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At least 109 records · Page 6Linked to original sources
USGS2017

A review of surface energy balance models for estimating actual evapotranspiration with remote sensing at high spatiotemporal resolution over large extents

Many approaches have been developed for measuring or estimating actual evapotranspiration ( ET a ), and research over many years has led to the development of remote sensing methods that are reliably reproducible and effective in estimating ET a . Several remote sensing methods can be used to estimate ET a at the high spatial resolution of agricultural fields and the large extent of river basins. More complex remote sensing methods apply an analytical approach to ET a estimation using physically based models of varied complexity that require a combination of ground-based and remote sensing data, and are grounded in the theory behind the surface energy balance model. This report, funded through cooperation with the International Joint Commission, provides an overview of selected remote sensing methods used for estimating water consumed through ET a and focuses on Mapping Evapotranspiration at High Resolution with Internalized Calibration (METRIC) and Operational Simplified Surface Energy Balance (SSEBop), two energy balance models for estimating ET a that are currently applied successfully in the United States. The METRIC model can produce maps of ET a at high spatial resolution (30 meters using Landsat data) for specific areas smaller than several hundred square kilometers in extent, an improvement in practice over methods used more generally at larger scales. Many studies validating METRIC estimates of ET a against measurements from lysimeters have shown model accuracies on daily to seasonal time scales ranging from 85 to 95 percent. The METRIC model is accurate, but the greater complexity of METRIC results in greater data requirements, and the internalized calibration of METRIC leads to greater skill required for implementation. In contrast, SSEBop is a simpler model, having reduced data requirements and greater ease of implementation without a substantial loss of accuracy in estimating ET a . The SSEBop model has been used to produce maps of ET a over very large extents (the conterminous United States) using lower spatial resolution (1 kilometer) Moderate Resolution Imaging Spectroradiometer (MODIS) data. Model accuracies ranging from 80 to 95 percent on daily to annual time scales have been shown in numerous studies that validated ET a estimates from SSEBop against eddy covariance measurements. The METRIC and SSEBop models can incorporate low and high spatial resolution data from MODIS and Landsat, but the high spatiotemporal resolution of ET a estimates using Landsat data over large extents takes immense computing power. Cloud computing is providing an opportunity for processing an increasing amount of geospatial “big data” in a decreasing period of time. For example, Google Earth Engine TM has been used to implement METRIC with automated calibration for regional-scale estimates of ET a using Landsat data. The U.S. Geological Survey also is using Google Earth Engine TM to implement SSEBop for estimating ET a in the United States at a continental scale using Landsat data.

Scientific Investigations Report↗
USGS2019

Managing dams for energy and fish tradeoffs: What does a win-win solution take?

Management activities to restore endangered fish species, such as dam removals, fishway installations, and periodic turbine shutdowns, usually decrease hydropower generation capacities at dams. Quantitative analysis of the tradeoffs between energy production and fish population recovery related to dam decision-making is still lacking. In this study, an integrated hydropower generation and age-structured fish population model was developed using a system dynamics modeling method to assess basin-scale energy-fish tradeoffs under eight dam management scenarios. This model ran across 150 years on a daily time step, applied to five hydroelectric dams located in the main stem of the Penobscot River, Maine. We used alewife ( Alosa pseudoharengus ) to be representative of the local diadromous fish populations to link projected hydropower production with theoretical influences on migratory fish populations on the model river system. Our results show that while the five dams can produce around 427 GWh/year of energy, without fishway installations they would contribute to a 90% reduction in the alewife spawner abundance. The effectiveness of fishway installations is largely influenced by the size of reopened habitat areas and the actual passage rate of the fishways. Homing to natal habitat has an insignificant effect on the growth of the simulated spawner abundance. Operating turbine shutdowns during alewives' peak downstream migration periods, in addition to other dam management strategies, can effectively increase the spawner abundance by 480–550% while also preserving 65% of the hydropower generation capacity. These data demonstrate that in a river system where active hydropower dams operate, a combination of dam management strategies at the basin scale can best balance the tradeoff between energy production and the potential for migratory fish population recovery.

