Date of Award:

8-2015

Document Type:

Dissertation

Degree Name:

Doctor of Philosophy (PhD)

Department:

Geosciences

Department name when degree awarded

Geology

Committee Chair(s)

Joel L. Pederson

Committee

Joel L. Pederson

Committee

Brett Shelton

Committee

James Evans

Committee

Andrew Walker

Committee

Michelle Fleck

Abstract

This dissertation encompasses two studies: one developing virtual field trips for mobile devices for an innovative approach to lower-division geoscience education, and the other examining the role of rock strength in river erosion and landscape evolution.

The education study involves the development of three virtual field trip modules (Geologic Time, Geologic Structures, and Hydrologic Processes, all free on iTunes and Google Play) that lead students down a virtual Colorado River through Grand Canyon by physically moving around their campus quad, football field or other location, using their GPS-equipped smart phone or tablet. As students reach each location in the scaled down and geo-referenced virtual Grand Canyon, an informative video appears with a themed geological question and an interactive touchscreen activity. The effectiveness of these three modules in terms of student engagement and learning was tested at five U.S. Colleges with a range of missions and student demographics. Results show that the virtual field trip modules are effective at increasing student interest across races and genders in the geosciences, do not detract from student learning, and have the potential to increase content comprehension.

The second study is the examination of the relation between rock strength and topography in the Colorado Plateau. This work contributes empirical data to the age-old debate over the mechanisms and patterns of stream erosion through statistical relations between rock strength and stream power, river steepness, and valley width along the Green-Colorado River system. Estimates of an “effective” tensile strength were calculated for units too incompetent to test directly, such as the shales prevalent in the region. Results indicate bedrock strength is a first-order control on river erosion in this landscape, as suggested by John Wesley Powell in 1896: “where the rocks are firm and stable, corrasion [sic] of the stream is slow; where the rocks are soft, corrasion [sic] is more rapid,” which is intuitive yet frequently overlooked.

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