Q:

How did Alfred Wegener support his theory of continental drift?

A:

When Alfred Wegener first made his case for continental drift, he relied on two main lines of argument: the shape of the continents and the relative positions of glacial till deposits. Evidence later accumulated from other areas of research, but the theory was not taken seriously until well after Wegener's death.

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The first argument Wegener put forward in support of his theory was that the continents seemed to fit together like the pieces of a jigsaw puzzle. This relationship is apparent from a map, but the exactness of the match improves if the underwater continental shelves are compared. The true edges of South America and Africa, for example, fit together to a high degree of precision, allowing for millions of years of erosion.

Wegener's second argument was more complex. He traveled the world and charted the locations and orientation of glacial till deposits. These deposits are the alluvial remnant of a glacier's progress across the landscape, and they remain long after the glacier has melted away. By plotting out the latitudes of ancient till deposits, Wegener was able to demonstrate that, for his evidence to be consistent with unmoving continents, much of the world would have had to be covered in ice sheets in the relatively recent past, even in the tropics. He argued that this was evidence that the tropical continents had once been at higher latitudes.

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Related Questions

  • Q:

    What evidence is there of the continental drift theory?

    A:

    According to National Geographic, sea floor spreading and plate tectonics indicate that the continents do move or shift, which supports continental drift theory. Fossils of the Mesosaurus, an ancient freshwater reptile found in the southern parts of South America and Africa, also indicate that the two continents could have once been one solid continent that drifted apart, since the reptile could not have swum across the ocean.

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  • Q:

    How does continental drift happen?

    A:

    Continents rest on massive plates known as tectonic plates, which are fluid and able to move due to the mantle and magma underneath, and as the tectonic plates move about, they cause continental drift to happen. The concept of continental drift was first described in the early 20th century by German scientist Alfred Wegener, who explained that continental landmasses were actually drifting across the Earth. This is opposed to the original theory that landmasses are fixed and immobile.

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  • Q:

    What causes continental drift?

    A:

    Continental drift is caused by movement of the tectonic plates that continents sit on top of. Continental drift has continuously occurred throughout time, and continues to do so today. Rough estimates say that Europe and North America are drifting away from each other 2.5 centimeters per year.

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  • Q:

    What is the difference between continental drift and plate tectonics?

    A:

    Plate tectonics is the theory that explains the structure, composition and internal workings of the Earth on a worldwide scale, while continental drift refers to the theory that the continents all used to be connected in one megacontinent which scientists dub Pangaea. Both theories attempt to explain the movement of parts of the Earth's crust.

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