(b, Hebburn on Tyne, England, 14 January 1890; d London, England, 20 September 1965)
geology, geophysics, petrology.
Holmes came of Northumbrian farming stock and gained his early interest in earth science at Gateshead High School. Entering Imperial College, London, in 1907, he read physics under R. J. Strutt (later Lord Rayleigh) for his first degree; subsequently, under the influence of W. W. Watts, he changed to geology and graduated Associate of the Royal College of Science in 1910. Postgraduate studies with Strutt led him to investigate the application of radioactivity to geology. An expedition to Mozambique gave Holmes experience in field and petrographic work on Precambrian ultrametamorphics and Tertiary lavas and stimulated his interest in geomorphology. Thus were laid the foundations of the three main lines of research to which he was to become a major contributor: geochronology, the genesis of igneous rocks, and physical geology.
From 1912 to 1920 Holmes was demonstrator in geology at Imperial College, teaching petrology, conducting research, and writing extensively. From 1920 to 1924 he was chief geologist of an oil exploration company in Burma, returning to England to become professor of geology at the University of Durham (Durham Colleges division) in 1925. Here he refounded the department and spent some of his most productive years until he was transferred to the Regius chair of geology at Edinburgh in 1943. He retired in 1956. He was twice married: to Margaret Howe of Gateshead in 1914 and, after her death, to the distinguished petrologist Doris L. Reynolds in 1939.
Holmes made a great impact upon his times through his pioneer work on radiometric methods of rock dating, his controversial views on the origins of deep-seated rocks, and his brilliant synthesis of the contributions of geophysics and geomorphology to the understanding of the history of the earth. He was one of the most able expositors the earth sciences have ever had, writing in clear, lucid English with a gift for apt quotation and illustration. He never wished or attempted to be a public figure, but great numbers of scientists were influenced by his writings and international correspondence. He was elected a fellow of the Royal Society in 1942 and received many international honors, including the Penrose Medal of the Geological Society of America in 1956 and the Vetlesen Prize in 1964.
By 1910 the discoveries of Becquerel, the Curies, and Rutherford had revolutionized the conception of matter; and Strutt had shown that radioactive minerals are widespread in rocks. The fundamental importance of these developments for geology emerged as a result of Holmes’s work. of the various attempts to derive an “absolute” time scale for our planet, Kelvin’s calculations—based on the assumption of a uniformly cooling earth and gravitational and the then known chemical sources for terrestrial and solar energies—appeared more satisfactory than those depending upon rate of denudation, rate of accumulation of sodium chloride in the oceans, or rate of sedimentation. Yet Kelvin’s method allowed only twenty to forty million years for the whole of geological time—far too short, in the opinion of most geologists. Holmes showed that Kelvin’s assumptions are invalidated by the availability of radioactive heat; he derived a figure of at least 1,600 million years by comparing the amounts of uranium and thorium in rocks with those of their daughter elements lead and helium, assuming a constant half-life for each of the radioactive elements.
Although some of the earliest experimental determinations were made by Holmes himself in Strutt’s laboratory, the later refinements, especially the discrimination of the isotopes of uranium, thorium, and lead which became possible with the rise of mass spectrometry, were the work of other investigators. The earliest modern time scale was proposed by Holmes; and throughout his life he remained the leading figure in the field, critically discussing each new set of results as it appeared and modifying the time scale as it became necessary. A figure of 4,550 million years had become accepted as the “age of the earth” by the time Holmes’s final scale was published.
The recognition that radioactive heat was available from disintegration of uranium, thorium, and potassium was shown by Holmes to have important implications for the thermal history of the earth. It was no longer safe to assume that a cooling earth was contracting; in fact, Holmes advocated cyclical expansion alternating with contraction as a means of explaining tectonic movements in the crust. He also became a strong supporter of A. L. Wegener’s hypothesis of drifting continents at a time when few geologists favored the notion and was the first advocate of convection currents in the substratum (now generally called the mantle) of the earth. Paleomagnetic and paleontological evidence of large-scale movements of the continents has accumulated to an impressive degree, and the hypothesis of convection in the mantle has gained many supporters. His results in geological time, the mechanism of earth movements, and mantle convection illustrate the importance of Holmes as an innovator in fundamental geophysics.
