Earth Science Applications Research Articles

Scenario Reduction Applied to Geostatistical Simulations

Having a large number of geostatistical simulations of a mineral or petroleum deposit provides a better idea of its upside potential and downside risk; however, large numbers of simulated realizations of a deposit may pose computational difficulties in subsequent decision-making phases. Hence, depending on the specific case, there can be a need to select a representative subset of conditionally simulated deposit realizations. This paper examines and extends an approach developed by the stochastic optimization community based on stochastic mathematical programming with recourse and is discussed here in the context of mineral deposits while it is possibly suitable for other earth science applications. The approach is based on measuring the “distance” between simulations and the introduced distance measure between simulated realizations of a mineral deposit is based on the metal above a given set of cutoff grades while a pre-existing mine design is available. The approach is tested on 100 simulations of the Walker Lake data with promising results.

PHOTOGRAMMETRY AND LASER SCANNING FOR THE EARTH SCIENCESWORKING GROUP V6

Abstract. With the UK gaining responsibility for Commission V at the Beijing Congress in 2008, there was an opportunity to create a new working group focusing on earth science applications at close range. The earth science community has had a long tradition of using close range photogrammetry, and more recently laser scanning, and such opportunities have not been fully recognised by ISPRS in the past. Formation of a new ISPRS Working Group helps to bridge this gap and promotes the skills of ISPRS members more widely. The purpose of this paper is to justify the creation of Working Group V6 and identify some of the activities conducted over the last four years. In particular, reference will be made to the various technical sessions which have been organised and supported across the world, the first resulting in a Special Issue of The Photogrammetric Record published in September 2010. In addition, Working Group V6 has been responsible for the creation of two freely available guidance documents entitled "tips for the effective use of digital close range photogrammetry and terrestrial laser scanning". The former focuses on close range digital photogrammetry and has developed through several iterations with input from both academic and industrial users from around the world. For this reason it should be of distinct value to new and perhaps non-expert users interested in using photogrammetry for earth science applications. The paper includes a discussion which considers whether the initial four years of activity have been successful. A superficial assessment based upon the number of members attracted worldwide would suggest that this has indeed been the case. A deeper comparison between proposed activities and those actually achieved suggest some discrepancy, which is perhaps inevitable as Working Group Officers clearly have other responsibilities. However, examination of papers published in the earth surface journals reveal high incidence of photogrammetry and laser scanning appearing in recent work. This should encourage members of Working Group V6 in future activities and collaborations.

Small unmanned aircraft systems for remote sensing and Earth science research

To understand and predict Earth‐surface dynamics, scientists often rely on access to the latest remote sensing data. Over the past several decades, considerable progress has been made in the development of specialized Earth observation sensors for measuring a wide range of processes and features. Comparatively little progress has been made, however, in the development of new platforms upon which these sensors can be deployed. Conventional platforms are still almost exclusively restricted to piloted aircraft and satellites. For many Earth science research questions and applications these platforms do not yet have the resolution or operational flexibility to provide answers affordably. The most effective remote sensing data match the spatiotemporal scale of the process or feature of interest. An emerging technology comprising unmanned aircraft systems (UAS), also known as unmanned aerial vehicles (UAV), is poised to offer a viable alternative to conventional platforms for acquiring high‐resolution remote sensing data with increased operational flexibility, lower cost, and greater versatility (Figure 1).

