Phase-equilibrium geobarometers for silicic rocks based on rhyolite-MELTS. Part 2: application to Taupo Volcanic Zone rhyolites     

Florence?BéguéEmail author  Guilherme?A.?R.?Gualda  Mark?S.?Ghiorso  Ayla?S.?Pamukcu  Ben?M.?Kennedy  Darren?M.?Gravley  Chad?D.?Deering  Isabelle?Chambefort 《Contributions to Mineralogy and Petrology》2014,168(5):1082

Constraining the pressure of crystallisation of large silicic magma bodies gives important insight into the depth and vertical extent of magmatic plumbing systems; however, it is notably difficult to constrain pressure at the level of detail necessary to understand shallow magmatic systems. In this study, we use the recently developed rhyolite-MELTS geobarometer to constrain the crystallisation pressures of rhyolites from the Taupo Volcanic Zone (TVZ). As sanidine is absent from the studied deposits, we calculate the pressures at which quartz and feldspar are found to be in equilibrium with melt now preserved as glass (the quartz +1 feldspar constraint of Gualda and Ghiorso, Contrib Mineral Petrol 168:1033. doi: 10.1007/s00410-014-1033-3. 2014). We use glass compositions (matrix glass and melt inclusions) from seven eruptive deposits dated between ~320 and 0.7 ka from four distinct calderas in the central TVZ, and we discuss advantages and limitations of the rhyolite-MELTS geobarometer in comparison with other geobarometers applied to the same eruptive deposits. Overall, there is good agreement with other pressure estimates from the literature (amphibole geobarometry and H₂O–CO₂ solubility models). One of the main advantages of this new geobarometer is that it can be applied to both matrix glass and melt inclusions—regardless of volatile saturation. The examples presented also emphasise the utility of this method to filter out spurious glass compositions. Pressure estimates obtained with the new rhyolite-MELTS geobarometer range between ~250 to ~50 MPa, with a large majority at ~100 MPa. These results confirm that the TVZ hosts some of the shallowest rhyolitic magma bodies on the planet, resulting from the extensional tectonic regime and thinning of the crust. Distinct populations with different equilibration pressures are also recognised, which is consistent with the idea that multiple batches of eruptible magma can be present in the crust at the same time and can be tapped simultaneously by large eruptive events.  相似文献   

Marine introductions in the Southern Ocean: an unrecognised hazard to biodiversity     

Lewis PN  Hewitt CL  Riddle M  McMinn A 《Marine pollution bulletin》2003,46(2):213-223

This study investigated the potential for transport of organisms between Hobart, Macquarie Island and the Antarctic continent by ships used in support of Antarctic science and tourism. Northward transport of plankton in ballast water is more likely than southward transport because ballast is normally loaded in the Antarctic and unloaded at the home port. Culturing of ballast water samples revealed that high-latitude hitchhikers were able to reach greater diversities when cultured at temperate thermal conditions than at typical Southern Ocean temperatures, suggesting the potential for establishment in the Tasmanian coastal environment. Several known invasive species were identified among fouling communities on the hulls of vessels that travel between Hobart and the Southern Ocean. Southward transport of hull fouling species is more likely than northward transport due to the accumulation of assemblages during the winter period spent in the home port of Hobart. This study does not prove that non-indigenous marine species have, or will be, transported and established as a consequence of Antarctic shipping but illustrates that the potential exists. Awareness of the potential risk and simple changes to operating procedures may reduce the chance of introductions in the future.  相似文献   

Extension′s role in disseminating information about climate change to agricultural stakeholders in the United States     

Linda Stalker Prokopy  J. Stuart Carlton  J. Gordon Arbuckle Jr.  Tonya Haigh  Maria Carmen Lemos  Amber Saylor Mase  Nicholas Babin  Mike Dunn  Jeff Andresen  Jim Angel  Chad Hart  Rebecca Power 《Climatic change》2015,130(2):261-272

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Reliable Support Design for Excavations in Brittle Rock Using a Global Response Surface Method     

J. Connor Langford  Mark S. Diederichs 《Rock Mechanics and Rock Engineering》2015,48(2):669-689

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Decadal predictability of soil water,vegetation, and wildfire frequency over North America     

Yoshimitsu Chikamoto  Axel Timmermann  Samantha Stevenson  Pedro DiNezio  Sally Langford 《Climate Dynamics》2015,45(7-8):2213-2235

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Latitudinal Range Variation of Trees in the United States: A Reanalysis of the Applicability of Rapoport's Rule*     

Chad S. Lane 《The Professional geographer》2007,59(1):115-130

In 1975 E. H. Rapoport described a pattern of increasing latitudinal range sizes for organisms with increasing latitude, a pattern that is now known as Rapoport's rule. The universal applicability of Rapoport's rule has been long contested, making it one of the more controversial biogeographic “rules.” This study aims to reassess the applicability of Rapoport's rule to U.S. tree species. Data presented here suggest that Rapoport's rule does indeed apply to most tree taxa within the United States, but may be taxon specific. In addition, data presented here suggest that tree range patterns consistent with Rapoport's rule in the United States are not restricted to high latitudes and are not the result of a “boundedness effect” but may be intimately linked with the glacial history and physical geography of North America. The analyses conducted here are intended to emphasize the utility of such biogeographic rules even if they are not universally applicable and should, in turn, only be considered biogeographic patterns.  相似文献   

Device for finely resolved sampling of littoral lake regions: Design and operation     

Chad P. Gubala  Charles T. Driscoll  Robert M. Newton  Carl Schofield 《水文研究》1993,7(1):99-104

