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Dynamics Of Pyroclastic Density Currents: Conditions That Promote Substrate Erosion And Self-Channelization - Mount St Helens, Washington (Usa), Brittany D. Brand, Chelsea Mackaman-Lofland, Nicholas M. Pollock, Sylvana Bendaña, Blaine Dawson, Pamela Wichgers 2016 Boise State University

Dynamics Of Pyroclastic Density Currents: Conditions That Promote Substrate Erosion And Self-Channelization - Mount St Helens, Washington (Usa), Brittany D. Brand, Chelsea Mackaman-Lofland, Nicholas M. Pollock, Sylvana Bendaña, Blaine Dawson, Pamela Wichgers

Brittany D. Brand

The May 18th, 1980 eruption of Mount St. Helens (MSH) produced multiple pyroclastic density currents (PDCs), burying the area north of the volcano under 10s of meters of deposits. Detailed measurements of recently exposed strata from these PDCs provide substantial insight into the dynamics of concentrated currents including inferences on particle-particle interactions, current mobility due to sedimentation fluidization and internal pore pressure, particle support mechanisms, the influence of surface roughness and the conditions that promote substrate erosion and self-channelization. Four primary flow units are identified along the extensive drainage system north of the volcano. Each flow unit has intricate vertical ...


Explosive Dome Eruptions Modulated By Periodic Gas-Driven Inflation, Jeffrey B. Johnson, J. J. Lyons, B. J. Andrews, J. M. Lees 2016 Boise State University

Explosive Dome Eruptions Modulated By Periodic Gas-Driven Inflation, Jeffrey B. Johnson, J. J. Lyons, B. J. Andrews, J. M. Lees

Jeffrey Lyons

Volcan Santiaguito (Guatemala) “breathes” with extraordinary regularity as the edifice's conduit system accumulates free gas, which periodically vents to the atmosphere. Periodic pressurization controls explosion timing, which nearly always occurs at peak inflation, as detected with tiltmeters. Tilt cycles in January 2012 reveal regular 26 ± 6 min inflation/deflation cycles corresponding to at least ~101 kg/s of gas fluxing the system. Very long period (VLP) earthquakes presage explosions and occur during cycles when inflation rates are most rapid. VLPs locate ~300 m below the vent and indicate mobilization of volatiles, which ascend at ~50 m/s. Rapid gas ...


A Modified Delay-Time Method For Statics Estimation With The Virtual Refraction, T. Dylan Mikesell, Kasper van Wijk, Elmer Ruigrok, Andrew Lamb, Thomas E. Blum 2016 Boise State University

A Modified Delay-Time Method For Statics Estimation With The Virtual Refraction, T. Dylan Mikesell, Kasper Van Wijk, Elmer Ruigrok, Andrew Lamb, Thomas E. Blum

Dylan Mikesell

Topography and near-surface heterogeneities lead to traveltime perturbations in surface land-seismic experiments. Usually, these perturbations are estimated and removed prior to further processing of the data. A common technique to estimate these perturbations is the delay-time method. We have developed the “modified delay-time method,” wherein we isolate the arrival times of the virtual refraction and estimate receiver-side delay times. The virtual refraction is a spurious arrival found in wavefields estimated by seismic interferometry. The new method removes the source term from the delay-time equation, is more robust in the presence of noise, and extends the lateral aperture compared to the ...


Quasi-Static Eocene–Oligocene Climate In Patagonia Promotes Slow Faunal Evolution And Mid-Cenozoic Global Cooling, Matthew J. Kohn, Caroline A.E. Strömberg, Richard H. Madden, Regan E. Dunn, Samantha L. Evans, Alma Palacios, Alfredo A. Carlini 2016 Boise State University

Quasi-Static Eocene–Oligocene Climate In Patagonia Promotes Slow Faunal Evolution And Mid-Cenozoic Global Cooling, Matthew J. Kohn, Caroline A.E. Strömberg, Richard H. Madden, Regan E. Dunn, Samantha L. Evans, Alma Palacios, Alfredo A. Carlini

Matthew J. Kohn

New local/regional climatic data were compared with floral and faunal records from central Patagonia to investigate how faunas evolve in the context of local and global climates. Oxygen isotope compositions of mammal fossils between c. 43 and 21 Ma suggest a nearly constant mean annual temperature of 16 ± 3 °C, consistent with leaf physiognomic and sea surface studies that imply temperatures of 16–18 °C. Carbon isotopes in tooth enamel track atmospheric δ13C, but with a positive deviation at 27.2 Ma, and a strong negative deviation at 21 Ma. Combined with paleosol characteristics and reconstructed Leaf ...


