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The discovery of fullerenes in the 1.85 billion-year-old Sudbury meteorite crater

Description: Fullerenes (C{sub 60}, C{sub 70}) have been identified by laser time-of-flight and electron-ionization mass spectroscopy in rock samples (black tuff in the Onaping formation) from the crater. They were likely synthesized within the impact plume from carbon contained in the meteorite. The isotopic ratios suggest {sup 13}C enrichment. They are associated with sulfur which may have protected them. This is the largest known deposit of naturally occurring fullerenes.
Date: February 1, 1996
Creator: Becker, L.; Bada, J.L.; Winans, R.E.; Hunt, J.E.; Bunch, T.E. & French, B.M.
Partner: UNT Libraries Government Documents Department

Meteorological data for four sites at surface-disruption features in Yucca Flat, Nevada Test Site, Nye County, Nevada, 1985--1986

Description: Surface-disruption features, or craters, resulting from underground nuclear testing at the Nevada Test Site may increase the potential for ground-water recharge in an area that would normally produce little, if any, recharge. This report presents selected meteorological data resulting from a study of two surface-disruption features during May 1985 through June 1986. The data were collected at four adjacent sites in Yucca Flat, about 56 kilometers north of Mercury, Nevada. Three sites (one in each of two craters and one at an undisturbed site at the original land surface) were instrumented to collect meteorological data for calculating bare-soil evaporation. These data include (1) long-wave radiation, (2) short-wave radiation, (3) net radiation, (4) air temperature, and (5) soil surface temperature. Meteorological data also were collected at a weather station at an undisturbed site near the study craters. Data collected at this site include (1) air temperature, (2) relative humidity, (3) wind velocity, and (4) wind direction.
Date: December 1, 1994
Creator: Carman, R.L.
Partner: UNT Libraries Government Documents Department

The Beaverhead impact structure, SW Montana and Idaho: Implications for the regional geology of the western U.S.

Description: The Beaverhead impact structure in SW Montana and Idaho is an allochthonous fragment of a large impact structure ({approximately} 100 km diameter) that was transported some distance eastward during the Cretaceous Sevier orogeny. It is the first tectonic fragment of a large impact structure identified in the geologic record. The present evidence for impact consists of shatter cones, pseudotachylites, and planar deformation features in quartz. The age of the impact is not well constrained but is estimated to be Neoproterozoic to Cambrian (1000-500 Ma). The Beaverhead impact event must have created other features that may be preserved, elsewhere in western Montana and Idaho. These include proximal and distal ejecta (which may be misinterpreted as diamictites and/or tuff horizons) and other fragments of the crater floor containing shatter cones and pseudotachylite. A large circular gravity, magnetic and topographic anomaly, which could be the root of the impact structure, has been identified near Challis, Idaho. An enigmatic lithic tuff, identified in drill cores from the Challis area and an intraformational quartzite breccia in the Leaton Gulch area may be impact-related deposits, but no definitive evidence of shock metamorphism has been observed in these materials. The discovery of more pieces of the Beaverhead puzzle, as well as the recognition of other large impacts in the geologic record, are likely once the regional geologic community grows to accept the incidence of such events and becomes more familiar with the features of shock metamorphism in the field. To that end, the community of geologists in this area should integrate the Beaverhead structure into their research and teaching curriculum.
Date: March 17, 1994
Creator: Fiske, P.S. & Hargaves, R.B.
Partner: UNT Libraries Government Documents Department

Radiation Damage From Single Heavy Ion Impacts on Metal Surfaces

Description: The effects of single ion impacts on the surfaces of films of Au, Ag, In and Pb have been studied using in-situ transmission electron microscopy. On all of these materials, individual ion impacts produce surface craters, in some cases, with associated expelled material. The cratering efficiency scales with the density of the irradiated metal. For very thin Au foils ({approx} 20--50 nm), in some cases individual ions are seen to punch small holes completely through the foil. Continued irradiation results in a thickening of the foil. The process giving rise to crater and hole formation and other changes observed in the thin foils has been found to be due to pulsed localized flow--i.e. melting and flow due to the thermal spikes arising from individual ion impacts. Experiments carried out on thin films of silver sandwiched between SiO{sub 2} layers have indicated that pulsed localized flow also occurs in this system and contributes to the formation of Ag nanoclusters in SiO{sub 2}--a system of interest for its non-linear optical properties. Calculation indicates that, when ion-induced, collision cascades occur near surfaces (within {approx} 5 nm) with energy densities sufficient to cause melting, craters are formed. Crater formation occurs as a result of the explosive outflow of material from the hot molten core of the cascade. Processes occurring in the sandwiched layer are less well understood.
Date: June 1, 1998
Creator: Donnelly, S. E. & Birtcher, R. C.
Partner: UNT Libraries Government Documents Department

Crater Wells, Richland Gas Field, Louisiana

Description: Technical paper issued by the Bureau of Mines over "the history of the craters in the Richland gas field. The data have been collected at various times over a period of four years. The equipment and methods of control are discussed, and photographs show the surface conditions at various intervals in the life of the craters" (p. 1). This paper includes tables, maps, photographs, and illustrations.
Date: 1932
Creator: Hill, Harry Blackburn
Partner: UNT Libraries Government Documents Department

