『Abstract
Theories that propose feedbacks among climate, tectonics, and
surface processes commonly assume that erosion is enhanced by
glacial activity. Indeed, studies have shown that glaciers appear
to limit the elevation of mountain ranges; however, comparisons
between rates of glacial and nonglacial erosion are difficult
to make. Ideally, such comparisons must hold precipitation and
lithology constant, while only varying the erosional regime. Located
in a climatic transition zone during the Pleistocene, the east-west−trending
valleys of the Bitterroot Range present an opportunity for a quantitative
analysis of glacial and nonglacial erosion because the north-facing
sides of the valleys were glaciated, whereas the south-facing
slopes were not. The different erosional regimes operating on
either side of the valleys created strongly asymmetric ridges.
Ridgelines separating the east-west−trending valleys have been
pushed south-ward by glacial headwall retreat such that ridge-to-valley
distances are 〜50% greater on the north-facing slopes than on
the south-facing slopes. In addition, mean hillslope angles are
6゜ lower on the glaciated slopes than on the unglaciated slopes,
and calculations of geophysical relief suggest that, on average,
glaciers have removed nearly twice as much rock as nonglacial
processes. Finally, we conclude that, although rates of vertical
incision by glacial processes in the Bitterroot Range were more
rapid than nonglacial processes, the dominant geomorphological
impact of glaciers was lateral erosion by headwall retreat.
Keywords: glacial erosion; cirque headwall retreat; divide migration;
relief; Bitterroot Range.』
Introduction
Methods
Field site description
Topographic analyses
Results
Discussion
Conclusion
Acknowledgments
References cited