​In Memoriam: Rodger Chapman​

Rodger H. Chapman, a dedicated scientist with the California Geological Survey, passed away at age 88 in Davis, California, on April 27, 2014. Rodger was a Senior Geologist and manager of the CGS (then the California Division of Mines and Geology) Applied ​​Geophysics Program for many years. He retired in 1991. Rodger began his career with the CDMG in 1961 at its San Francisco District office where he organized and directed the Division’s geophysical research program. He established the original objectives of the program, which were to 1) produce geophysical anomaly maps of California, and 2) evaluate the application of geophysical techniques for mineral-resource investigations throughout the state. H​e also directed the move of the geophysical program from San Franci​sco to Sacramento in 1971.

Rodger was born in Highland Park, Michigan, a suburb of Detroit, in 1925. He served in World War II in the U.S. Army Infantry from 1943 to 1946 in Europe and the Philippines. Rodger later received a B.S. degree in geological engineering and an M.S. degree in geophysics from the Michigan College of Mining and Technology (now Michigan Technological University). The University of Wisconsin, Madison, awarded him a Ph.D. in geophysics in 1956.

In 1948, Rodger conducted geologic field mapping for the Newfoundland Geological Survey in areas not then covered by topographic maps. His expertise in the application of geophysical techniques for mining exploration became apparent while employed at Pickands, Mather and Company (an iron-ore mining enterprise) in Minnesota (1949-1951) and at the U.S. Steel Corporation in Provo, Utah (1956-1961).

Upon his arrival at the CDMG in San Francisco in 1961, Rodger helped organize the Bay Area Geophysical Society (BAGS) as a local section of the Society of Exploration Geophysicists. He became the first president of BAGS in 1962. Rodger’s other professional affiliations included the American Geophysical Union, the European Association of Exploration Geophysicists, the Society for Mining, Metallurgy, and Exploration/American Institute of Mining, Metallurgy, and Petroleum Engineers (AIME). He was president of the AIME Sacramento Chapter in 1990.

Rodger published more than 130 geophysical reports and maps of California, a monumental contribution that brought him, as well as the CDMG, national prominence in the field of geophysics. His investigations ranged from basic field measurements of geophysical properties of the Earth to studies of mineral and geothermal resources as well as geologic hazards. Rodger’s studies of gravity of the Clear Lake region in the 1960’s and 1970’s were the first to suggest that the heat source for The Geysers geothermal field and surrounding geothermal phenomena is an igneous intrusive or magma chamber at shallow depth. He also conducted studies of the Ione clay/lignite deposits, the Bodie gold-mining district, and many other mineral deposits and geothermal areas, which have proven to be of economic value to California. Rodger supervised the CDMG’s publication of the Bouguer Gravity Atlas of California and the accompanying compilation of 1o x 2o aeromagnetic map sheets of California. These regional geophysical maps are useful for interpreting California’s complex geologic structures. Rodger also made thousands of gravity measurements throughout the state and established the CDMG’s Gravity Base Station Network.

Rodger’s dedication to, and expertise in, the use of geophysical principles to aid understanding of the geology of California was widely recognized. He enthusiastically shared this knowledge with his scientific peers and the public. Among his colleagues at the CDMG, Rodger was known for his ability to patiently and clearly explain geophysical principles and observations. He was unfailingly polite and friendly, a true gentleman.

Rodger greatly enjoyed the outdoors. That interest ranged from riding his bicycle around Davis to annual backpacking trips in the Sierra Nevada.

Rodger is survived by his wife, Hildur, whom he married in 1951, and by his son, Mark, and daughter, Ann.