Bowen, Norman L. (earth scientist)


(1887-1956) Canadian Petrologist, Geochemist

Norman L. Bowen was the greatest petrologist of the 20th century and one of the most influential geologists of all time. His name is known by anyone who has attended a college course in physical geology by virtue of the famous Bowen’s ReactionSeries which appears in every physical geology and petrology textbook in the world. This diagram and concept shows the crystallization sequence of common minerals in igneous rocks of “average” compositions. Plagioclase forms the continuous reaction series because it continuously changes composition with temperature from calcium-rich at high temperature to sodium-rich at low temperature. The discontinuous reaction series shows the crystallization of a sequence of iron-magnesium-rich minerals during cooling of magma or lava from about 1,400 to 750 degrees centigrade. The continuous reaction series crystallizes at the same time as the discontinuous series to form all of the common igneous rocks. Conversely, the diagram and concept shows how minerals melt if rocks are heated to their melting point. It neatly explains assemblages of minerals in igneous rocks, their temperatures of formation and many igneous textures. Although a simplification of a very complex series of processes, the Bowen’s Reaction Series concept is surprisingly applicable in most rocks.

This widely applicable concept was derived through years of research. Norman Bowen solved many of the basic petrologic (study of rocks) field problems by defining laws and principles derived from experimentally determined chemical relationships (phase diagrams) of common minerals. As a result of this groundbreaking research, petrologists were able to approach igneous rocks quantitatively, whereas previously the main focus was only on description and classification. His experimental work involved the melting and quenching of rocks at a series of temperatures to determine their relations of crystallization. From these data he would construct a “phase diagram” from which melt percentages, melt compositions, types, and percentages of minerals crystallized could be determined at any given temperature. The nepheline-anorthite diagram was the first completed very efficiently using 17 different mixtures and 55 quenching experiments. This system was the first example found in silicates of solid solution. Bowen then studied the two-component system of plagio-clase, albite-anorthite. These results helped determine the basis for Bowen’s views on magma differentiation and crystal fractionation. Both of these theories had not been demonstrated experimentally prior to the research Bowen and his colleagues had accomplished. Bowen subsequently experimented with many other systems.

Bowen published numerous papers but probably his most famous work was his 1928 book, The Evolution of Igneous Rocks. In this topic, he explains phase diagrams for common rock systems. Although still a simplification, the results apply so well to field and petrographic observations of igneous rocks that it became an instant handbook for igneous petrologists. It still remains one of the most important topics in geology.

Norman L. Bowen was born in Kingston, Ontario, on June 21, 1887. He completed his elementary and high school education in Kingston public schools, and entered Queen’s University, Canada. Bowen had his sights set on becoming a teacher but after one year decided to join an Ontario Bureau of Mines geological mapping party to Larder Lake with the allure of money and travel. It was a revelation for him and he enrolled in the School of Mining upon his return, registering in mineralogy and petrology. He graduated with a bachelor of science degree in chemistry and geology in 1909. He received medals in chemistry and mineralogy and was named the 1851 Exhibition Scholar. Bowen continued with his graduate studies at Massachusetts Institute of Technology in Cambridge.

In 1910, Bowen applied to the Geophysical Laboratory at the Carnegie Institution of Washington, D.C., to complete an experimental study related to a geological field problem as part of the requirement for his Ph.D. During this time, Bowen married his college sweetheart, Mary La-mont, on October 3, 1911. The following spring (1912) Bowen graduated with a Ph.D. in geology and was busy fielding job offers. Bowen accepted the position as assistant petrologist at the Geophysical Laboratory. Besides a 10-year period of teaching at the University of Chicago, Illinois (1937 to 1946), including two years as department chair, Bowen remained at the Geophysical Lab for his entire career and directed it for most of the time. He embodied the Geophysical Laboratory. Bowen officially retired in 1952 and the next year he moved to Clearwater, Florida, to enjoy his golden years. However, he grew restless after only a few months and returned to Washington, D.C., and was appointed research associate at the Geophysical Laboratory. Norman L. Bowen died on September 11, 1956.

Norman Bowen led a phenomenally productive career not only in terms of total publications but also in terms of impact on the field. For example, between 1945 and 1954, five of the 20 most often cited articles in all of geology were written by Bowen and his associates. There are no truer classics in petrology than those written by Bowen. As recognition for these outstanding contributions, he received numerous honors and awards. He was a member of the U.S. National Academy of Sciences, the American Academy of Arts and Sciences, the Indian Academy of Sciences, and the Finland Academy of Sciences. He received honorary degrees from Harvard University, Yale University, and his alma matter, Queen’s University. He also received the Bigsby Medal and the Wollaston Medal from the Geological Society of London, the Penrose Medal from the Geological Society of America, the Roebling Medal from the Mineralogical Society of America, the Miller Medal from the Royal Society of Canada, the Hayden Medal from the Academy of Natural Sciences of Philadelphia, and the Bakhuis Rooze-boom Medal from the Royal Netherlands Academy. The American Geophysical Union named a medal in his honor.

Bowen was also very active in service to the profession. In addition to serving as president of both the Geological Society of America (1946) and the Mineralogical Society of America (1937) he was a member and chair of numerous committees and panels for both societies and the government.

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