Maine↗
USGS2012

Uncovering the nonadiabatic response of geosynchronous electrons to geomagnetic disturbance

We describe an energy spectrum method for scaling electron integral flux, which is measured at a constant energy, to phase space density at a constant value of the first adiabatic invariant which removes much of the variation due to reversible adiabatic effects. Applying this method to nearly a solar cycle (1995 - 2006) of geosynchronous electron integral flux (E>2.0MeV) from the GOES satellites, we see that much of the diurnal variation in electron phase space density at constant energy can be removed by the transformation to phase space density at constant μ (4000 MeV/G). This allows us a clearer picture of underlying non-adiabatic electron population changes due to geomagnetic activity. Using scaled phase space density, we calculate the percentage of geomagnetic storms resulting in an increase, decrease or no change in geosynchronous electrons as 38%, 7%, and 55%, respectively. We also show examples of changes in the electron population that may be different than the unscaled fluxes alone suggest. These examples include sudden electron enhancements during storms which appear during the peak of negative Dst for μ-scaled phase space density, contrary to the slow increase seen during the recovery phase for unscaled phase space density for the same event.

Journal of Geophysical Research↗
USGS2008

Distributed energy balance modeling of South Cascade Glacier, Washington and assessment of model uncertainty

We have developed a physically based, distributed surface energy balance model to simulate glacier mass balance under meteorological and climatological forcing. Here we apply the model to estimate summer ablation on South Cascade Glacier, Washington, for the 2004 and 2005 mass balance seasons. To arrive at optimal mass balance simulations, we investigate and quantify model uncertainty associated with selecting from a range of physical parameter values that are not commonly measured in glaciological mass balance field studies. We optimize the performance of the model by varying values for atmospheric transmissivity, the albedo of surrounding topography, precipitation-elevation lapse rate, surface roughness for turbulent exchange of momentum, and snow albedo aging coefficient. Of these the snow aging parameter and precipitation lapse rates have the greatest influence on the modeled ablation. We examined model sensitivity to varying parameters by performing an additional 103 realizations with parameters randomly chosen over a ??5% range centered about the optimum values. The best fit suite of model parameters yielded a net balance of -1.69??0.38 m water equivalent (WE) for the 2004 water year and -2.10??0.30 m WE up to 11 September 2005. The 2004 result is within 3% of the measured value. These simulations account for 91% and 93% of the variance in measured ablation for the respective years. Copyright 2008 by the American Geophysical Union.

Journal of Geophysical Research F: Earth Surface↗
USGS1994

Dynamic growth of mixed-mode shear cracks

A pure mode II (in-plane) shear crack cannot propagate spontaneously at a speed between the Rayleigh and S -wave speeds, but a three-dimensional (3D) or two-dimensional (2D) mixed-mode shear crack can propagate in this range, being driven by the mode III (antiplane) component. Two different analytic solutions have been proposed for the mode II component in this case. The first is the solution valid for crack speed less than the Rayleigh speed. When applied above the Rayleigh speed, it predicts a negative stress intensity factor, which implies that energy is generated at the crack tip. Burridge proposed a second solution, which is continuous at the crack tip, but has a singularity in slip velocity at the Rayleigh wave. Spontaneous propagation of a mixed-mode rupture has been calculated with a slip-weakening friction law, in which the slip velocity vector is colinear with the total traction vector. Spontaneous trans-Rayleigh rupture speed has been found. The solution depends on the absolute stress level. The solution for the in-plane component appears to be a superposition of smeared-out versions of the two analytic solutions. The proportion of the first solution increases with increasing absolute stress. The amplitude of the negative in-plane traction pulse is less than the absolute final sliding traction, so that total in-plane traction does not reverse. The azimuth of the slip velocity vector varies rapidly between the onset of slip and the arrival of the Rayleigh wave. The variation is larger at smaller absolute stress.