On Cratering: A Brief History, Analysis, and Theory of Cratering

Description: Cratering is a subject that has been studied by many investigators for many years for many purposes. These purposes range from experimental studies of physical properties to large scale excavations using explosive charges of kiloton size. In the past ten years considerable effort has been devoted to cratering experiments for the purposes of determining the effects of cratering by nuclear explosions, with recent accent on Plowshare applications. From the large amount of data available for craters in alluvian has been possible to establish very reliable relationships between charge size, depth of bursty crater radii, and crater depths. In addition it has been possible to construct a preliminary theory of the mechanics of explosive crater formation. The available experimental data for nuclear and high explosive craters are reviewed, with particular emphasis on the data for desert alluvium, and the pertinent relationships are derived. A theory of the important cratering mechanisms, which has been evolved on the basis of these data and data from other sources, is outlined. (auth)
Date: August 22, 1961
Creator: Nordyke, M. D.
Partner: UNT Libraries Government Documents Department

Ejecta Studies

Description: One-hundred and forty-six ejecta measurement stations encircled ground zero at eight radial distances ranging from 373 to 1707 meters. The twenty-four sampling lines were spaced at fifteen-degree intervals. Data presented were recovered from stations located at radial distances of 640, 853, 1067, 1280, and 1707 meters. An attempt will be made to recover data at stations located closer to ground zero at a later time. Preliminary analysis of ejecta data indicates that areal density varies inversely as distance raised to the 3.64 power. Circumferential variation of areal density is about a factor of 30 at the 1707 meter radial distance, a factor of 10 at the 1280 meter radial distance, and a factor of 7 at the 853 meter radial distance. Cursory treatment is given to several related subjects, including outer limit of base surge dust deposit, volumetric ejecta densities, locations of natural missiles and impact craters, and the outer limit of ballistic debris. One case of missile damage to a reinforced concrete structure is documented. Raw data are included in the appendix. (auth)
Date: October 1, 1962
Creator: Roberts, W. A. & Carlson, R. H.
Partner: UNT Libraries Government Documents Department

Application of NMR shock barometer to naturally shocked minerals

Description: The shock-loading of natural materials by an impact, such as a comet or meteorite, can result in the formation of modified and altered phases in the target rock. In order to characterize the resulting material and to evaluate the extent of shock modification, the authors have used nuclear magnetic resonance (NMR) spectroscopy to examine several natural and experimentally shocked minerals. NMR spectroscopy is used to characterize the formation of high pressure silica polymorphs and amorphous material associated with the shocked Coconino Sandstone from Meteor Crater, Arizona. Five samples of the sandstone were obtained from several locations at the crater to represent a range of shock conditions associated with the hypervelocity impact of a 30 meter-diameter meteorite. The NMR spectra for these powdered materials exhibit peaks assigned to quartz, coesite, stishovite, and glass. A new resonance, identified as a densified form of amorphous silica with silicon in tetrahedra with one hydroxyl group, is observed for two of the moderately shocked samples. Experimental shock-loading of dry and water-saturated Coconino Sandstone powders provides shock-metamorphosed material that exhibit broadening of NMR resonances with increasing shock pressure, but no evidence of the new dense silica phase.
Date: July 1, 1994
Creator: Cygan, R. T. & Boslough, M. B.
Partner: UNT Libraries Government Documents Department

Fuel dispersal in high-speed aircraft/soil impact scenarios

Description: The objective of this study is to determine how the jet fuel contained in aircraft wing tanks disperses on impact with a soft terrain, i.e., soils, at high impact velocities. The approach used in this study is to combine experimental and numerical methods. Tests were conducted with an approximately 1/42 linear-scale mass-model of a 1/4 span section of a C-141 wing impacting a sand/clay mixture. The test results showed that within the uncertainty of the data, the percentage of incident liquid mass remaining in the crater is the same as that qualitatively described in earlier napalm bomb development studies. Namely, the percentage of fuel in the crater ranges from near zero for grazing impacts to 25%--50% for high angles of impact. To support a weapons system safety assessment (WSSA), the data from the current study have been reduced to correlations. The numerical model used in the current study is a unique coupling of a Smooth Particle Hydrodynamics (SPH) method with the transient dynamics finite element code PRONTO. Qualitatively, the splash, erosion, and soil compression phenomena are all numerically predicted. Quantitatively, the numerical method predicted a smaller crater cross section than was observed in the tests.
Date: January 1, 1996
Creator: Tieszen, S.R. & Attaway, S.W.
Partner: UNT Libraries Government Documents Department

Craters produced on metals by single ion impacts.

Description: Single ion impacts have been observed using in-situ transmission electron microscopy during irradiation. In addition to internal defects, single-ion impacts create surface craters as large as 12 nm on In, Ag, Pb and Au. Crater formation rates have been determined from video recordings with a time-resolution of 33 milliseconds. The cratering rate for Xe ions increases linearly with increasing target mass density above a threshold density of approximately 7 gm/cm{sup 3}. The cratering rate increases as the ion mass is increased. These results suggest that cratering requires a high energy-density, near-surface displacement cascade. TRIM calculations have been made in an effort to establish a near-surface energy-density criterion for cratering.
Date: December 23, 1998
Creator: Birtcher, R. C.
Partner: UNT Libraries Government Documents Department