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Publications

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The relocation of microearthquakes in the northern Mississippi Embayment The relocation of microearthquakes in the northern Mississippi Embayment

Three-component seismograms, recorded by a small array of digital instruments in the northern Mississippi embayment, consistently show a high-amplitude phase on the vertical component that arrives approximately 0.8 s before the shear wave. On the basis of its timing and apparent velocity, this phase is identified as an S-P conversion from the boundary between the unconsolidated Cenozoic...
Authors
M.C. Andrews, Walter D. Mooney, R.P. Meyer

Remote sensing of lunar pyroclastic mantling deposits Remote sensing of lunar pyroclastic mantling deposits

Mantling deposits on the Moon are considered to be pyroclastic units emplaced on the lunar surface as a result of explosive fire fountaining. These pyroclastic units are characterized as having low albedos, having smooth fine-textured surfaces, and consisting in part of homogeneous, Febearing volcanic glass and partially crystallized spheres. Mantling units exhibit low returns on...
Authors
Lisa R. Gaddis, Carle M. Pieters, B. Ray Hawke

Plasticity at crack tips in Gd3Ga5O12 garnet single crystals deformed at temperatures below 950°C Plasticity at crack tips in Gd3Ga5O12 garnet single crystals deformed at temperatures below 950°C

Single crystals of Gd3Ga5O12 have been strained under confining pressure (1 5 GPa) at temperatures below 950°C. No evidence for macroscopic plasticity was found, but transmission electron microscopy revealed dislocation generation at crack tips. Deformation mechanisms are different from those operating in the high-temperature regime: extending stacking faults in {110} planes and the 〈010...
Authors
H. Garem, J. Rabier, Stephen H. Kirby

Geomorphologic evidence for ground ice on Mars Geomorphologic evidence for ground ice on Mars

For ground ice to exist on Mars, two conditions have to be met. One is the presence of permafrost; the second is the availability of water. Because the mean temperature of Mars’surface is − 80 C., permafrost 1–3 km thick occurs over the entire planet. Remote-sensing measurements suggest that water presently exists in the atmosphere and in the polar caps; frost has been observed at the...
Authors
Baerbel K. Lucchitta

Impact on the Columbia River of an outburst of Spirit Lake Impact on the Columbia River of an outburst of Spirit Lake

A one-dimensional sediment-transport computer model was used to study the effects of an outburst of Spirit Lake on the Columbia River. According to the model, flood sediment discharge to the Columbia from the Cowlitz would form a blockage to a height of 44 feet above the current streambed of the Columbia River, corresponding to a new streambed elevation of -3 feet, that would impound the...
Authors
W. G. Sikonia

Rapid postglacial shoreline changes in the western Gulf of Maine and the Paleo-Indian environment Rapid postglacial shoreline changes in the western Gulf of Maine and the Paleo-Indian environment

Rapid shoreline regression and transgression along the western Gulf of Maine between 13,000 and 9000 years B.P. are inferred to have produced a nearshore marine environment low in biologic productivity. Paleo-Indians living near the coast of the Gulf were probably forced to rely on nonmarine resources landward of the late-glacial marine limit. Thus, Paleo-Indian sites of the time period...
Authors
Robert N. Oldale
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