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Articles 241 - 270 of 1880

Full-Text Articles in Earth Sciences

Speleothems In Quartz-Sandstone Caves Of Ponta Grossa Municipality, Campos Gerais Region, Paraná State, Southern Brazil, Henrique S. Pontes, Luiz A. Fernandes, Mário S. De Melo, Gilson B. Guimarães, Laís L. Massuqueto Jun 2020

Speleothems In Quartz-Sandstone Caves Of Ponta Grossa Municipality, Campos Gerais Region, Paraná State, Southern Brazil, Henrique S. Pontes, Luiz A. Fernandes, Mário S. De Melo, Gilson B. Guimarães, Laís L. Massuqueto

International Journal of Speleology

The present communication characterizes and discusses the genesis of cave speleothems developed in Furnas Formation (Silurian-Devonian) and Vila Velha sub-unit (Campo Mourão Formation, Upper Carboniferous) quartz-sandstones, in southern Brazil. The research, which involved stratigraphic and petrographic studies, was conducted to identify the faciological context of occurrence of these features, and to determine, through different analytical methods, their mineralogical composition and porosity, and also the action of microbial markers on the genesis of these secondary mineral deposits. The speleothems were classified into six types based on form, composition and genesis: (1) arborescent (coral), (2) mushroom-shaped, (3) stalactitic, (4) stalagmitic, (5) columnar …

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Cosmogenic Nuclide Dating Of Cave Sediments In The Eastern Alps And Implications For Erosion Rates, Philipp Häuselmann, Lukas Plan, Peter Pointner, Markus Fiebig Jun 2020

Cosmogenic Nuclide Dating Of Cave Sediments In The Eastern Alps And Implications For Erosion Rates, Philipp Häuselmann, Lukas Plan, Peter Pointner, Markus Fiebig

International Journal of Speleology

Karstic caves are created by water eroding and corroding rocks that can be dissolved. Since both the spring areas of caves (normally at the valley bottom) as well as the recharge is controlled by superficial processes, the morphology of the cave bears strong links to these influences. Lowering of local base levels promotes the development of horizontal phreatic cave passages at progressively lower elevations, resulting in the formation of multi-level karst systems. Upon the next lowering of base level, these upper systems become fossilized, and sediment trapped within them may remain preserved for millions of years. Dating these sediments gives …

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Evaluating The Influences Of Harvesting Activity And Eutrophication On Loss Of Aquatic Vegetations In Taihu Lake, China, Juhua Luo, Ruiliang Pu, Hongtao Duan, Ronghua Ma, Zhigang Mao, Yuan Zeng, Linsheng Huang, Qitao Xiao May 2020

Evaluating The Influences Of Harvesting Activity And Eutrophication On Loss Of Aquatic Vegetations In Taihu Lake, China, Juhua Luo, Ruiliang Pu, Hongtao Duan, Ronghua Ma, Zhigang Mao, Yuan Zeng, Linsheng Huang, Qitao Xiao

School of Geosciences Faculty and Staff Publications

A rapid degradation of aquatic vegetations in Taihu Lake has roused a wide attention in recent years. Giving large-scale harvesting activity on aquatic vegetation since 2012, whether water eutrophication or the human harvest activity induced the degradation remains controversial and unclear. In this study, based on Landsat and HJ-CCD data acquired from 1984 to 2016 and a 12-year field observation (2005–2016) of water quality, a method was proposed to quantitatively assess impacts of harvesting activity and water quality change on degradations of both floating-leaved aquatic vegetation (FAV) and submerged aquatic vegetation (SAV) in Taihu Lake. First, areas of FAV and …

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Resolution Of Lava Tubes With Ground Penetrating Radar: The Tubex Project, Sanaz Esmaeili, Sarah Kruse, Sajad Jazayeri, P. Whelley, E. Bell, J. Richardson, W. B. Garry, K. Young May 2020

Resolution Of Lava Tubes With Ground Penetrating Radar: The Tubex Project, Sanaz Esmaeili, Sarah Kruse, Sajad Jazayeri, P. Whelley, E. Bell, J. Richardson, W. B. Garry, K. Young

