5.13 Glacially Influenced Tectonic Geomorphology: The Impact of the Glacial Buzzsaw on Topography and Orogenic Systems

Abstract

Glacial erosion is approximated as a simple linear function of basal sliding, but is actually dependent on a myriad of spatially and temporally varying boundary conditions. Glacial erosion is more proficient than fluvial erosion, but both are limited by the local rate of tectonic rock uplift. The unique characteristics of glacial topography can be linked to mechanics of the erosion process and local conditions (e.g., selective linear erosion under polythermal ice conditions), as demonstrated in surface process models. Some kinematic aspects of glacial erosion are exclusive, including a focusing of erosion at equilibrium-line altitude, aggressive headwall retreat, and relatively rapid topographic adjustment to climate change. As a result of these characteristics, orogenic systems behave differently when dominated by glaciers. Under the right conditions, rapid rock uplift and efficient glacial erosion limit topography, induce steady-state orogenic flux, and focus crustal strain, thus imparting geodynamic significance to glacial climate. This hypothesis of a ‘glacial buzzsaw’ has been verified both topographically and exhumationally in a variety of settings worldwide, as well as in numerical models of orogenic evolution. Unraveling exceptions to this, including ‘teflon peaks’ and glacial thresholds, is key to improving understanding of the tectonic geomorphology of glaciated terrain.