Crustal Deformation in the St. Elias Mountains

NEW: Google Earth files with STEEP related stuff.

During two field seasons in the summers of 2005 and 2006, Julie Elliott, Max Kaufman and I established a geodetic network of approximately 70 GPS sites across the eastern Chugach and western St. Elias Mountains. This network incorporates many sites from earlier GPS surveys done by Jeanne Sauber in the 1990’s. A map of the network is shown below.

Logistics to access these sites involved helicopters, boats (in Prince William Sound) and bush aircraft. Photos from fieldwork can be found here.

The purpose of these surveys is to establish a baseline against which crustal deformation can be measured. We set out geodetic GPS receivers over benchmarks set in bedrock, and allow them to record data over the period of several days. After post-processing the GPS data, we have coordinates of the benchmarks accurate to a few millimeters. Over the course of several years, we will revisit the sites and record data again. As the forces of plate tectonics deform the mountains, we track the changes in coordinates of the benchmarks.

The driving force behind the mountain building and tectonic activity across southern Alaska is the Yakutat Terrane, which is loosely riding along with the Pacific Plate and colliding with the edge of the North American Plate (see tectonic setting).

Julie Elliott is a Ph.D. candidate at the University of Alaska, and will base her thesis on this study. This study is also part of the Saint Elias Tectonics and Erosion Project (STEEP), a five year, multi-disciplinary study that addresses the evolution of the highest coastal mountain range on Earth. The main STEEP website can be found at http://www.ig.utexas.edu/steep/. Within the St. Elias, the rapid uplift caused by the Yakutat collision is being countered by massive erosion, particularly by glaciers. The photo of Mt. Miller to the right shows a heavy mantle of ice draping the steep mountain, and illustrates the interaction between uplift and erosion that is central to the research of STEEP.

This project is funded by NSF Continental Dynamics Program Grant 0409426. GPS equipment is provided by UNAVCO. Logistical support for the fieldwork is provided by NSF Arctic Logistics (http://www.vecopolar.com/).