Water contents, temperatures and diversity of the magmas of the catastrophic eruption of Nevado del Ruiz, Colombia, November 13, 1985     

William G. Melson  James F. Allan  Deborah Reid Jerez  Joseph Nelen  Marta Lucia Calvache  Stanley N. Williams  John Fournelle  Mike Perfit 《Journal of Volcanology and Geothermal Research》1990,41(1-4)

The petrology of the highly phyric two-pyroxene andesitic to dacitic pyroclastic rocks of the November 13, 1985 eruption of Nevado del Ruiz, Colombia, reveals evidence of: (1) increasingly fractionated bulk compositions with time; (2) tapping of a small magma chamber marginally zoned in regard to H₂O contents (1 to 4%), temperature (960–1090°C), and amount of residual melt (35 to 65%); (3) partial melting and assimilation of degassed zones in the hotter less dense interior of the magma chamber; (4) probable heating, thermal disruption and mineralogic and compositional contamination of the magma body by basaltic magma “underplating”; and (5) crustal contamination of the magmas during ascent and within the magma chamber. Near-crater fall-back or “spill-over” emitted in the middle of the eruptive sequence produced a small pyroclastic flow that became welded in its central and basal portions because of ponding and thus heat conservation on the flat glaciated summit near the Arenas crater. The heterogeneity of Ruiz magmas may be related to the comparatively small volume (0.03 km³) of the eruption, nearly ten times less than the 0.2 km³ of the Plinian phase of Mount St. Helens, and probable steep thermal and P_H2O gradients of a small source magma chamber, estimated at 300 m long and 100 m wide for an assumed ellipsoidal shape.  相似文献   

Uniform-hazard response spectra—An alternative approach     

Chin-Hsiung Loh  Wen-Yu Jean  Joseph Penzien 《地震工程与结构动力学》1994,23(4):433-445

An alternative method is presented for generating uniform-hazard response spectra making use of a seismic hazard curve expressing annual probability of exceedance as a function of Peak Ground Acceleration (PGA), a set of normalized (PGA = 1g) mean response spectra, and a coefficient-of-variation function for the random normalized spectral values in terms of period T. The practice of using mean + 1σ normalized response spectra, scaled to specified PGA levels, is discussed and associated mean return periods are evaluated.  相似文献   

U.S. Bank Failures and Regional Economic Structure*     

Barney Warf  Joseph C. Cox 《The Professional geographer》1995,47(1):3-16

U.S. commercial bank failures approached historically high levels in the 1980s. The collapse of such institutions can have severe impacts on local economies, disrupting the supply of available investment credit. This paper situates bank failures within the broader transformation of global capitalism in the late 20th century. Next, it reviews the causes of bank insolvency, including mismanagement, deregulation, the glutted commercial real estate market, and depressed agricultural and petroleum-dependent local economies. It then illustrates multiple aspects of the spatial distribution of bank failures. A pooled time-series regression analysis, using primary causal variables as well as location quotients of state output in four industrial sectors, indicates that with the vital exception of petroleum, and to a lesser extent services, regional economic structure is not strongly related to bank failures. This finding likely reflects the structural and spatial transformation of the industry as it adapted to the highly competitive conditions of the last decade.  相似文献   

Employment Trends in Geography,Part 1: Enrollment and Degree Patterns*   总被引：1，自引：0，他引：1  

Patricia Gober  Amy K. Glasmeier  James M. Goodman  David A. Plane  Howard A. Stafford  Joseph S. Wood 《The Professional geographer》1995,47(3):317-328

This paper is the first in a series of three papers dealing with the current and future labor market for geographers. It is based on a report prepared by the Association of American Geographers' (AAG) Employment Forecasting Committee to the National Research Council's (NRC) Rediscovering Geography Committee. This report provides a data-based analysis of the past and future supply of geographers, the current labor market conditions in the field, and the factors likely to influence the future demand for geographers (faculty hiring, geographic education initiatives, trends in private-sector jobs, etc.). Each year some 4,000 individuals receive degrees in geography from America's institutions of higher education. They, or some portion of them, make up the new supply of geographers entering the labor market. In the near future (up to five years), the availability of new geographers is related to the number of geography students now in the educational pipeline. Their current specialties, and the specialties of the programs from which they come, tell us about the types of skills and the kinds of interests to be held by future labor force entrants. In the longer term (five to ten years), the number of new geographers will be influenced by geographic education initiatives at the precollegiate level. More and better geographic instruction in elementary and secondary schools will expose more students to geography as a field of study and as a potential career path. The purposes of this paper are to (1) review degree and enrollment trends in geography, (2) assess the “trickle-up” effects of geographic education initiatives at the precollegiate level, and (3) investigate the characteristics of future supply as evidenced by the types of occupations for which geography departments are now preparing students.  相似文献   

The western border of the Archaean province of the Baltic shield: evidence from northern Sweden   总被引：1，自引：0，他引：1  

Björn Öhlander  Torbjörn Skiöld  P. Joseph Hamilton  Lars -Åke Claesson 《Contributions to Mineralogy and Petrology》1987,95(4):437-450

