Warren B. Hamilton (May 13, 1925 – October 26, 2018) was an American geologistHamilton, L.C., G.R. Foulger, S.R. Hamilton, K.A. Howard & S.A. Stein. 2019. "Memorial to Warren B. Hamilton, 1925–2018." Geological Society of American Memorials 48. https://www.geosociety.org/documents/gsa/memorials/v48/Hamilton-WB.pdf known for integrating observed geology and geophysics into planetary-scale syntheses describing the dynamic and petrologic evolution of Earth's crust and mantle. His primary career (1952–1995) was as a research scientist with the US Geological Survey (USGS) in geologic, then geophysical, branches. After retirement, he became a Distinguished Senior Scientist in the Department of Geophysics, Colorado School of Mines (CSM). He was a member of the National Academy of Sciences, and a holder of the Penrose Medal, highest honor of the Geological Society of America (GSA). Hamilton served in the US Navy from 1943 to 1946, completed a bachelor's degree at the University of California, Los Angeles (UCLA) in a Navy training program in 1945, and was a commissioned officer on the aircraft carrier . After returning to civilian life, he earned an MSc in geology from the University of Southern California in 1949, and a PhD in geology from UCLA in 1951. He married Alicita V. Koenig (1926–2015) in 1947. Hamilton died in October 2018 at the age of 93; until the last few weeks he was working on new research.Warren B. Hamilton obituary His final paper, "Toward a myth-free geodynamic history of Earth and its neighbors," was published posthumously (2019) in Earth-Science Reviews. In 2022 the Geological Society of America published an edited volume in his honor, with 33 papers: In the Footsteps of Warren B. Hamilton: New Ideas in Earth Science. The first chapterHamilton, L.C. 2022. "On the last paper of Warren B. Hamilton," in Foulger, G.R.; Hamilton, L.C.; Jurdy, D.M.; Stein, C.A.; Howard, K.A.; Stein, S. (eds.), 2022, In the Footsteps of Warren B. Hamilton: New Ideas in Earth Science, Geological Society of America. https://doi.org/10.1130/SPE553. of this book describes how Hamilton's last paper was written; the second applies Thomas Kuhn's model of scientific change to interpreting Hamilton's career.
Early career
Following a year, 1951–1952, teaching at the University of Oklahoma, Hamilton began his principal career as a research scientist with the USGS in Denver (1952–1995). Early projects included field and laboratory work in the Sierra Nevada batholith, the Idaho batholith and what later became known as accreted terranes west of it, metamorphic rocks of east Tennessee, a major crustal-extension earthquake in Montana, and extreme deformation of cratonic strata in southeast California.
Antarctic insights
Hamilton led a two-man field party in Antarctica (October 1958–January 1959) for the International Geophysical Year, and launched a new understanding of Antarctica. He was the first to apply the name trans-Antarctic Mountains (two years later, formalized as Transantarctic Mountains) to that 3,500 km range. Hamilton recognized that a large sector of this range contained distinctive granitic rocks like South Australia's Adelaide orogenic belt. Associated fossils of diverse ages in Antarctica, Australia, and southernmost Africa further linked these continents, and supported then-radical explanations of continental drift. Before traveling to Antarctica, Hamilton was what he later described as a "closet drifter," aware that Southern Hemisphere geology provided powerful evidence favoring continental drift.Frankel, H.R. 2012. The Continental Drift Controversy: Wegener and the Early Debate. Cambridge, UK: Cambridge University Press. He returned to Antarctica for fieldwork in 1963 and 1964 in other parts of the Transantarctic Mountains, including those once continuous with other Australian tracts. He also investigated in the field evidence for drift in Australia and South Africa, integrating his work with that of other researchers to show how Antarctica and other Gondwana continents had drifted apart.
Continental Drift to Plate Tectonics
Continental mobility was important also to Hamilton's research in western North America in the 1960s, at a time when lateral motions were rejected by most northern hemisphere geoscientists. He recognized that Baja California had pulled away from Mexico, opening the Gulf of California, as components of the San Andreas Fault system. He studied the petrology and mobile settings of several volcanic provinces, and variations in magmatic complexes in relation to their depths of formation. He was first to recognize that both ocean floors and island arcs were incorporated in continental orogenic complexes (although the mechanism was not then clear) and could be discriminated petrologically, and that the Basin and Range region had doubled in width by crustal extension. Geoscience historian Henry Frankel characterized Hamilton as "the most active North American mobilist who developed his ideas independently of contemporaneous advances in paleomagnetism and oceanography."Frankel, H.R. 2012. The Continental Drift Controversy: Wegener and the Early Debate. Cambridge, UK: Cambridge University Press.
