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Cryostratigraphic mapping in the main shaft of the CRREL tunnel indicates secondary modification of original Pleistocene-age syngenetic permafrost. Layered, lenticular-layered and micro-lenticular cryostructures within undisturbed silt characterise the syngenetic permafrost. Thawed and refrozen deposits are characterised by massive and reticulate-chaotic cryostructures. The micro-morphology of typical cryostructures, as observed through an environmental scanning electron microscope (ESEM), is described. It is inferred that preferential cryogenic modification has occurred due to fluvio-thermal erosion operating along ice wedges. Soil and ice pseudomorphs are the manifestation of this process. Gravel, silt, ice and...
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...
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;...
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.
map background search result map search result map Characteristics of discontinuous permafrost based on ground temperature measurements and electrical resistivity tomography, southern Yukon, Canada Germanium/silicon ratios in the Copper River basin, Alaska: weathering and partitioning in periglacial versus glacial environments Three decades of landscape change in Alaska’s Arctic National Parks: Analysis of aerial photographs, c. 1980-2010 Air Quality Monitoring Protocol for Denali National Park & Preserve, Alaska Further cryostratigraphic observations in the CRREL permafrost tunnel, Fox, Alaska Geology and new mineralization in the Joss’alun belt, Atlin area Monitoring Geohazards near Pipeline Corridors with an Advanced InSAR Technique and Geomechanical Modelling Relations between water physico-chemistry and benthic algal communities in a northern Canadian watershed: defining reference conditions using multiple descriptors of community structure Dicarboxylic acids, oxocarboxylic acids and α-dicarbonyls in fine aerosols over central Alaska: Implications for sources and atmospheric processes Further cryostratigraphic observations in the CRREL permafrost tunnel, Fox, Alaska Germanium/silicon ratios in the Copper River basin, Alaska: weathering and partitioning in periglacial versus glacial environments Geology and new mineralization in the Joss’alun belt, Atlin area Air Quality Monitoring Protocol for Denali National Park & Preserve, Alaska Relations between water physico-chemistry and benthic algal communities in a northern Canadian watershed: defining reference conditions using multiple descriptors of community structure Characteristics of discontinuous permafrost based on ground temperature measurements and electrical resistivity tomography, southern Yukon, Canada Three decades of landscape change in Alaska’s Arctic National Parks: Analysis of aerial photographs, c. 1980-2010 Monitoring Geohazards near Pipeline Corridors with an Advanced InSAR Technique and Geomechanical Modelling Dicarboxylic acids, oxocarboxylic acids and α-dicarbonyls in fine aerosols over central Alaska: Implications for sources and atmospheric processes