School of Geosciences Faculty and Staff Publications

Remote sensing surveys of the Moon and Mars show evidence of lava tubes, which are potential safe havens for human crews and their equipment. Ground penetrating radar (GPR) can be used to map tubes because the void/rock interface at tube ceilings and floors strongly reflects radar pulses. We have tested the capacity of GPR to sense lava tube geometry at Lava Beds National Monument in California, USA. GPR and detailed light detection and ranging (LiDAR) data are presented for two tubes: Skull Cave, with a few meters of overburden, diameter ~10–20 m, and a rubbly floor; and Valentine Cave, with …

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Biogenic Silica And Organic Carbon Records In Zhoushan Coastal Sea Over The Past One Hundred Years And Their Environmental Indications, Hao Xu, Shangwei Jiang, Jialin Li, Ruiliang Pu, Jia Wang, Wanghai Jin, Longbin Sha, Dongling Li May 2020

Biogenic Silica And Organic Carbon Records In Zhoushan Coastal Sea Over The Past One Hundred Years And Their Environmental Indications, Hao Xu, Shangwei Jiang, Jialin Li, Ruiliang Pu, Jia Wang, Wanghai Jin, Longbin Sha, Dongling Li

School of Geosciences Faculty and Staff Publications

The influence of terrestrial and marine input has dramatically changed eutrophication in coastal seas over the past 100 years. In this study, Zhoushan coastal sea (ZCS) is taken as a study area. We studied ZCS as it is a sink of the temporal and spatial variation of primary productivity, dominant species of algae, and the variation of provenance in this area over the past 100 years. We performed analysis using three sediment cores and the carbon and silicon deposition records. The analysis results demonstrate that: (1) The primary productivity in the northern area of the ZCS close to the Yangtze …

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Surface Deformation And Induced Seismicity Due To Fluid Injection And Oil And Gas Extraction In Western Texas, Fanghui Deng, Timothy H. Dixon, Surui Xie May 2020

Surface Deformation And Induced Seismicity Due To Fluid Injection And Oil And Gas Extraction In Western Texas, Fanghui Deng, Timothy H. Dixon, Surui Xie

School of Geosciences Faculty and Staff Publications

Texas is experiencing increasing seismicity, likely related to the oil and gas production process. We used satellite InSAR (Interferometric Synthetic Aperture Radar) to monitor surface deformation at three study sites in western Texas with similar geologic characteristics. The deformation data were compared to earthquake distribution, groundwater changes, volumes of produced and injected fluid, and calculated pore pressure change and Coulomb failure stress change to assess causes of deformation and seismicity. Site 1 experienced surface uplift due to fluid injection but no increase in seismicity. The average media properties were estimated based on the deformation using a poroelastic model. Site 2 …

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Full Issue 49(1) Apr 2020

Full Issue 49(1)

International Journal of Speleology

No abstract provided.

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Table Of Contents Apr 2020

Table Of Contents

International Journal of Speleology

No abstract provided.

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Cave Airflow Mechanism Of A Crevice-Type Cave: A Case Study From Czechia, Martin Kašing, Jan Lenart Apr 2020

Cave Airflow Mechanism Of A Crevice-Type Cave: A Case Study From Czechia, Martin Kašing, Jan Lenart

International Journal of Speleology

At present, crevice-type caves are investigated mainly by means of geomorphic and geophysical methods. Microclimatic research of this type of caves is underrepresented and is often limited to temperature and humidity measurement only. Yet, microclimatic research of such caves can significantly help in the management and conservation of caves, speleological exploration or analysis of speleothems. Being the first ever research of ventilation within a crevice-type cave, a complex analysis of cave ventilation was performed within the Velká Ondrášova Cave, a crevice-type cave in the Outer Western Carpathians, Czechia. Long-term temperature recording, airflow tracing within the cave, and a total of …

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Modeling The Contribution Of Poroelastic Deformation To Postseismic Geodetic Signals, Kimberly Mccormack, Marc A. Hesse, Timothy H. Dixon, Rocco Malservisi Apr 2020

