Origin and Environmental Significance of Large-scale Patterned Ground, Donnelly Dome Area, Alaska
Origin and Environmental Significance of Large-scale Patterned Ground, Donnelly Dome Area, Alaska

Author: Richard E. Church

Publisher:

Published: 1965

Total Pages: 102

ISBN-13:

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Large-scale patterned ground in the Donnelly Dome area of central Alaska consists of polygons 25 to 46 m in diameter bounded by shallow troughs 1 to 2 m wide that form the sides of the polygons. The troughs are underlain by wedge-shaped masses of sediments that extend downward 2 to 3 m. Texture of the sediments of the wedges is distinct from that of the poorly stratified glacial outwash gravel that the wedges transect. Sediments of the wedge vary texturally along the strike and vertically within a given wedge. The coarsest material in the wedge is about 75 mm in diameter, which is the same size as the coarsest material in the outwash. The fine material in the wedges is silt, the same as that which blankets the area. The patterned ground of the Donnelly Dome area originated during Wisconsin time when the mean annual air temperature was at least 3C colder than now. Wigh the warming of the climate in post-Wisconsin time most of the perennially frozen gravel thawed and the ice wedges melted. The voids created by the melting of the ice wedges were filled with sediment that was washed from the surface or collapsed from the thawed sides of the voids. The troughs bounding the polygons are now, however, no longer underlain with ice wedges but with ice wedge pseudomorphs (fossil ice wedges). (Author).

Hydrologic Reconnaissance of the Delta River and Its Drainage Basin, Alaska
Hydrologic Reconnaissance of the Delta River and Its Drainage Basin, Alaska

Author:

Publisher:

Published: 1971

Total Pages: 100

ISBN-13:

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A one-year reconnaissance study was made of a large braided glacial river and its drainage basin for which a minimum of hydrometric and meteorologic data existed. The report includes estimates of the water balance, flow-duration curves, and sediment characteristics, and descriptions of stream response to glacial melt and rain, channel geometry and channel processes. Mean annual basin precipitation is estimated at 40.4 in. and mean annual loss of permanent glacial storage is about 1 in. About 30% of this leaves the basin as evapotranspiration, 50% as stream flow, and 20% as groundwater flow. Characteristics of response to glacial melt are outlined. Flow peaks near the mouth occur within 24 hours of rainfall greater than 0.5 in./day at foothills meteorological stations; rains of less than that amount do not generally produce discernible stream response. Stream channel geometry is described in detail. Most channels on the lower floodplain are asymmetrical and are roughly triangular or parabolic, and have high width/depth ratios. At-a-station hydraulic geometry is described. Surveys and ground and aerial photography are used to describe channel changes. (Author).