Restricted areas of acid to intermediate gneisses in northernmost Sweden are known to be Archaean and several other gneissic granodioritic to tonalitic massifs have been suggested to be of this age. To delimit the western border of the Archaean province of the Baltic Shield, and to characterize the Swedish Archaean, we have studied the 2.83 Ga old Soppero gneiss and 8 of the proposed Archaean massifs in northern Sweden by Sm-Nd isotopic analyses, U-Pb zircon dating (in two cases), and geochemistry.Of the Archaean gneisses proposed thus far, only those from the Soppero and Kukkola areas have Archaean ages (2.83 and 2.67 Ga, respectively). These gneisses have geochemical characteristics such as LREE-enrichment, low U-contents, and low K/Na-ratios, which are typical of Archaean TTG (tonalite-trondhjemite-granodiorite) rocks worldwide. The REE results indicate that the Soppero and the Kukkola gneisses were generated by partial melting of basic rocks, presumably amphibolites. According to the Sm-Nd isotopic data for the Soppero gneiss, this process occurred only a short time after initial segregation from the mantle ( _Nd values between +0.9 and +3.5). The Kukkola gneiss, however, has longer crustal residence time as indicated by negative _Nd values (–1.0 and –2.5) at the U-Pb zircon age of 2.67 Ga. Evidence in support of an important event at that time is given by secondary overgrowth on zircon cores in the 2.83 Ga old Soppero gneiss.The Sm-Nd isotope results show that the Proterozoic granitoids in northern Sweden have a decreasing involvement of Archaean source material with increasing distance from the Archaean areas. Before the Proterozoic reworking, the rather small Archaean areas in northern Sweden presumably belonged to a large continuous Archaean craton. The western palaeoboundary of this craton in Sweden probably follows approximately a line extrapolated from the western limit of the Archaean of central Finland, passing west of Kukkola, and then continues to the Lofoten area in northern Norway.  相似文献   

Dynamics of polychlorinated biphenyls in striped bass from the Hudson River. III. Tissue disposition and routes for elimination     

Joseph M. O’Connor  John C. Pizza 《Estuaries and Coasts》1987,10(1):68-77

Striped bass were exposed to¹⁴C-polychlorinated biphenyls (PCB) in single-dose and multiple-dose experiments. Samples were analyzed to determine rate constants for PCB elimination from individual tissues, PCB concentration in tissues, the proportion of the PCB burden retained and the proportion of the cumulative dose retained by each tissue at various times after exposure. An experiment was also conducted to determine both the potential for secondary PCB uptake in dietary exposure studies and the relative tissue disposition of PCBs assimilated from dietary sources as compared to direct water uptake. PCBs were present in the tissues of striped bass within 6 h after administration of a single dose. Certain tissue compartments, such as the liver/gall bladder, accumulated PCBs over a period of 48 h even though the whole-body burden had decreased between 24 and 48 h. Except for the gills, elimination rate constants for all tissues were similar and were similar to the whole body elimination rate constant. Elimination during the first few hours following exposure to PCBs may be due to equilibrium partitioning from the gill to the environment. The multiple-dose study showed that PCB burdens in striped bass continued to increase with dosing. However, tissue-specific rate constants for PCB elimination led to an increased flux of PCB out of tissues, and an overall decline in the percent of the cumulative dose remaining in the body 48 h after administration of each dose. The most likely route for PCB elimination from striped bass was from tissues to the liver and thence to the intestine via the bile. There were no differences in the tissue disposition of PCB related to route of exposure.  相似文献   

FM Radiotelemetry Coupled with Sonic Transducers for Remote Monitoring of Water Levels in Deep Aquifers     

Joseph W. Alderman 《Ground Water Monitoring & Remediation》1986,6(2):114-116

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Assessment of trace element geochemistry of Hampton Roads harbor and lower Chesapeake Bay area sediments   总被引：5，自引：1，他引：5  

Rule  Joseph H. 《Environmental Geology》1986,8(4):209-219

Acid extractable Cd, Co, Cr, Cu, Fe, Mn, Ni, Pb. and Zn were determined in sediments from the Inner Virginia Shelf, and from shipping channels in the lower Chesapeake Bay and Hampton Roads, Virginia, harbor system. Data were evaluated by a variety of techniques Levels of Cd, Cu, Pb, and Zn exceeded average crustal abundances for most of the study sites. Cumulative frequency curves suggested that there were two major populations for all metals and perhaps a third and smaller, one for Cd, Cr, and Mn Plots of metal vs Fe indicated no anthropogenic inputs of metals for shelf and Chesapeake Bay channel sites, but suggested anthropogenic influences for all metals in several of the inshore sites. Enrichment factor calculations showed enrichment of Cd, Pb, and Zn with respect to average crustal abundances for all sites and of Cu for the industrial harbor system. A recommendation of this study for evaluation of environmental geochemical metals data is to utilize mean concentrations, cumulative frequency plots, and metal vs Fe and/or enrichment factor calculations when evaluating the pollution status of sediments.  相似文献   

Widespread distribution of some estuarine crustaceans (Cyathura polita,Chiridotea almyra,Almyracuma proximoculi) in the limnetic zone of the lower Hudson River,New York     

Karl W. Simpson  Joseph P. Fagnani  Dean M. DeNicola  Robert W. Bode 《Estuaries and Coasts》1985,8(4):373-380

From June through September 1983, a survey was conducted to document the occurrence, abundance and distribution of benthic macroinvertebrates in the main channel, Hudson River Estuary. The survey was restricted to a 118-km reach of the limnetic zone from just below Albany to New Hamburg, New York. Results indicated that two crustacean species,Cyathura polita (Stimpson) andChiridotea almyra Bowman, are widely distributed and common throughout the limnetic zone, including areas more than 100 km upstream from the northernmost(=most upstream) intrusion of ocean-derived brackish water.Almyracuma proximoculi Jones and Burbanck was much less common, but also was found in areas well removed from any brackish-water influences. All three species previously have been thought to occur primarily in estuarine waters with at least some salinity. We could find no evidence to suggest that non-ocean derived sources were supplementing the levels of dissolved ions in the river water or sediments. Therefore, it appears that all three species have established permant populations in a truly freshwater habitat.  相似文献   

Biological marker distribution and significance in oils and rocks of the Monterey Formation,California     

Joseph A. Curiale  Douglas Cameron  Dean V. Davis 《Geochimica et cosmochimica acta》1985,49(1):271-288

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