Modeling The Contribution Of Poroelastic Deformation To Postseismic Geodetic Signals, Kimberly Mccormack, Marc A. Hesse, Timothy H. Dixon, Rocco Malservisi

School of Geosciences Faculty and Staff Publications

To constrain the poroelastic component of postseismic deformation, we model the subsurface hydrologic response to the Mw 7.6 subduction zone earthquake that occurred on the plate interface beneath the Nicoya peninsula in Costa Rica on 5 September 2012. The model shows that poroelastic relaxation occurs on multiple time scales and the associated deformation can be up to 2 cm for the trench‐perpendicular component. By modeling the time‐dependent deformation associated with poroelastic relaxation, we can begin to remove its contribution from the observed geodetic signal. Inversions for after slip that ignore poroelastic deformation have errors of 10–20% overall and up …

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Estimation Of Aboveground Biomass Of Robinia Pseudoacacia Forest In The Yellow River Delta Based On Uav And Backpack Lidar Point Clouds, Jinbo Lu, Hong Wang, Shuhong Qin, Lin Cao, Ruiliang Pu, Guilin Li, Jing Sun Apr 2020

Estimation Of Aboveground Biomass Of Robinia Pseudoacacia Forest In The Yellow River Delta Based On Uav And Backpack Lidar Point Clouds, Jinbo Lu, Hong Wang, Shuhong Qin, Lin Cao, Ruiliang Pu, Guilin Li, Jing Sun

School of Geosciences Faculty and Staff Publications

Forest plantations are an important source of terrestrial carbon sequestration. The forest of Robinia pseudoacacia in the Yellow River Delta (YRD) is the largest artificial ecological protection forest in China. However, more than half of the forest has appeared different degrees of dieback and even death since the 1990s. Timely and accurate estimation of the forest aboveground biomass (AGB) is a basis for studying the carbon cycle of forests. Light Detecting and Ranging (LiDAR) has been proved to be one of the most powerful methods for forest biomass estimation. However, because of an irregular and overlapping shape of the broadleaved …

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Spatiotemporal Changes Of Microbial Community Assemblages And Functions In The Subsurface, Madison C. Davis Mar 2020

Spatiotemporal Changes Of Microbial Community Assemblages And Functions In The Subsurface, Madison C. Davis

USF Tampa Graduate Theses and Dissertations

The subsurface hosts diverse microbial community assemblages and functions. These communities play an important role in biogeochemical cycling and groundwater purification. Many physicochemical factors affect microbial communities and can cause short-term or long-term perturbations. Subsurface microbes are susceptible to anthropogenic changes in the environment, which can be caused by nutrient inputs or municipal groundwater extraction. Despite the importance of the subsurface microbiome, these microbial communities are poorly characterized. This dissertation describes the characterization of spatiotemporal drivers of subsurface microbial communities through a variety of techniques that include eDNA analyses, bioinformatics, hydrochemical analyses, stable isotope geochemistry, and multivariate statistics. Three coastal …

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The Ecology And Conservation Of An Urban Karst Subterranean Estuary, Robert J. Scharping Mar 2020

The Ecology And Conservation Of An Urban Karst Subterranean Estuary, Robert J. Scharping

USF Tampa Graduate Theses and Dissertations

Sulphur Springs is an artesian spring and part of the limestone karst topography of metropolitan Tampa, Florida, USA. Underlying this spring is an extensive cave system that hosts saltwater vents and conspicuous microbial biofilm communities. For decades, water from Sulphur Springs has been extracted and used to supplement public water supply and dry season flows in the Hillsborough River Estuary. This dissertation describes research conducted at Sulphur Springs to determine the impacts of urban land use on the underlying cave and downstream estuary ecosystems, and presents the use of this system as a model to fill certain ecological knowledge gaps. …

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Mechanisms Of Carbon Movement And Stabilization In Mangrove Wetlands, Carey Schafer Feb 2020

Mechanisms Of Carbon Movement And Stabilization In Mangrove Wetlands, Carey Schafer