Bulletin of the Seismological Society of America↗
USGS2008

A Regional Approach to Wildlife Monitoring Related to Energy Exploration and Development in Colorado

The U.S. Bureau of Land Management (BLM) is currently developing a National Monitoring Strategy that will guide efforts to create an efficient and effective process for monitoring land health by BLM. To inform the ongoing development of the national strategy, BLM selected two States (Colorado, Alaska) to serve as focal areas on which to base a flexible framework for developing monitoring programs that evaluate wildlife responses to energy development. We developed a three-phase monitoring plan to serve as a template and applied it to the design of a monitoring program for the Colorado focal area (White River and Glenwood Springs Field Offices of the BLM). Phase I is a synthesis and assessment of current conditions that capitalizes on existing but under used data sources. A key component is the use of existing habitat and landscape models to evaluate the cumulative effects of surface disturbance. Phase II is the data collection process that uses information provided in Phase I to refine management objectives and provide a linkage to management decisions. The linkage is established through targeted monitoring, adaptive management, and research. Phase III establishes priorities and strategies for regional and national monitoring, and facilitates coordination among other land management agencies and organizations. The three phases are designed to be flexible and complementary. The monitoring plan guides an iterative process that is performed incrementally, beginning with the highest-priority species and management issues, while building on lessons learned and coordination among administrative levels. The activities associated with each phase can be repeated or updated as new information, data, or tools become available. This allows the development of a monitoring program that expands gradually and allows for rapid implementation. A demonstration application of the three-phase monitoring plan was conducted for a study area encompassing five BLM field offices in Colorado: White River, Glenwood Springs, Kremmling, Grand Junction, and Little Snake. The overall study area was selected to encompass the primary distribution of sagebrush and greater sage-grouse (Centrocercus urophasianus) in Colorado and to provide a larger context for evaluating priority management issues of the White River and Glenwood Springs Field Offices. Within the study area, we selected an additional scale of analysis: the Roan Plateau, an area of increased energy development. We focused our demonstration project on the primary objectives identified by the BLM and other stakeholders: (1) How do we evaluate the cumulative effects of energy development and mitigation activities on species of management interest or concern? (2) How can cumulative effects, including direct and indirect effects, be quantified relative to natural variation? (3) How can we implement compliance and effectiveness monitoring to determine whether lease stipulations are met and restoration/mitigation goals are achieved? We targeted greater sage-grouse because this species was identified as a monitoring priority for the White River Field Office. We also evaluated landscape-level indices to address fragmentation resulting from surface disturbance. The primary purpose of this exercise was to highlight the types of analyses and approaches that could be used to evaluate energy development in an application of the three-phase framework. We provide examples of Phase I products that can be used to guide the refinement of management objectives, development of adaptive management and research frameworks, and planning activities in Phase II. Finally, we report on the BLM's National Sage-Grouse Habitat Conservation Strategy as an example of Phase III activities. The development of an effective monitoring program is a daunting task, and will be difficult to implement by the BLM independently due to the current work load of staff. However, the scientific expertise and experience for developing cr

Open-File Report↗
USGS2003

Atmospheric nitrogen deposition in the Rocky Mountains of Colorado and southern Wyoming - A review and new analysis of past study results

