Harmon Craig

Harmon Craig (March 15, 1926 – March 14, 2003) was an American geochemist.

Craig studied geology and chemistry at the University of Chicago, where he earned a Ph.D. under Nobel Laureate Harold Urey with a thesis on carbon isotope geochemistry in 1951. He remained at the University of Chicago as a research associate at the Enrico Fermi Institute. In 1955 he was recruited to Scripps Institution of Oceanography by Roger Revelle. Craig developed new methods in radiocarbon dating and applied the radioisotope and isotope distribution to various topics in marine-, geo-, and cosmochemistry. As professor of Geochemistry and Oceanography at Scripps, Craig produced fundamental findings about how the deep earth, oceans and atmosphere work.

In 1970, Craig teamed up with colleagues at Scripps, Columbia University's Lamont–Doherty Earth Observatory and the Woods Hole Oceanographic Institution to direct the GEOSECS Programme (geochemical ocean sections study) to investigate the chemical and isotopic properties of the world's oceans. GEOSECS produced the most complete set of ocean chemistry data ever collected.

Craig discovered submarine hydrothermal vents by measuring helium 3 and radon emitted from seafloor spreading centers. He made 17 dives to the bottom of the ocean in the ALVIN submersible, including the first descent into the Mariana Trough, where he discovered hydrothermal vents nearly 3700m deep.

Craig led 28 oceanographic expeditions and traveled to the East African Rift Valley, The Dead Sea, Tibet, Yunnan (China) and many other places to sample volcanic rocks and gases. He visited all the major volcanic island chains of the Pacific and Indian Oceans to collect lava samples. He identified 16 mantle hotspots where volcanic 'plumes' rise from the Earth's core through the deep mantle by measuring their helium 3 to helium 4 ratio, identifying the higher helium 3 content present in the hotspots as primordial helium.

He was elected to the National Academy of Sciences. Craig won the VM Goldschmidt Medal of the Geochemical Society in 1979, the National Science Foundation's Special Creativity Award in Oceanography in 1982 and the Arthur L Day Prize of the National Academy of Sciences in 1987. In 1998 he was awarded the Balzan Prize for Geochemistry. On that occasion, he was quoted as saying "The Prize's most significant effect was to establish that Geochemistry, especially Isotope Geochemistry, which began in 1947, had come of age and is a mature science. This was much more important than the specific person chosen for the award."