USF Tampa Graduate Theses and Dissertations

Mangrove forests have higher rates of carbon storage per unit area than any other coastal or terrestrial habitat, largely due to their significant soil stocks. More effort has been placed on quantifying mangrove soil carbon stock, the amount of carbon stored in the upper meter of mangrove soils, than identifying the processes governing in situ soil organic carbon (SOC) cycling and stabilization. An understanding of the mechanisms related to carbon transport and stability is necessary to constrain current wetland carbon stocks and to determine how sea level rise will impact future carbon stores. This study uses a variety of radiometric …

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Assessment Of Land Cover Change In St. Martin’S Marsh Aquatic Preserve, Florida, Usa, Katie Wagner Feb 2020

Assessment Of Land Cover Change In St. Martin’S Marsh Aquatic Preserve, Florida, Usa, Katie Wagner

USF Tampa Graduate Theses and Dissertations

St. Martin’s Marsh Aquatic Preserve (SMMAP) is a 28,461 acre (115.18 km2) preserve located on the coast of Citrus County, Florida, USA. There has been no published research that focused on coastal change on this unique coast. This thesis research focuses on coastal land cover change that has occurred within the preserve from 1988 to 2018. Multitemporal Landsat images were classified using a support vector machine (SVM) classification, while changes in vegetation were evaluated using the normalized difference vegetation index (NDVI). Field research was conducted to examine nineteen sites for classification training and test data and notes on habitat composition. …

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Shallow Water Seafloor Geodesy: Gps On An Anchored Spar Buoy, Surui Xie Feb 2020

Shallow Water Seafloor Geodesy: Gps On An Anchored Spar Buoy, Surui Xie

USF Tampa Graduate Theses and Dissertations

Measuring seafloor motion in shallow coastal water is challenging due to strong and highly variable oceanographic effects. Such measurements are potentially useful for monitoring near-shore coastal subsidence, subsidence due to petroleum withdrawal, strain accumulation/release processes in marine shelves and submerged volcanoes, and certain fresh water applications, such as volcano deformation in caldera-hosted lakes. I participated in a project to develop a seafloor geodetic system for this environment based on an anchored spar buoy topped by high precision GPS. Orientation of the buoy is measured using a digital compass that provides heading, pitch, and roll information. The combined orientation and GPS …

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Quantifying Rates Of “Rifting While Drifting” In The Southern Gulf Of California: The Role Of The Southern Baja California Microplate And Its Eastern Boundary Zone, Paul J. Umhoefer, C. Plattner, Rocco Malservisi Feb 2020

Quantifying Rates Of “Rifting While Drifting” In The Southern Gulf Of California: The Role Of The Southern Baja California Microplate And Its Eastern Boundary Zone, Paul J. Umhoefer, C. Plattner, Rocco Malservisi

School of Geosciences Faculty and Staff Publications

The southern Baja California (Mexico) microplate has been rapidly moving away from the North America plate since ca. 12 Ma. This relative motion toward the northwest developed an oblique-divergent plate boundary that formed the Gulf of California. The rift-drift hypothesis postulates that when a continent ruptures and seafloor spreading commences, rifting on the plate margins ceases, and the margins start to drift, subside, and accumulate postrift sediments, eventually becoming a passive margin. In contrast to this hypothesis, the southern part of the Baja California microplate (BCM), and in particular its actively deforming eastern boundary zone, has continued significant rifting for …

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Uncertainties Associated With The Use Of Erosional Cave Scallop Lengths To Calculate Stream Discharges, Gregory S. Springer, Andrew Hall Jan 2020

Uncertainties Associated With The Use Of Erosional Cave Scallop Lengths To Calculate Stream Discharges, Gregory S. Springer, Andrew Hall

International Journal of Speleology

Scallops are extremely valuable indicators of past water flows in caves because they often record events that cannot be safely witnessed nor measured. Qualitatively, the inverse relationship between their lengths and formative water velocities is useful for determining how flow changes along a cave passage, but they are most valuable because they can be used to directly estimate actual water velocities and discharges. We explore the effects of sample size, measurement choices, and other methods commonly applied to the use of cave scallops in estimating cave stream velocities and discharges. We measured 100 scallops on a cave wall and find …

