Walter Langbein (1907–1982)
Walter Langbein was a public servant in every sense of the word. Born in New Jersey in 1907, he obtained his civil engineering degree in 1931 from Cooper Union while attending night classes and working for a construction company. In 1935 he joined the U.S. Geological Survey (USGS) in Albany, but within a year he was transferred to the national headquarters, where he served as a research engineer and senior scientist until his partial retirement in 1969 to avoid administrative duties.
Langbein was the leader in all fields of hydrology for the country as well as the USGS. His 1955 book Floods, with W. G. Hoyt, was instrumental in the development of the National Flood Insurance Program. With Luna Leopold he worked to establish a national program in water resources research, which led to the development of the Office of Water Resources Research and the recognition of hydrology as a scientific discipline in the academic community in the United States. Walter was instrumental in founding the International Hydrologic Decade (1965–1974), and his participation in the Decade focused attention on the determination of the worth of hydrologic data for water resources development. The theory of scientific network design for water data networks grew out of his work.
Langbein was an innovator and leader in every subject in surface water hydrology. He developed methods in flood hydrology and the application of statistical methods to the analysis of hydrologic data. He studied evaporation from water bodies varying from small stock ponds on the Navajo Reservation to Lake Mead. He studied infiltration in stream channels and its effect on flood wave passage. As early as 1944, Langbein was interested in the use of hydrologic data for the estimation of climate change. He early tried to determine a rational method for the prediction of sediment movement in rivers and lake sedimentation. His work on quantitative geomorphology of river channels was innovative and pioneering. Langbein was full of ideas and freely gave those ideas and the credit for them to others. He was able to outline a problem and point to a solution, meanwhile convincing others that the idea and the solution was theirs. In this selfless manner he contributed more than is gathered from reading his bibliography.
His final full-time assignment for the USGS was to integrate the budget justification of all the water agencies in the Department of the Interior. This grew out of his interest in the application of operations research to water resources. Langbein retired in 1969 so he could return to research. He continued to work for the USGS in retirement, in particular on the International Hydrologic Decade and rational network design. He died in 1982.
Walter Langbein received the William Bowie and Robert E. Horton Medals from the American Geophysical Union, the J. C. Stevens Award of the American Society of Civil Engineers, the Distinguished Service Award of the Department of the Interior, and the Warren Prize of the National Academy of Sciences.
—David R. Dawdy
San Francisco, California
William Bowie (1872–1940)
William Bowie was born in 1872 near Annapolis, Maryland, and attended Saint John’s College in Annapolis before graduating from Trinity College (Hartford, Connecticut) with a B.S. in 1893. He was interested in pursuing engineering studies and subsequently attended Lehigh University from which he received a bachelor’s degree in civil engineering in 1895. Immediately thereafter he joined the U.S. Coast and Geodetic Survey, where he spent his entire career. Initially, he was engaged in field work involving geodetic, topographic, and hydrographic measurements in the continental United States, Alaska, Puerto Rico, and the Philippines. His performance was so outstanding that in 1909 he succeeded John Hayford as chief of the Division of Geodesy. He held this position until his retirement in 1936. During World War I he served as a major in the U.S. Army in the Mapping Division of the Office of the Corps of Engineers. His postwar activities included the establishment of triangulation networks using the “Bowie method,” and the North American Datum of 1927. He was also instrumental in the adoption of the Hayford geoid by the International Union of Geodesy and Geophysics (IUGG) in 1924. His other activities include urging the preparation of more and better maps and coordination between various map-making agencies of the federal government. Hayford had introduced isostasy into U.S. Coast and Geodetic Survey work; Bowie added gravity data into the determination of the geoid and made isostasy his own specialty. His book Isostasy, published in 1927, became a classic and made him an expert on and a champion of the subject. Bowie’s leadership was instrumental in making the U.S. Coast and Geodetic Survey one of the world’s leading geodetic institutions. His achievements were recognized by his membership in the National Academy of Sciences, the French Academy of Sciences, and various academies in Norway, Mexico, Russia, and Finland. He was the recipient of honorary degrees from Trinity College, Lehigh University, George Washington University, and Edinburgh University.
