"Doesn’t the east coast of South America exactly match the west coast of Africa?"

Alfred Wegener asked this question back in 1910, at that time only in private circles. In an interview scientific historian Dr Reinhard Krause explains how the meteorologist and polar researcher expanded this idea into a hypothesis by the time of his legendary lecture and attempted to substantiate it with proof.

How did Alfred Wegener arrive at the supposition that the continents could move?

There is a written remark on this point from which we can draw the conclusion that he noticed that the continents of South America and Africa fit together well while looking at a new Andrees Handatlas. He then set out to investigate the matter. It must be mentioned at this juncture that before him all sorts of people had noted the fact that the continents of South America and Africa match, including Alexander von Humboldt. That alone, therefore, isn’t enough to be considered the impetus for a new theory.

Later Wegener wrote once that some time after this impression he came across a collective geological paper. And only in connection with this collective paper did he realise that he had to look into this idea again. He then plunged into this topic with great vehemence and collected all arguments for a continental drift.

What expert opinion did the geologists of the “old school” hold at that time?

They gave thought to the similarity of the continents, for example their geological similarity. You knew you could find stones in South America and similar formations or layers in Africa, for instance. In addition, up to a certain period it was possible to verify the pronounced similarity in flora and fauna. And how do I explain similarity? If I have butterflies in South America and Africa that are similar, I cannot assume that these butterflies flew over the Atlantic. I somehow have to bring other connections into play. Scientists always had only one explanation for that, i.e. there was a link between the continents in the form of land bridges. Since it was no longer possible to see these land bridges, however, they must have sunk. To this extent Alfred Wegener came out with an entirely new idea.

Can Wegener’s move to hold this lecture in Frankfurt be regarded as bold?

One has to keep in mind that this lecture was held at the Geological Association. That was a completely new association. It was, so to speak, the counter-society to the established German Geological Society and held its second annual conference that year. Hence it alone had a kind of revolutionary touch. In other words his thesis fit in well there. However, Wegener then supplied, at an astonishing speed, detailed reasons backing up his theory following his lecture – namely in the April, May and June issues of Petermann’s Geografische Mitteilungen. And this magazine had an international audience.

How did Wegener substantiate his supposition?

Wegener was a physicist and thus far afield from geology. His reasoning is therefore primarily of a physical nature. He, of course, recognised that the globe isn’t a rigid body that functions like a stone, but is a mass held together by its own gravity. His conception was that there were two different elements in the Earth’s crust. He called one of them sial and the other sima. Wegener assumed that the oceans were composed of a heavier material than the continents. He thus presumed that the lighter continents float on the heavier subsurface, like ice floes on the water. That was the core of his idea! It was associated with the concept of so-called isostasy. This says land bridges or the like couldn’t come into being or sink because everything is in gravitational equilibrium. In this way he reduced the idea of land bridges and sunken continents to absurdity.

How did Alfred Wegener attempt to find evidence for his theory?

Wegener gathered evidence in various fields: firstly in geophysics, then in geology and palaeontology. He systematically put together the arguments from these three main fields. That means he put all his efforts into collecting evidence for the accuracy of this theory. Together with his colleague Koch, he even carried out highly precise position measurements on the northeast coast of Greenland and then compared them with measurements of earlier expeditions. In this way he attempted to demonstrate a change in distance between Europe and Greenland. The values derived back then were at least one, sometimes two orders of magnitude too high, however. Initially the reference was to an annual drift on the range of 30 metres. That shrunk very quickly, however, to a figure of three metres. And today we know that in reality it was three centimetres at most.

Did the initial mockery of his colleagues hurt Wegener’s feelings?

According to everything I’ve been able to read and what I interpret between the lines, that was not the case. Right from the beginning he was firmly convinced that this theory was correct – and took it so seriously that he said: I have to put forward my arguments even more precisely and find even better indications that the theory is correct. Wegener got profoundly involved in the matter. We have proof of his meticulousness in that we possess his personal copy of the first edition of his book “The Formation of Continents and Oceans”. This copy contained blank white pages between the normal pages. This was customary at that time. Authors used such copies to write down improvements on these pages for future editions. With the help of this book we can thus understand what thought he gave to improvement of the entire matter. What newspapers he read, what articles he wanted to quote and so on. Recently we have made a transcription of these entries by Wegener and published them online.

Transcription of Wegener's entries (in German language only)