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Active Growth Of Non-Hydrothermal Subaqueous And Subaerial Barite (Baso4) Speleothems In Lechuguilla Cave (New Mexico, Usa), Max Wisshak, Hazel A. Barton, Katey E. Bender, Harvey R. Duchene Jan 2020

Active Growth Of Non-Hydrothermal Subaqueous And Subaerial Barite (Baso4) Speleothems In Lechuguilla Cave (New Mexico, Usa), Max Wisshak, Hazel A. Barton, Katey E. Bender, Harvey R. Duchene

International Journal of Speleology

Barite (BaSO4) speleothems have been reported from caves around the globe and interpreted to have chiefly formed in phreatic, hypogene, hydrothermal settings. Here we report two contrasting types of barite speleothems (bluish tabular crystals in a shallow pool and actively dripping greenish stalactites), which today form at lower temperatures in the non-hydrothermal and vadose environment of Lechuguilla Cave, New Mexico, USA. Scanning electron microscopy analysis, along with energy- and wavelength-dispersive X-ray spectroscopy (EDS, WDS), as well as X-ray diffraction (XRD), characterize the habit and chemical composition as barite. Fractionation of the minor element calcium is related to growth …

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Mariana Serpentinite Mud Volcanism Exhumes Subducted Seamount Materials: Implications For The Origin Of Life, Patricia Freyer, C. G. Wheat, Trevor Williams, Christopher Kelley, Kevin Johnson, Jeffrey Ryan, Walter Kurz, John Shervais, Elmar Albers, Barbara Bekins Jan 2020

Mariana Serpentinite Mud Volcanism Exhumes Subducted Seamount Materials: Implications For The Origin Of Life, Patricia Freyer, C. G. Wheat, Trevor Williams, Christopher Kelley, Kevin Johnson, Jeffrey Ryan, Walter Kurz, John Shervais, Elmar Albers, Barbara Bekins

School of Geosciences Faculty and Staff Publications

The subduction of seamounts and ridge features at convergent plate boundaries plays an important role in the deformation of the overriding plate and influences geochemical cycling and associated biological processes. Active serpentinization of forearc mantle and serpentinite mud volcanism on the Mariana forearc (between the trench and active volcanic arc) provides windows on subduction processes.  Here, we present (1) the first observation of an extensive exposure of an undeformed Cretaceous seamount currently being subducted at the Mariana Trench inner slope; (2) vertical deformation of the forearc region related to subduction of Pacific Plate seamounts and thickened crust; (3) recovered Ocean …

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Scientist Of The Week!, Sarah L. Sheffield, Lisette Melendez, Kristin Houdyshell, Mathew Burgos Jan 2020

Scientist Of The Week!, Sarah L. Sheffield, Lisette Melendez, Kristin Houdyshell, Mathew Burgos

School of Geosciences Faculty and Staff Publications

No abstract provided.

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Space-Time Hierarchical Clustering For Identifying Clusters In Spatiotemporal Point Data, David S. Lamb, Joni Downs, Steven Reader Jan 2020

Space-Time Hierarchical Clustering For Identifying Clusters In Spatiotemporal Point Data, David S. Lamb, Joni Downs, Steven Reader

School of Geosciences Faculty and Staff Publications

Finding clusters of events is an important task in many spatial analyses. Both confirmatory and exploratory methods exist to accomplish this. Traditional statistical techniques are viewed as confirmatory, or observational, in that researchers are confirming an a priori hypothesis. These methods often fail when applied to newer types of data like moving object data and big data. Moving object data incorporates at least three parts: location, time, and attributes. This paper proposes an improved space-time clustering approach that relies on agglomerative hierarchical clustering to identify groupings in movement data. The approach, i.e., space–time hierarchical clustering, incorporates location, time, and attribute …

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Agua Para El Futuro: Estrategia De Seguridad Hídrica Para América Latina Y El Caribe, Fernando Bretas, Guillermo Casanova, Thomas L. Crisman, Antonio Embid, Liber Martin, Fernando Miralles Jan 2020

Agua Para El Futuro: Estrategia De Seguridad Hídrica Para América Latina Y El Caribe, Fernando Bretas, Guillermo Casanova, Thomas L. Crisman, Antonio Embid, Liber Martin, Fernando Miralles

School of Geosciences Faculty and Staff Publications

No abstract provided.

