YELLOWSTONE CALDERA YNP: THE UPS AND DOWNS OF A GROUND DEFORMATION SURVEY

Eastern Illinois University field camp, with assistance from Wilkes University GPS specialists, conducts an annual ground deformation survey at Yellowstone National Park (YNP). The objectives of the survey are to (1) demonstrate to undergraduate students how GPS technology is used to monitor crustal movement associated with the Yellowstone Caldera; and (2) establish short-term patterns of volcano-tectonic ground deformation in the western region of the Caldera. Carrier phase measurements are made using three dual-frequency GPS receivers and a network of eight NGS control stations. Data from two UNAVCO continuously operating reference stations are used for geodetic control. The design of the network was guided by the regional pattern of maximum deformation, geometrical considerations, access and ease of occupation, and conditions for conducting research at YNP. The rapid-static GPS survey runs for 40 continuous hours and employs eight four-hour occupations with a one-hour transition period. Students assist with instrument set up and operation, and monitor the receivers during log sessions. Baseline data are processed at Wilkes University using Trimble GPS Survey (V2.35) and Trimnet software. Relative displacements indicate overall subsidence of the western Caldera region. Ongoing assessment of the survey has resulted in improved data acquisition, data processing, and student learning.