Leibniz (1691) wrote that the Earth has cooled down from a liquid state. Dana (1843-1873) described oceanic subsidence and mountain-building as results of the thermal contraction of the Earth. Lyell suggested that, due to unequal cooling, parts of the Earth sink faster than the rest, so that continents of the past have become ocean floors today and vice versa. Suess (1885, Vol. 1, p. 778) said that “the collapse of the world is what we are witnessing”. This paper reviews the Contracting Earth Theory.
The Contracting Earth Hypothesis was once a dominant paradigm in geology (Wegener, 1929). The origins of this theory can be found in the works of European scientists such as ...view middle of the document...
Gottfried Leibniz (1691, p. 12) wrote “the globe of the Earth was at first a regular form, and has hardened from liquid”. James D. Dana (1847b) says that very few geologists of his time would not admit the initial fluidity of the planet. However, thermal contraction as the principal tectonic force was not taken to be as obvious; there were alternative theories of orogenesis (mountain-building) as well. Below, we discuss this point in further detail.
The alternative paradigm in which to think of the face of the Earth was the Continental Drift of A. Wegener (1929). While the Contraction Theory had a hidden assumption that prevented large horizontal displacements of crustal units, Wegener proposed that the continents move relative to each other, so much that the entire Atlantic basin opened up in this way. In supporting his thesis, Wegener made use of evidence drawn from the full range of Earth sciences: geodesy, geophysics, geology and paleontology. He concluded that the continental crust and the oceanic crust are two different layers and the former floats above the latter similar to ice cubes floating on water. In this picture, the ocean floors are the exposure of the inner crust where the outermost layer vanishes. Wegener attempted to explain mountain-building in the framework of his theory as well.
J. D. Dana (1846) noted that the greater volcanic activity of the ocean floors relative to the continents implies a more rapid cooling, thus a higher rate of thermal contraction. This was consistent with Darwin’s Pacific subsidence theory, to which Dana (1843) had contributed earlier. Dana (1846) suggested a generalized oceanic subsidence and argued that the elevation of the continents was a result of this process. Many European geologists held a similar view of the continental elevation, however with an important difference: they believed that different parts of the globe subside at different times, constantly interchanging oceanic and continental areas (Wegener, 1929). Dana opposed this view; he stated that “the oceanic and continental areas were defined when the Earth’s crust first began to form” (Dana, 1873b, p. 170). He had earlier contrasted the simple composition of the oceanic crust with the vast heterogeneity of continents (Dana, 1843) and emphasized the permanence of these features (Dana, 1856). Dana’s version of the Contraction Theory, which was most popular among American geologists, was sometimes called “the Permanence Theory” (Wegener, 1929).
Bertrand, M., 1884, Rapport de structure des Alpes de Glaris et du Bassin houiller du Nord: Bulletin Société Géologique de France, 12, p. 318-330.
Dana, J. D., 1843, On the areas of subsidence in the Pacific, as indicated by the distribution of coral islands: American Journal of Science and Arts, 1st series,...