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We measured the surface velocity field during the summers of 1999 and 2000 on the 7 km long, 185 m thick Bench Glacier, Alaska, USA. In the spring of both years, a short-lived pulse of surface velocity, 2-4 times the annual mean velocity, propagated up-glacier from the terminus at a rate of similar to 200-250 m d super(-1). Displacement attributable to rapid sliding is similar to 5-10% of the annual surface motion, while the high-velocity event comprised 60-95% of annual basal motion. Sliding during the propagating speed-up event peaked at 6-14 cm super(-1), with the highest rates in mid-glacier. Continuous horizontal and vertical GPS measurements at one stake showed divergence and then convergence of the ice surface...
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Tags: Monitoring 1-Changes in Plant and Animal Distribution: Flora,
Monitoring 5-Physical Science
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Tags: A1-US Parks,
Monitoring 5-Physical Science
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Tags: MONITORING 5-PHYSICAL SCIENCE
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Tags: MONITORING 5-PHYSICAL SCIENCE
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Tags: MONITORING 5-PHYSICAL SCIENCE
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Tags: Monitoring 5-Physical Science
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Tags: Monitoring 5-Physical Science
Observations of surface motion and ice deformation from 2002-03 were used to infer mean stress fields in a cross-section of Black Rapids Glacier, Alaska, USA, over seasonal timescales. Basal shear stresses in a well-defined zone north of the center line (orographic left) were approximately 7% and 16% lower in spring and summer, respectively, than in winter. Correspondingly higher stresses were found near the margins. These changes in the basal shear stress distribution were sufficiently large to cause mean surface velocities to be 1.2 and 1.5 times larger in spring and summer than in winter. These results were inferred with a simple inverse finite-element flow model that can successfully reproduce bulk surface velocities...
From its origin in rugged granitic highlands of the central Brooks Range, the Noatak River flows westward between the De Long Mountains and the Baird Mountains before turning south to enter Kotzebue Sound. Glaciers of middle and late Pleistocene age entered the Noatak River valley from the east, north, and south. Glaciers flowed down the upper Noatak River valley from the rugged peaks at its head, merging with tributary glaciers that issued from cirque-headed valleys along its south flank. Farther downvalley, small glaciers flowed northward from the Baird Mountains and much larger glaciers issued from the De Long Mountains. The De Long Mountains glaciers expanded southward to cover parts of the Noatak valley floor;...
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Tags: Monitoring 1-Changes in Plant and Animal Distribution: Ecosystems,
Monitoring 5-Physical Science
Studies the implication of the modeling gravity and magnetism of ophiolites on Cordilleran terranes in Brooks Range, Australia. Geophysical characteristics of mafic and ultramafic rocks; Effect of low-density Cenozoic cover rocks on isostatic residual gravity values of the Noatak region; Causes of spatial separation strains.
The surfical geologic map incorporates parts of ten surficial geologic maps previously published at 1:250,000 scale. In addition, a small part of the buffer zone mapped in the southwest corner of the map area was compiled from unpublished surficial geologic mapping of the Shungnak 1:250,000-scale quadrangle. Each of those individual maps was developed from (1) aerial and surface observations of morphology and composition of unconsolidated deposits, (2) tracing the distribution and interrelation of terraces, abandoned meltwater channels, moraines, abandoned lake beds, and other landforms, (3) stratigraphic study of exposures along lake shores and river bluffs, (4) examination of sediments and soil profiles in auger...
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