 Remaining at Harvard, he became a Harvard Junior Fellow, then received his Ph.D. in geology in 1954.MacDonald was a faculty member at MIT (1954–1958), UCLA (1958–1966), UC Santa Barbara (1968–1970), Dartmouth (1972–1983) and UCSD (1990–1996).Outside of academia, MacDonald was a long-time member of the elite JASON advisory group of scientists.