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Measuring Functional Urban Shrinkage With Multi-Source Geospatial Big Data: A Case Study Of The Beijing-Tianjin-Hebei Megaregion, Qiwei Ma, Zhaoya Gong, Jing Kang, Ran Tao, Anrong Dang Jan 2020

Measuring Functional Urban Shrinkage With Multi-Source Geospatial Big Data: A Case Study Of The Beijing-Tianjin-Hebei Megaregion, Qiwei Ma, Zhaoya Gong, Jing Kang, Ran Tao, Anrong Dang

School of Geosciences Faculty and Staff Publications

Most of the shrinking cities experience an unbalanced deurbanization across different urban areas in cities. However, traditional ways of measuring urban shrinkage are focused on tracking population loss at the city level and are unable to capture the spatially heterogeneous shrinking patterns inside a city. Consequently, the spatial mechanism and patterns of urban shrinkage inside a city remain less understood, which is unhelpful for developing accommodation strategies for shrinkage. The smart city initiatives and practices have provided a rich pool of geospatial big data resources and technologies to tackle the complexity of urban systems. Given this context, we propose a …

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Boosting Computational Effectiveness In Big Spatial Flow Data Analysis With Intelligent Data Reduction, Ran Tao, Zhaoya Gong, Qiwei Ma, Jean-Claude Thill Jan 2020

Boosting Computational Effectiveness In Big Spatial Flow Data Analysis With Intelligent Data Reduction, Ran Tao, Zhaoya Gong, Qiwei Ma, Jean-Claude Thill

School of Geosciences Faculty and Staff Publications

One of the enduring issues of spatial origin-destination (OD) flow data analysis is the computational inefficiency or even the impossibility to handle large datasets. Despite the recent advancements in high performance computing (HPC) and the ready availability of powerful computing infrastructure, we argue that the best solutions are based on a thorough understanding of the fundamental properties of the data. This paper focuses on overcoming the computational challenge through data reduction that intelligently takes advantage of the heavy-tailed distributional property of most flow datasets. We specifically propose the classification technique of head/tail breaks to this end. We test this approach …

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Geoscience Videos And Animations: How To Make Them With Your Students, And How To Use Them In The Classroom, Robert J. Stern, Jeff Ryan, Ning Wang, Victor J. Ricchezza, Siloa Willis Jan 2020

Geoscience Videos And Animations: How To Make Them With Your Students, And How To Use Them In The Classroom, Robert J. Stern, Jeff Ryan, Ning Wang, Victor J. Ricchezza, Siloa Willis

School of Geosciences Faculty and Staff Publications

We are in the midst of a “tectonic shift” in the way that undergraduate students want to learn. They will attend lectures and read assignments if they must, but they are especially interested in information that they can receive as videos on their cell phones and other mobile devices (Prensky, 2001; Thomas, 2011). The geosciences are uniquely well-suited to presentation via well-crafted, scientifically robust videos and animations. Geologic processes often take place over thousands to hundreds of millions of years and occur deep under water or within the Earth, where direct observation is not possible. Geology is synonymous with travel: …

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Mapping Long-Term Spatiotemporal Dynamics Of Pen Aquaculture In A Shallow Lake: Less Aquaculture Coming Along Better Water Quality, Juhua Luo, Ruiliang Pu, Ronghua Ma, Xiaolong Wang, Xijun Lai, Zhigang Mao, Li Zhang, Zhaoliang Peng, Zhe Sun Jan 2020

Mapping Long-Term Spatiotemporal Dynamics Of Pen Aquaculture In A Shallow Lake: Less Aquaculture Coming Along Better Water Quality, Juhua Luo, Ruiliang Pu, Ronghua Ma, Xiaolong Wang, Xijun Lai, Zhigang Mao, Li Zhang, Zhaoliang Peng, Zhe Sun

