The Origin of Oceans

Alfred Wegener’s theory of “continental drift” directs attention to the origin of the continents, and in Wegener’s first publication on the topic this emphasis was reflected in the title: Die Entstehung der Kontinente (1912). By 1915, Wegener’s thinking had already evolved to an understanding that the “origin of continents,” was also, of necessity, the “origin of the oceans.” If the continents were not fixed, primordial features of the planet, always in the same place and in the same shape, and having roughly the same elevation, then neither were the oceans primordial features of the planet having the same shape and place and depth.

If the continents, as they do in Wegener’s theory, split and drift apart, in doing so they must create new oceans in the places between the fragments of a former continent. When Wegener published his first book-length treatment on the subject in 1915, he changed the title to Die Entstehung der Kontinente und Ozeane to reflect this aspect of the evolution of the Earth’s surface features.

Wegener went even further, postulating that the primordial earth was covered entirely by an ocean a few kilometers deep, and ocean he named Panthalassa. The still relatively warm floor of this primordial ocean was subject to folding and crumpling as a consequence of the Earth’s axial rotation, and gradually became rumpled enough to emerge here and there from the ocean creating the first continents. This emergence was not symmetrical, and led to the appearance of a land hemisphere and a water hemisphere. This original large proto-continent, that Wegener named Pangaea, split and drifted apart throughout geological history until it reached the present configuration.

The theory that Wegener proposed stood in opposition to two current theories at the beginning of the 20th century. One of these was the theory of the permanence of continents and oceans, which found favor principally in North America. The other was the theory of earth contraction, championed by many European theorists as an explanation for the formation of mountain ranges,. It was also, however a theory of the origin of oceans, especially in the work of Eduard Sueß. In Das Antlitz der Erde (The Face of the Earth), Sueß’s multivolume treatise on the origin and character of the Earth’s surface features, oceans were supposed to have been created by the down-faulting and collapse (through time) of large continental blocks on the shrinking Earth.

These two theories accounted for the the appearance of identical animals and plants on different sides of abyssal ocean basins in two different ways. The theory of continental and oceanic permanence hypothesized the existence of relatively narrow land bridges and island arcs that rose and fell throughout geologic history, allowing corridors through which the animals and plants might pass. The theory of the contraction of the earth, on the other hand, proposed that it was the sinking of these large continental fragments and the creation of ocean basins, that cut off a former continuity that had allowed animals and plants to spread across areas now cut off by emergent oceans.

Among the supporters of Wegener’s hypothesis of the origin of continents and oceans were paleobiogeographers like Edgar Dacqué and Edgar Irmscher, who pointed out, in a number of publications between 1915 and 1922, that Wegener has solved an important problem which the other two candidate theories could not address. This was the problem or the question of the volume of ocean water: Die Wasserfrage. There were actually two “water questions.” The theory of continental and oceanic permanence could not explain why, when land bridges emerged, they did not cause synchronous transgressions on the continents: they must displace huge volumes of water. Yet no such record of transgressions attributable to the rise and fall of land bridges appeared in the geologic column. The contraction theory faced the opposite problem: if huge fragments of the continents sank to the bottom of the ocean, where was sufficient water to come from to fill these newly created basins? Wegener’s theory had no such problem. Once the original proto-continent had emerged from beneath the waves through the crumpling of the thin, still-warm outer shell of the solid earth, the relative surface area of continent and ocean would remain the same throughout geologic history, but the relative position of the continents and oceans would be constantly rearranged.

While the theory of plate tectonics today treats continental displacement as an epiphenomenon of the appearance of new oceanic crust spreading out from the ocean ridges, still, like Wegener’s theory, it proposes that the relative coverage of the surface by land and water is very ancient, if not primordial, and that only the relative position and shape of land and water portions changes through time.

Wegener’s theory was thus recognized as an oceanographic as well as a continental theory by supporters and opponents alike, and Wegener’s importance to oceanography in the early 20th century was sufficiently great that when Alfred Merz died in 1925, Wegener was immediately offered (he declined) the professorship of oceanography at Berlin, and the directorship of the Berlin Oceanographic Institute. Between 1919 in 1924, Wegener had headed the meteorological section of the German Marine Observatory (Deutsche Seewarte) in Hamburg, and had he not just accepted a professorship at Graz in Austria in 1924, would quite likely have become the head oceanographer in Berlin. As we all know, Germany’s polar and oceanographic research institute today is the Alfred Wegener Institute, in Bremerhaven, and reflects the linkage between polar science and oceanography that were also united in Wegener’s work.

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