I am currently a 2nd year Ph.D. student at the University of Minnesota in Geology and want to report the advantages that C&M DiffEq has given me. It turns out that describing the mathematics of deformation in rocks is simply the flow section of C&M Diffeq expanded to 3-D. If you can find the strain matrix of the rocks (matrix of the diffeq in C&M), you can get flow paths and watch how the rock deforms. Another one of my advisor's students had been working on this before I came and has developed the theory behind relating these flow paths to rock deformation. It was considered quite neat that I had actually learned how to do this as an undergrad in C&M. I am using the C&M DiffEq lessons to teach new geology grad students the mathematics behind our work.