Volcanoes
Robert I. Tilling
1998, Report
Volcanoes destroy and volcanoes create. The catastrophic eruption of Mount St. Helens on May 18, 1980, made clear the awesome destructive power of a volcano. Yet, over a time span longer than human memory and record, volcanoes have played a key role in forming and modifying the planet upon which...
In situ FTIR and flash pyrolysis/GC-MS characterization of Protosalvinia (Upper Devonian, Kentucky, USA): Implications for maceral classification
Maria Mastalerz, J.C. Hower, A. Carmo
1998, Organic Geochemistry (28) 57-66
Protosalvinia from Devonian rocks in Kentucky has been analyzed using petrographic and in situ FTIR and flash pyrolysis/GC-MS techniques in order to discuss its origin and placement in organic matter classification. In reflected light, Protosalvinia resembles cutinite in shape, color and reflectance, whereas in fluorescent mode it reveals yellow-green fluorescence,...
The Chesapeake Bay bolide: Modern consequences of an ancient cataclysm
C. Wylie Poag
1998, Report
During the late Eocene, the formerly quiescent geological regime of the Virginia Coastal Plain was dramatically transformed when a bolide struck in the vicinity of the Delmarva Peninsula, and produced the following principal consequences:The bolide carved a roughly circular crater twice the size of the state of Rhode Island (~6400...
Ice sheet history from Antarctic Continental Margin sediments: The ANTOSTRAT approach
P.F. Barker, P. J. Barrett, Angelo Camerlenghi, Alan K. Cooper, F.J. Davey, E.W. Domack, C. Escutia, Y. Kristoffersen, P. E. O’Brien
1998, Terra Antarctica (5) 737-760
The Antarctic Ice Sheet is today an important part of the global climate engine, and probably has been so for most of its long existence. However, the details of its history are poorly known, despite the measurement and use, over two decades, of low-latitude proxies of ice sheet volume. An...
Interactions between pool geometry and hydraulics
Douglas M. Thompson, Jonathan M. Nelson, Ellen E. Wohl
1998, Water Resources Research (34) 3673-3681
An experimental and computational research approach was used to determine interactions between pool geometry and hydraulics. A 20-m-long, 1.8-m-wide flume was used to investigate the effect of four different geometric aspects of pool shape on flow velocity. Plywood sections were used to systematically alter constriction width, pool depth, pool length,...
Multi-level slug tests in highly permeable formations: 1. Modification of the Springer-Gelhar (SG) model
V.A. Zlotnik, V. L. McGuire
1998, Journal of Hydrology (204) 271-282
A multi-level slug test model and a method for the evaluation of vertical profiles of hydraulic conductivity in highly permeable formations are developed. A double-packer system is employed to estimate local hydraulic conductivity. Depending on the formation and double-packer system parameters, the water level recovery in the tested well can...
Verification of the Rhea-orographic-precipitation model
L.E. Hay, G.J. McCabe
1998, Journal of the American Water Resources Association (34) 103-112
ABSTRACT: Observed April 1 snowpack accumulations within and near the Gunnison River basin in southwestern Colorado are compared with simulations from the Rhea-orographic-precipitation model to determine if the model simulates reliable magnitudes and temporal and spatial variability in winter precipitation for the basin. Twenty simulations of...
Late Pleistocene C4 plant dominance and summer rainfall in the southwestern United States from isotopic study of herbivore teeth
S.L. Connin, J. Betancourt, Jay Quade
1998, Quaternary Research (50) 179-193
Patterns of climate and C4 plant abundance in the southwestern United States during the last glaciation were evaluated from isotopic study of herbivore tooth enamel. Enamel ??13C values revealed a substantial eastward increase in C4 plant consumption for Mammuthus spp., Bison spp., Equus spp., and Camelops spp. The ??13C values...
