81 Pleistocene-Holocene Glaciation, Earthquakes, and Environmental Change (Posters)

Sunday, 25 September 2016
9:00 AM - 5:30 PM
Exhibit Hall E/F

PRELIMINARY GIS-BASED ANALYSIS OF THE PRESENCE AND DISTRIBUTION OF ICE-FILLED CIRQUES

Paper number: 81-15
Program: Technical Sessions
Time: 9:00 AM – 5:30 PM

Authors

Abstract

While the significance of alpine glacial erosion in limiting mountain altitudes worldwide appears to be robust, questions remain about the erosional mechanisms involved and how the creation of erosional glacial landforms (such as cirques) contribute to this process. Previous work has shown a correspondence between glacial cirque and adjacent peak altitudes and local and global trends in “Quaternary average” equilibrium line altitudes (ELAs), suggesting that the formation of cirques plays a role in the hypothesized “glacial buzzsaw” process. However, the global study was performed on mountains that are now mostly or entirely ice-free, raising the possibility that cirque altitude distributions in these regions are simply a result of being on mountains high enough to have been glaciated but not so high as to be ice covered today. We are testing these competing models by determining the relationships between floor height, relief, and ELAs for valley head overdeepenings in mountain ranges that extend well above local ELAs and are therefore currently ice-covered, such as the Aletsch Glacier valley of the Swiss Alps. Our goal is to test a method for determining whether cirques form a certain distance below adjacent peaks, suggesting that peak altitude controls the altitude of cirque formation, or if cirques form at the elevation of the regional Quaternary average ELA, which would suggest that the ELA controls the altitude of cirque formation. We develop and evaluate a GIS-based method for locating potential sub-ice “cirques” by measuring ice surface topographic profiles and modeling the corresponding sub-ice bedrock topographic profiles in the study area. We then use these modeled profiles to determine the presence of flat or overdeepened areas, and finally estimate the location and altitude of any “potential cirque” floors. We compare the spatial and altitudinal distribution and relief of these ice covered overdeepenings with those in nearby, ice-free drainage basins, and with the regional ELA.

Geological Society of America Abstracts with Programs. Vol. 48, No. 7

doi: 10.1130/abs/2016AM-285647

© Copyright 2016 The Geological Society of America (GSA), all rights reserved. Permission is hereby granted to the author(s) of this abstract to reproduce and distribute it freely, for noncommercial purposes. Permission is hereby granted to any individual scientist to download a single copy of this electronic file and reproduce up to 20 paper copies for noncommercial purposes advancing science and education, including classroom use, providing all reproductions include the complete content shown here, including the author information. All other forms of reproduction and/or transmittal are prohibited without written permission from GSA Copyright Permissions.