This project provides funds for a two-year renewal of the St. Elias Erosion-tectonics Project (STEEP). STEEP is a 9 institution, multidisciplinary study of the St. Elias orogen in southern Alaska that involves researchers examining the system from the outcrop to lithosphere scale. To date, STEEP has produced 17 papers with another 9 submitted or nearing submission, sponsored 71 abstracts, will have matriculated 5 masters and 4 Doctoral students by Spring 2010, and fundamentally changed our understanding of Alaskan tectonics and the interaction of tectonics and climate in mountain building. The renewal funds will be used for: 1) final processing and interpretation of some key datasets that were not acquired until year 5 of the project including the marine seismic survey (ship delays) and reoccupation of key GPS sites (weather problems in 2008); and 2) a complete integration of results which was not possible until now due to these delays. A complete integration and synthesis of these superb datasets has the potential to be transformative in our understanding of how crustal structure and tectonic forces interact with Earth surface processes of glacial erosion and sedimentary transport to grow a mountain range and a massive continental shelf.
was focused on measuring rates of long-term erosion associated with the glaciated Yakutat microplate collision in southern Alaska. We used a technique that measures erosion by using the proxy of how rocks have cooled as they rose through the upper few kilometers of the earth. We applied this method to over one hundred rock samples in the St. Elias Mountains, thereby documenting the spatial pattern of erosion over the past few million years. Our primary finding was that erosion is concentrated on the southern flank of the mountains, where precipitation is greater and glaciers are lower in elevation. We identified a correlation between the location of maximum erosion and rock uplift and the zone of maximum sliding of glaciers, beneath their equilibrium line altitude. This implies that the change in climate to more glacially-dominated conditions over the past few million years had a profound effect on the structural arrangement within this collision zone. Onset of glaciation totally reorganize the geometry of the deformation. Glaciated mountain ranges are also fundamentally different than ones eroded mainly by rivers. That glaciers spatially control where rock is coming out of the mountain also means that processes on the surface, controlled by climate, exert a first-order control on how tectonic motions are accommodated by rock deformation. This illustrates a profound link between internal and external earth processes. Our results also documented the amount of rock that is being removed from this collision zone, which had implications for tectonic and sedimentary budgets. An added practical benefit our research is a better understanding of what impact climate change might have on mountain scale erosion.
