Fractal analysis of Laurentide glacial boundaries in the conterminous United States : an honors thesis (HONRS 499)

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Adams, Byron A.
Rice-Snow, Robin S.
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Thesis (B.?.)
Honors College
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The Wisconsinan event of the Laurentide Ice Sheet covered a wide fetch of land from New Jersey to Montana in the conterminous United States. The contact it created between new tills and older units formed a boundary that exhibits irregular curves with many scales of wandering. This boundary crosses five physiographic provinces: the Piedmont, Valley and Ridge, Appalachian Plateau, Central Lowlands and Great Plains Provinces. We have performed divider analyses on the Wisconsinan maximum advance to correlate plan-view geometry of the boundary with local geomorphology. In addition to dividing the boundary into sections according to province, large provinces were also split up into smaller segments to reduce the issue of scale discrepancy. A total of 37 line segments were created including: five of the whole province sections and 32 subsequent divisions.All sections of this boundary of maximum advance were found to have fractal character. Richardson plots showed at least one area of linearity and in some cases two. These linear areas led to calculated fractal dimension (D) values. The ranges of these D values are quite broad. The fine scales showed values of 1.01-1.17 and the coarse scales had values of 1.01-1.32. The Appalachian Plateau Province shows a fractal character pattern that is different from that of most other plots, where the amount of wandering decreases in the coarse scales. The subsections of this area also show D values that occur over similar ranges of step lengths. These studies are significant, as they may imply an active scale-specific process in the formation of these boundary segments.