Robert J. Twiss
Ph.D., Princeton (1971)
Professor Emeritus

General research interests include the mechanisms and mechanics of rock deformation and the interpretation of associated structures. Subjects studied recently include continuum mechanical models for the formation of slickenline patterns in brittle deformation zones; paleopiezometry, which is the use of the microstructures of mineral grains to infer the paleostresses associated with deformation; the description of fold geometry; and the mechanisms and rheology of ductile flow. Research is currently focused on the theoretical development and practical application of a generalized continuum model (micropolar theory) that accounts for the effects of rigid block rotations on the orientation patterns of slickenlines in brittle shear zones and of seismic P and T axes. Twiss co-authored with Moores the textbooks Structural Geology (W.H. Freeman & Co., 1992) and Tectonics (Moores and Twiss; W.H. Freeman & Co., 1993).

twiss@geology.ucdavis.edu
(530) 752-0352