This project will investigate the role of rock type on glacial erosion. While the processes of glacial erosion are understood, the significance of this research lies in addressing the control of both the type of rock and the degree of fracturing of the rock mass on the rates and patterns of erosion. Erosion rates control sediment delivery to rivers and oceans, while erosion patterns dictate both the topographic architecture and the heights of mountain ranges being attacked by glaciers. Determination of erosion rates in contrasting rock types, exposed in the granitic cores and metamorphic country rocks of the spectacular Kichatna Range and Denali Massif of the Alaska Range, will be accomplished using three cutting-edge methods: 4He/3He in apatites from glacial headwall and sidewall profiles, cosmogenic radionuclide concentrations in modern rockfall and medial moraines, and Nd in the sediments of outlet streams. Modern and decadal scale glacial speeds will be documented using GPS and analysis of archived air photographs. The results will be synthesized using numerical models of the glaciers, the valleys they erode, and the evolving thermal field within the remaining rock.
Broader impacts While it has long been acknowledged that rock type should influence the rates of erosion by a variety of geomorphic processes, this research will be novel in its focus on the role of rock type, and should highlight the toolkit now available to address such issues. The research will be the focus of one PhD student, and will provide another testbed for the new 4He/3He method being developed by the junior PI. The results of the research will be incorporated in college courses, and in public talks at both university and public venues, including national parks in which glacial processes have dominated in the producing the landscapes in which the public recreates.