Bowie was one of the organizers and original members of AGU, and he served as its first President (1919–1922). He served a second term as President (1929–1933) and has been the only person to hold this position twice. In l939, the eighth AGU President, Richard Field (1938–1941), conceived the idea of an AGU medal to honor Bowie, and with private donations and the cooperation of Trinity College, the William Bowie Medal was created. It was AGU’s first medal, and naturally, Bowie was its first recipient in April l939. It is AGU’s most prestigious award and is awarded annually for outstanding contributions to fundamental geophysics and unselfish cooperation in research.
On the international stage, Bowie was active in the International Geodetic Association following World War I and was a leading figure in the creation of IUGG. He served as its President from 1933 to 1936, the first American to have this honor, and was President of the International Association of Geodesy from 1920 to 1933.
Bowie was not only a scientist of great distinction, but he was also a skilled scientific diplomat and organizer. His dignified bearing, geniality, and commanding presence enabled him to resolve many national and international difficulties of both political and scientific nature. He was always “ready and willing to serve,” and his presence was crucial in the successful establishment and founding of AGU and IUGG in the years before World War II. His legacy of achievement and cooperation is lasting and does honor to both him and his country.
—Joseph D. Zund
New Mexico State University
Las Cruces, New Mexico
James A. Van Allen (1914–2006)
James A. Van Allen was born in Mount Pleasant, Iowa, on September 7, 1914. He received his Ph.D. in physics from the University of Iowa in 1939 and was a Research Fellow at the Carnegie Institution of Washington’s Department of Terrestrial Magnetism until 1942. As a Navy officer during World War II, he worked at the Johns Hopkins University Applied Physics Laboratory (APL), where he helped develop the proximity fuse, and then sailed with the Pacific Fleet to advise on the use and operation of this important device. After the war, he worked at APL on instrumenting V-2 rockets for scientific research and on various rocket- and balloon-borne instruments for studying cosmic rays at high altitudes and high latitudes. He also headed the development of the first sounding rocket, the Aerobee. In 1951 he returned to the University of Iowa as Head of the Department of Physics and Astronomy, where he remained an active and respected scientist and teacher.
It was at Van Allen’s home in 1950 that he, Sidney Chapman, Lloyd Berkner, S. Fred Singer, Harry Vestine, and others developed the first plans for an International Geophysical Year (IGY); a coordinated, international, and comprehensive study of Earth for an 18-month period from July 1957 through December 1958. This first integrated study of Earth as a planet ushered in the space age by providing the model for large-scale, government-funded science, and because the United States and the Soviet Union included the first satellite launchings in their contributions. Van Allen’s instruments were aboard the first successful American satellites, Explorers 1 and 3, launched in 1958, and provided data for the first space-age scientific discovery: the existence of a doughnut-shaped region of charged particle radiation trapped by Earth’s magnetic field. With various colleagues he sent instruments to the Moon (Explorer 35), Venus (Mariners 2 and 5), Mars (Mariner 4), Jupiter (Pioneers 10 and 11), and Saturn, and throughout interplanetary space, serving as principal investigator on more than 25 space science missions. Author of nearly 200 papers, he personally directed the dissertations of most of the scores young scientists receiving Ph.D. degrees in space physics from the University of Iowa.
Van Allen was been among the most sought-after committee members and advisers, working with the highest levels of government and scientific administration. A member of the National Academy of Sciences’ Space Science Board at its inception in 1958 and working with NASA since its creation in 1959, he helped plan and select the initial suite of space-based observations and experiments. He was among the most influential of individuals in the late 1960s, laying the groundwork for the exploration of the outer solar system and the missions that became Pioneer 10 and 11, Voyager, and Galileo. He was an articulate and outspoken advocate of small, inexpensive missions long before this view became popular.
A member of the American Geophysical Union since 1948, Van Allen helped to organize the first planetary sciences section in 1959 and served as its President from 1964 to 1968. He was President of AGU’s solar-planetary relationships section from 1976 to 1978. Van Allen was elected an AGU Fellow and named John Adam Fleming Medalist in 1963,was awarded the William Bowie Medal in 1977, and served as Union President from 1982-1984.
