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11.
Timescales of melt generation and the thermal evolution of the Himalayan metamorphic core,Everest region,eastern Nepal 总被引：9，自引：1，他引：8
Karen?ViskupicEmail author Kip?V?Hodges Samuel?A?Bowring 《Contributions to Mineralogy and Petrology》2005,149(1):1-21
In the Everest region of the Nepalese Himalaya, 40Ar/39Ar and U-Pb geochronology provide evidence for a complex thermal history marked by multiple episodes of granite intrusion. The oldest mobilized melt formed syn-deformational granitic sills that have U-Pb crystallization ages of 21.33±0.03 and 21.80±0.05 Ma. Preserved in these same granites is a record of earlier magmatic crystallization of xenotime, zircon and monazite between ca. 26 Ma and ca. 23 Ma. This pattern of accessory phase crystallization is interpreted to reflect incremental melting and crystallization in the source region of the sills before ultimate melt migration, and provides the earliest evidence for anatexis in the Everest region. The beginning of crustal melting in the Everest region predates the earliest known movement on both the Main Central Thrust and the South Tibetan fault systems, but is temporally associated with the implied pressure decrease between Eohimalayan and Neohimalayan metamorphism. 相似文献
12.
We designed and evaluated a “tube seepage meter” for point measurements of vertical seepage rates (q), collecting groundwater samples, and estimating vertical hydraulic conductivity (K) in streambeds. Laboratory testing in artificial streambeds show that seepage rates from the tube seepage meter agreed well with expected values. Results of field testing of the tube seepage meter in a sandy‐bottom stream with a mean seepage rate of about 0.5 m/day agreed well with Darcian estimates (vertical hydraulic conductivity times head gradient) when averaged over multiple measurements. The uncertainties in q and K were evaluated with a Monte Carlo method and are typically 20% and 60%, respectively, for field data, and depend on the magnitude of the hydraulic gradient and the uncertainty in head measurements. The primary advantages of the tube seepage meter are its small footprint, concurrent and colocated assessments of q and K, and that it can also be configured as a self‐purging groundwater‐sampling device. 相似文献
13.
Tristan D. Pearce James D. Ford Gita J. Laidler Barry Smit Frank Duerden Mishak Allarut Mark Andrachuk Steven Baryluk rew Dialla Pootoogoo Elee Annie Goose Theo Ikummaq Eric Joamie Fred Kataoyak Eric Loring Stephanie Meakin Scott Nickels Kip Shappa Jamal Shirley & Johanna Wandel 《Polar research》2009,28(1):10-27
Research on climate change impacts, vulnerability and adaptation, particularly projects aiming to contribute to practical adaptation initiatives, requires active involvement and collaboration with community members and local, regional and national organizations that use this research for policy-making. Arctic communities are already experiencing and adapting to environmental and socio-cultural changes, and researchers have a practical and ethical responsibility to engage with communities that are the focus of the research. This paper draws on the experiences of researchers working with communities across the Canadian Arctic, together with the expertise of Inuit organizations, Northern research institutes and community partners, to outline key considerations for effectively engaging Arctic communities in collaborative research. These considerations include: initiating early and ongoing communication with communities, and regional and national contacts; involving communities in research design and development; facilitating opportunities for local employment; and disseminating research findings. Examples of each consideration are drawn from climate change research conducted with communities in the Canadian Arctic. 相似文献
14.
Martin A. Briggs Nora Nelson Philip Gardner D. Kip Solomon Neil Terry John W. Lane 《Ground water》2019,57(5):737-748
Quantitative evaluation of groundwater/surface water exchange dynamics is universally challenging in large river systems, because existing methodology often does not yield spatially-distributed data and is difficult to apply in deeper water. Here we apply a combined near-surface geophysical and direct groundwater chemical toolkit to refine fresh groundwater discharge estimates to the Colorado River through a 4-km2 wetland that borders the town of Moab, Utah, USA. Preliminary characterization of raw electromagnetic imaging (EMI) data, collected by kayak and by walking, was used to guide additional direct-contact electrical measurements and installation of new monitoring wells. Chemical data from the wells strongly supported the EMI spatial characterization of preferential fresh groundwater discharge embedded in natural brine groundwaters and weighted to the southern wetland section. Inversion of the EMI data revealed sub-meter scale detail regarding bulk electrical conductivity zonation across approximately 15.5 km of transects, collected in only 3 days. This electrical detail indicates processes such as salinization of the unsaturated zone and direct discharge through the Colorado River sediments and a tributary creek bed. Overall, the study contributed to a substantial reduction in fresh groundwater discharge estimates previously made using sparse existing well data and a simplified assumption of diffuse fresh groundwater discharge below the entire wetland. EMI will likely become a widely used tool in systems with natural electrical contrast as groundwater/surface water hydrogeologists continue to recognize the prevalence of preferential groundwater discharge processes. 相似文献
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Massimiliano Galeazzi Meng Chiao Michael R. Collier Thomas Cravens Dimitra Koutroumpa Kip D. Kuntz Susan Lepri Dan McCammon Frederick S. Porter Krishna Prasai Ina Robertson Steve Snowden Youaraj Uprety 《Experimental Astronomy》2011,32(2):83-99
The Diffuse X-rays from the Local galaxy (DXL) mission is an approved sounding rocket project with a first launch scheduled around December 2012. Its goal is to identify and separate the X-ray emission generated by solar wind charge exchange from that of the local hot bubble to improve our understanding of both. With 1,000 cm2 proportional counters and grasp of about 10 cm2 sr both in the 1/4 and 3/4 keV bands, DXL will achieve in a 5-min flight what cannot be achieved by current and future X-ray satellites. 相似文献
17.