The Rocky Mountain region of Colorado and southern Wyoming receives as much as 7kgha-1yr-1 of atmospheric nitrogen (N) deposition, an amount that may have caused changes in aquatic and terrestrial life in otherwise pristine ecosystems. Results from published studies indicate a long-term increase in the rate of atmospheric N deposition during the 20th century, but data from the National Atmospheric Deposition Program and Clean Air Status and Trends Network show no region-wide increase during the past 2 decades. Nitrogen loads in atmospheric wet deposition have increased since the mid-1980s, however, at three high elevation (>3000m) sites east of the Continental Divide in the Front Range. Much of this increase is the result of increased ammonium (NH4+) concentrations in wet deposition. This suggests an increase in contributions from agricultural areas or from vehicles east of the Rocky Mountains and is consistent with the results of previous studies that have suggested a significant eastern source for atmospheric N deposition to the Front Range. The four sites with the highest NH4+ concentrations in wet deposition were among the six easternmost NADP sites, which is also consistent with a source to the east of the Rockies. This analysis found an increase in N loads in wet deposition at Niwot Ridge of only 0.013kgha-1yr-1, more than an order of magnitude less than previously reported for this site. This lower rate of increase results from application of the non-parametric Seasonal Kendall trend test to mean monthly data, which failed a test for normality, in contrast to linear regression, which was applied to mean annual data in a previous study. Current upward trends in population growth and energy use in Colorado and throughout the west suggest a need for continued monitoring of atmospheric deposition of N, and may reveal more widespread trends in N deposition in the future.

Atmospheric Environment↗
USGS2012

Acidification of Earth: An assessment across mechanisms and scales

In this review article, anthropogenic activities that cause acidification of Earth’s air, waters, and soils are examined. Although there are many mechanisms of acidification, the focus is on the major ones, including emissions from combustion of fossil fuels and smelting of ores, mining of coal and metal ores, and application of nitrogen fertilizer to soils, by elucidating the underlying biogeochemical reactions as well as assessing the magnitude of the effects. These widespread activities have resulted in (1) increased CO 2 concentration in the atmosphere that acidifies the oceans; (2) acidic atmospheric deposition that acidifies soils and bodies of freshwater; (3) acid mine drainage that acidifies bodies of freshwater and groundwaters; and (4) nitrification that acidifies soils. Although natural geochemical reactions of mineral weathering and ion exchange work to buffer acidification, the slow reaction rates or the limited abundance of reactant phases are overwhelmed by the onslaught of anthropogenic acid loading. Relatively recent modifications of resource extraction and usage in some regions of the world have begun to ameliorate local acidification, but expanding use of resources in other regions is causing environmental acidification in previously unnoticed places. World maps of coal consumption, Cu mining and smelting, and N fertilizer application are presented to demonstrate the complex spatial heterogeneity of resource consumption as well as the overlap in acidifying potential derived from distinctly different phenomena. Projected population increase by country over the next four decades indicates areas with the highest potential for acidification, so enabling anticipation and planning to offset or mitigate the deleterious environmental effects associated with these global shifts in the consumption of energy, mineral, and food resources.

Applied Geochemistry↗
USGS2015

Toward a mechanistic understanding of human-induced rapid environmental change: A case study linking energy development, avian nest predation, and predators

Demographic consequences of human-induced rapid environmental change (HIREC) have been widely documented for many populations. The mechanisms underlying such patterns, however, are rarely investigated and yet are critical to understand for effective conservation and management. We investigated the mechanisms underlying reduced avian nest survival with intensification of natural gas development, an increasing source of human-induced rapid environmental change globally. We tested the hypothesis that energy development increased the local activity of important nest predator species, thereby elevating nest predation rates. During 2011–2012, we surveyed predators and monitored 668 nests of Brewer's sparrows Spizella breweri (BRSP), sagebrush sparrows Artemisiospiza nevadensis (SASPs) and sage thrashers Oreoscoptes montanus (SATHs) breeding at twelve sites spanning a gradient of habitat loss from energy development in western Wyoming, USA. Nine species, representing four mammalian and three avian families, were video-recorded depredating eggs and nestlings. Important nest predator species differed across songbird species, despite similar nesting habitats. Approximately 75% of depredation events were by rodents. Consistent with our predictions, detections of most rodent nest predators increased with surrounding habitat loss due to natural gas development, which was associated with increased probability of nest predation for our three focal bird species. An altered nest predator assemblage was therefore at least partly responsible for elevated avian nest predation risk in areas with more surrounding energy development. Synthesis and applications . We demonstrate one mechanism, that is the local augmentation of predators, by which human-induced rapid environmental change can influence the demography of local populations. Given the accelerating trajectory of global energy demands, an important next step will be to understand why the activity and/or abundance of rodent predators increased with surrounding habitat loss from energy development activities.