Proactive responses to human impacts that balance development and Atlantic salmon (Salmo salar) conservation: An integrative model
M.A. Wilzbach, M. E. Mather, C.L. Folt, A. Moore, R.J. Naiman, A.F. Youngson, J. McMenemy
1998, Conference Paper, Canadian Journal of Fisheries and Aquatic Sciences
Incorporating human impacts into conservation plans is critical to protect natural resources. Using a model that examines how anthropogenic changes might be proactively influenced to promote conservation, we argue that a denser human population does not spell inevitable doom for Atlantic salmon (Salmo salar). Humans affect the Atlantic salmon ecosystem...
Sulphur-radical control on petroleum formation rates
M. D. Lewan
1998, Nature (391) 164-166
Most petroleum is formed through the partial decomposition of kerogen (an insoluble sedimentary organic material) in response to thermal stress during subsurface burial in a sedimentary basin. Knowing the mechanisms and kinetics of this process allows the determination of the extent and timing of petroleum formation, which, in turn, are...
Effects of slip, slip rate, and shear heating on the friction of granite
M.L. Blanpied, T.E. Tullis, J.D. Weeks
1998, Journal of Geophysical Research B: Solid Earth (103) 489-511
The stability of fault slip is sensitive to the way in which frictional strength responds to changes in slip rate and in particular to the effective velocity dependence of steady state friction Δμss/Δ ln V. This quantity can vary substantially with displacement, temperature and slip rate. To investigate the physical basis...
A comparison of zero-order, first-order, and monod biotransformation models
B.A. Bekins, E. Warren, E.M. Godsy
1998, Ground Water (36) 261-268
Under some conditions, a first-order kinetic model is a poor representation of biodegradation in contaminated aquifers. Although it is well known that the assumption of first-order kinetics is valid only when substrate concentration, S, is much less than the half-saturation constant, K(s), this assumption is often made without verification of...
A controlled experiment in ground water flow model calibration
M. C. Hill, R.L. Cooley, D.W. Pollock
1998, Groundwater (36) 520-535
Nonlinear regression was introduced to ground water modeling in the 1970s, but has been used very little to calibrate numerical models of complicated ground water systems. Apparently, nonlinear regression is thought by many to be incapable of addressing such complex problems. With what we believe...
Rheological equations in asymptotic regimes of granular flow
Chiu-Lan Chen, C. #NAME? Ling
1998, Journal of Engineering Mechanics (124) 301-310
This paper assesses the validity of the generalized viscoplastic fluid (GVF) model in light of the established constitutive relations in two asymptotic flow regimes, namely, the macroviscous and grain-inertia regimes. A comprehensive review of the literature on constitutive relations in both regimes reveals that except for some material constants, such...
Radiogenic heat production in sedimentary rocks of the Gulf of Mexico basin, south Texas
Thomas E. Mckenna, J. M. Sharp Jr.
1998, American Association of Petroleum Geologists Bulletin (82) 484-496
Radiogenic heat production within the sedimentary section of the Gulf of Mexico basin is a significant source of heat. Radiogenic heat should be included in thermal models of this basin (and perhaps other sedimentary basins). We calculate that radiogenic heat may contribute up to 26% of the overall surface heat-flow...
Boron-rich mud volcanoes of the Black Sea region: Modern analogues to ancient sea-floor tourmalinites associated with Sullivan-type Pb-Zn deposits?
J. F. Slack, R.J.W. Turner, P.L.G. Ware
1998, Geology (26) 439-442
Large submarine mud volcanoes in the abyssal part of the Black Sea south of the Crimean Peninsula are similar in many respects to synsedimentary mud volcanoes in the Mesoproterozoic Belt-Purcell basin. One of the Belt-Purcell mud volcanoes directly underlies the giant Sullivan Pb-Zn-Ag...
A collapsible trap for capturing ruffe
Andrew J. Edwards, Gary D. Czypinski, James H. Selgeby
1998, North American Journal of Fisheries Management (18) 465-469
A modified version of the Windermere trap was designed, constructed, and tested for its effectiveness in capturing ruffe Gymnocephalus cernuus. The inexpensive, lightweight, collapsible trap was easily deployed and retrieved from a small boat. Field tests conducted at the St. Louis River estuary in western Lake Superior in...
