International Geologiical Congress - Oslo 2008


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IEH-01 General contributions to history of geosciences


Did Esmark's (1824) glacial theory impel the discovery of the "greenhouse" effect (Tyndall, 1861), lithospheric isostasy (Jamieson, 1882) and continental drift (Wegener, 1912)?


Paul F. Hoffman, Harvard University (United States)


The glacial theory for Pleistocene tills and associated landforms in northern Europe and North America was proposed by Esmark (1824) in Norway, Venetz (1830) in Switzerland and Bernhardi (1832) in Germany, but was not widely accepted until after the Scottish glacial revival led by Jamieson (1862) and Geikie (1863). Resolution of the glacial controversy was good for geology-How could older strata be understood if those closest to the Recent remain mysterious? (James Smith, 1836)-but was more deeply felt in climate physics. Experimental demonstration of the selective absorbtion of infra-red but not visible radiation by certain gases (Tyndall, 1861, 1863) was carried out expressly to account "for all the perturbations of climate that the researches of geology have revealed". Tyndall recognized that although absorbtion by water vapor is "more essential to the vegetable life of England than clothing is to man", it is the atmosphere's variable minor constituents, notably carbon dioxide, that must be responsible for bidirectional climate change of geological magnitude. "Revolutions in the Sea" (Adhemar, 1842) may seem an odd title for an orbital theory of ice ages, but the book is directed at a problem more central to the ice age controversy than most historians admit, the problem of submergence of the land and its slow reemergence after the ice had disappeared. The titles of papers from "On indications of changes in the relative levels of Sea and Land in the West of Scotland" (Smith, 1836) onward refer to the occurrence of marine faunas in the tills and overlying stratified drift, now raised high above the sea. Adhemar (1842) envisioned gigantic polar ice caps, alternating between the hemispheres, which displace the planet's center of mass, causing sea levels to rise toward the glaciated pole and fall toward its opposite. Although Croll (1864) revised Adhemar's theory of climate change, he accepted his ideas on submergence (Croll, 1866, 1875). Croll's writings on submergence were intended to refute the suggestion of Jamieson (1865) that the submergence was due to "the enormous weight of ice laid down upon the land". The latter emerged triumphant, however, based on geological observations insightfully marshalled (Jamieson, 1882), including the development of peripheral bulges and their collapse, causing drowned forests, upon deglaciation. Jamieson, the most creative and original of the Scottish glacial revivalists, deserves to be better known. The identification in 1859 of late Paleozoic tillites in coastal India, in 1870 in southern Africa and later throughout Gondwanaland (ice always flowing onshore) aroused a young German meteorologist. "The Permian ice age poses an unsolvable riddle for all models that do not dare to assume horizontal displacements of the continents" (Wegener, 1912). Closing the Atlantic and Indian oceans "takes everything mysterious away from the problem".


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