Joseph N. Tatarewicz
University of Maryland Baltimore County
Jacob Bjerknes (1897–1975)
Jacob Aall Bonnevie Bjerknes was born in Stockholm, Sweden, in 1897. He continued a legacy of hydrodynamic application theory that began with his physics professor grandfather Carl and was extended by Jacob’s father, the theoretical physicist Vilhelm Bjerknes. From 1914 to 1916, Bjerknes attended the University of Kristiania (Oslo), where he became interested in his father’s work relating hydrodynamic theory to atmospheric motion and weather prediction. Jacob followed his father and his group of young Norwegian meteorologists to the University of Leipzig, where their research focused on the formation of heavy precipitation along ordered cloud boundaries then called “squall lines.” Through surface map analysis, Jacob discovered that these boundaries coincided with the convergence of wind fields, making the latter a potential detector and predictor of weather patterns.
Vilhelm Bjerknes returned to Norway in 1918 and founded a geophysical institute at the University of Bergen, where he organized an analysis and forecasting branch which would evolve into a weather bureau by 1919. During this period, Jacob’s research resulted in the identification of two boundary lines of convergence (one leading, one following) as an integral part of atmospheric wave development (cyclogenesis) which could progress to the formation of a low-pressure center and the southward transfer of polar air. In his classic paper “On the structure of moving cyclones” in 1919, Bjerknes introduced the concept of the “extratropical cyclone,” which became a foundation for the long-range weather forecasting envisioned by his father. The group at Bergen, now including the Swedish meteorologists Carl Gustav Rossby and Tor Bergeron, used balloon data to investigate the “squall line” boundary in three dimensions and realized that it was a thermal discontinuity of hemispheric proportions. Defining it as the “polar front” (borrowed from World War I terminology), they named the two active convergence lines of the cyclone model the “warm front” and the “cold front.” As pointed out in a key paper by Jacob and Halvor Solberg in 1922 (“The life cycle of cyclones and the polar front theory of atmospheric circulation”), the dynamics of the polar front, integrated with the cyclone model, provided the major mechanism for north-south heat transport in the atmosphere. For this and other research, Jacob was awarded the Ph.D. from the University of Kristiania in 1924.
In 1926, Jacob served as a support meteorologist for Roald Amundsen’s polar dirigible flight. In 1928 he married Hedvig Borthen. In 1931, he left his position as head of the weather service at Bergen to become professor of meteorology at the geophysical institute his father had founded. By 1933 he discovered yet another aspect of the cyclone phenomenon, the upper atmospheric wave. His preliminary formulation of the use of pressure tendency as a surface indication of cyclone development appeared in 1937.
Jacob lectured at the Massachusetts Institute of Technology during the 1933–1934 school year and emigrated to the United States in 1940 where he headed a government-sponsored meteorology annex, for weather forecasting, to the department of physics at the University of California, Los Angeles (UCLA). That same year of 1940 saw the invasion of Norway by Germany and Bjerknes’ receipt of the Symons Medal from the Royal Meteorological Society. At UCLA, Bjerknes and fellow Norwegian Jorgen Holmboe further developed the pressure tendency and the extratropical cyclone theories.
The science of meteorology entered the computer and space ages during the 1950s. Bjerknes, then head of the department of meteorology at UCLA, was an early advocate of using photography from rockets to image atmospheric weather patterns, and he would later help usher in the use of satellites for the same purpose. Bjerknes’ cyclone model was a key element in the Princeton atmospheric program used to obtain the first accurate computer-aided weather forecast in 1952. Bjerknes’ later research focused on the energy exchange of the atmosphere and oceans and, specifically, the El Niño effect.
To his friends, Bjerknes was just “Jack.” With his students, he was always conscientious in sharing his gift for simplifying the complexity of atmospheric motion. The American Geophysical Union honored Bjerknes’ pathbreaking work in meteorology in 1945 with the William Bowie Medal, its highest award, recognizing fundamental contributions to geophysics and the AGU principle of unselfish cooperation in research. Additional honors included the American Meteorological Society’s Rossby Medal (1960) and the National Medal of Science (1966). Bjerknes died in 1975.