Journal of Applied Ecology↗
USGS2013

Mobile laser scanning applied to the earth sciences

Lidar (light detection and ranging), a method by which the precise time of flight of emitted pulses of laser energy is measured and converted to distance for reflective targets, has helped scientists make topographic maps of Earth's surface at scales as fine as centimeters. These maps have allowed the discovery and analysis of myriad otherwise unstudied features, such as fault scarps, river channels, and even ancient ruins [Glennie et al., 2013b].

Eos, Transactions, American Geophysical Union↗
USGS2004

Application of near real-time radial semblance to locate the shallow magmatic conduit at Kilauea Volcano, Hawaii

Radial Semblance is applied to broadband seismic network data to provide source locations of Very-Long-Period (VLP) seismic energy in near real time. With an efficient algorithm and adequate network coverage, accurate source locations of VLP energy are derived to quickly locate the shallow magmatic conduit system at Kilauea Volcano, Hawaii. During a restart in magma flow following a brief pause in the current eruption, the shallow magmatic conduit is pressurized, resulting in elastic radiation from various parts of the conduit system. A steeply dipping distribution of VLP hypocenters outlines a region extending from sea level to about 550 m elevation below and just east of the Halemaumau Pit Crater. The distinct hypocenters suggest the shallow plumbing system beneath Halemaumau consists of a complex plexus of sills and dikes. An unconstrained location for a section of the conduit is also observed beneath the region between Kilauea Caldera and Kilauea Iki Crater.

Hawaii↗
USGS2020

Wind, sun, and wildlife: Do wind and solar energy development “short-circuit” conservation in the western United States?

Despite the trade-offs between renewable energy development, land use, humans, and wildlife, wind and solar development continues to transform the southwestern US into a green energy landscape. While renewable energy reduces carbon emissions and reliance on fossil fuels, many studies have emerged on the associated ecological and social impacts of this technology. Here, we review the current state of knowledge on the nexus between wildlife conservation and energy development in the western US since 2010. We revisit pertinent ecological concepts and questions presented in earlier reviews to assess how far the field has progressed in mitigating negative effects. Specifically, we ask, what density or design of development maximizes energy benefits while minimizing negative effects on wildlife, whether the results of previously-deficient before-after control-impact studies are now more readily-available, and ultimately, can the impacts of renewable energy development on wildlife be mitigated? We also provide a case study on the federally-protected Desert Tortoise, a conservation-reliant species in the Desert Southwest US, to highlight efforts to mitigate the negative effects of renewable energy development. Our review concludes that successful mitigation is possible via use of spatial decision support tools, applying novel wildlife deterrence and detection systems developed for existing installed facilities, and incorporating impact studies that provide managers with conservation metrics for evaluating different future development land-use scenarios.

Environmental Research Letters↗
USGS2021

New insights into organic matter accumulation from high-resolution geochemical analysis of a black shale: Middle and Upper Devonian Horn River Group, Canada

