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Eugene Merle Shoemaker

Publications and source records attributed to Eugene Merle Shoemaker.

66 records · Page 4Linked to original sources
USGS1961

Paper A: Terrestrial features of impact origin

Craters made by meteorites striking the earth are discussed, with attention given to geological evidence for discriminating them from craters formed by other structural processes. The major known meteorite craters are briefly described, as well as other features that are considered probable or possible meteorite craters on the basis of less conclusive evidence. Separate tabulations are given of (1) topographic features either known to be meteorite craters, or considered as possible meteorite craters through lack of conclusive evidence to the contrary, and (2) topographic features once considered to be possible meteorite impact craters, but which are now believed to be of other origin.

Conference Paper↗
USGS1959

Impact mechanics at Meteor Crater, Arizona

Meteor Crator is a bowl-shaped depression encompassed by a rim composed chiefly of debris stacked in layers of different composition. Original bedrock stratigraphy is preserved, inverted, in the debris. The debris rests on older disturbed strata, which are turned up at moderate to steep angles in the wall of the crater and are locally overturned near the contact with the debris. These features of Meteor Crater correspond closely to those of a crater produced by nuclear explosion where depth of burial of the device was about 1/5 the diameter of the resultant crater. Studies of craters formed by detonation of nuclear devices show that structures of the crater rims are sensitive to the depth of explosion scaled to the yield of the device. The structure of Meteor Crater is such as would be produced by a very strong shock originating about at the level of the present crater floor, 400 feet below the original surface. At supersonic to hypersonic velocity an impacting meteorite penetrates the ground by a complex mechanism that includes compression of the target rocks and the meteorite by shock as well as hydrodynamic flow of the compressed material under high pressure and temperature. The depth of penetration of the meteorite, before it loses its integrity as a single body, is a function primarily of the velocity and shape of the meteorite and the densities and equations of state of the meteorite and target. The intensely compressed material then becomes dispersed in a large volume of breccia formed in the expanding shock wave. An impact velocity of about 15 km/sec is consonant with the geology of Meteor Crater in light of the experimental equation of state of iron and inferred compressibility of the target rocks. The kinetic energy of the meteorite is estimated by scaling to have been from 1.4 to 1.7 megatons TNT equivalent.

Open-File Report↗
USGS1952

Distribution of ore deposits and spectrographic analyses of some rocks and ores on the Colorado Plateau

The geographic pattern of known igneous rocks and ore deposits on the Colorado Plateau suggests a zonal arrangement of several types of ore deposits around centers of igneous activity. Spectrographic analyses of rocks and ores on the Plateau have been obtained in an effort to determine the distribution of elements and to examine the relationships between types of ore deposits and between the ore deposits and igneous rocks. Over 170 analyses of rocks and ores are given in this report. A preliminary study of these analyses suggests that the proportion of uranium, vanadium, copper, and silver in the uranium ores varies geographically, and that the pattern of variation may be in part concentric about some of the major laccolithic intrusions. It is also suggested that the following ratios of metals contained in the uranium ores are possible guides to larger-than-average ore deposits: (1) lead/uranium greater than 1, (2) lead/zinc greater than 10, and (3) zinc/geometric mean of cobalt and nickel less than 10.

Colorado↗