School of Geosciences Faculty and Staff Publications

Pen aquaculture is the main form of aquaculture in some shallow lakes in eastern China. It is valuable to map the spatiotemporal changes of pen aquaculture in eutrophic lakes to assess its effect on water quality, thereby helping the relevant decision-making agencies to manage the water quality (WQ) of lakes. In this study, an automatic approach for extracting the pen aquaculture area was developed based on Landsat data. The approach integrates five algorithms, including grey transformation, discrete wavelet transform, fast Fourier transform, singular value decomposition and k-nearest neighbor classification. It was successfully applied in the automatic mapping of the pen …

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New Insights Into The 2070calyrbp Pyroclastic Currents At El Misti Volcano (Peru) From Field Investigations, Satellite Imagery And Probabilistic Modeling, Sylvain J. Charbonnier, J.-C. Thouret, Valentin Gueugneau, Robert Constantinescu Jan 2020

New Insights Into The 2070calyrbp Pyroclastic Currents At El Misti Volcano (Peru) From Field Investigations, Satellite Imagery And Probabilistic Modeling, Sylvain J. Charbonnier, J.-C. Thouret, Valentin Gueugneau, Robert Constantinescu

School of Geosciences Faculty and Staff Publications

Pyroclastic currents (PCs) are the most challenging volcanic hazards for disaster planners in populated areas around volcanoes. “El Misti” volcano (5,825 m above sea level), located only 17 km from the city center of Arequipa (>1.1 million inhabitants), South Peru, has produced small-to-moderate volume (<1 km3) PCs with a frequency of 2,000–4,000 years over the past 50 kyr. The most recent Plinian eruption dated at 2070 cal yr BP (VEI 4) has been selected as one of the reference events for the hazard assessment and risk mitigation plan of Arequipa. Associated pumice- and lithic-rich PC deposits were emplaced …

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Estimating Dispersal And Evolutionary Dynamics In Diploporan Blastozoans (Echinodermata) Across The Great Ordovician Biodiversification Event, Adriane R. Lam, Sarah L. Sheffield, Nicholas J. Matzke Jan 2020

Estimating Dispersal And Evolutionary Dynamics In Diploporan Blastozoans (Echinodermata) Across The Great Ordovician Biodiversification Event, Adriane R. Lam, Sarah L. Sheffield, Nicholas J. Matzke

School of Geosciences Faculty and Staff Publications

Echinoderms make up a substantial component of Ordovician marine invertebrates, yet their speciation and dispersal history as inferred within a rigorous phylogenetic and statistical framework is lacking. We use biogeographic stochastic mapping (BSM; implemented in the R package BioGeoBEARS) to infer ancestral area relationships and the number and type of dispersal events through the Ordovician for diploporan blastozoans and related species. The BSM analysis was divided into three time slices to analyze how dispersal paths changed before and during the great Ordovician biodiversification event (GOBE) and within the Late Ordovician mass extinction intervals. The best-fit biogeographic model incorporated jump dispersal, …

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Late Holocene Droughts And Cave Ice Harvesting By Ancestral Puebloans, Bogdan P. Onac, Steven M. Baumann, Dylan S. Parmenter, Eric Weaver, Tiberiu B. Sava Jan 2020

Late Holocene Droughts And Cave Ice Harvesting By Ancestral Puebloans, Bogdan P. Onac, Steven M. Baumann, Dylan S. Parmenter, Eric Weaver, Tiberiu B. Sava

School of Geosciences Faculty and Staff Publications

Water availability for Native Americans in the southwestern United States during periods of prolonged droughts is poorly understood as regional hydroclimate records are scant or contradicting. Here, we show that radiocarbon-dated charcoal recovered from an ice deposit accumulated in Cave 29, western New Mexico, provide unambiguous evidence for five drought events that impacted the Ancestral Puebloan society between ~ AD 150 and 950. The presence of abundant charred material in this cave indicates that they periodically obtained drinking water by using fire to melt cave ice, and sheds light on one of many human–environment interactions in the Southwest in a …

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