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Earthquakes and volcanic eruptions are episodic, related phenomena, resulting from an unstable, evolving Earth. Earthquakes span at least 2 orders of magnitude of energy release (2 of Richter magnitude), and volcanic eruptions at least 3 orders of magnitude in both volume and energy. The largest known earthquakes, of magnitude about...

Many seismically active regions occur throughout the world as concentrated zones surrounded by the relatively stable crust of shields or platforms. Examples occur in central and eastern North America, northeastern Brazil, Australia, Norway, Svalbard, Greenland, and other places. Some of these zones, such as those at New Madrid, Missouri, and...

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Earthquake prediction is inherently statistical. Although some people continue to think of earthquake prediction as the specification of the time, place, and magnitude of a future earthquake, it has been clear for at least a decade that this is an unrealistic and unreasonable definition. the reality is that earthquake prediction...

My approach to seismology over the years has always been from the point of view of applied mathematics, as exemplified broadly by the work of the late Sir Harold Jeffreys and Professor K. E. Bullen. Both stresses the development of mathematics in the context of physical systems and of modeling,...

The reflectance spectrum of Callisto from 0.2 to 4.1 μm is modeled using a simultaneous intimate plus areal mixture solution of ice and dark material which satisfies absorption band depths and reflectance levels. The model uses the radiative transfer theory based on Hapke's (1981, J. Geophys. Res. 86, 3039–3054) work, optical constants...

The record of felt earthquakes around Naples Bay in southern Italy is probably complete since the mid-15th century. According to this record, intense earthquake swarms originating beneath Campi Flegrei, an explosive caldera located along the north coast of Naples Bay, have occurred only twice: (1) before the only historical eruption...

The problems of how warm and wet Mars once was and when climate transitions may have occurred are not well understood. Mars may have had an early environment similar to Earth's that was conductive to the ermergence of life. In addition, increasing geologic evidence indicates that water, upon which terrestrial...

This paper introduces a simple convective-flow model that can be used as a screening tool and for conducting sensitivity analyses for in situ vapor extraction of organic compounds from porous media. An assumption basic to this model was that the total mass of volatile organic chemicals (VOC) exists in three...

An aerial geomorphic mapping system was developed to examine the spatial and temporal variability in the coastal geomorphology of Louisiana. Between 1984 and 1990 eleven sequential annual and post-hurricane aerial videotape surveys were flown covering periods of prolonged fair weather, hurricane impacts and subsequent post-storm recoveries. A coastal geomorphic classification...

Improved precision in the H2-H2O equilibration method for δD analysis has been achieved in an automated system. Reduction in 1-σ standard deviation of a single mass-spectrometer analysis to 1.3‰ is achieved by (1) bonding catalyst to glass rods and assigning use to specific equilibration chambers to monitor performance of catalyst,...

A small tract of heretofore-unrecognized Paleogene rocks lies about 30 km northeast of Santa Maria and 1 km southwest of the Sur-Nacimiento fault zone near upper Pine Creek. This poorly exposed assemblage of rocks is less than 50 m thick, lies unconformably on regionally distributed Upper Cretaceous submarine-fan deposits, and...

Most of the storm surge models presented in the literature are vertically averaged and calculate only the sea-surface elevation and mean flow. Whereas these models may be adequate for predicting storm surge heights for flooding purposes, they neglect the vertical structure of the flow and the boundary shear stress, which...

Rb-Sr mean model ages of  for glauconites from the Cambrian lower Bonneterre Formation in southern and central Missouri (in contrast to mean model ages of  from the middle and upper Bonneterre) are in excellent agreement with...

Studies have demonstrated the utility of fluvial bed sediment chemical data in assesing local water-quality conditions. However, establishing local background trace element levels can be difficult. Reference to published average concentrations or the use of dated cores are often of little use in small areas of diverse local petrology, geology,...

Detrital amber pebbles and granules have been discovered in Upper Triassic strata on the Colorado Plateau. Although amber pre-viously has been reported from Pennsylvanian, Jurassic, Cretaceous, and Tertiary strata, we know of no other reported Triassic occurrence in North America or the Western...

Evaporative concentration of irrigation water diverted from the Colorado River to the Salton Sea basin for several decades has produced an overlying system (that includes drainwater and surface waters) whose composition is highly variable and differs from that of the shallow regional ground water beneath it. The role of hydrologic...

The one-dimensional consolidation theory equation is solved for an aquifer system using a pseudospectral method. The spatial derivatives are computed using Fast Fourier Transforms and the time derivative is solved using a fourth-order Runge-Kutta scheme. The computer model calculates compaction based on the void ratio changes accumulated during the simulated...

As part of a comprehensive geologic study of coastal Alabama and Mississippi, the U.S. Geological Survey is investigating coastal sediment transport in Mobile Bay and the adjacent shelf. Satellite imagery from the NOAA AVHRR is being used to provide data on the variability of spatial patterns in the near-surface suspended...

Sm/1bNd and Rb/1bSr isotopic systematics have been determined for rare-earth element (REE) rich samples of carbonate, iron ore, and silicate types from the world's largest known REE deposit at Bayan Obo, China. The results yielded neither Rb/1bSr nor Sm/1bNd isochrons within analytical error. Isochronous relationships may have been disturbed in...

In part of a large abandoned mining complex, electromagnetic geophysical surveys were used along with data derived from cores and monitoring wells to infer sources of contamination and subsurface hydrologic connections between acidic refuse deposits and adjacent undisturbed geologic materials. Electrical resistivity increases sharply along the boundary of an elevated...

Demethylation of monomethylmercury in freshwater and estuarine sediments and in bacterial cultures was investigated with 14CH3HgI. Under anaerobiosis, results with inhibitors indicated partial involvement of both sulfate reducers and methanogens, the former dominating estuarine sediments, while both were active in freshwaters. Aerobes were the most significant demethylators in estuarine sediments, but...

Methane oxidation was measured in an unconfined sand and gravel aquifer (Cape Cod, Mass.) by using in situ natural-gradient tracer tests at both a pristine, oxygenated site and an anoxic, sewage-contaminated site. The tracer sites were equipped with multilevel sampling devices to create target grids of sampling points; the injectate...

Three informal palynological assemblage zones can be distinguished in samples from Chinle Formation outcrops in Utah, Arizona and New Mexico. The oldest zone (zone I) is in the Temple Mountain Member in southeastern Utah; the middle zone (zone II) is in the Shinarump, Moss Back, Monitor Butte and (lower part...

A systematic U Pb, Sm Nd, and Rb Sr isotopic study shows that the Estherville mesosiderite was formed between 4.56 and 4.43 Ga. Observed isotopic heterogeneity is in agreement with multiple generations of meteoritic impacts described in other mesosiderites.At least part of the Estherville silicate fraction was formed early in...