—William J. McPeak
Lake Forest, California
Eugene N. Parker (1912– )
Eugene N. Parker was born in Houghton, Michigan, in 1927. After receiving a B.S. degree from Michigan State College in 1948 and a Ph.D. from the California Institute of Technology in 1951, he held various positions at the University of Utah from 1951 to 1955. In 1955, he joined the University of Chicago, where John Simpson and others were beginning to challenge the then-prevalent concept of interplanetary space being largely empty, traversed by a few fast-moving particles. With only a few in situ observations in the immediate neighborhood of the Earth, theorists had to rely on a variety of ambiguous observable geophysical and astronomical phenomena.
In 1958, Parker published his theory of the solar wind, in which the solar corona expands supersonically to the outer reaches of the solar system, now the foundation of modern solar-terrestrial research and solar-planetary relationships. Prior to Parker’s work, the existence of a continuous, but slight, flow of particles from the Sun was suggested by a variety of circumstantial evidence. The idea of such a vigorous, dense, and dynamically complex outflow was so radical for its time that it drew criticism and disbelief from most of the scientific community. In 1960, Soviet scientists reported suggestive observations by Lunik 2; in 1961, Explorer 10 data provided convincing confirmation, followed by Mariner 2 observations in 1962 between the orbits of Earth and Venus. Studying the detailed structure and dynamics of the solar wind animated much of the scientific exploration of the inner solar system during the 1960s, and the concept, extended to other stars, became one of the most important foundations of modern astrophysics.
Not just because of his theoretical work but also because of his active participation in advisory committees and his organizational work within the American Geophysical Union, Parker has been one of the most influential architects of the exploration of interplanetary space during the past four decades. His AGU awards include the John Adam Fleming Medal in 1968 and the William Bowie Medal in 1990. He was elected to the National Academy of Sciences in 1967 and in 1989 received the National Medal of Science. The astronomical community also recognized his contributions with the Henry Norris Russell lectureship and the George Ellery Hale Award (American Astronomical Society) and the Sydney Chapman Medal of the Royal Astronomical Society.
—Joseph N. Tatarewicz
University of Maryland Baltimore County
Edward Crisp Bullard (1907–1980)
Sir Edward Bullard, universally known as Teddy, was born in Norwich, England, on September 21st, 1907, into a wealthy family whose prosperity derived from brewing. Although his father intended him to become an accountant and join the family firm, Teddy was deeply influenced late in his school career at Repton (an English Public School) by A.W. Barton, a teacher of physics who had worked under Rutherford at the Cavendish. With Barton’s help, Teddy entered Cambridge University in 1926; he was awarded a first class degree in Natural Sciences and, in 1929, he himself began as a research student in Rutherford’s laboratory. His graduate work was mainly experimental—to determine the scattering cross-section of low-energy electrons in various gases. His student scholarship having run out in 1931, and having married, Teddy was faced with rather dim prospects for employment at the height of the depression. An unlikely opportunity presented itself—Sir Gerald Lenox-Conyngham, the head (and sole member) of a newly formed Department of Geodesy and Geophysics was seeking an assistant. On Rutherford’s advice, despite serious misgivings, Teddy took the position of demonstrator. He quickly finished his Ph.D. and began a career in geophysics.
In the years before the Second World War, Teddy mounted field programs in three of the four major divisions of geophysics. Having refined pendulums to achieve an accuracy of better than one part in a million, Teddy took them to the East African Rift to measure gravity there. This, his first geophysical project, already characterized his bold attack on major questions, in this case the process that formed one of the world’s greatest continental structures. At the suggestion of the influential American geologist Richard Field, whom he had met in Edinburgh in 1936, Teddy initiated a marine seismic refraction program, with instruments of his own construction deployed from chartered trawlers. Together with Maurice Ewing’s work on the other side of the Atlantic, these studies marked the first serious marine geological investigations, showing thick wedges of sediment under the continental shelf; almost without exception up until this time, geologists had been content merely to speculate about the nature of Earth under the sea. As we now know, the marine realm held the key to a deeper knowledge of the whole Earth. The third topic receiving Teddy’s attention was the measurement of the heat flowing from the Earth; he fundamentally improved the measurement techniques and then mounted a major observational expedition to South Africa.
