Volatile element signatures in the mantles of Earth,Moon, and Mars: Core formation fingerprints from Bi,Cd, In,and Sn     

K. Righter  K. Pando  N. Marin  D. K. Ross  M. Righter  L. Danielson  T. J. Lapen  C. Lee 《Meteoritics & planetary science》2018,53(2):284-305

Volatile element concentrations in planets are controlled by many factors such as precursor material composition, core formation, differentiation, magma ocean and magmatic degassing, and late accretionary processes. To better constrain the role of core formation, we report new experiments defining the effect of temperature, and metallic S and C content on the metal-silicate partition coefficient (or D(i) metal/silicate) of the volatile siderophile elements (VSE) Bi, Cd, In, and Sn. Additionally, the effect of pressure on metal-silicate partitioning between 1 and 3 GPa, and olivine-melt partitioning at 1 GPa have been studied for Bi, Cd, In, Sn, As, Sb, and Ge. Temperature clearly causes a decrease in D(i) metal/silicate for all elements. Sulfur and C have a large influence on activity coefficients in metallic Fe liquids, with C causing a decrease in D(i) metal/silicate, and S causing an increase. Pressure has only a small effect on D(Cd), D(In), and D(Ge) metal/silicate. Depletions of Bi, Cd, In, and Sn in the terrestrial and Martian mantles are consistent with high PT core formation and metal-silicate equilibrium at the high temperatures indicated by previous studies. A late Hadean matte would influence Bi the most, due to its high D(sulfide/silicate) ~2000, but segregation of a matte would only reduce the mantle Bi content by 50%; all other less chalcophile elements (e.g., Sn, In, and Cd) would be minimally affected. The lunar depletions of highly VSE require a combination of core formation and an additional depletion mechanism—most likely the Moon-forming giant impact, or lunar magma ocean degassing.  相似文献   

Pedestal crater heights on Mars: A proxy for the thicknesses of past, ice-rich, Amazonian deposits     

Seth J. Kadish  James W. Head  Nadine G. Barlow 《Icarus》2010,210(1):92-101

Mid-latitude pedestal craters on Mars offer crucial insights into the timing and extent of widespread ice-rich deposits during the Amazonian period. Our previous comprehensive analysis of pedestal craters strongly supports a climate-related formation mechanism, whereby pedestals result from impacts into ice-rich material at mid latitudes during periods of higher obliquity. The ice from this target deposit later sublimates due to obliquity changes, but is preserved beneath the protective cover of the armored pedestal. As such, the heights of pedestals act as a proxy for the thicknesses of the paleodeposits. In this analysis, our measurement of 2300 pedestal heights shows that although pedestals can reach up to ∼260 m in height, ∼82% are shorter than 60 m and only ∼2% are taller than 100 m. Mean pedestal heights are 48.0 m in the northern mid latitudes and 40.4 m in the southern mid latitudes, with the tallest pedestals located in Utopia Planitia, Acidalia Planitia and Malea Planum. We use these data in conjunction with prior climate model results to identify both regional and global trends regarding ice accumulation during obliquity excursions. Our data provide evidence for multiple episodes of emplacement and removal of the mid-latitude ice-rich deposit based on stratigraphic relationships between pedestal craters and the close proximity of pedestals with significantly different heights.  相似文献   

Field Demonstrations Using the Waterloo Ground Water Profiler   总被引：3，自引：0，他引：3  

Seth E. Pitkin  John A. Cherry  Robert A. Ingleton  Mette Broholm 《Ground Water Monitoring & Remediation》1999,19(2):122-131

Use of direct-push sampling tools fur rapid investigations of contaminated sites has proliferated in the past several years. A direct-push device, referred to as a ground water sampling profiler, was recently developed at the University of Waterloo. This tool differs from oilier direct-push tools in that point samples are collected at multiple depths in the same hole without retrieving, decontaminating, and re-driving the tool alter each sampling event. The collection of point samples, rather than samples from a longer screened interval, allows an exceptional level of detail to be generated about the vertical distribution of contamination from each hole. The benefits of acquiring this level of detail arc contingent on minimization of vertical cross contamination of samples caused by drag down from high concentration zones into underlying low concentration zones. In a detailed study of chlorinated solvent plumes in sandy aquifers, we found that drag down using the profiler is minimal or non-detectable even when the tool is driven through high concentration zones of dissolved chlorinated solvent contamination. Chlorinated solvent concentrations, primarily PCE and TCE at or below a detection limit of 1 μg/L, were obtained directly beneath plumes with maximum concentrations up to thousands of μg/L. Minimal drag down, on the order of a few μg/L to 20 μg/L, may have been observed below chlorinated solvent concentrations of several tens of thousands to hundreds of thousands of μg/L. Drag down through DNAPL zones was not evaluated.  相似文献   

