Bowen, Norman Levi
Bowen, Norman Levi
(b. Kingston, Ontario, 21 June 1887; d. Washington, D.C., 11 September 1956)
geology.
Norman L. Bowen was the principal investigator and leader, in the twentieth century, of the magmatist school of geology. The son of English immigrants to Canada, he was educated in Kingston’s public schools before entering Queen’s University in 1903. He took honors courses in chemistry and mineralogy before being granted the M.A. in 1907. He then entered the Faculty of Applied Science. In 1909 he was awarded the B.S. by the School of Mining.
Preparation for his work in experimental petrology continued when Bowen was employed by the Ontario Bureau of Mines before entering the Massachusetts Institute of Technology for doctoral studies in 1909. During the summers of 1910 and 1911, he worked for the Canadian Geological Survey in western Canada, supplementing his investigations at the Geo-physical Laboratory of the Carnegie Institution of Washington, D.C. These years of advanced study saw the development of his pattern of research, which combined laboratory experiments with field investigations.
In preparing his doctoral dissertation on a phase-equilibrium study of the nepheline-carnegieite-anorthite system, Bowen followed the work of the Norwegian J. H. L. Vogt, who had made petrological analyses using physical chemistry. He worked under the direction of A. L. Day of the Geophysical Laboratory and was also influenced by early association with R. A. Daly.
Bowen published critical phase diagrams for the study of the major igneous rocks: the plagioclase system in 1913, the MgO-SiO2 system and the ternary system diopside-forsterite-silica in 1914, and, with colleagues, another twenty-one phase diagrams; the last appeared almost coincidentally with his death. From the beginning, his principal concern was the differentiation of igneous rocks. In 1927 he wrote: “… rock series can not be partitioned off into such divisions as gabbro, diorite, etc., each having a eutectic of its own. All of these belong to a single crystallization series, to a single polycomponent system, which is dominated by reaction series.”
Silicate phase-equilibria studies, in particular his own plagioclase diagram, formed the bases on which Bowen published his carefully reasoned theory of the evolution of the igneous rocks (1915). “… The rocks of any area,” he stated, “vary among themselves in a systematic manner which indicates derivation from a common stock… through differentiation.” He ruled out assimilation of country rock as a major factor in differentiation and dismissed palingenesis (the refusion of sedimentary terranes), holding that gravitative separation by sinking and floating of early-formed crystals, and the separation of residual liquids, were the “all-important instruments of differentiation.” Bowen formulated a simplified reaction series for the subalkaline rocks to illustrate his reaction principle.
According to Bowen’s reaction principle, typical series of igneous rocks are produced from a primary basaltic magma by the continual reaction, during crystallization, of early-formed crystals with liquid, the differentiation being brought about by the separation of crystals from liquid in various proportions and at various stages. The implications of these ideas for the ory of ore formation (through residual volatile fluids), for volcanology, for the basic physics of the earth, as well as for his primary field of petrogenesis, supplied work not only for the remainder of Bowen’s life, but also for many of the most distinguished scientists of his time. His reaction principle is now ensconced in elementary textbooks of geology as one of the fundamental concepts of the science.
Bowen’s studies were interrupted by work on optical glass projects during World War I. In 1919 he served at Queen’s University as a professor of mineralogy, returning to the Geophysical Laboratory in 1920. Between 1937 and 1945 he resumed academic duties as professor of petrology at the University of Chicago. He returned to the Washington laboratory in 1947.
Until his death Bowen examined the physical-chemical bases for geological processes. His major conclusions were brought together in The Evolution of Igneous Rocks (1928).
In his work Bowen bridged gaps between the chemist and the geologist. He was among the first to analyze the behavior of inclusions in magma by physical-chemical methods. He influenced thought in petrology by skilled experimentation that supplemented inferences made from field investigations. Through numerous papers in professional journals, he contributed significantly to the mineralogical knowledge of rock-forming minerals.
Active in numerous professional societies, Bowen served as president of the Geological Society of America and of the Mineralogical Society of America. His accomplishments were recognized by medals from various professional societies, including the Penrose Medal of the Geological Society of America (1941).
BIBLIOGRAPHY
I. Original Works. Among Bowen’s writings are “The Later Stages of the Evolution of the Igneous Rocks,” in Journal of Geology, supp. 23 (1915), and The Evolution of Igneous Rocks (Princeton, 1928).
II. Secondary Literature. Articles on Bowen are C. Tilley, in Biographical Memoirs of Fellows of the Royal Society, III (London, 1957), 7–22; and C. R. Longwell and John Rodgers, eds., Science, 250A (New Haven, 1952).
Cortland P. Auser