During the War, Teddy worked in the British Admiralty with remarkable effectiveness, primarily to protect ships from German mines. A major achievement was the successful ‘degaussing’ of the fleet by laying current-carrying wires inside the hulls, thus neutralizing the induced vertical magnetization of the steel ships and rendering them much less detectable to magnetic mines. Losses to mines of all kinds fell from being a major factor to only one-tenth of those suffered from submarine attack, largely as a result of the efforts of Teddy and his team.
Upon returning to Cambridge after the war, Teddy found no sympathy on the part of the University for his plans to expand geophysics. In frustration, he accepted the Professorship of physics at Toronto University, but stayed only one year, departing in 1949. While there he began his work on the Earth’s magnetic field, thus penetrating the fourth major branch of geophysics. Teddy clearly nursed his ambition to create a geophysical Cavendish laboratory at Cambridge, but it was obvious to everyone that the time was not ripe. He returned to England as head of the National Physical Laboratory, the British equivalent of the National Bureau of Standards in the U.S. Here he proved himself a deft administrator, supporting the NPL in a variety of successful programs, including the development of digital computers and numerical methods for them, and the establishment of atomic standards for frequency and time. And yet he found time to write some of his most important papers. He carried out theoretical studies of the self-exciting dynamo (using methods closely paralleling those used for calculating quantum transitions in atoms) and backed them up with extensive numerical calculations on the early digital computers. This work was profoundly influential in the field and encouraged a flourishing of dynamo theory, which continues to this day; the original idea of Lamor had been effectively suppressed by Cowling’s ‘anti-dynamo’ theorem in 1933; Teddy realized that Cowling’s theorem was far from universal in its applicability and his inspired work convinced everyone else of this. While visiting Scripps Institution of Oceanography, he continued his experimental work into heat flow, now making the most important advance—the taking of observations of heat flux through the ocean floor. These revealed the puzzling fact that the flux was at least as great as that on the continents, yet radioactive heat sources were virtually absent in the oceanic crust.
At last, in 1956, Teddy perceived the opportunity to return to Cambridge and realize his ambition. He left the NPL to return to the Department of Geodesy and Geophysics rising to the position of chair bu 1964. It is accurate to say that Teddy’s own scientific publications in the period 1960–1974, when he ran the department, were not as significant as his earlier ones. But he presided over and made possible the British contribution to the revolution in Earth sciences that took place in the 1960s. He guided the main work of the department into the study of marine geology, whose unraveling he understood would be the crowning achievement of twentieth century geophysics. So many major discoveries came from the Cambridge laboratory in the late 1960s: Fred Vine and Drummond Matthews discovered sea-floor spreading and interpreted the magnetic stripes; Tuzo Wilson understood transform faults while visiting; Dan McKenzie explained the origin of the high oceanic heat flow and formalized plate tectonics. It is no exaggeration to say that Madingley Rise was the geophysical Cavendish of the 60s and 70s and Teddy was its Rutherford.
In 1974, Teddy reached Cambridge University’s mandatory retirement age and at once moved to a professorship at the University of California, San Diego. Scripps Institution of Oceanography had become a second home to Teddy after the war. Beginning in 1949, he visited Scripps quite regularly in the summer months, where he carried out some of his most important experimental work on marine heat flow. For a number of years, he taught Earth sciences at UCSD to nonscience majors with great enthusiasm, although his health was already failing. His last paper, with Stuart Malin, entitled The history of the Earth’s magnetic field at London 1570-1975, was completed the day before he died, and his last act was to write the letter communicating it to the Royal Society.
An official history does little to convey the side of Teddy that endeared him to those of us lucky enough to know him: his unfailing common sense, his good humor at all times, his indifference to rank, and his remarkable generosity, particularly to his students and junior colleagues.
—J. Freeman Gilbert
—John A. Orcutt
—Robert L. Parker
University of California, San Diego
Beno Gutenberg (1889–1960)
Beno Gutenberg was born in Darmstadt, Germany, on June 4, 1889. He completed all of his university education at the University of Göttingen, receiving his Ph.D. there in 1911. As a student, he chose geophysics as his field of endeavor and joined the Geophysical Institute, newly established by Emil Wiechert, a pioneer in the emerging science of seismology. His dissertation was on microseisms, a topic he returned to in the latter years of World War II when he attempted to use them to track hurricanes and typhoons in the western Pacific.