Although littoral regions in northern lakes may sustain fish spawning grounds, little is known of the temporal or spatial aspects of their thermal and chemical regimes. This shortcoming is due in part to the difficulty in properly sampling these regions throughout the year with adequate spatial resolution. This problem is especially critical in lakes affected by episodic acidification during the spring snowmelt, a period of substantial importance to fisheries recruitment. A device was constructed to alleviate the problems associated with conventional water quality sampling of littoral regions. Constructed of thick walled polyvinyl chloride and permanently installed in the nearshore regions of an Adirondack lake, the episodic event sampler (EES) provided finely resolved (0.25 m) temperature and water chemistry data during the spring snowmelt period (February to May) of 1989. Although the construction and installation of the sampler represented a significant investment in labour and materials, this was offset by the high quality of the data collected. As the samplers were relatively undamaged by freeze-thaw activity, it is expected that they will continue to provide excellent information for several years.  相似文献   

GIScience,environmental justice, & estimating populations at risk: The case of landfills in Wales     

Gary Higgs  Mitch Langford 《Applied geography (Sevenoaks, England)》2009,29(1):63-76

There has been a notable increase in the use of geographic information systems (GIS) in studies of environmental (in)justice in the last two decades. Whilst the potential of such techniques is increasingly being recognised, there remain some key research challenges facing researchers interested in wider notions of environmental justice (EJ). One avenue of research concerns the estimation of population denominator and the influence of the estimation model on the conclusions emanating from such studies. Whilst the potential of so-called dasymetric mapping techniques have been explored in other substantive areas such as crime and health geography, their use in EJ applications remains under-explored. This paper represents a preliminary attempt to redress this gap in the literature through a comparison of the deprivation profiles of residents living in the vicinity of landfill sites in Wales using both ‘traditional’ and innovative methods of population estimation that provide a more realistic representation of actual population distribution. The results as we demonstrate suggest that more emphasis needs to be placed on the methods by which population is estimated if the results of GIS-based environmental justice studies are to be more widely applied.  相似文献   

Integrated measurements of acoustical and optical thin layers II: Horizontal length scales     

Mark A. Moline  Kelly J. Benoit-Bird  Ian C. Robbins  Maddie Schroth-Miller  Chad M. Waluk  Brian Zelenke 《Continental Shelf Research》2010,30(1):29-38

The degree of layered organization of planktonic organisms in coastal systems impacts trophic interactions, the vertical availability of nutrients, and many biological rate processes. While there is reasonable characterization of the vertical structure of these phenomena, the extent and horizontal length scale of variation has rarely been addressed. Here we extend the examination of the vertical scale in the first paper of the series to the horizontal scale with combined shipboard acoustic measurements and bio-optic measurements taken on an autonomous underwater vehicle. Measurements were made in Monterey Bay, CA from 2002 to 2008 for the bio-optical parameters and during 2006 for acoustic scattering measurements. The combined data set was used to evaluate the horizontal decorrelation length scales of the bio-optical and acoustic scattering layers themselves. Because biological layers are often decoupled from the physical structure of the water column, assessment of the variance within identified layers was appropriate. This differs from other studies in that physical parameters were not used as a basis for the layer definition. There was a significant diel pattern to the decorrelation length scale for acoustic layers with the more abundant nighttime layers showing less horizontal variability despite their smaller horizontal extent. A significant decrease in the decorrelation length scale was found in bio-optical parameters over six years of study, coinciding with a documented shift in the plankton community. Results highlight the importance of considering plankton behavior and time of day with respect to scale when studying layers, and the challenges of sampling these phenomena.  相似文献   

Possible impacts of climate change on extreme weather events at local scale in south–central Canada     

Chad Shouquan Cheng  Heather Auld  Qian Li  Guilong Li 《Climatic change》2012,112(3-4):963-979

Synoptic weather typing and regression-based downscaling approaches have become popular in evaluating the impacts of climate change on a variety of environmental problems, particularly those involving extreme impacts. One of the reasons for the popularity of these approaches is their ability to categorize a complex set of meteorological variables into a coherent index, facilitating the projection of changes in frequency and intensity of future daily extreme weather events and/or their impacts. This paper illustrated the capability of the synoptic weather typing and regression methods to analyze climatic change impacts on a number of extreme weather events and environmental problems for south–central Canada, such as freezing rain, heavy rainfall, high-/low-streamflow events, air pollution, and human health. These statistical approaches are helpful in analyzing extreme events and projecting their impacts into the future through three major steps or analysis procedures: (1) historical simulation modeling to identify extreme weather events or their impacts, (2) statistical downscaling to provide station-scale future hourly/daily climate data, and (3) projecting changes in the frequency and intensity of future extreme weather events and their impacts under a changing climate. To realize these steps, it is first necessary to conceptualize the modeling of the meteorology, hydrology and impacts model variables of significance and to apply a number of linear/nonlinear regression techniques. Because the climate/weather validation process is critical, a formal model result verification process has been built into each of these three steps. With carefully chosen physically consistent and relevant variables, the results of the verification, based on historical observations of the outcome variables simulated by the models, show a very good agreement in all applications and extremes tested to date. Overall, the modeled results from climate change studies indicate that the frequency and intensity of future extreme weather events and their impacts are generally projected to significantly increase late this century over south–central Canada under a changing climate. The implications of these increases need be taken into consideration and integrated into policies and planning for adaptation strategies, including measures to incorporate climate change into engineering infrastructure design standards and disaster risk reduction measures. This paper briefly summarized these climate change research projects, focusing on the modeling methodologies and results, and attempted to use plain language to make the results more accessible and interesting to the broader informed audience. These research projects have been used to support decision-makers in south–central Canada when dealing with future extreme weather events under climate change.  相似文献