior in the vicinity of the measurement. For example, use of lysimeters requires extraction and repacking of soil samples, and time- domain reflectometry (TDR) requires insertion of probes into the soil profile.

This field trip examines the unusual and highly metamorphosed mafic and ultramafic rock associati... more This field trip examines the unusual and highly metamorphosed mafic and ultramafic rock associations of the central Blue Ridge province in western North Carolina. The aim of the trip is to show attendees the variability and common features among these units, and their use as tectonic indicators for the latest Precambrian geologic history of the Blue Ridge mountains. It was

Tectonophysics, 1988

ABSTRACT

Journal of Hydrology, 2003

The freshwater lens on small islands may easily be overexploited or polluted due to dense develop... more The freshwater lens on small islands may easily be overexploited or polluted due to dense development combined with improper management. On small carbonate islands complexities in fresh groundwater distribution are most commonly driven by geologic heterogeneities and their attendant impact on permeability and effective recharge patterns. Siliciclastic islands (composed primarily of quartz sand and other silica-based minerals) have been less

Journal of Geophysical Research, 1995

... В12, PAGES 24,431-24,447, DECEMBER 10, 1995 Why there are no earthquakes on the Marquesas Fra... more ... В12, PAGES 24,431-24,447, DECEMBER 10, 1995 Why there are no earthquakes on the Marquesas Fracture Zone Kelsey A. Jordahl,1 Marcia К. ... Two gravimeters were available on the Ewing: a Bell Aerospace BGM-3 marine gravimeter and a Boogen-werk KSS-30 gravimeter ...

Hydrogeology Journal, 2006

The freshwater lens morphologies of the barrier islands Dog Island and St. George Island on the p... more The freshwater lens morphologies of the barrier islands Dog Island and St. George Island on the panhandle coast of Florida (FL), USA, are controlled to varying degrees by both natural and anthropogenic factors. Variable-density groundwater flow models confirm that spatial variability of recharge values can account for the observed lens asymmetry on these islands. The depth to the base of

Geophysical Research Letters, 1994

The Marquesas fracture zone (MFZ), one of the great fracture zones that formed on the Pacific-Far... more The Marquesas fracture zone (MFZ), one of the great fracture zones that formed on the Pacific-Farallon ridge system, shows dramatic variations in morphology along its strike that cannot be explained by models for lithospheric flexure in response to thermal stresses and differential subsidence. Marine geophysical data collected by the R/V Maurice Ewing in fall 1991 show that major structures in

Geophysical Research Letters, 1988

Four magnetic anomaly profiles across the Marquesas swell were obtained on the Crossgrain expedit... more Four magnetic anomaly profiles across the Marquesas swell were obtained on the Crossgrain expedition of the R/V Thomas Washington in April 1987. The data cover a poorly dated region of the Pacific between the Galapagos and Marquesas fracture zones. Magnetic lineations trending approximately 350° in the vicinity of the swell were identified as anomalies 20 through 29, differing from identifications proposed by previous workers. Our identifications imply that the seafloor beneath the Marquesas Islands formed at a half-spreading rate of approximately 40-45 mm/yr during Paleocene and early Eocene time (65 to 50 Ma). The offset across the Marquesas fracture zone apparently increased from approximately 700 to 850 km between the times of anomalies 21 and 13.