Paleomagnetism of the Middle Proterozoic Electra Lake Gabbro, Needle Mountains, southwestern Colorado
S. S. Harlan, J. W. Geissman
1998, Journal of Geophysical Research B: Solid Earth (103) 15497-15507
The Electra Lake Gabbro is a small 1.435 Ga pluton that intrudes 1.7 to 1.6 Ga gneisses and schists of the Needle Mountains in southwestern Colorado. Paleomagnetic samples were collected from the main phases of the gabbro, diabase dikes, granite, and alaskite dikes that cut the gabbro and from a...
Detecting influential observations in nonlinear regression modeling of groundwater flow
Richard M. Yager
1998, Water Resources Research (34) 1623-1633
Nonlinear regression is used to estimate optimal parameter values in models of groundwater flow to ensure that differences between predicted and observed heads and flows do not result from nonoptimal parameter values. Parameter estimates can be affected, however, by observations that disproportionately influence the regression, such as outliers that exert...
Extremely acid Permian lakes and ground waters in North America
K.C. Benison, R.H. Goldstein, B. Wopenka, R.C. Burruss, J. D. Pasteris
1998, Nature (392) 911-914
Evaporites hosted by red beds (red shales and sandstones), some 275-265 million years old, extend over a large area of the North American mid- continent. They were deposited in non-marine saline lakes, pans and mud- flats, settings that are typically assumed to have been alkaline. Here we use laser Raman...
Comparison of hydrochemical tracers to estimate source contributions to peak flow in a small, forested, headwater catchment
Karen C. Rice, George M. Hornberger
1998, Water Resources Research (34) 1755-1766
Three-component (throughfall, soil water, groundwater) hydrograph separations at peak flow were performed on 10 storms over a 2-year period in a small forested catchment in north-central Maryland using an iterative and an exact solution. Seven pairs of tracers (deuterium and oxygen 18, deuterium and chloride, deuterium and sodium, deuterium and...
A comparison of methods for deriving solute flux rates using long-term data from streams in the mirror lake watershed
P.A. Bukaveckas, G.E. Likens, T. C. Winter, D.C. Buso
1998, Water, Air, & Soil Pollution (105) 277-293
Calculation of chemical flux rates for streams requires integration of continuous measurements of discharge with discrete measurements of solute concentrations. We compared two commonly used methods for interpolating chemistry data (time-averaging and flow-weighting) to determine whether discrepancies between the two methods were large relative to other sources of error in...
Regression models of herbicide concentrations in outflow from reservoirs in the midwestern USA, 1992-1993
W.A. Battaglin, D. A. Goolsby
1998, Journal of the American Water Resources Association (34) 1369-1390
Reservoirs are used to store water for public water supply, flood control, irrigation, recreation, hydropower, and wildlife habitat, but also often store undesirable substances such as herbicides. The outflow from 76 reservoirs in the midwestern USA, was sampled four times in 1992 and four times in 1993. At least one...
Potentially hazardous elements in coal: Modes of occurrence and summary of concentration data for coal components
Allan Kolker, Robert B. Finkelman
1998, Coal Preparation (19) 133-157
Mode-of-occurrence data are summarized for 13 potentially hazardous elements (Be, Cr, Mn, Co, Ni, As, Se, Cd, Sb, Hg, Pb, Th, U) in coal. Recent work has refined mode-of-occurrence data for Ni, Cr, and As, as compared to previous summaries. For Cr, dominant modes of occurrence include the clay mineral...
Issues and prospects for the next generation of the spatial data transfer standard (SDTS)
D. Arctur, D. Hair, G. Timson, E.P. Martin, R. Fegeas
1998, International Journal of Geographical Information Science (12) 403-425
The Spatial Data Transfer Standard (SDTS) was designed to be capable of representing virtually any data model, rather than being a prescription for a single data model. It has fallen short of this ambitious goal for a number of reasons, which this paper investigates. In addition to issues that might...