Monitoring Southwest Greenland’S Ice Sheet Melt With Ambient Seismic Noise, Aurélien Mordret, T. Dylan Mikesell, Christopher Harig, Bradley P. Lipovsky, Germán A. Prieto 2016 Massachusetts Institute of Technology

Monitoring Southwest Greenland’S Ice Sheet Melt With Ambient Seismic Noise, Aurélien Mordret, T. Dylan Mikesell, Christopher Harig, Bradley P. Lipovsky, Germán A. Prieto

Dylan Mikesell

The Greenland ice sheet presently accounts for ~70% of global ice sheet mass loss. Because this mass loss is associated with sea-level rise at a rate of 0.7 mm/year, the development of improved monitoring techniques to observe ongoing changes in ice sheet mass balance is of paramount concern. Spaceborne mass balance techniques are commonly used; however, they are inadequate for many purposes because of their low spatial and/or temporal resolution. We demonstrate that small variations in seismic wave speed in Earth’s crust, as measured with the correlation of seismic noise, may be used to infer seasonal ...


The Need To Adapt The Exploration Model From The Oil Patch To Contaminated-Site Characterization: A Case From Hill Afb, Utah, Usa, John H. Bradford, Esther Babcock 2016 Boise State University

The Need To Adapt The Exploration Model From The Oil Patch To Contaminated-Site Characterization: A Case From Hill Afb, Utah, Usa, John H. Bradford, Esther Babcock

John H. Bradford

For decades, the oil industry has employed a working model for hydrocarbon exploration in which large-scale geophysical surveys are undertaken prior to a second phase of intensive, targeted drilling. This latter phase may be conducted in conjunction with further focused geophysical studies. The geophysical surveys provide lateral coverage and continuity that are used to drive placement of drilling locations. The reason for this approach is simple: wells are expensive relative to geophysical surveys. Also, practical limits on lateral coverage preclude optimization of exploration targets based on well information alone.


Trace Element Diffusivities In Bone Rule Out Simple Diffusive Uptake During Fossilization But Explain In Vivo Uptake And Release, Matthew J. Kohn, Randolph J. Moses 2016 Boise State University

Trace Element Diffusivities In Bone Rule Out Simple Diffusive Uptake During Fossilization But Explain In Vivo Uptake And Release, Matthew J. Kohn, Randolph J. Moses

Matthew J. Kohn

Diffusion rates of numerous trace elements in bone at 20 °C were determined using laser-ablation inductively coupled plasma mass spectrometry analysis of experimentally induced diffusion profiles. Diffusivities are about 1 order of magnitude slower than current semiquantitative geochemical views and about 1.5 orders of magnitude faster than indirect radiotracer estimates. Intrabone volume diffusion is too slow and too similar among many elements to explain trace element profiles in young fossils and archeological materials. Diffusivity differences among elements do, however, explain disparate biokinetic washout of Sr vs. Ba and of light vs. heavy rare earth elements (REEs). These results improve ...


Elastic Block Modeling Of Fault Slip Rates Across Southern California, Liam P. DiZio 2016 Macalester College

Elastic Block Modeling Of Fault Slip Rates Across Southern California, Liam P. Dizio

Macalester Journal of Physics and Astronomy

We present fault slip rate estimates for Southern California based on Global Positioning System (GPS) velocity data from the University NAVSTAR Consortium (UNAVCO), the Southern California Earthquake Center (SCEC), and new campaign GPS velocity data from the San Bernardino Mountains and vicinity. Fault slip-rates were calculated using Tdefnode, a program used to model elastic deformation within lithospheric blocks and slip on block bounding faults [2]. Our block model comprised most major faults within Southern California. Tdefnode produced similar slip rate values as other geodetic modeling techniques. The fastest slipping faults are the Imperial fault (37.4±0.1 mm/yr ...


