Chapter 2, Problem 1RQ

To determine

The continental drift hypothesis by Wegener and the controversies of other geologists on his theory.

Answer to Problem 1RQ

Wegener gave all the possible evidences which prove that the continents were once together as Pangaea and drifted apart during the late Mesozoic period. But he couldn’t formulate a reason for such a drift. Also, he didn’t explain the massive force that makes such huge blocks to drift apart. Hence, at first, other geologists couldn’t accept his proposal.

Explanation of Solution

Alfred Wegener is a German geologist who formulated the idea of the continental drift theory.

Wegener hypothesized that all continents present now were once making up a large super continent together, called Pangea, surrounded by a vast ocean. Later, due to some natural forces, they were broken and drifted apart at the end of the Mesozoic period. He formulated some evidences for his theory.

Evidences:

He observed the match of edges of continents. Wegener observed the match of the Atlantic coast lines, that is, the Eastern coast of North America and the North-western coast of Africa. Also, he pointed out the bulge of Eastern South America into South-western Africa. Australia, Antarctica, and India could all connect to the southeast of Africa, while Greenland, Europe, and Asia could pack against the northeastern margin of North America.

Wegener found that the same distinctive Precambrian rock assemblages occurred on the eastern coast of South America and the western coast of Africa; regions now separated by an ocean. He also noticed that some of the features of the Appalachian Mountains of the United States and Canada closely match mountain belts in southern Greenland, Great Britain, Scandinavia, and Northwestern Africa. Therefore, he stated that not only coast lines but also rock units have matched.

Land dwelling animals cannot swim across oceans. Thus, Wegener observed the fossil record of late Paleozoic and Mesozoic time and fortunately, he observed that the same species existed on several continents which he placed adjacent to each other. He also observed the Paleozoic coal, reef, sand-dune, and salt deposits which define the climatic belts on Pangaea and that even matched his theory.