Grace Macdonald and her two children moved to California (1926); Mac graduated the Garfield High School, East Los Angeles in 1928.
Macdonald and Earl Irving graduated in geology, at the University of California, Los Angeles with the joint senior thesis "The Genesis of Certain Banded Gneisses and Trachtitoidal Diorites in the San Rafael and Verdugo Hills, Los Angeles County, California".
Mac had sabbatical leaves 1964–65 and 1970–71; he spent time in residence at Berkeley and mapped the Lassen Peak area, northern California again.
Macdonald, Francis Shepard of Scripps and Doak Cox, geologist for the Hawaii Sugar Planter's Association, wrote a study on it.
The National Park Service, which had administered the Hawaiian Volcano Observatory (HVO) since 1935, transferred control back to the U.S. Geological Survey (1948).