Plate Tectonics Initiation On Earth-Like Planets: Insights From Numerical And Theoretical Analysis Of Convection-Induced Lithospheric Failure, Teresa Wong 2016 Washington University in St. Louis

Plate Tectonics Initiation On Earth-Like Planets: Insights From Numerical And Theoretical Analysis Of Convection-Induced Lithospheric Failure, Teresa Wong

Arts & Sciences Electronic Theses and Dissertations

Plate tectonics is central to many aspects of the geology and evolution of terrestrial planets, yet it is only observed on the Earth while all other known planets are covered with a stagnant lithosphere. Plate motions on the Earth are mostly driven by the pull of subducting slabs, therefore understanding the initiation of subduction is crucial to understanding plate tectonics initiation. On a one-plate planet which lacks the forces due to plate motions, some other mechanisms will have to cause the first episode of subduction to mobilize the surface. Sublithospheric convection has been proposed as a possible mechanism that induce ...


Search For An Artificially Buried Karst Cave Entrance Using Ground Penetrating Radar: A Successful Case Of Locating The S-19 Cave In The Mt. Kanin Massif (Nw Slovenia), Andrej Gosar, Teja Čeru 2016 University of Ljubljana

Search For An Artificially Buried Karst Cave Entrance Using Ground Penetrating Radar: A Successful Case Of Locating The S-19 Cave In The Mt. Kanin Massif (Nw Slovenia), Andrej Gosar, Teja Čeru

International Journal of Speleology

The S-19 Cave was with its explored depth of 177 m one of the most important caves of the Mt. Kanin massif, but after its discovery in 1974, a huge snow avalanche protection dyke was constructed across the cave entrance. To excavate the buried cave, the accurate location of the cave had to be determined first. Since the entrance coordinates were incorrect and no markers were available, application of geophysical techniques was necessary to do this. A Ground Penetrating Radar (GPR) with special 50 MHz rough terrain antennas was selected as the single suitable geophysical method for the given conditions ...


Monitoring Southwest Greenland’S Ice Sheet Melt With Ambient Seismic Noise, Aurélien Mordret, T. Dylan Mikesell, Christopher Harig, Bradley P. Lipovsky, Germán A. Prieto 2016 Massachusetts Institute of Technology

Monitoring Southwest Greenland’S Ice Sheet Melt With Ambient Seismic Noise, Aurélien Mordret, T. Dylan Mikesell, Christopher Harig, Bradley P. Lipovsky, Germán A. Prieto

CGISS Publications and Presentations

The Greenland ice sheet presently accounts for ~70% of global ice sheet mass loss. Because this mass loss is associated with sea-level rise at a rate of 0.7 mm/year, the development of improved monitoring techniques to observe ongoing changes in ice sheet mass balance is of paramount concern. Spaceborne mass balance techniques are commonly used; however, they are inadequate for many purposes because of their low spatial and/or temporal resolution. We demonstrate that small variations in seismic wave speed in Earth’s crust, as measured with the correlation of seismic noise, may be used to infer seasonal ...


Complex Rupture Of The M6.3 2015 March 10 Bucaramanga Earthquake: Evidence Of Strong Weakening Process, P. Poli, G. A. Prieto, C. Q. Yu, M. Florez, H. Agurto-Detzel, T. D. Mikesell, G. Chen, V. Dionicio, P. Pedraza 2016 Massachusetts Institute of Technology

Complex Rupture Of The M6.3 2015 March 10 Bucaramanga Earthquake: Evidence Of Strong Weakening Process, P. Poli, G. A. Prieto, C. Q. Yu, M. Florez, H. Agurto-Detzel, T. D. Mikesell, G. Chen, V. Dionicio, P. Pedraza

Dylan Mikesell

We use seismic waves for a magnitude 6.3 intermediate-depth (160 km) earthquake in the Bucaramanga Nest, Colombia, to infer a complex rupture process with two distinct stages, characterized by different rupture velocities possibly controlled by the evolution of strength on the fault. Our integrated data processing permitted to precisely characterize the multistage rupture and the presence of a strong weakening event. The resulting seismic radiation is interpreted as resulting from an extreme weakening due to a cascading thermal shear runaway, with an initial inefficient radiation process followed by a fast and dynamic efficient rupture. Our results imply dynamic complexity ...