Organic matter (OM) accumulation in organic matter-rich mudstones, or black shales, is generally recognized to be controlled by combinations of bioproductivity, preservation, and dilution. However, specific triggers of OM deposition in these formations are commonly difficult to identify with geochemical proxies, in part because of feedbacks that cause geochemical proxies for these controls to vary synchronously. This apparent synchronicity is partly a function of sample spacing, commonly at decimeter to meter intervals, which may represent longer periods of time than is required for the development of feedbacks. Higher resolution data sets may be required to fully interpret OM accumulation. This study applies a novel combination of technologies to develop a high-resolution geochemical data set, integrating energy-dispersive X-ray fluorescence (EDXRF) and infrared imagery analyses, to record proxies for redox conditions, bioproductivity, and clastic and carbonate dilution in millimeter-resolution profiles of 133 core slabs from the Middle and Upper Devonian Horn River shale in the Western Canada Sedimentary Basin, which provides decadal-scale temporal resolution. A comparison to a more coarsely sampled data set from the same core results in substantially different interpretations of variations in bioproductivity, redox, and dilution proxies. Stratigraphic distributions of organic matter accumulation patterns (bioproductivity-control, siliciclastic/carbonate-dilution, and redox conditions-control) show that organic enrichment events were highly varied during deposition of the shale and were closely related to second- and third-order sea-level changes. High-resolution profiles indicate that bioproductivity was the predominant trigger for organic matter accumulation in a second-order highstand, particularly during deposition of third-order transgressive systems tracts. Organic matter accumulation was largely controlled by dilution from either carbonate or clastic sediments in a second-order lowstand. Bioproductivity-redox feedbacks developed on timescales of decades to centuries.

British Columbia, Northwest Territories↗
USGS1958

Selected topics of fluid mechanics

The fundamental equations of fluid mechanics are specific expressions of the principles of motion which are ascribed to Isaac Newton. Thus, the equations which form the framework of applied fluid mechanics or hydraulics are, in addition to the equation of continuity, the Newtonian equations of energy and momentum. These basic relationships are also the foundations of river hydraulics. The fundamental equations are developed in this report with sufficient rigor to support critical examinations of their applicability to most problems met by hydraulic engineers of the Water Resources Division of the United States Geological Survey. Physical concepts are emphasized, and mathematical procedures are the simplest consistent with the specific requirements of the derivations. In lieu of numerical examples, analogies, and alternative procedures, this treatment stresses a brief methodical exposition of the essential principles. An important objective of this report is to prepare the user to read the literature of the science. Thus, it begins With a basic vocabulary of technical symbols, terms, and concepts. Throughout, emphasis is placed on the language of modern fluid mechanics as it pertains to hydraulic engineering. The basic differential and integral equations of simple fluid motion are derived, and these equations are, in turn, used to describe the essential characteristics of hydrostatics and piezometry. The one-dimensional equations of continuity and motion are defined and are used to derive the general discharge equation. The flow net is described as a means of demonstrating significant characteristics of two-dimensional irrotational flow patterns. A typical flow net is examined in detail. The influence of fluid viscosity is described as an obstacle to the derivation of general, integral equations of motion. It is observed that the part played by viscosity is one which is usually dependent on experimental evaluation. It follows that the dimensionless ratios known as the Euler, Froude, Reynolds, Weber, and Cauchy numbers are defined as essential tools for interpreting and using experimental data. The derivations of the energy and momentum equations are treated in detail. One-dimensional equations for steady nonuniform flow are developed, and the restrictions applicable to the equations are emphasized. Conditions of uniform and gradually varied flow are discussed, and the origin of the Chezy equation is examined in relation to both the energy and the momentum equations. The inadequacy of all uniform-flow equations as a means of describing gradually varied flow is explained. Thus, one of the definitive problems of river hydraulics is analyzed in the light of present knowledge. This report is the outgrowth of a series of short schools conducted during the spring and summer of 1953 for engineers of the Surface Water Branch, Water Resources Division, U. S. Geological Survey. The topics considered are essentially the same as the topics selected for inclusion in the schools. However, in order that they might serve better as a guide and outline for informal study, the arrangement of the writer's original lecture notes has been considerably altered. The purpose of the report, like the purpose of the schools which inspired it, is to build a simple but strong framework of the fundamentals of fluid mechanics. It is believed that this framework is capable of supporting a detailed analysis of most of the practical problems met by the engineers of the Geological Survey. It is hoped that the least accomplishment of this work will be to inspire the reader with the confidence and desire to read more of the recent and current technical literature of modern fluid mechanics.

