Chapter 11: Problem 17

Briefly review the history of the theory of continental drift, sea-floor spreading, and the all-inclusive plate tectonics theory. What was Alfred Wegener's role?

Short Answer

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The theory of continental drift was proposed by Alfred Wegener in 1912, suggesting all continents were once a single landmass called Pangea. The theory of sea-floor spreading, proposed by Harry Hess, states new ocean crust forms at mid-ocean ridges and spreads out. These theories culminated in the plate tectonics theory in the late 1960s and early 1970s, explaining how Earth's crust is divided into several plates that move because of mantle convection currents. Wegener collected extensive evidence to support his continental drift theory and helped pave the way for developing the theory of plate tectonics.

Step by step solution

Explanation of the Continental Drift Theory

Explain that the theory of continental drift was proposed by Alfred Wegener in 1912. According to this theory, all the continents were once joined together in a single landmass known as Pangea. The continents then drifted apart, ending up in their current locations.

Explanation of the Sea-floor Spreading Theory

Next, explain the theory of sea-floor spreading, which was proposed by Harry Hess in the 1960s. According to this theory, new oceanic crust is formed at mid-ocean ridges and spreads outwards from these elevated areas. This is caused by convection currents in the molten Mantle beneath the Earth's crust.

Explanation of Plate Tectonics Theory

Then, explain the theory of plate tectonics, which synthesizes the theories of continental drift and sea-floor spreading. This theory, proposed by several scientists in the late 1960s and early 1970s, proposes that the Earth's crust is divided into several large and small plates that float atop the semi-fluid mantle. These plates move independently of each other due to convection currents in the mantle.

Alfred Wegener's Role

Finally, be sure to emphasize the role of Alfred Wegener in these theories. Wegener is best known for proposing the theory of continental drift. But more than that, he collected a great deal of evidence in support of his theory, such as matching fossils on different continents and similar rock formations across oceans. Wegener's ideas laid the groundwork for the development of the theory of plate tectonics.

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Briefly review the history of the theory of continental drift, sea-floor spreading, and the all-inclusive plate tectonics theory. What was Alfred Wegener's role?

Short Answer

Step by step solution

Explanation of the Continental Drift Theory

Explanation of the Sea-floor Spreading Theory

Explanation of Plate Tectonics Theory

Alfred Wegener's Role

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