He was also influential in petrography, through his work on techniques and systematics, and in petrology. For many years an orthodox follower of K. H. F. Rosenbusch and Alfred Harker in considering extrusive and intrusive igneous rocks to be of liquid magmatic origin, he became increasingly dissatisfied with ideas based on the limited physicochemical and thermodynamic information of the time. His collaboration with the Geological Survey of Uganda on the remarkable alkalic volcanics found in the Western Rift Valley led him to contemplate solid-state metasomatism and “transfusion” of preexisting rocks by differential introduction of fluxes of emanations. When the “granite controversy” hit its stride in the 1940’s it was natural for Holmes to be found on the side of the “soaks,” as N. L. Bowen once described the advocates of metasomatism. In addition Holmes’s interest in the kimberlite rocks of the diamond pipes and in eclogite as a high-pressure equivalent of basalt pointed the way to important links between petrology and geophysics.
While standing watch against German incendiary bombs at the Durham laboratories, Holmes began writing his Principles of Physical Geology, in which he brought together the whole range of earth processes: those of the deep interior, as revealed by geophysics; those of the crust, displayed by petrology, tectonics, and sedimentation; and those of the surface, revealed by geomorphology. The second edition of this great work, which appeared shortly before his death, is a fitting memorial to the man and his philosophy.
I. Original Works. A full list of Holmes’s writings is in The Phanerozoic Time Scale (London, 1964), which was published in Holmes’s honor; and in the biographical memoir mentioned below. The Age of the Earth (London-New York, 1913; 2nd ed., London, 1937) is of historical interest and should be compared with his “A Revised Geological Time Scale,” in Transactions of the Edinburgh Geological Society, 17 (1959), 183–216. The Nomenclature of Petrology, 2nd ed. (London, 1930), and Petrographic Methods and Calculations, 2nd ed. (London, 1930), are standard works. The convection hypothesis is first proposed in “Radioactivity and Earth Movements,” in Transactions of the Geological Society of Glasgow, 18 (1928–1929), 559–606. Transfusionist petrological arguments are developed in “The Volcanic Area of Bufumbira, Part II, The Petrology of the Volcanic Field...,” in Memoirs of the Geological Survey of Uganda, vol. 3 (1937), written with H. F. Harwood. Principles of physical Geology (London, 1944; 2nd ed., London, 1964; New York, 1965) is the most important reference.
II. Secondary Literature. See “Award of the Penrose Medal to Arthur Holmes,” in Proceedings of the Geological Society of America for 1956 (1958), pp. 73–74; and K. C. Dunham, “Arthur Holmes,” in Biographical Memoirs of Fellows of the Royal Society, 12 (1966), 291–310.
Holmes, Arthur (1890-1965)
Holmes, Arthur (1890-1965)
Arthur Holmes, geologist and geophysicist, was born in Gateshead, England. From a modest family background, in 1907 he gained a scholarship to study physics at the Royal College of Science (Imperial College), London, where he became interested in the newly emerging science of radioactivity and its application to dating minerals to solve geological problems.
Throughout his early life, Holmes struggled against financial hardship and frequently sought other work to support his research. Thus in 1911, he accepted a contract to prospect for minerals in Mozambique, where he conceived his vision of building a geological timescale based on radiometric dates. It was also there that he contracted a severe form of malaria.
In 1912, as a demonstrator at Imperial College, Holmes pioneered radiometric dating techniques and wrote the first of three editions of his celebrated booklet The Age of the Earth. In it, he estimated the earth to be 1,600 million years old, at that time an immense age and considered by many to be unacceptable. For the next 30 years, he pursued the topic, but it was not until the early 1940s that real progress was made on the geological timescale. By 1947, Holmes had pushed back the earth's age to 3,350 million years. However, it was not until 1956 that it was established at 4,550 million years.
Holmes married Maggie Howe (1885–1938) in 1914 and his first son was born in 1918. He escaped active service in the First World War due to recurring bouts of malaria but, by 1920, he was still only earning 200 pounds a year. Once again financial necessity compelled him to accept a post abroad, this time in Burma as chief geologist to the Yomah Oil Company (1920) Ltd. By 1922, however, the company had collapsed. Six weeks before leaving for home his young son caught dysentery and died. Eighteen months of unemployment followed Holmes' return to England, during which time he opened a Far Eastern craft shop in Newcastle-upon-Tyne.
In 1924, Holmes was offered the headship of a oneman geology department at Durham University. With his fortunes revived, and enhanced by the birth of his second son, this period saw an invigorated renewal of his research activities. An immediate supporter of the continental drift theory , originally proposed by Wegener in 1912, Holmes saw at once that it explained how identical fossils and rock formations occurred on either side of the Atlantic. However, the theory was then highly controversial, as no force was considered adequate to move continental slabs over the surface of the globe. It was Holmes' profound understanding of radioactivity—the amount of heat it generated and the enormous time it bestowed on geology for infinitely slow processes—that placed him in a unique position to formulate such a mechanism.
