Tag: Wegener

Continental Drift

Tap for animated GIF

Public Domain

Alfred Wegener had a lot of evidence for continental drift, but he didn’t have an explanation for how they did it. He had the curious way South America and Africa looked as if they should fit together. This was noticed almost as soon as good maps were available, but it was largely dismissed as coincidence. After all, it would imply that the two land masses had moved apart, and everyone knew that couldn’t happen. The idea was ridiculous.

He also had a geological connection. The rocks of South America and Africa matched up where they would have been joined had they once been a single land mass. It is the same two billion year old rock on the two separate continents.

In a similar example, there is an old mountain range — over 400 million years old — that today has its remnants in the widely separated areas of Canada, Greenland, Ireland, Scotland, England and Scandinavia. When these areas are put together, the so-called Caledonian mountain belt re-emerges.

Old glacial deposits put down during the Permo-Carboniferous glaciation 300 million years ago are found in the present day Antarctica, Africa, Australia, India and South America. The most economical explanation for this is that these continents were gathered around the south pole at the time.

Finally there is the fossil evidence. Often the same type of fossil is found on continents that are separated today, while being found nowhere else. Either this is because the continents drifted apart after the fossils were laid down, or something more improbable happened, such as breeding pairs swimming together to another continent and establishing the species there.

Public Domain

Alfred Wegener was born in 1880 and died in 1930, but his continental drift theory, first put forward in 1912, didn’t achieve wide acceptance until the 1950s. The expanding theory was developed in the four editions of his book, The Origins of Continents and Oceans, accumulating increasingly impressive evidence as it went. The theory had a few supporters, such as Milutin Milankovich, but since Wegener couldn’t come up with a convincing mechanism for how the continents moved, most scientists were sceptical. One even argued that the continents simply couldn’t “plow through” the oceanic crust. They also found fault with the imperfect fit of the jigsaw coastlines, not realizing that he was matching them at their continental shelves, where it is a much better fit.

Paleomagnetism, a new science in the 1950s, produced much evidence to support Wegener. The ancient magnetic field was imprinted in the rocks and can be read today. India is in the northern hemisphere today, but its paleomagnetic signature shows that it was in the southern hemisphere in the past, as predicted by Wegener. As the evidence quickly mounted, and with additional evidence of seafloor spreading, scientists came to accept the theory. Eventually the theory of plate tectonics brought it all together.

Pangea animation 03.gif
Original upload by en:User:TbowerUSGS animation A08, Public Domain, Link

Today we can directly measure the movement of the continents with the Global Positioning System (GPS.) Alfred Wegener could have used that when he was exploring Greenland, the continent that eventually killed him.

rjb

Alfred Wegener

Alfred Lothar Wegener was born in Berlin, Germany on November 1st, 1880. He was the youngest of the five children of Richard Wegener, clergyman, theologian and classical language teacher. The family was well-off enough to own a vacation home, as well as to afford to educate all their children. Alfred did very well in school and went on to study physics, meteorology and astronomy. He got a doctorate in astronomy in 1905, but had formed a strong interest in the growing disciplines of climatology and meteorology.

Public Domain

Wegener made four expeditions to Greenland in his study of the polar climate, the first in 1906. He built a weather station and made observations using kites and tethered balloons, in addition to the usual instruments. He had his first experience with the killing harshness of Greenland’s climate when the expedition leader and two others died while exploring. He returned to Germany in 1908.

His second expedition to Greenland in 1913 began with a calving glacier that almost wiped it out, and ended with a fortunate and unlikely rescue as their crossing of the interior resulted in their having to eat all of their dogs and ponies before its completion.

His military service in World War One lasted only a few months. He faced fierce fighting, was injured twice and declared unfit for duty. He spent the rest of the war in the meteorological service and published 20 papers by its end. Having published on his ideas about continental drift for the first time in 1912, Wegener followed up with a major work — “The Origin of Continents and Oceans” — in 1915. Interest was small.

After the war he worked as a climatologist and as senior lecturer at the University of Hamburg. In collaboration with Milutin Milankovich, he did pioneering work in a field that would become known as paleoclimatology, where they reconstructed ancient climates. He published the third edition of “The Origin of Continents and Oceans,” provoking discussion of his theory of continental drift, and disparagement by the experts of the day.

By 1924 he attained a position that provided stability for his family, and he was able to concentrate on his studies for the rest of the decade. In 1926 he presented his ideas on continental drift at a symposium in New York, to near-uniform rejection. In 1929 he published the fourth and final edition of “The Origin of Continents and Oceans,” and made his third expedition to Greenland.

Wegener led the 1930 Greenland expedition, his fourth, and his sense of personal responsibility ultimately led to his death. A combination of a late thaw and harsh conditions resulted in the failure of a re-supply mission and the death of Alfred Wegener. His body remains buried where he died.

Public Domain

Alfred Wegener was accomplished at astronomy, meteorology and climatology, but what he is known for today is continental drift. We’ll cover that in more detail in future posts.

rjb

%d bloggers like this: