Research about Alaska, Utah

USGS2010

Viscosity and finite strength of the mantle as determined from water and ice loads

Some recent examples of transient Earth loads (Lake Bonneville, Utah; Glacier Bay, Alaska; northeast Greenland) indicate that both the viscosity and finite strength of the mantle are lower than is commonly presumed. A time constant (1/ e ) of 4000 years is estimated for Lake Bonneville, and of 1000 years for northeast Greenland. A strain rate of 10 −14 is typical. These figures imply viscosities in a homogeneous half space ranging from 10 20 to 10 21 poises. An upper limit of finite strength is set by Lake Bonneville at a few times 10 6 dyn/cm 2 . If mountain ranges like the Sierra Nevada or Himalaya are regarded as dynamically supported rather than static systems, this low value is not incompatible with other geologic observations.

Alaska, Utah↗

USGS1955

Photogeologic procedures in geologic interpretation and mapping

In the past few years increasing use has been made of aerial photographs for geologic interpretation and mapping within the U.S. Geological Survey. As a specialized technique in interpretation and mapping, however, photogeologic procedures were extensively used (1947-1953) in the Survey's geologic mapping of Naval Petroleum Reserve No. 4 in northern Alaska and in mapping part of the Colorado Plateau of western United States, principally in Utah (1951-present). Photogeologic work was performed by a specialized group of geologists that was organized as the Photogeology Section in June 1953. This group has more recently made studies of northeastern Utah, southern and southeastern Alaska, and central Alaska. Various photogeologic procedures have been used in these studies; some procedures have been modified, and new ones have been developed. It is primarily the purpose of this paper to discuss these procedures. Photogeologic procedures or techniques used outside the Geological Survey are not discussed herein.

Alaska, Utah↗