An atom counter for measuring 81Kr and 85Kr in environmental samples

Due to its simple production and transport processes in the terrestrial environment, the long-lived noble-gas isotope 81Kr is the ideal tracer for old water and ice in the age range of 105–106 years, a range beyond the reach of 14C. 81Kr-dating, a concept pursued in the past four decades by numerous laboratories employing a variety of techniques, is now available for the first time to the earth science community at large. This is made possible by the development of ATTA-3, an efficient and selective atom counter based on the Atom Trap Trace Analysis method and capable of measuring both 81Kr/Kr and 85Kr/Kr ratios of environmental samples in the range of 10−14–10−10. The instrument was calibrated with 12 samples whose 85Kr/Kr ratios were independently measured using Low Level Decay Counting, including six samples that were measured in a blind arrangement. Compared to the previously reported ATTA-2 instrument, the counting rates of ATTA-3 are higher by two orders of magnitude and the required sample size lower by one order of magnitude. For 81Kr-dating in the age range of 150–1500kyr, the required sample size is 5–10μL STP of krypton gas, which can be extracted from approximately 100–200kg of water or 40–80kg of ice. Moreover, a laser-induced quenching scheme was developed to enable measurements of both the rare 81,85Kr and the abundant 83Kr, whose isotopic abundances differ by 11 orders of magnitude. This scheme allows ATTA-3 to directly determine 81Kr/Kr and 85Kr/Kr ratios without other supplemental measurements. Combining the significant reduction in sample size with numerous advances in the measurement procedure, ATTA-3 represents the state-of-the-art instrument for routine analysis of these rare noble gas tracers in a wide range of earth science applications.

Solid-state NMR analysis of Fe-bearing minerals: implications and applications for Earth sciences

Solid-state nuclear magnetic resonance (NMR) is commonly used in the study of solid structures in Earth sciences; however, it suffers from the impossibility to analyse solid structures containing ferromagnetic particles or paramagnetic elements. We have attempted to decipher the effect of (1) ferromagnetic particles (Fe- Ti-bearing mineral phase) and (2) paramagnetic elements (Fe, Cr, Ni) on the signature of diamagnetic elements ( 1 H, 29 Si, 27 Al) in natural clino- and orthopyroxene from peridotite. The results obtained on these natural minerals have been compared with results obtained for a synthetic mixture of kaolinite + magnetite. The 29 Si, 27 Al Echo-MAS NMR spectra acquired for pyroxenes show signatures that are consistent with previous data. Weak additional anomalous peaks are detected in 29 Si spectra. Both elements show a broadening in the spectra, which is commonly observed when paramagnetic elements are present. The perturbations induced by paramagnetic elements are the result of several interactions: (1) pseudocontact shift and (2) Fermi contact shift. 1 H Echo-MAS NMR spectra for pyroxenes are dramatically affected by the presence of ferromagnetic impurities and are chemical shifted beyond the known range for 1 H in solids. The effect of ferromagnetic particles is also confirmed by the results obtained for the kaolinite + magnetite mixture showing increasing perturbation with increasing magnetite content. We suggest that the presence of paramagnetic elements and/or ferromagnetic particles is only weakly affecting the 29 Si and 27 Al NMR spectra. Thus, new perspectives on the use of NMR technique for mineralogy and geochemistry are envisaged.

Improved 36Cl performance at the ASTER HVE 5 MV accelerator mass spectrometer national facility

The HVE 5MV ASTER AMS national facility at CEREGE was accepted in 2007. Since then we have continued to optimize performance for 36Cl. Cl-36 analyses use AgCl, a Cs negative ion sputter source, Ar stripping to +5 in the terminal of the Tandetron™ accelerator at 5MV and a silicon nitride post-acceleration stripper foil to enhance suppression of 36S relative to 36Cl. The major challenges to obtaining the desired performance for Earth science applications are ion source memory, mass fractionation effects, 36S isobar suppression and sensitivity. Redesign of the SO110 ion source by HVE to change the size of the aperture and the shape of cathode significantly reduced ion source memory to less than ∼0.1%, a level that can be compensated for by matching standards to samples. We observe small systematic drifts in 35Cl/37Cl ratios over time, the source of which is not yet determined. Measurement of standards indicates that this effect limits the precision of 35Cl/37Cl ratio determination to about 2%. 36S is suppressed in several ways. First, the sample chemistry has been designed to reduce S to low levels. Second, cathodes are constructed of low-S nickel, enabling direct target loading without the use of AgBr pre-packing. Third, a post-acceleration Si3N4 stripper foil differentially absorbs energy from 36Cl and 36S. A subsequent electrostatic deflector is then able to suppress 36S by a factor of ∼240 relative to 36Cl. Differential energy loss in the detector further suppresses 36S by about 10−4, for an overall suppression factor of 4×10−7. 36S count rates are typically equivalent to a background 36Cl/Cl of ∼10−15. At typical 35Cl currents of ∼20μA Cl5+ samples with 36Cl/35Cl of 6×10−14 can be measured to ±5% statistical uncertainty with 1h of analysis time. Typical machine blanks have 36Cl/Cl ∼2×10−15.

