Question

Wegener's theory of continental drift was largely dismissed by the mid-1900s. What new evidence was able to revive this theory, and why?
Continental ridges were found, suggesting that parts of the land used to be below sea level.
Sonar technology found mid-ocean ridges, where new ocean floor was being created.
The coastlines of South America and Africa were similar in shape, suggesting that they shared a common tectonic plate.
The mantle moves through radiation, suggesting that rock in the Earth is not solid.

Answer 1

Answer: Option (C)

Explanation: Wegener's theory of Continental drift was replaced by a modern theory called the 'plate tectonic theory'. This theory was able to prove what wegener could not and so was universally accepted.

The new evidences supporting this theory were-

• The coastlines of east America and west Africa are similar in shape suggesting that they might have existed together once upon a time
• Similar fossils were found at different continents such as the glossopteris fauna
• Similar rock sequences found at different places determined by the correlation method

Hence the correct option that satisfies the above question is option (C)

Answer 2

Answer:

Option (3)

Explanation:

The continental drift refers to the drifting of the continents over the earth's crustal portion. This theory was initially not accepted as Mr. Alfred Wegener was not able to explain the main mechanism behind the plate motion.

Later, it was modified and more universally accepted theory was added, known as the Plate tectonic theory.

Some of the evidences that were suggested in favor of this theory included-

(a) The coastlines of most of continents such as Africa, South America matches perfectly with each other. This continental margin has been eroded in most of the places due to the continuous action of waves over the geological time.  Thus suggested that the continents were all once together forming a super-continent.

(b) Similar plant and animal fossil assemblages such as ptilophyllum, gangamopteris and marsupials were found in separate countries, suggesting the union of the plates in the past.

(c) Similar rock sequences are also observed at many places near the plate margin, that enables a reader to have a brief idea about how the continents were earlier together and how they have changed their location with respect to the poles due to the plate tectonic movement.

Thus, the correct answer is option (3).