| Summary: | Remnants of late Wisconsin drift on bedrock benches 800-1,500 feet above Wolf Creek are the oldest evidence of glaciation recognized. Deposits of very latest Wisconsin and possibly, in part, earliest post-Wisconsin drift are the product of a limited advance or extended pause in recession from the late Wisconsin climax. Wolf Glacier was then at least several hundred feet thicker, and its terminus was not less than 4 or 5 miles beyond the present snout. Post-Wisconsin xerothermic conditions caused extensive ice shrinkage, and the glaciers become smaller than at present. During this period an extensive valley train was formed, alluvial cones and fans were built, and a mature white spruce forest developed up-valley to its natural tree line. A subsequent expansion and readvance culminated between 1840 and 1890. Large raw lateral and terminal moraines and a trim line in the mature spruce forest are the principal manifestations of this advance, which is believed to be of climatic, rather than of orogenic or seismic, origin. Subsequently shrinkage, recession, and stagnation have ruled. The lower 9 miles of Wolf Glacier are stagnant, and this section has experienced 350-500 feet of vertical ablation, with terminal recession of only a few hundred yards. Degradation was interrupted by expansion and advance of certain favorably situated ice streams, starting in the late 1930's and extending into the 1940's. Slight rejuvenation also occurred in the uppermost stagnant part of Wolf Glacier. This reactivation was on the wane by 1947 and appears to have been but a minor interruption in the general shrinkage and degradation of the last fifty to a hundred years. Analysis of records suggests a climatic, rather than a seismic, cause for this recent rejuvenation. © 1951 University of Chicago Press. The assistance of all members of the 1941 Wood Yukon Expedition and especially of its leader, Walter A. Wood, is warmly acknowledged. A grant in support of this work was made by the University of Illinois. Dr. H. S. Bostock has kindly ...
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