In the late 1960s, geophysicists working with new technologies of marine magnetic surveying and earthquake seismology proved the operation of seafloor spreading, devised explanations with the new concepts of plate tectonics, and showed that ocean floors and mobile continents jointly formed tectonic plates. Hamilton was a pioneer in showing how land geology also had evolved by plate interactions, like those now active, for which submarine evidence was newly generated. He published in 1969 and 1970 syntheses of the evolution of California, and of much of the Soviet Union, as controlled by converging tectonic plates. He "paved new paths for the structure and tectonics community to integrate plate-tectonic concepts and on-land geology."Keith Howard, 2007, citation for the Structural Geology and Tectonics Career Contribution Award presented to Warren B. Hamilton. https://www.geosociety.org/awards/07speeches/sgt.htm
Top-Down Plate Tectonics
Hamilton was invited in 1969 to make a plate-tectonic analysis of Indonesia and surrounding regions, funded by the US Department of State, to aid petroleum exploration ramping up there. This large region is the most complex part of the Earth wherein small oceans still intervene between complexly interacting plates so that many separate mobile histories can be deciphered. He integrated onshore geology with offshore geophysics, most of it previously unstudied. Resulting publications include wall maps, many articles, and a large monograph.Hamilton, W.B. 1979, Tectonics of the Indonesian Region: USGS Prof. Paper 1078, 345 p. (reprinted with minor revisions, 1981) This work contained new understanding of convergent-plate interactions, with observations showing that plate boundaries change shapes and move relative to most others. Hinges roll back into subducting oceanic plates which sink broadside, not down their inclined dips. These sinking plates, and not the conventionally pictured rising mantle-convection cells, control surface-plate motions. Arcs advance toward each other over sinking slabs and collide; new subduction breaks through outside the new aggregates. Oceanic lithosphere thickens with age away from spreading centers because it is chilled from the top, becoming denser than hotter material beneath it, and therefore capable of sinking (the process of subduction). Oceanic plates are propelled by their mass, and their commonly inclined basal boundaries, toward subduction exits from the surface. William Dickinson reported that this "magnificent monograph on Indonesian tectonics includes the first regional tectonic map to depict the whole of a classic orogenic region in the framework of plate tectonics."Dickinson, W.R. 1990. Citation for Penrose Medal award to Warren B. Hamilton. GSA Bulletin 102, 1139 Keith Howard described it as "a standard of comparison for countless newer studies of subduction belts worldwide."
Hamilton's other work of the 1970s through early '90s was also aimed at understanding the evolution of continental crust. He concentrated on the geology and crustal geophysics that define the products of the last 540 million years of Earth history (the Phanerozoic eon), throughout which plate tectonics had produced convergent-plate geologic assemblages like those forming today. He traveled extensively to study rock complexes of varying types, ages, and depths of formation, including two that exposed the Mohorovičić discontinuity between crustal and mantle rocks of magmatic arcs. He accepted 5 visiting professorships, and also gave many invited short courses and lectures around the world.
Hamilton's emphasis on empirical evidence kept him at odds with conventional explanations. Although many geoscientists adopted mobilistic viewpoints as seafloor spreading was documented, most of them did so with the assumption that plates are passive passengers on convection systems driven by heating from the bottom. This speculation still dominates theoretical geodynamics. Hamilton argued that this view is incompatible with information on actual plate interactions, and with much other evidence from physics and geoscience.
Alternative Earth and Terrestrial Planets
In 1996, Hamilton moved to the Department of Geophysics at Colorado School of Mines, continuing research with some teaching. He worked at multidisciplinary integration of data on whole-Earth geophysics and mantle evolution, understanding the kinematics of plate tectonics, interpreting the profound contrasts between the rock assemblages and relationships produced by Phanerozoic plate tectonics and those of the first four billion years of Earth history, and integrating those insights with new interpretations of evolution of the terrestrial planets. These broad topics were advanced in parallel, as can be seen from the list of his publications. Major themes were updated and summarized in a 2015 paper.see
The widely accepted explanations for the dynamics and internal evolution of Earth and its neighbors are still based on speculations from the 1970s and 1980s. These assume slow net separation of continental crust from mantles that are still mostly unfractionated and are vigorously undergoing convection in the same bottom-driven fashions, and yet produce different shallow and surface effects on each planet.
Hamilton developed radically new interpretations by re-evaluating the bases for those conventional assumptions independently for Earth, Venus, Mars, and Earth's Moon. In his view, these assumptions are contrary both to empirical knowledge and to physical principles, including the second law of thermodynamics. Independent evidence for each planet indicates growth of each to essentially full size, with magmatically separated mantle and mafic crust, no later than about 4.50 billion years (b.y.) ago. The heat source for melting synchronously with accretion remains unclear, however. Uranium, Thorium and Potassium 40, suggested in Hamilton's 2015 paper, were inadequate for the task. Those elements all partition selectively into melts, however, and so were concentrated in the protocrusts and their derivatives, wherein the radioisotopes increased shallow temperatures while producing non-convecting lower mantles.
Mechanisms of Plate Tectonics