Water Supply Paper↗
USGS1993

Alternative solution model for the ternary carbonate system CaCO3 - MgCO3 - FeCO3 - I. A ternary Bragg-Williams ordering model

The minerals of the ternary carbonate system CaCO3 - MgCO3 - FeCO3 represent a complex series of solid solutions and ordering states. An understanding of those complexities requires a solution model that can both duplicate the subsolidus phase relationships and generate correct values for the activities. Such a solution model must account for the changes in the total energy of the system resulting from a change in the ordering state of the individual constituents. Various ordering models have been applied to binary carbonate systems, but no attempts have previously been made to model the ordering in the ternary system. This study derives a new set of equations that allow for the equilibrium degree of order to be calculated for a system involving three cations mixing on two sites, as in the case of the ternary carbonates. The method is based on the Bragg-Williams approach. From the degree of order, the mole fractions of the three cations in each of the two sites can be determined. Once the site occupancies have been established, a Margules-type mixing model can be used to determine the free energy of mixing in the solid solution and therefore the activities of the various components. ?? 1993 Springer-Verlag.

Physics and Chemistry of Minerals↗
USGS2018

A practical primer on geostatistics

Introduction The Challenge —Most geological phenomena are extraordinarily complex in their interrelationships and vast in their geographical extension. Ordinarily, engineers and geoscientists are faced with corporate or scientific requirements to properly prepare geological models with measurements involving a small fraction of the entire area or volume of interest. Exact description of a system such as an oil reservoir is neither feasible nor economically possible. The results are necessarily uncertain. Note that the uncertainty is not an intrinsic property of the systems; it is the result of incomplete knowledge by the observer. The Aim of Geostatistics —The main objective of geostatistics is the characterization of spatial systems that are incompletely known, systems that are common in geology. A key difference from classical statistics is that geostatistics uses the sampling location of every measurement. Unless the measurements show spatial correlation, the application of geostatistics is pointless. Ordinarily the need for additional knowledge goes beyond a few points, which explains the display of results graphically as fishnet plots, block diagrams, and maps. Geostatistical Methods —Geostatistics is a collection of numerical techniques for the characterization of spatial attributes using primarily two tools: probabilistic models, which are used for spatial data in a manner similar to the way in which time-series analysis characterizes temporal data, or pattern recognition techniques. The probabilistic models are used as a way to handle uncertainty in results away from sampling locations, making a radical departure from alternative approaches like inverse distance estimation methods. Differences with Time Series —On dealing with time-series analysis, users frequently concentrate their attention on extrapolations for making forecasts. Although users of geostatistics may be interested in extrapolation, the methods work at their best interpolating. This simple difference has significant methodological implications. Historical Remarks —As a discipline, geostatistics was firmly established in the 1960s by the French engineer Georges Matheron, who was interested in the appraisal of ore reserves in mining. Geostatistics did not develop overnight. Like other disciplines, it has built on previous results, many of which were formulated with different objectives in various fields. Pioneers —Seminal ideas conceptually related to what today we call geostatistics or spatial statistics are found in the work of several pioneers, including: 1940s: A.N. Kolmogorov in turbulent flow and N. Wiener in stochastic processing; 1950s: D. Krige in mining; 1960s: B. Mathern in forestry and L.S. Gandin in meteorology Calculations —Serious applications of geostatistics require the use of digital computers. Although for most geostatistical techniques rudimentary implementation from scratch is fairly straightforward, coding programs from scratch is recommended only as part of a practice that may help users to gain a better grasp of the formulations. Software —For professional work, the reader should employ software packages that have been thoroughly tested to handle any sampling scheme, that run as efficiently as possible, and that offer graphic capabilities for the analysis and display of results. This primer employs primarily the package Stanford Geomodeling Software (SGeMS) - recently developed at the Energy Resources Engineering Department at Stanford University - as a way to show how to obtain results practically. This applied side of the primer should not be interpreted as the notes being a manual for the use of SGeMS. The main objective of the primer is to help the reader gain an understanding of the fundamental concepts and tools in geostatistics. Organization of the Primer —The chapters of greatest importance are those covering kriging and simulation. All other materials are peripheral and are included for better comprehension of these main geostatistical modeling tools. The choice of kriging versus simulation is often a big puzzle to the uninitiated, let alone the different variants of both of them. Chapters 14, 18, and 19 are intended to shed light on those subjects. The critical aspect of assessing and modeling spatial correlation is covered in chapter 7. Chapters 2 and 3 review relevant concepts in classical statistics. Course Objectives —This course offers stochastic solutions to common problems in the characterization of complex geological systems. At the end of the course, participants should have: an understanding of the theoretical foundations of geostatistics; a good grasp of its possibilities and limitations; and reasonable familiarity with the SGeMS software, thus opening the possibility of practically applying geostatistics.