Assessing the relevance of wetlands for storm surge protection: a coupled hydrodynamic and geospatial framework     

Jana Haddad  Seth Lawler  Celso M. Ferreira 《Natural Hazards》2016,80(2):839-861

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Changing climate extremes in the Northeast United States: observations and projections from CMIP5   总被引：1，自引：0，他引：1  

Jeanne M. Thibeault  Anji Seth 《Climatic change》2014,127(2):273-287

Climate extremes indices are evaluated for the northeast United States and adjacent Canada (Northeast) using gridded observations and twenty-three CMIP5 coupled models. Previous results have demonstrated observed increases in warm and wet extremes and decreases in cold extremes, consistent with changes expected in a warming world. Here, a significant shift is found in the distribution of observed total annual precipitation over 1981-2010. In addition, significant positive trends are seen in all observed wet precipitation indices over 1951-2010. For the Northeast region, CMIP5 models project significant shifts in the distributions of most temperature and precipitation indices by 2041-2070. By the late century, the coldest (driest) future extremes are projected to be warmer (wetter) than the warmest (wettest) extremes at present. The multimodel interquartile range compares well with observations, providing a measure of confidence in the projections in this region. Spatial analysis suggests that the largest increases in heavy precipitation extremes are projected for northern, coastal, and mountainous areas. Results suggest that the projected increase in total annual precipitation is strongly influenced by increases in winter wet extremes. The largest decreases in cold extremes are projected for northern and interior portions of the Northeast, while the largest increases in summer warm extremes are projected for densely populated southern, central, and coastal areas. This study provides a regional analysis and verification of the latest generation of CMIP global models specifically for the Northeast, useful to stakeholders focused on understanding and adapting to climate change and its impacts in the region.  相似文献   

A New Delhi every day: multiplicities of governance regimes in a transforming metropolis     

Seth Schindler 《Urban geography》2013,34(3):402-419

In this article I demonstrate the coexistence of multiple urban governance regimes in Delhi, India. While formal urban governance is geared toward transforming Delhi into a “world-class” city, I present original research that shows how the everyday governance of urban space in three very different areas of Delhi is determined by relations among non-state actors. These regimes foster access to space for street hawkers on an everyday basis while they allow powerful local interest groups to collect rent and influence flows of people and commodities. I argue that, in contrast to formal electoral politics, these governance regimes emerge from a parallel politics of everyday interactions, negotiations, and transgressions. Although the emancipatory potential of these regimes should not be overstated, they do offer street hawkers limited contingency to improve their access to urban space. This article contributes to a growing body of work on urban governance by showing how multiplicities of governance regimes coexist and determine how and by whom urban space is used in a metropolis in the global South.  相似文献   

Introduction to the special issue: historical and projected climatic changes to Australian natural hazards     

Seth Westra  Christopher J. White  Anthony S. Kiem 《Climatic change》2016,135(1):1-7

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Evaluating regional climate models for simulating sub-daily rainfall extremes     

Virginia Edith Cortés-Hernández  Feifei Zheng  Jason Evans  Martin Lambert  Ashish Sharma  Seth Westra 《Climate Dynamics》2016,47(5-6):1613-1628

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Intracontinental Earthquakes: Complex Spatio-temporal Patterns and Implications for Hazards     

Mian Liu  Seth Stein  Yuxuan Chen  Gang Luo 《《地质学报》英文版》2018,92(Z1):265-265

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Accurate Ocean Bottom Seismometer Positioning Method Inspired by Multilateration Technique     

Omar Benazzouz  Luis M. Pinheiro  Luis M. A. Matias  Alexandra Afilhado  Daniel Herold  Seth S. Haines 《Mathematical Geosciences》2018,50(5):569-584

The positioning of ocean bottom seismometers (OBS) is a key step in the processing flow of OBS data, especially in the case of self popup types of OBS instruments. The use of first arrivals from airgun shots, rather than relying on the acoustic transponders mounted in the OBS, is becoming a trend and generally leads to more accurate positioning due to the statistics from a large number of shots. In this paper, a linearization of the OBS positioning problem via the multilateration technique is discussed. The discussed linear solution solves jointly for the average water layer velocity and the OBS position using only shot locations and first arrival times as input data.  相似文献