R. A. Daly's early model of seafloor generation 40 years before the Vine-Matthews hypothesis; an outstanding theoretical achievement inspired by field work on St. Helena in 1921-1922

Large-scale lateral mobility of the Earth's lithosphere (mobilism) was a hotly debated issue in Earth Sciences during some two decades following publication of Wegener's (1912) theory of continental displacement. The final acceptance of lithospheric mobility was brought about with the plate tectonics revolution during the late 1960s. Support for mobilism was rather popular in certain European countries during the 1920s, whereas the reactions in North America were mostly hostile. One of the very few influential mobilists in the New World was Reginald Aldworth Daly of Harvard University. The present paper discusses his model of continental displacement which is very remarkable in many aspects. We focus on the hitherto neglected fact that Daly proposed in the mid-1920s a mechanism to create oceanic crust which would have been totally consistent with the Vine-Matthews hypothesis of seafloor generation published in 1963. It is furthermore suggested that Daly's geotectonic proposals were inspired by small-scale analogues of lava flows and multiple dike swarms he observed on Atlantic islands such as St. Helena and Ascension. His model to account for the construction of new oceanic crust is reminiscent of the models of Vine and Moores (1972) and Cann (1970) which eventually led to the "Penrose-definition" of ophiolites in 1972. As these scientists arrived at their conclusions absolutely independently of Daly, this episode is an instructive example of a multiple or repeated discovery in the Earth Sciences which renders it difficult to believe certain theories of science which assume scientific models to depend mostly on social factors.