Development of a Ring-Shear Device for Study of Subglacial Processes

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This award supports the development of a ring-shear device for the study of a wide range of sliding-driven processes that influence the geomorphic effects and dynamics of ice masses. The intellectual merit of the project is that it will provide a controlled laboratory environment in which to study phenomenon which are difficult to observe in nature. The features of the device will include use of a rigid or sediment bed, unlimited sliding displacement, control of either shear stresses or sliding rates, uninhibited movement of ice normal to the sliding direction, control of basal water pressure, temperature control to 0.01 C, and continuous observation of sliding, sediment movement and cavity growth at the bed. Groups from outside Iowa State University will be encouraged to use the device to study specific sub-glacial processes which include but are not limited to sliding of wet-based glaciers as a function of basal water pressure, lodgment-till deposition, till strengthening by water withdrawal associated with basal freezing, erosion of rock and sediment beds, sliding and sediment entrainment by polar glaciers, sliding of debris-laden ice over rock, and sub-glacial till deformation and plowing. Support is requested for only design, construction, and testing of the device. The broader impacts of this project are that this device will provide a new research tool for study of sub-glacial processes. Other geoscientists with interests in glacial sedimentation or processes similar to those that occur sub-glacially might also benefit. Examples include geotechnical engineers (stress/strain history of tills), geophysicists (fault mechanics), and permafrost scientists (frost-heave mechanics). The new more versatile device will replace an existing system which has been used to train 9 students. This device will provide an even broader range of student research opportunities and will enhance classroom teaching by allowing direct observation of sub-glacial processes. In addition, the device will be used as a vehicle for outreach to the public, as has been done with sub-glacial experiments beneath Engabreen in Norway.