12.SP51: Seminar in Geophysics – David Goldsby (UPenn)

The Rheological Behavior of Ice: From Plasticity to Diffusion Creep

Abstract. Knowledge of the rheological behavior of ice over a wide range of stresses is critical for understanding the mechanics and dynamics of glaciers, ice sheets, and icy planetary bodies. In glaciology, the flow behavior of ice has been classically described by the Glen law, a power law relationship between strain rate and stress with a canonical value of the stress exponent of ~3. We have demonstrated that the Glen law does not describe a single creep mechanism, but rather averages the contributions from two creep mechanisms, dislocation creep at comparatively high stresses and grain boundary sliding creep at lower stresses. Each of these creep mechanisms dominates the flow behavior of terrestrial and planetary ice bodies at appropriate conditions of temperature, stress and grain size. At higher and lower stresses than are accessible in most ice deformation apparatus, transitions to plasticity and diffusion creep, respectively, are expected. Here I will describe our recent experimental efforts to study these deformation mechanisms by 1) mapping out the transition from dislocation creep to power law breakdown and plasticity in a high-pressure gas apparatus, and 2) discovering the diffusion creep regime for ice via cryo-nanoindentation.

About this Series
Only students may enroll in this class but all members of the MIT community are welcome to attend the talks. This seminar series is an overview of classical papers and recent research in geophysics. Fields to be covered include geodesy and earthquake physics (e.g. tectonic earthquakes, induced seismicity, glacial earthquakes). For questions, contact maubantl@mit.edu