The Geophysics Ph. D. Program was approved by the Colorado Commission on Higher Education in 1973 as an interdepartmental degree program under the Graduate School of the University of Colorado at Boulder. The initial emphasis of the program was on Solid-earth Geophysics. In January 1993, the Graduate School approved the addition of an option in Hydrologic Sciencesunder the program, as the graduate-level course requirements for the two subfields of geophysics are different.