Global geopotential models from Satellite Laser Ranging data with geophysical applications: A review

The launch of artificial satellites (as early as in 1957), specifically the launch of the first laser tracked satellite, Beacon-B, in 1964, has provided data sets which have allowed researchers to probe the long to medium components of the gravitational field of the Earth. In particular, observational data recorded at satellite laser ranging tracking stations have since been used to develop models that quantify the global long-wavelength and medium-wavelength gravity field of the Earth. Currently, literature reviewing gravity field models with geophysical applications is scarce and not up to date. The most recent review paper was published more than a decade ago. In the interim, there has been an unprecedented increase in gravity field modelling, which can be attributed to the deployment of new and dedicated satellite missions. As a result, a number of existing geopotential models have been improved and new models have been developed. Each of these models differs in accuracy and spatial-temporal scale. This review extends the earlier review of gravity field models, by incorporating up-to-date research efforts in geopotential modelling with geophysical applications in oceanography, hydrology, geodesy and solid Earth science.

Google Earth as a virtual globe tool for Earth science applications at the global scale: progress and perspectives

Research on global environmental change requires new data processing and analysis tools that can integrate heterogeneous geospatial data from real-time in situ measurement, remote sensing (RS) and geographic information systems (GISs) at the global scale. The rapid growth of virtual globes for global geospatial information management and display holds promise to meet such a requirement. Virtual globes, Google Earth in particular, enable scientists around the world to communicate their data and research findings in an intuitive three-dimensional (3D) global perspective. Different from traditional GIS, virtual globes are low cost and easy to use in data collection, exploration and visualization. Since 2005, a considerable number of papers have been published in peer-reviewed journals and proceedings from a variety of disciplines. In this review, we examine the development and applications of Google Earth and highlight its merits and limitations for Earth science studies at the global scale. Most limitations are not unique to Google Earth, but to all virtual globe products. Several recent efforts to increase the functionalities in virtual globes for studies at the global scale are introduced. The power of virtual globes in their current generations is mostly restricted to functions as a ‘geobrowser’; a better virtual globe tool for Earth science and global environmental change studies is described.

Earth science applications of ICESat/GLAS: a review

The Ice, Cloud, and Land Elevation Satellite (ICESat) completed 19 successful campaigns for Earth observation missions following its launch in 2003. The Geoscience Laser Altimeter System (GLAS) on board ICESat provided data of high quality with unprecedented accuracy over the globe. The three laser sensors of GLAS acquired a large volume of data between 2003 and 2009. These data were used widely to detect changes in Greenland and Antarctic ice sheets and to determine forest heights, sea-ice freeboard heights and the distribution of cloud and aerosols. Here, we provide a review of these applications, describe the methodology involved in GLAS data processing and summarize some of the challenges to make better use of GLAS data. Other applications, including ice-sheet slope extraction, distinguishing between water, bare land, urban building and high forest, urban building height extraction, changes in glaciers and ice caps and water levels in lakes are discussed more briefly.