Effects Of Changes In Moisture Source And The Upstream Rainout On Stable Isotopes In Precipitation – A Case Study In Nanjing, Eastern China, Y. Tang, H. Pang, W. Zhang, Y. Li, Shuang-Ye Wu, S. Hou 2016 Nanjing University

Effects Of Changes In Moisture Source And The Upstream Rainout On Stable Isotopes In Precipitation – A Case Study In Nanjing, Eastern China, Y. Tang, H. Pang, W. Zhang, Y. Li, Shuang-Ye Wu, S. Hou

Shuang-ye Wu

In the Asian monsoon region, variations in the stable isotopic composition of speleothems have often been attributed to the "amount effect". However, an increasing number of studies suggest that the "amount effect" in local precipitation is insignificant or even non-existent. To explore this issue further, we examined the variability of daily stable isotopic composition (δ18O) in precipitation from September 2011 to November 2014 in Nanjing, eastern China. We found that intra-seasonal variations of δ18O during summer were not significantly correlated with local rainfall amount but could be linked to changes in the moisture source location and rainout processes in the ...


Reconstruction Of The Hirnantian (Late Ordovician) Palaeotopography In The Upper Yangtze Region, Linna Zhang, Junxuan Fan, Qing Chen, Shuang-Ye Wu 2016 University of Chinese Academy of Sciences

Reconstruction Of The Hirnantian (Late Ordovician) Palaeotopography In The Upper Yangtze Region, Linna Zhang, Junxuan Fan, Qing Chen, Shuang-Ye Wu

Shuang-ye Wu

Reconstruction of the Hirnantian (Late Ordovician) palaeotopography in South China is important for understanding the distribution pattern of the Hirnantian marine depositional environment. In this study, we reconstructed the Hirnantian palaeotopography in the Upper Yangtze region based on the rankings of the palaeo-water depths, which were inferred according to the lithofacies and biofacies characteristics of the sections. Data from 374 Hirnantian sections were collected and standardized through the online Geobiodiversity Database. The Ordinary Kriging interpolation method in the ArcGIS software was applied to create the continuous surface of the palaeo-water depths, i.e. the Hirnantian palaeotopography. Meanwhile, the line transect ...


Fluoride: A Naturally-Occurring Health Hazard In Drinking-Water Resources Of Northern Thailand, C. Joon Chuah, Han Rui Lye, Alan D. Ziegler, Spencer H. Wood, Chatpat Kongpun, Sunsanee Rajchagool 2016 National University of Singapore

Fluoride: A Naturally-Occurring Health Hazard In Drinking-Water Resources Of Northern Thailand, C. Joon Chuah, Han Rui Lye, Alan D. Ziegler, Spencer H. Wood, Chatpat Kongpun, Sunsanee Rajchagool

Spencer H. Wood

In Northern Thailand, incidences of fluorosis resulting from the consumption of high-fluoride drinking-water have been documented. In this study, we mapped the high-fluoride endemic areas and described the relevant transport processes of fluoride in enriched waters in the provinces of Chiang Mai and Lamphun. Over one thousand surface and sub-surface water samples including a total of 995 collected from shallow (depth: ≤30 m) and deep (>30 m) wells were analysed from two unconnected high-fluoride endemic areas. At the Chiang Mai site, 31% of the shallow wells contained hazardous levels (≥1.5 mg/L) of fluoride, compared with the 18% observed ...


Transition From Contraction To Extension In The Northeastern Basin And Range: New Evidence From The Copper Mountains, Nevada, Jeffrey M. Rahl, Allen J. McGrew, Kenneth A. Foland 2016 Yale University

Transition From Contraction To Extension In The Northeastern Basin And Range: New Evidence From The Copper Mountains, Nevada, Jeffrey M. Rahl, Allen J. Mcgrew, Kenneth A. Foland

Allen J. McGrew

New mapping, structural analysis, and 40Ar/39Ar dating reveal an unusually well‐constrained history of Late Eocene extension in the Copper Mountains of the northern Basin and Range province. In this area, the northeast‐trending Copper Creek normal fault juxtaposes a distinctive sequence of metacarbonate and granitoid rocks against a footwall of Upper Precambrian to Lower Cambrian quartzite and phyllite. Correlation of the hanging wall with footwall rocks to the northwest provides an approximate piercing point that requires 8–12 km displacement in an ESE direction. This displaced fault slice is itself bounded above by another normal fault (the Meadow ...