In 1927, Holmes gave a seminal paper which proposed that differential heating of the earth's interior, generated by the decay of radioactive elements, caused convection of the substratum (mantle). He calculated that convection could produce a force sufficient to drag continents apart, allowing the substratum to rise up and form new ocean floor. Evidence to corroborate this theory was not found until 1965, the year of Holmes' death, but by then his ideas were largely forgotten.
During the Second World War, Holmes was commissioned to write Principles of Physical Geology. Published in 1944, this famous book with its heretical chapter on continental drift, became an international best-seller that influenced generations of geologists. When Holmes retired in 1956, he set out to update the book, but with failing health it was a mammoth task, completed only months before he died.
Recognition of Holmes' outstanding contributions to geology came when he was elected Fellow of the Royal Society in 1942 and a year later appointed to the Regius chair in geology at Edinburgh University. In 1956, the Geological Societies of London and America awarded him their highest honors. In 1964, he was presented with the Vetlesen Prize, the geologist's equivalent of the Nobel Prize, for his "uniquely distinguished achievement in the sciences resulting in a clearer understanding of the earth, its history, and its relation to the universe."
Holmes was a deep thinker on the broad philosophical aspects of geology, with ideas far ahead of his time. Always of smart appearance, he was a gentleman of quiet charm and unfailing kindness. He had an exceptional talent for playing the piano, was fascinated by history, and loved poetry. In 1931, Holmes met Doris Reynolds (1899–1985), a geologist then working at University College, London. He engineered a lectureship for her in the Durham geology department, but they were unable to marry until 1939, nine months after the death of his first wife from cancer. Holmes died of bronchial pneumonia in 1965, leaving his beloved Doris to succeed him by 20 years.
See also Dating methods; Geologic time
The English geologist Arthur Holmes (1890-1965) was a pioneer in geochronology, a gifted petrologist, and a lucid expositor of the physics and history of the earth's outer layers.
Arthur Holmes was born on Jan. 14, 1890, at Heb-burn-on-Tyne. At school he became interested in the age of the earth through reading Lord Kelvin's Addresses. Winning a scholarship to London's Imperial College, he graduated in geology and physics in 1911 and immediately began research on the radioactivity of rocks, guided by R. J. Strutt (later 4th Baron Rayleigh). Strutt's studies had revealed a source of heat within the earth, unsuspected when Kelvin made his estimate that not more than 40 million years had elapsed since the earth's crust had solidified from the molten state. Holmes shared with Strutt in overthrowing this conclusion, and he made successive advances toward establishing a new and much longer geological time scale, eventually showing the earth to be at least 4.5 billion years old.
Holmes's researches were twice interrupted by participation as geologist in commercial explorations, first in Mozambique (1911-1912), where he contracted tropical diseases which precluded military service in World War I, and in Burma (1921-1924); the latter expedition failed, and he had to sue for his pay on return to England.
Holmes was demonstrator in geology at the Imperial College from 1912 to 1921, where he wrote three books and published many scientific memoirs. From 1924 to 1943 he headed the geology department of Durham University, which gained international fame as a center of petrological research. He was regius professor of geology and mineralogy at the University of Edinburgh from 1943 until his retirement, in poor health, in 1956. While at Durham his wife died in 1938; in 1939 he married the distinguished petrologist Doris L. Reynolds, with whom he made important researches on the evolution of igneous rock.
Holmes's work touched nearly all aspects of geology except paleontology. His geological researches were widespread, concerning India, Mozambique, and elsewhere in Africa, besides his native Britain. His textbook Principles of Physical Geology (1944; 2d ed. 1965) is considered a classic. Though a man of quiet demeanor, whose main outside interest was music, he did not shrink from the controversies that have figured so notably in the history of his science. He was one of the earliest and most forceful supporters of the theory of continental drift and held that it must be produced by convection currents in the substratum of the crust. In his textbook Holmes gives some diagrams describing the formation of new ocean floor by rising materials—diagrams which are almost prophetic in their anticipation of later results. He died, after a prolonged illness, in London on Sept. 20, 1965.
Information on Arthur Holmes can be found in W. B. Harland, A. Gilbert Smith, and B. Wilcock, eds., The Phanerozoic Time-Scale (1964). □