G. Chapter 2 - Chapter 2 Early Ideas about Continental...

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Chapter 2 Early Ideas about Continental Drift 1. 1600’s – 1700’s – mapping the coasts of Africa and South America led to speculation that the continents could once have been joined together. 2. 1885 – Austrian geologist Edward Seuss - Similarity of late Paleozoic plant fossils in India, Australia, South Africa, and South America. The “Glossopteris flora. - These plant fossils occur just above glacial deposits on all the continents. - Proposed an ancient supercontinent called Gondwanaland (today we just say Gondwana). - He thought the continents were connected by land bridges that appeared and disappeared! 3. 1910 – American Frank Taylor - Explained the formation of mountain ranges as the result of lateral movement of continents. - Proposed a mechanism for this movement called continental drift. He felt this movement was the result of gigantic tidal forces resulting from the earth’s gravity capture of the moon. (an incorrect mechanism!) - Was the first to propose the Mid-Atlantic Ridge (discovered 1872-1876) as the site along which the ancient “polar” continent broke apart. 4. 1915 – German Alfred Wegener - Published a massively documented work - entitled “The Origin of Continents and Oceans” in which he presented a tremendous amount of geologic, paleontologic, and climatologic evidence for his theory. - Today, he is generally credited with - developing the hypothesis of continental drift, but at the time his work was met with a very mixed reaction. - Wegener grouped all continents into one giant landmass called Pangaea . - He developed a series of maps representing the breakup of Pangaea and the movement of the continents to their present day position.
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5. 1937 – South African Andrew de Toit - Further developed Wegener’s ideas - Presented more geologic evidence, but discovered a climatologic problem. - To resolve this problem, he placed the southern continents of Gondwana at or near the South Pole, but arranged the northern landmass near the equator (to explain coal deposits). He named this landmass Laurasia . 6. 1960’s – the hypothesis of Continental Drift is generally accepted as a correct theory. - more and more evidence is discovered that supports this hypothesis - a workable mechanism driving the process is proposed. Evidence Supporting Continental Drift 1. Continental Fit - Critics of Wegener pointed out that coastlines result from erosional and depositional processes so Africa and South America did not fit exactly. - But the true margin of a continent is not the coastline, but beneath the continental shelf where continental crust changes to oceanic crust. - 1965 English geophysicist Sir Edward Bullard and two associates showed the best fit of the continents occurs at about 2000 m. 2.
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G. Chapter 2 - Chapter 2 Early Ideas about Continental...

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