Aquifer Arsenic Cycling Induced By Seasonal Hydrologic Changes Within The Yangtze River Basin, Michael V. Schaefer, Samantha C. Ying, Shawn G. Benner, Yanhua Duan, Yanxin Wang, Scott Fendorf 2016 Stanford University

Aquifer Arsenic Cycling Induced By Seasonal Hydrologic Changes Within The Yangtze River Basin, Michael V. Schaefer, Samantha C. Ying, Shawn G. Benner, Yanhua Duan, Yanxin Wang, Scott Fendorf

Geosciences Faculty Publications and Presentations

Consumption of groundwater containing >10 μg L−1 arsenic (As) adversely impacts more than 100 million people worldwide. Multiyear trends in aquifer As concentrations have been documented, but strong seasonal variations are not commonly observed. Here we report dramatic seasonal changes in As concentrations and aquifer chemistry within the Jianghan Plain of the Yangtze River, China. At some wells, concentrations fluctuate by more than an order of magnitude within a single year (100−1200 μg L−1). Groundwater extraction and sustained water levels of surface channels during the dry season induces a strong downward hydraulic gradient, seasonally supplying ...


Paleomagnetic Analysis Of The Scottsville Mesozoic Rift Basin, Virginia: Implications For Regional Geologic History, Nathan Charles Keithline 2016 College of William and Mary

Paleomagnetic Analysis Of The Scottsville Mesozoic Rift Basin, Virginia: Implications For Regional Geologic History, Nathan Charles Keithline

College of William & Mary Undergraduate Honors Theses

The Scottsville basin forms one of the westernmost Mesozoic rift basins in Virginia. The basin lies ~25 km SW of Charlottesville, VA astride the transition zone between the Eastern Blue Ridge and Western Piedmont geologic provinces. The ~110 km2 basin is a half-graben bounded by a normal fault to the northwest, and unconformably overlies phyllitic rocks of the Piedmont on its southeast margin. Sedimentary rocks in the basin range from boulder conglomerates to sandstone and siltstone red beds and are sourced primarily from the Proterozoic units of the Blue Ridge. NNW striking diabase dikes associated with the Central Atlantic ...


Reservoir Study And Facies Analysis Of The Big Clifty Sandstone In South Central Kentucky, Tyler S. Bodine 2016 Western Kentucky University

Reservoir Study And Facies Analysis Of The Big Clifty Sandstone In South Central Kentucky, Tyler S. Bodine

Masters Theses & Specialist Projects

The Big Clifty (Jackson) Sandstone Member of the Golconda Formation is the most important of the Mississippian (Chesterian) heavy-oil reservoirs in the southeastern Illinois Basin. Heavy oil reservoirs, or asphalt rock deposits, have been studied extensively in south central and western Kentucky, and ~2 billion barrels of original oil in place (OOIP) have been proposed to occur in the Big Clifty Sandstone. Despite high OOIP estimates, heterogeneities in the reservoir negatively impact the production of heavy oil deposits. Heterogeneities related to depositional facies changes are poorly understood in the Big Clifty Sandstone of Kentucky, where it has been mostly described ...


Georgetown Lake Seismic Survey, Timothy Clayton Rodriguez 2016 Montana Tech of the University of Montana

Georgetown Lake Seismic Survey, Timothy Clayton Rodriguez

Graduate Theses & Non-Theses

A near surface seismic survey was performed in order to locate the Georgetown Thrust Fault. The location of the thrust fault relative to Georgetown Lake has been previously proposed by field mapping methods (Lonn et al.,2004). A seismic survey could be useful to identify the thrust fault because of possible geologic discontinuities at the boundaries of the thrust fault that could give rise to diffraction energy indicative of the presence of those discontinuities. The Montana Tech summer field camp recorded a seismic survey along the southern edge of Georgetown Lake. This report focuses on the optimal processing methods for ...


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