GSA Annual Meeting in Denver, Colorado, USA - 2016

Paper No. 236-11
Presentation Time: 9:00 AM-6:30 PM


LEHNIGK, Karin, University of Massachusetts Amherst, Department of Geosciences, 611 North Pleasant Street, 233 Morrill Science Center, Amherst, MA 01003-9297,

Devils Tower is a prominent feature and popular tourist destination in Northeast Wyoming. Its position within the sedimentary strata, the lack of volcanic material in the stratigraphic record, and morphology led previous researchers to classify Devils Tower as an intrusive feature—the remnant of a volcanic neck, laccolith, sill, or stock. The most recently proposed mode of formation is extrusive emplacement of a lava coulée in the caldera of a maar-diatreme volcano. This study compares the traditional intrusive hypothesis with the recently proposed extrusive hypothesis by modeling erosion mechanisms since the tower’s formation. The model is a 2-dimensional MATLAB simulation through time in a weathering-limited environment. Weathering rates for the tower’s phonolite porphyry and the surrounding sedimentary rocks are varied stochastically within reasonable parameters and multiple potentially-active weathering processes are simulated in combination in two separate models, each representing the predicted morphology of Devils Tower in relation to the surrounding sedimentary rocks as predicted by each of the two formation mechanisms, either the intrusive or extrusive emplacement hypothesis. The progressive change of the tower is used to assess the likelihood of Devils Tower achieving its current form of a roughly symmetrical feature protruding out of the landscape with dimensions similar to its present size by eroding from either of the two proposed original forms. Public reaction of visitors to learning about ongoing geologic research within Devils Tower National Monument is also assessed by controlled informal surveys.