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  3. Early Theories of Continental DriftP1: The idea that the geography of Earth was

Early Theories of Continental DriftP1: The idea that the geography of Earth was

游客2025-02-05  9
问题 Early Theories of Continental Drift
P1: The idea that the geography of Earth was different in the past than it is today is not new. As far back as 1620, Francis Bacon spotted that the west coast of Africa and the east coast of South America looked as if they would fit together, like pieces of a jigsaw puzzle. Between then and 1912, other people identified further similarities between other continental coastlines. But because much of the early support for mobilism was based on far-flung intercontinental similarities, geologists tended to be skeptical of the fieldwork of others.
P2: During the late nineteenth century, Austrian geologist Eduard Suess proposed the name "Gondwanaland" in his book The Face of the Earth (1885) and gave far greater emphasis to the evolutionary nature of the earth and he noted the similarities among the Late Paleozoic plant fossils of India, Australia, South Africa, and South America. Based upon glossopteris fern fossils in such regions, he explained that the three land masses were once connected in a supercontinent which he names Gondwanaland, and that the ocean flooded the spaces currently between those lands. Thus, in his view, the similarities of fossils on these continents could be accounted for by postulating the concept of a land bridge that existed once but subsided later.
P3: Later, a number of refinements to Suess’s theory were made. The American geologist Frank Taylor published a pamphlet in 1910 presenting his concept of "horizontal displacement". He explained the formation of mountain ranges as a result of the lateral movements of continents. With the earth’s capture of the moon, the gravitational forces between them generated a pull towards lower latitudes where they thickened and formed folded mountain belts especially in middle latitudes. Although we now know that Taylor’s explanation of continental drift is erroneous, one of his most significant contributions was his suggestion that the Mid-Atlantic Ridge— an underwater mountain range discovered by the 1872-1876 British HMS Challenger expeditions—might mark the site at which an ancient continent broke apart, forming the present-day Atlantic Ocean.
P4: However, it is Alfred Wegener, a German meteorologist, who is generally credited with developing the hypothesis of continental drift. In his monumental book, The Origin of Continents and Oceans (1915), Wegener theorized that a single supercontinent he called "Pangaea" existed sometime between 350 million to 225 million years ago. Wegner portrayed his grand concept of continental movement in a series of maps showing the breakup of Pangaea and the movement of various continents to their present-day locations. What evidence did Wegener use to support his hypothesis of continental drift? First, Wegener noted that there is geographical similarity along both the coasts of the Atlantic Ocean. The opposing coasts of the Atlantic can be fitted together in the same way as two cut off pieces of wood can be refitted. Furthermore, mountain ranges and glacial deposits seem to match up in such a way that suggests continents could have once been a single landmass. Finally, many of the same fossils and vegetative remains are found today on widely separated continents, indicating that the continents must have been in proximity at one time. During his days, Wegener was regarded as an advocate rather than as an impartial scientific observer, appearing to ignore vast evidence unfavorable to his ideas and distort other evidence to bring it into harmony with the theory.
P5: After Wegener’s death, a South African geologist Alexander Du Toit continued to assemble fossil evidence for Pangaea. He noted that fossils of the now extinct reptile "Mesosaurus" occur in rocks of the same age in both Brazil and South Africa. Because the physiology of freshwater and marine animals is completely different, it is hard to imagine how a freshwater reptile could have swum across the Atlantic Ocean and then found a freshwater environment nearly identical to its former habitat. Moreover, if Mesosaurus could have swum across the ocean, its fossil remains should be widely dispersed. It is more logical to assume that Mesosaurus lived in lakes in what were once adjacent areas of South America and Africa when it was united into a single continent. Notwithstanding all of the empirical evidence in favor of continental drift theory presented here, most geologists at the time refused to entertain the idea.
P6 :The debate over continental drift has the same role and stature in the history of the earth sciences as the debate over Darwinian evolution in the history of life sciences and the debates over relativity and quantum theory in the history of physics. In the largest sense, the history of earth science, the history of biology, and the history of physics in the 20th century are all histories of the consolidation of opinion and the formation of broad consensus—that these theories were the best way to organize and advance these sciences.
P5: After Wegener’s death, a South African geologist Alexander Du Toit continued to assemble fossil evidence for Pangaea.■ He noted that fossils of the now extinct reptile "Mesosaurus" occur in rocks of the same age in both Brazil and South Africa.■ Because the physiology of freshwater and marine animals is completely different, it is hard to imagine how a freshwater reptile could have swum across the Atlantic Ocean and then found a freshwater environment nearly identical to its former habitat. ■ Moreover, if Mesosaurus could have swum across the ocean, its fossil remains should be widely dispersed. It is more logical to assume that Mesosaurus lived in lakes in what were once adjacent areas of South America and Africa when it was united into a single continent. ■ Notwithstanding all of the empirical evidence in favor of continental drift theory presented here, most geologists at the time refused to entertain the idea. [br] The word "vast" in the passage is closest in meaning to
选项 A、enormous
B、significant
C、convincing
D、additional
答案 A
解析 【词汇题】vast意为“大量的，巨大的”。
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