The Perception and Valuation of the Risks of Climate Change: A Rational and Behavioral Blend 总被引：3，自引：1，他引：3
Over 250 respondents – graduate students in law and public policy – assessed the risks of climate change and valued climate-change mitigation policies. Many aspects of their behavior were consistent with rational behavior. For example, respondents successfully estimated distributions of temperature increases in Boston by 2100. The median value of best estimates was 1–3 degrees Fahrenheit. In addition, people with higher risk estimates, whether for temperature or related risks (e.g., hurricane intensities) offered more to avoid warming. Median willingness to pay (WTP) to avoid global warming was $0.50/gallon, and 3% of income. And important scope tests (e.g., respondents paid more for bigger accomplishments) were passed. However, significant behavioral propensities also emerged. For example, accessibility of neutral information on global warming boosted risk estimates. Warming projections correlated with estimates for unrelated risks, such as earthquakes and heart attacks. The implied WTP for avoidance was much greater when asked as a percent of income than as a gas tax, a percent thinking bias. Home team betting showed itself; individuals predicting a Bush victory predicted smaller temperature increases. In the climate-change arena, behavioral decision tendencies are like a fun-house mirror: They magnify some estimates and shrink others, but the contours of rational decision rmain recognizable. 相似文献
18.
This article examines age variations in support for environmental protection policies that affect climate change using a sample of over 14,000 respondents to a 1999 Eurobarometer survey. There is a steady decline with age in whether respondents are willing to incur higher gasoline prices to protect the environment. This relationship remains after controlling for socioeconomic characteristics. There are age-related differences in information about environmental risks, information sources about the environment, perceived health risks from climate change, and degree of worry about climate change. However, taking these factors into account does not eliminate the age variation in willingness to pay more for gasoline to protect the environment. 相似文献
19.
Quaternary deformation, river steepening, and heavy precipitation at the front of the Higher Himalayan ranges 总被引：9，自引：0，他引：9
Kip V Hodges Cameron Wobus Katharine Ruhl Taylor Schildgen Kelin Whipple 《Earth and Planetary Science Letters》2004,220(3-4):379-389
New geologic mapping in the Marsyandi Valley of central Nepal reveals the existence of tectonically significant Quaternary thrust faults at the topographic front of the Higher Himalaya. The zone of recent faulting is coincident with an abrupt change in the gradient of the Marsyandi River and its tributaries, which is thought to mark the transition from a region of rapid uplift in the Higher Himalayan ranges to a region of slower uplift to the south. Uplift of the Higher Himalaya during the Quaternary is not entirely due to passive uplift over a deeply buried ramp in the Himalayan sole thrust, as is commonly believed, but partially reflects active thrusting at the topographic front. The zone of active thrusting is also coincident with a zone of intense monsoon precipitation, suggesting a positive feedback relationship between focused erosion and deformation at the front of the Higher Himalayan ranges. 相似文献
20.
Arthur P. White Kip V. Hodges Mark W. Martin Arild Andresen 《International Journal of Earth Sciences》2002,91(2):187-208
Structural and U-Pb geochronologic data from the Forsblad Fjord area of East Greenland (72°30'N) indicate close spatial and temporal ties between orogen-parallel shear and extensional deformation during Caledonian orogenesis. This territory is composed of three tectonostratigraphic units separated by two splays of the Fjord Region Detachment System (FRDS), a principal extensional fault system of the East Greenland Caledonides that was active in Silurian time. The oldest Caledonian fabrics in Forsblad Fjord, which developed at upper amphibolite facies metamorphic conditions, indicate that there was north-south, lateral extrusion of ductile middle-crustal material synchronous with approximately east-west shortening. U-Pb dating of synkinematic granitic leucosomes in migmatitic schists and gneisses demonstrates that this process was underway at ca. 425 Ma. Subsequently, east-west extension along the two splays of the FRDS truncated the older fabrics; the structurally highest of these shear zones - the Tindern detachment - was active as early as ca. 424 Ma. This implies either that there was a rapid transition from Caledonian shortening and possible transpressional deformation to post-orogenic collapse, or our preferred interpretation that extension was synorogenic. The FRDS shares many structural characteristics with the South Tibetan Detachment System of the Cenozoic Himalayan orogen but exhibits two important differences. First, while the South Tibetan system developed in the down-going Indian plate during the India-Eurasia collision, the Fjord Region system developed in the overriding Laurentian plate during the collision of Laurentia with Baltica. Second, whereas the exposed extensional structures in the Himalayas developed in the upper crust and are only inferred to have extended to deeper levels, those in the Forsblad Fjord area were demonstrably active at middle-crustal levels. Evidence for broadly coeval extension and contraction at differen t structural levels in both mountain belts emphasizes the general importance of crustal decoupling in the collisional orogenic process, and implies that synorogenic extensional deformation is not strictly an upper crustal phenomenon. 相似文献