Performances of 800 nm femtosecond laser ablation on natural and synthetic quartz

A commercial femtosecond laser system operating at its fundamental wavelength (λ = 800 nm, near Infra-Red) was used to ablate both synthetic and natural quartz on polished and unpolished surfaces. Ablation rates and maximum depths were determined using two distinct optical setups: a 25 mm focal length Cassegrain reflecting objective, and a 50 mm focal length convergent coated lens. All samples were ablated with the same laser beam at E = 1 mJ, τ = 60 fs, f = 5 Hz and N = 10–8000 shots. The depth of ablation craters obtained with the lens shows a linear increase with shot number N up to N = 2000 shots. Then the depth increases much less with N and reaches a plateau above N = 3000 shots. Maximum depth was close to 1300 μm for N = 3000 shots. Using the reflecting objective, ablation rate starts from 0.42 μm/shot and decreases rapidly to 0.02 μm/shot at a maximum depth of 350 μm for N =1500 shots. Ablation thresholds ( F th) were calculated for 1 and 10 consecutive shots with energy increasing from E = 0.1–2 mJ/pulse. Threshold values varies from F th=0.1 J.cm−2 (unpolished, 10 shots) to F th = 2.9 J.cm−2 (polished, single shot). The energy penetration of IR-femtosecond laser pulses in quartz has been calculated at l = 271 nm. The low absorption of IR wavelengths in quartz affects the ablation efficiency in the first shots. The associated non-linear effects are visible on a crater FIB foil observed with TEM as progressive high-pressure photomechanical damage developing under the ablation pit. The present study emphasizes the potential of IR-femtosecond laser for ablation of highly transparent material, and provides reliable data for LA-ICP-MS applications in earth sciences.

J. P. Smol and E. F. Stoermer (eds): The diatoms: applications for the environmental and earth sciences

J. P. Smol and E. F. Stoermer (eds): The diatoms: applications for the environmental and earth sciences

Assessing the accuracy of sequential Gaussian simulation and cosimulation

Sequential Gaussian simulation is widespread in Earth Science applications to quantify the uncertainty about regionalized properties. Its practical implementation relies on the screen effect approximation in order to determine the successive conditional distributions by considering only the information available in the neighborhood of the target location. A methodology is presented to assess the accuracy of sequential Gaussian simulation, by calculating the theoretical moments (expectation and variance–covariance matrix) of the simulated random vector and comparing them with the moments of the underlying model. The methodology can be applied in both the conditional and non-conditional contexts, as well as for univariate or multivariate simulation. It is helpful to determine appropriate implementation parameters, in particular about the visiting sequence and the design of the moving neighborhood for selecting relevant conditioning information, prior to performing simulation.

Modeling the height of young forests regenerating from recent disturbances in Mississippi using Landsat and ICESat data

Many forestry and earth science applications require spatially detailed forest height data sets. Among the various remote sensing technologies, lidar offers the most potential for obtaining reliable height measurement. However, existing and planned spaceborne lidar systems do not have the capability to produce spatially contiguous, fine resolution forest height maps over large areas. This paper describes a Landsat–lidar fusion approach for modeling the height of young forests by integrating historical Landsat observations with lidar data acquired by the Geoscience Laser Altimeter System (GLAS) instrument onboard the Ice, Cloud, and land Elevation (ICESat) satellite. In this approach, “young” forests refer to forests reestablished following recent disturbances mapped using Landsat time-series stacks (LTSS) and a vegetation change tracker (VCT) algorithm. The GLAS lidar data is used to retrieve forest height at sample locations represented by the footprints of the lidar data. These samples are used to establish relationships between lidar-based forest height measurements and LTSS–VCT disturbance products. The height of “young” forest is then mapped based on the derived relationships and the LTSS–VCT disturbance products. This approach was developed and tested over the state of Mississippi. Of the various models evaluated, a regression tree model predicting forest height from age since disturbance and three cumulative indices produced by the LTSS–VCT method yielded the lowest cross validation error. The R 2 and root mean square difference (RMSD) between predicted and GLAS-based height measurements were 0.91 and 1.97 m, respectively. Predictions of this model had much higher errors than indicated by cross validation analysis when evaluated using field plot data collected through the Forest Inventory and Analysis Program of USDA Forest Service. Much of these errors were due to a lack of separation between stand clearing and non-stand clearing disturbances in current LTSS–VCT products and difficulty in deriving reliable forest height measurements using GLAS samples when terrain relief was present within their footprints. In addition, a systematic underestimation of about 5 m by the developed model was also observed, half of which could be explained by forest growth that occurred between field measurement year and model target year. The remaining difference suggests that tree height measurements derived using waveform lidar data could be significantly underestimated, especially for young pine forests. Options for improving the height modeling approach developed in this study were discussed.