Environmental Science & Technology, 2007

Geochemical tracer data (i.e., 222Rn and four naturally occurring Ra isotopes), electromagnetic (... more Geochemical tracer data (i.e., 222Rn and four naturally occurring Ra isotopes), electromagnetic (EM) seepage meter results, and high-resolution, stationary electrical resistivity images were used to examine the bi-directional (i.e., submarine groundwater discharge and recharge) exchange of a coastal aquifer with seawater. Our study site for these experiments was Lynch Cove, the terminus of Hood Canal, WA, where fjord-like conditions dramatically limit water column circulation that can lead to recurring summer-time hypoxic events. In such a system a precise nutrient budget may be particularly sensitive to groundwater-derived nutrient loading. Shore-perpendicular time-series subsurface resistivity profiles show clear, decimeter-scale tidal modulation of the coastal aquifer in response to large, regional hydraulic gradients, hydrologically transmissive glacial terrain, and large (4-5 m) tidal amplitudes. A 5-day 222Rn time-series shows a strong inverse covariance between 222Rn activities (0.5-29 dpm L(-1)) and water level fluctuations, and provides compelling evidence for tidally modulated exchange of groundwater across the sediment/water interface. Mean Rn-derived submarine groundwater discharge (SGD) rates of 85 +/- 84 cm d(-1) agree closely in the timing and magnitude with EM seepage meter results that showed discharge during low tide and recharge during high tide events. To evaluate the importance of fresh versus saline SGD, Rn-derived SGD rates (as a proxy of total SGD) were compared to excess 226Ra-derived SGD rates (as a proxy for the saline contribution of SGD). The calculated SGD rates, which include a significant (&amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;gt;80%) component of recycled seawater, are used to estimate associated nutrient (NH4+, Si, PO4(3-), NO3 + NO2, TDN) loads to Lynch Cove. The dissolved inorganic nitrogen (DIN = NH4 + NO2 + NO3) SGD loading estimate of 5.9 x 10(4) mol d(-1) is 1-2 orders of magnitude larger than similar estimates derived from atmospheric deposition and surface water runoff, respectively.

ABSTRACT Tephra fallout models used to forecast volcanic hazards rely on the advection-diffusion ... more ABSTRACT Tephra fallout models used to forecast volcanic hazards rely on the advection-diffusion equation to forecast hazards. If the advection-diffusion equation applies, then the thickness of tephra blanket deposits should show Gaussian crosswind profiles and exponential decay with distance from the vent. Complications may arise due to factors such as particle size distributions, particle density, and atmospheric effects not incorporated in the advection-diffusion model. Continuous profiles derived from GPR surveys collected on the tephra blanket of Cerro Negro Volcano, Nicaragua allow us to test the advection-diffusion model. Steady trade winds coupled with eruptions that tend to be brief and relatively low energy create relatively simple deposits. Data was collected for cross wind profiles at varying distances from the vent. Horizons identified in these profiles exhibit Gaussian distributions with a high degree of statistical confidence. Additionally, the shape of one continuous profile leading from the crater rim out onto the tephra blanket is examined.

AGU Fall Meeting …, 2001

Title: The ABYSS Mission: Satellite Altimetry Optimized for Seafloor Geophysics. ... of Hawaii, H... more Title: The ABYSS Mission: Satellite Altimetry Optimized for Seafloor Geophysics. ... of Hawaii, Honolulu, HI 96822 United States ; ). Publication: American Geophysical Union, Fall Meeting 2001, abstract #OS12C-0438. Publication Date: 12/2001. Origin: AGU. ...

ABSTRACT Located 25 kilometers east of Flagstaff, Arizona, Rattlesnake Crater is an oblong phreat... more ABSTRACT Located 25 kilometers east of Flagstaff, Arizona, Rattlesnake Crater is an oblong phreatomagmatic feature in the San Francisco Volcanic Field. The shallow crater is approximately 1.4 kilometers at its widest point, and surrounded by an uneven tuff ring which is overlapped by a scoria cone volcano on the southeastern side. Improved understanding of its formation and evolution requires geophysical study because there are very few outcrops, and no digging is permitted on site. Geologic features related to the crater are further obscured by deposits from the overlapping scoria cone, as well as tephra from eruptions at nearby Sunset Crater. We present the results of a detailed magnetic and gravity survey in and around Rattlesnake Crater. A substantial NW-SE trending elongate magnetic anomaly (1400 nT) and a smaller similarly trending anomaly are observed inside the crater, as well as a longer wavelength positive gravitational anomaly (+1.0-1.5 mGal) across the crater. The magnetic survey was completed on foot with a 50 meter line spacing inside the crater, and 100 meter line spacing across a portion of the surrounding area outside the crater. The gravity survey was done on two intersecting survey lines - one running west to east, and another roughly north to south, with recordings every 100 meters extending at least 1000 meters outside the crater in all four directions. 2D models of the magnetic and gravity data are presented illustrating the possible geometry of the diatreme, and the approximate size and shape of the major intrusive features. Eruption estimates based on the models are calculated, and the models are favorably compared to the size and depth estimates given in a recent publication (Valentine 2012) that used xenolith content to estimate the size and depth of the diatreme.