After earning his Ph.D., Gutenberg turned his attention to the Earth’s interior, basing his early research on the seismographic material that Wiechert had assembled for studying the Earth’s deep structure. In the best known of his early work he made the first correct determination of the radius of the Earth’s core, a study completed in 1913.
In 1913 he joined the German University of Strasbourg, which was then the headquarters of the International Seismological Association. He then spent a period of service with the Meteorological Service of the German army during World War I, followed by a professorship at the University of Frankfurt-am-Main. Because his university salary in the latter position was insufficient for support, he supplemented his income by employment as a factory executive. During this time he published many important research papers and contributed to, and edited, handbooks on geophysical topics. Of these, the best known are the volumes of Handbuch der Geophysik that he edited, and to which he made several contributions.
Gutenberg visited Pasadena in 1929 to participate in a conference to plan future directions for the Seismological Laboratory, then under the auspices of the Carnegie Institution of Washington. He joined the laboratory in 1930 and, at the same time, became a Professor of Geophysics at the California Institute of Technology. The Seismological Laboratory became part of Caltech in 1936 while under the directorship of H.O. Wood. A disabling illness forced Wood to retire in 1947, and Gutenberg succeeded him as director. Under his leadership the laboratory became a leading center for deep Earth and earthquake studies, a role that has continued under the leadership of later directors.
Gutenberg’s years at Caltech were marked by exceptional research productivity. With Charles Richter, he published a series of papers titled “On seismic waves” between 1931 and 1939. These papers provided some of the basic information on travel times of several seismic phases, information that several researchers used to derive velocity models of the Earth’s mantle and core. During this time, Gutenberg’s observational abilities led him to infer a low-velocity zone in the upper mantle, a feature that is still associated with his name.
Gutenberg and Richter published Seismicity of the Earth in 1941. The geographical patterns of earthquakes established in this book provided some of the basic information used by later Earth scientists who developed the theory of plate tectonics. Gutenberg and Richter also collaborated on the development of various magnitude scales using seismic waves of different types so that observers could assign magnitudes to earthquakes that have both shallow and deep foci and occur at various epicentral distances. Gutenberg summarized many of his views on earthquakes and the physics of the Earth’s internal structure in the book Physics of the Earth’s Interior, published in 1959. In addition, he published two other major books and almost 300 scientific articles during his career.
In spite of his unabated research activity and the time required to direct the Seismological Laboratory, Gutenberg still found time to take part in many professional organizations, often assuming a leadership role. He chaired many committees and sections in the International Union for Geodesy and Geophysics, served on the Board of Directors and as President of the Seismological Society of America, and was a foreign member of the Academia dei Lance and the Royal Society of New Zealand.
He received many scientific honors, including election to the National Academy of Sciences. He was awarded the Bowie Medal of the American Geophysical Union in 1933, the Lagrange Prize of the Royal Belgian Academy in 1950, the Wiechert Medal of the Deutsche Geophysikalische Gegellschaft, and an honorary degree from the University of Uppsala in 1955.
Gutenberg retired from Caltech in 1958 but continued to be active in some professional organizations and in research. He had to cease his work, however, when he contracted a virulent form of influenza in early 1960. It developed into a fatal pneumonia, and he died a few days later on January 25, 1960.
