The L-type Schmidt hammer is a hand-carried impact instrument that was originally designed and developed to test the compressive strength of concrete. When properly impacted against a stiff material the device measures the amount of rebound of a spring-loaded hammer, with the rebound of the hammer being directly proportional to the strength of the material tested. Application of this instrument to rock, specifically water-saturated zeolitized tuff, is demonstrated through a set of correlation diagrams that relate Schmidt hammer rebound values, obtained from core samples and from the sites where samples were taken, to physical properties measured on rock samples in the laboratory. The properties include compressive strength, compressional and shear velocities, and dynamic and static Young's shear and bulk moduli. The correlation diagrams apply only to zeolitized tuff of the type found at the Nevada Test Site in its natural state (freshly excavated). These diagrams enable the user of the L-type Schmidt hammer to immediately obtain values of physical properties of such rocks in place, a convenience desirable where conventional sampling is not feasible or is impossible, and when results are required on short notice. The charts apply to L-type hammers that are calibrated to a nominal rebound value of 74. Calibration is made on a 35-pound-(16-kg-) test anvil with a steel-hardened test surface of Brinell hardness = 500 kg/mm 2 .

Open-File Report↗

USGS1968

Geological interpretation of a Gemini photo

Study of the Gemini V photograph of the Salt Range and Potwar Plateau, West Pakistan, indicates that small-scale orbital photographs permit recognition of the regional continuity of some geologic features, particularly faults and folds that could he easily overlooked on conventional air photographs of larger scale. Some stratigraphic relationships can also be recognized on the orbital photograph, but with only minimal previous geologic knowledge of the area, these interpretations are less conclusive or reliable than the interpretation of structure. It is suggested that improved atmospheric penetration could be achieved through the use of color infrared film. Photographic expression of topography could also be improved by deliberately photographing some areas during periods of low sun angle.

Potwar Plateau;Salt Rrange↗

USGS1967

Source and size of the leakage zone of the natural dam, Lago Laja, Chile

Explore the source record for details and available documents.

Open-File Report↗