Harmon Craig

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Harmon Craig
Born(1926-03-15)March 15, 1926
DiedMarch 14, 2003(2003-03-14) (aged 76)
NationalityAmerican
Known forGeochemistry
AwardsV. M. Goldschmidt Award (1979)
Vetlesen Prize (1987)

Balzan Prize (1988)
Scientific career
InstitutionsScripps Institution of Oceanography
Doctoral advisorHarold C. Urey

Harmon Craig (March 15, 1926 – March 14, 2003) was an American geochemist. Craig was born in Manhattan, New York on 15 March 1926. His father's parents were actors, directors and producers. His father served in World War I, first with the AFS and then with the French Army. His mother was descended from Quakers who helped found schools for freed slaves. His mother's involvement with the Quaker ethos influenced Craig and the person he became.

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. Before Craig got his Ph.D, he took time off from school and joined the navy during World War II. After demobilization, Craig continued his education at University of Chicago to get his Ph.D. After his observation on Harold Urey, Craig created his own thesis in orderfind the measurement of ancient sea temperature. Craig referred back to the carbon dioxide released from calcium carbonate fossils to use for future researches involving the carbon system. The masses of carbon dioxide that is produced by 18O and 16O were used to calculate the respective masses. Craig’s study of the carbon isotope produced a lot of corrections that deals with mass fractionation and radiocarbon ages. As of today, Craig’s thesis is considered an important accomplishment for the studies of 13 C and 12 C in natural material. His theory has been used food chains to identifying sources of ancient statues.

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. Craig concluded that there was no uniform composition in a “chondrite”, a meteor from the Solar System. A misconception about chondrite was that there was a fixed composition of a chondrite. When Craig worked with Harold Urey, Craig deduced that a chondrite is made of two distinguished groups, concluding that there is no uniformity. Craig’s discovery affirms a better understanding of materials used to form planets.

Craig discovered the meteoric water line, a line that represents a linear relationship between hydrogen and oxygen ratios in terrestrial waters. He also established the oxygen isotope shift in geothermal and volcanic fluids. His establishment opposes a common assumption by identifying that the water is meteoric. His discovery outlined the relation between rocks and water in geothermal systems. Craig and fellow students studied the isotopic composition of atmospheric and dissolved oxygen in the composition of dissolved gases, where he discovered the biochemical oxygen demand and the intake in the ocean mixed layer. Craig determined that the element, 210Pb measurement is an indication of a particle-reactive species that concludes that another reactive particle would have the same effects in the ocean.

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 proved that there was excess 3He instead of 4He, affecting the understanding for ocean circulation and seafloor spreading.

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.

Craig was considered to be one of the people to analyze the gases trapped in the glacier ice. Craig reported that the methane in the atmosphere had increased twice due to human day to day activities in the last 300 years.

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." He received an honorary degree by the University of Paris whose his father had received a similar award for his efforts in World War I.

Craig died at Thornton Hospital in La Jolla, California on 14 March 2003 from a massive heart attack a day before his birthday.


References[edit]

  • Karl K. Turekian (2006). "Harmon Craig" (PDF). Biography of the National Academy of Science.
  • Karl K. Turekian (2003). "Obituary: Harmon Craig (1926–2003)". Nature. 423 (6941): 701. Bibcode:2003Natur.423..701T. doi:10.1038/423701a. PMID 12802321.
  • Ray Weiss. "Harmon Craig (1926–2003)". Eos, Transactions American Geophysical Union. 84: 207. Bibcode:2003EOSTr..84..207W. doi:10.1029/2003EO220005.
  • "Obituary Notice: Pioneer of Geochemistry Harmon Craig". Archived from the original on 2008-07-23.
  • "Harmon Craig: The Gumshoe of Geochemistry".
  • Douglas Page (2000). "Geochemistry Pioneer". Science Spectra. 423 (20): 14–18.
  • "Acceptance Speech – Rome 23.11.1998".
  • "Harmon Craig".
  • "Obituary Notice Pioneer of Geochemistry: Harmon Craig".