Validation Techniques for Geological Patterns Simulations Based on Variogram and Multiple-Point Statistics

Traditional simulation methods that are based on some form of kriging are not sensitive to the presence of strings of connectivity of low or high values. They are particularly inappropriate in many earth sciences applications, where the geological structures to be simulated are curvilinear. In such cases, techniques allowing the reproduction of multiple-point statistics are required. The aim of this paper is to point out the advantages of integrating such multiple-statistics in a model in order to allow shape reproduction, as well as heterogeneity structures, of complex geological patterns to emerge. A comparison between a traditional variogram-based simulation algorithm, such as the sequential indicator simulation, and a multiple-point statistics algorithm (e.g., the single normal equation simulation) is presented. In particular, it is shown that the spatial distribution of limestone with meandering channels in Lecce, Italy is better reproduced by using the latter algorithm. The strengths of this study are, first, the use of a training image that is not a fluvial system and, more importantly, the quantitative comparison between the two algorithms. The paper focuses on different metrics that facilitate the comparison of the methods used for limestone spatial distribution simulation: both objective measures of similarity of facies realizations and high-order spatial cumulants based on different third- and fourth-order spatial templates are considered.

On Precision Kinematic Accelerations for Airborne Gravimetry

On Precision Kinematic Accelerations for Airborne GravimetryAdvances in accelerometer technology promise many orders of magnitude improvement in sensitivity; which, consequently, also suggest progress in Earth Science applications, such as through new airborne gravimetric systems. However, a new capability for one sensor then usually demands commensurate requirements from auxiliary sensors in order to realize its full potential. Specifically, airborne gravimetry would benefit from improved inertial accelerometry only if the kinematic acceleration derived from vehicle tracking or positioning is equally precise. The latter is investigated in this study to determine the limits in precision due to errors in modeling the numerical derivative and due to errors in the positions, themselves. Simulations with actual aircraft trajectories show that the kinematic acceleration using current positioning capability (that is, GPS or similar satellite navigation systems) can be determined to an accuracy at the sub-milligal level only with sufficient smoothing over intervals of 60 s or longer. The effects of position error still dominate over the model error, and both are many orders of magnitude greater than the predicted precision of state-of-the-art accelerometry. This suggests that airborne gravity field determination likely will profit more if the advances in inertial sensor technology are directed toward gravity gradiometry.

Description of an aerodynamic levitation apparatus with applications in Earth sciences

BackgroundIn aerodynamic levitation, solids and liquids are floated in a vertical gas stream. In combination with CO2-laser heating, containerless melting at high temperature of oxides and silicates is possible. We apply aerodynamic levitation to bulk rocks in preparation for microchemical analyses, and for evaporation and reduction experiments.ResultsLiquid silicate droplets (~2 mm) were maintained stable in levitation using a nozzle with a 0.8 mm bore and an opening angle of 60°. The gas flow was ~250 ml min-1. Rock powders were melted and homogenized for microchemcial analyses. Laser melting produced chemically homogeneous glass spheres. Only highly (e.g. H2O) and moderately volatile components (Na, K) were partially lost. The composition of evaporated materials was determined by directly combining levitation and inductively coupled plasma mass spectrometry. It is shown that the evaporated material is composed of Na > K >> Si. Levitation of metal oxide-rich material in a mixture of H2 and Ar resulted in the exsolution of liquid metal.ConclusionsLevitation melting is a rapid technique or for the preparation of bulk rock powders for major, minor and trace element analysis. With exception of moderately volatile elements Na and K, bulk rock analyses can be performed with an uncertainty of ± 5% relative. The technique has great potential for the quantitative determination of evaporated materials from silicate melts. Reduction of oxides to metal is a means for the extraction and analysis of siderophile elements from silicates and can be used to better understand the origin of chondritic metal.