—Brian J. Mitchell
Saint Louis University
St. Louis, Missouri
Francis Birch (1903–1992)
Francis Birch was born in Washington, D. C., on August 22, 1903. He entered Harvard in 1920 and graduated magna cum laude in 1924 with a bachelor’s degree in electrical engineering. After working 2 years for the New York Telephone Company, he decided to shift to the study of physics. He obtained a fellowship that led to 2 years of study in France at the University of Strasbourg in the laboratory of Pierre Weiss, one of the founders of modem magnetism. Encouraged by this experience, he returned in 1928 to Harvard as a graduate student in physics, working chiefly in the high-pressure laboratory of Percy W. Bridgman, who was to receive the Nobel Prize for Physics in 1946. Birch was an instructor and tutor in physics from 1930 to 1932, received his master’s degree in 1929, and was awarded his Ph.D. in 1932. During this period, an almost daily visitor and consultant at Bridgman’s laboratory was Reginald A. Daly, the renowned Harvard professor of geology and textbook author. Long interested in the origins of igneous rocks and the structure and properties of the Earth’s deep interior, Daly clearly recognized the need to extend the very limited data on high-pressure physical properties of rocks and minerals in order to better interpret measurements made by seismological and gravity techniques. Daly frequently discussed such problems with his friend Bridgman, and together they set up the continuing interdepartmental Committee on Experimental Geology and Geophysics. In 1932 the Committee initiated two new research ventures at Harvard: a revitalized program in seismology and a program for comprehensive high-pressure studies devoted to geophysical problems. Birch was invited to lead the new high-pressure research program as Harvard’s first research associate in geophysics. Research on the physical and chemical properties of the Earth’s interior became his lifelong task.
Except for a 1942–1945 wartime leave of absence, Francis Birch spent his entire career at Harvard, advancing from research associate through the academic ranks to become the prestigious Sturgis-Hooper Professor of Geology and chairman of the Division of Geological Sciences. Retiring as professor emeritus in 1974, he continued active research and writing until his death, at age 88, on January 30, 1992.
Birch combined impressive theoretical as well as experimental competence in physics, electrical engineering, and geology. By bringing the full power of these disciplines to bear in his researches, he successfully treated many difficult and long-standing fundamental problems in a rigorous and decisive manner. His career was characterized throughout by clear insight into the physical basis of geological problems, practical ideas on how to go about solving them, and lucid presentations of the results in lectures and publications. His experiments, as well as most of his resulting general conclusions and interpretations pertaining to the Earth, have stood the test of time extremely well. Birch’s work was concerned chiefly with elasticity, phase relations, thermal properties and heat flow, and the composition of the Earth’s interior. Extensive laboratory studies of elastic velocities in rocks and their variation with pressure and temperature by himself and others provided the first realistic estimates of density-pressure relationships (equations of state) at high compressions, which Birch used to interpret global seismic data in terms of the composition and structure of the interior.
Probably Birch’s most significant contribution appeared in one of classic papers of geophysics in 1952. Here, he conclusively demonstrated that (1) the mantle is predominately composed of silicate minerals; (2) the upper mantle and lower mantle regions, each essentially homogeneous but of somewhat differing compositions, are separated by a thin transition zone associated with silicate phase transitions; and (3) the inner and outer core are alloys of crystalline and molten iron, respectively, rather than alternative interpretations proposed at the time. The essential details of this model are still valid; only a few refinements have been necessary in the light of subsequent research.
Birch and his students also made major contributions to our knowledge of terrestrial heat flow. Again combining experimental data on thermal conductivities of rocks with temperature gradient measurements from boreholes and tunnels, they helped establish heat flow as one of the key boundary conditions of terrestrial geophysics.
Another of Birch’s important contributions to science was his ever helpful role as mentor, teacher, advisor, and friend to numerous colleagues, postdoctoral fellows, and students who worked with him over more than 40 years; many became outstanding leaders in geophysics in subsequent years. Birch was a gracious person with a wry sense of humor, and associates held him in great respect.
During his lifetime, Birch received many honors, including election to the National Academy of Sciences (1950), the National Medal of Science (1968), and the Vetlesen Medal for 1960. A Fellow of the American Physical Society and of the Royal Astronomical Society of Great Britain, he received the Royal Astronomical Society’s Gold Medal in 1973. Particularly active in the Geological Society of America, he was awarded both its Arthur L. Day Medal (1950) and the Penrose Medal (1969) and served as president during 1964. For his distinguished contributions to geophysics, Birch received the William Bowie Medal, the highest award of the American Geophysical Union, in 1960. AGU has instituted a series of named lectureships in honor of former Bowie Medalists; these invited lectures for the Tectonophysics Section are known as Francis Birch Lectureships. A Francis Birch Lecture has been delivered annually since 1992 by a noted researcher in this field.
—Kenneth H. Olsen