On this date, the American geologist Joseph Barrell was born. He was professor of structural geology at Yale University from 1908 until his death in 1919.
Barrell proposed that sedimentary rocks were produced not only by marine sedimentation but also by the action of rivers, winds, and ice (continental sedimentation).
He also proposed (1916) that the bright red color of many Devonian rocks meant that the rocks had been baked dry, like bricks, in arid conditions. [Barrell had been only half right; red rocks do sometimes form in droughts, but they form in moist tropical soils as well.]
Barrell, and subsequently the American paleontologist Alfred Sherwood Romer, speculated that droughts had caused lungfish to evolve into air-breathing land vertebrates, including tetrapods. According to this hypothesis, as the ponds dried, the fish had to adapt to life on land and so evolved features that enabled them to hop from pond to pond. [However, evidence discovered more recently suggests that the fish-to-tetrapod transition likely happened not in creatures that were adapting to land but in creatures living in water. In fact, everything special about tetrapods – limbs, digits, ribs, neck, and so on – might well have evolved in water, not on land.]
At a meeting of the Geological Society of America held in Albany, New York, in 1916 Barrell presented a paper on “Rhythms and the measurement of geologic time” that was later published in full in the Society’s Bulletin in 1917. The article became an instant classic in geology. Barrell argued that geological processes vary in intensity in a cyclical rather than a uniform fashion. Thus, current rates of geological change could not, as uniformitarians claim, be a reliable guide to the past. He suggested that the new radiometric dates should be used to interpret the sedimentological record. Thus, he accepted an age for the Earth of a few billion years at a time when many geologists still preferred an age of 100 million years.
Nature vibrates with rhythms, climatic and diastrophic [tectonic], those finding stratigraphic expression ranging in period from the rapid oscillation of surface waters, recorded in ripple-mark, to those long-deferred stirrings of the deep imprisoned titans which have divided earth history into periods and eras. The flight of time is measured by the weaving of composite rhythms- day and night, calm and storm, summer and winter, birth and death such as these are sensed in the brief life of man. But the career of the earth recedes into a remoteness against which these lesser cycles are as unavailing for the measurement of that abyss of time as would be for human history the beating of an insect’s wing. We must seek out, then, the nature of those longer rhythms whose very existence was unknown until man by the light of science sought to understand the earth. The larger of these must be measured in terms of the smaller, and the smaller must be measured in terms of years. Sedimentation is controlled by them, and the stratigraphic series constitutes a record, written on tablets of stone, of these lesser and greater waves of change which have pulsed thru geologic time. [“Rhythms and the Measurements of Geologic Time”, Bulletin of the Geological Society of America (1917) 28: 746]
Although Barrell’s concerns were seemingly diverse, they were actually variations on a common theme: the effects of physical agents on the evolution of the Earth and its inhabitants. Thus, “The Origin of the Earth” (1916), a lecture delivered to Yale’s Sigma Xi Society, discussed the conditions required for the genesis of the solar system and the development of the Earth; Barrell’s papers on sedimentology always related sedimentological processes to the larger problems of historical geology, as did his treatments of structural geology; he maintained that biological evolution was the result of physical and chemical agents, in that these are the factors determining the environment of organisms.
- Joseph Barrell, “Rhythms and the Measurements of Geologic Time” Geol. Soc. America Bull. (1917) 28: 745-904.
- Patrick Wyse Jackson, The Chronologers’ Quest: The Search for the Age of the Earth (Cambridge, UK: Cambridge University Press, 2006) 195-6.