Open-File Report↗
USGS2025

Applying U-Th disequilbrium for dating siliceous sinters

Continental hydrothermal systems are critical avenues for the crustal transport of heat and mass captured for geothermal energy and mineral exploration. Thus, understanding their temporal evolution and longevity is important for resource characterization. Deposits of microlaminated siliceous sinter, common surface expressions of high temperature reservoirs (> 170 °C), have the potential to trace hydrothermal histories. Geothermal reservoirs are often located within uranium-bearing silicic volcanic rock where subsurface fluid-rock interactions extract U into hydrothermal fluids. U incorporated in the surface sinter deposit has the potential to provide a U— Th disequilibrium dating option. We focus on samples from El Tatio geyser field in the Altiplano of northern Chile, the largest geothermal system in the Andes. Our resulting 230 Th/U ages, along with the water and deposit elemental compositions, suggest concentrations of U and Th vary predictably along the sinter apron. While distal facies containing the highest U concentrations (> 50 μg/g) are least affected by detrital Th corrections, they can display suspected open-system behavior. In contrast, more medial facies, where bacterial mats and other porous textures are co mmonly concentrated, have only trace amounts of U (< 0.1 μg/g), which leads to unreliable or geologically improbable dates. Proximal facies tend to date most consistently. By comparing existing 14 C ages with 230 Th/U results, 230 Th/U ages tend to be younger than the 14 C ages, supporting the presence of a 14 C-dead carbon influence. New data confirm that the onset of geothermal activity at El Tatio goes back to the late Pleistocene.

Altiplano, El Tatio geyser field↗
USGS2022

Multidisciplinary constraints on the thermal-chemical boundary between Earth's core and mantle

Heat flux from the core to the mantle provides driving energy for mantle convection thus powering plate tectonics, and contributes a significant fraction of the geothermal heat budget. Indirect estimates of core-mantle boundary heat flow are typically based on petrological evidence of mantle temperature, interpretations of temperatures indicated by seismic travel times, experimental measurements of mineral melting points, physical mantle convection models, or physical core convection models. However, previous estimates have not consistently integrated these lines of evidence. In this work, an interdisciplinary analysis is applied to co-constrain core-mantle boundary heat flow and test the thermal boundary layer (TBL) theory. The concurrence of TBL models, energy balance to support geomagnetism, seismology, and review of petrologic evidence for historic mantle temperatures supports Q CMB ∼15 TW, with all except geomagnetism supporting as high as ∼20 TW. These values provide a tighter constraint on core heat flux relative to previous work. Our work describes the seismic properties consistent with a TBL, and supports a long-lived basal mantle molten layer through much of Earth's history.

Geochemistry, Geophysics, Geosystems↗