Scaling the Teflon Peaks: Rock type and the generation of extreme relief in the glaciated western Alaska Range

Journal of Geophysical Research F: Earth Surface
By: , and 

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Abstract

Parts of the Alaska Range (Alaska, USA) stand in prominent exception to the “glacial buzzsaw hypothesis,” which postulates that terrain raised above the ELA is rapidly denuded by glaciers. In this paper, we discuss the role of a strong contrast in rock type in the development of this exceptional terrain. Much of the range is developed on pervasively fractured flysch, with local relief of 1000–1500 m, and mean summit elevations that are similar to modern snow line elevations. In contrast, Cretaceous and Tertiary plutons of relatively intact granite support the range's tallest mountains (including Mt. McKinley, or Denali, at 6194 m), with 2500–5000 m of local relief. The high granitic peaks protrude well above modern snow lines and support many large glaciers. We focus on the plutons of the Denali massif and the Kichatna Mountains, to the west. We use field observations, satellite photos, and digital elevation data to demonstrate how exhumation of these plutons affects glacier longitudinal profiles, the glacial drainage network, and the effectiveness of periglacial processes. In strong granite, steep, smooth valley walls are maintained by detachment of rock slabs along sheeting joints. These steep walls act as low-friction surfaces (“Teflon”), efficiently shedding snow. Simple scaling calculations show that this avalanching may greatly enhance the health of the modern glaciers. We conclude that, in places such as Denali, unusual combinations of rapid tectonic uplift and great rock strength have created the highest relief in North America by enhancing glacial erosion in the valleys while preserving the peaks.

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Additional publication details

Publication type Article
Publication Subtype Journal Article
Title Scaling the Teflon Peaks: Rock type and the generation of extreme relief in the glaciated western Alaska Range
Series title Journal of Geophysical Research F: Earth Surface
DOI 10.1029/2011JF002068
Volume 117
Issue F1
Year Published 2012
Language English
Publisher American Geophysical Union
Contributing office(s) Alaska Science Center Geology Minerals
Description Article F01031: 20 p.
Country United States
State Alaska
Other Geospatial Western Alaska Range