Representation and transfer of geological knowledge in IT-supported projects

Information Technologies (IT) have the capability to improve the clearness and the usefulness of scientific information, and related applications in earth sciences could allow to make geological data more sharable among different users. This paper illustrates an approach to represent the knowledge paths followed by field geologists involved in assessment and description of complex structuralgeological settings and processes, through the use of specific IT applications. The proposed approach is based on three working steps: i) building of a conceptual map (cMap) that defines the project approach to the study matter, drives the acquisition of field data and gives rules for GIS representation of interpreted geological features (prefieldwork stage); ii) capturing of data directly in the field by means of digital devices, in a way suitable to retrace the acquisition data steps and to separate the observed features from the interpreted ones (fieldwork stage); iii) management of information in relational GIS databases by means of «geological» metadata that could define the «weight» of data and explain the adopted interpretations (postfieldwork stage). An application of these working steps is given in a case study of the stability evaluation of a quarry rock mass. In the example, different conceptualizations and investigation methods are combined so that they are sharable among field geologists and engineering geologists in order to allow crucial decision in characterization and modelling of the quarry slope. Besides, ITbased approaches should get retraceability of decisional processes possible

A new method for quantitative petrography based on image processing of chemical element maps: Part I. Mineral mapping applied to compacted bentonites

Most natural rocks or engineered materials display a multi-scale heterogeneity ranging from the nanometer to the centimeter. Their spatial textural heterogeneity can be approached from chemical element maps acquired using various techniques (SEM, EPMA, SXAM, synchrotron μ-XRF, TEM), depending on the chosen magnification. Chemical map processing that yields quantitative petrographic information is improved here according to newly developed mineral thresholding methods that accommodate mixtures and solid solutions. The complex case of an MX80 compacted bentonite is used as a test case. The 14 major chemical elements of this sample were mapped using an electron probe microanalyzer, and chemical map processing yielded a quantitative map of the 18 mineral species of bentonite with a spatial resolution of a few micrometers. The textural heterogeneity of the solid part of the sample is thus visualized and quantified on an area ranging between 0.1-1 cm 2 . The method also provides a complete modal analysis of the sample. The methodology is expected to have broad applications in Earth and materials sciences.

Profile Soil Moisture Across Spatial Scales Under Different Hydroclimatic Conditions

Soil moisture statistics across spatial scales have been considered critical to various Earth Science applications. Soil moisture measurements are available only at very fine scale (at in situ monitoring facilities) or at very coarse scale (by satellite retrieval) on a regular basis. These measurements have extremely contrasting features in terms of temporal and spatial scales. Although no immediate technological solution is available to bridge the gap in real measurements at the intermediate support scales that can be substantiated, an alternative scaled representation of soil moisture using a newly developed modeling approach is proposed here. In this article, we investigated the characteristic features of profile soil moisture (at 1-, 10-, and 50-cm depths) statistics at different spatial resolutions (i.e., ∼8, ∼25, and ∼60 km) modeled from scaled geophysical parameters and atmospheric forcings. We used Aqua satellite-based Advanced Microwave Scanning Radiometer (AMSR-E)-estimated soil moisture and local scale soil parameters to derive upscaled soil parameters for soil moisture modeling at the desired spatial scale. The soil moisture statistics including probability density functions (PDF) for multiple spatial resolutions and depths across the soil profile are presented for three contrasting hydroclimatic regions across the United States. These results could provide region-specific conditions for land-atmosphere interaction models and root zone soil moisture assimilation for various hydrologic and environmental applications.

An overlapping additive Schwarz preconditioner for interpolation on the unit sphere with spherical radial basis functions

The problem of interpolation of scattered data on the unit sphere has many applications in geodesy and Earth science in which the sphere is taken as a model for the Earth. Spherical radial basis functions provide a convenient tool for constructing the interpolant. However, the underlying linear systems tend to be ill-conditioned. In this paper, we present an additive Schwarz preconditioner for accelerating the solution process. An estimate for the condition number of the preconditioned system will be discussed. Numerical experiments using MAGSAT satellite data will be presented.