Wegener had no chance of proving his theory
During his lifetime Alfred Wegener had no chance of proving his theory of continental drift. He lacked the necessary technology, claims Dr. Wilfried Jokat, head of the Geophysics Section at the Alfred Wegener Institute for Polar and Marine Research in the Helmholtz Association. In an interview Wilfried Jokat talks about the research questions that he and his colleagues examine today and what young geophysicists can learn from Alfred Wegener.
For a long time Alfred Wegener attempted to find substantial evidence for his hypothesis. However, he didn’t succeed. Did he go about it the wrong way?
No, back then Alfred Wegener had no chance of proving his hypothesis because the technology wasn’t available yet. If you put yourself back into that time, you realise there were no reliable depth measurements in the ocean at all back then. People only knew it was deep. But they didn’t know how deep or whether there was a mountain range down there. The ocean was simply an unknown region. Only in the course of World War II were sonar and radar developed. In the fifties, sixties and seventies there was another leap in technology. In the field of research the geosciences started getting interested in processes in the ocean. A new branch of science, “marine geophysics/geology”, developed. In other words, technologies were developed to carry out magnetic field measurements or depth soundings on a routine basis. During Wegener’s lifetime they had just derived parts of fundamental physics on the basis of which these devices were later developed.
How did geophysics then help out?
Systematic sampling, seafloor depths and, in particular, systematic measurements of the Earth’s magnetic field from research vessels were important. Via the Earth’s magnetic field two scientists then discovered that the crust of the seafloor became older from the central section of the ocean towards the continents – and it did so symmetrically, i.e. on both sides of the mountain range that had been discovered in this central section. Today we call this mountain range in the Atlantic the “Mid-Atlantic Ridge”. This interpretation of the magnetic data in connection with core samples was clear proof of continental drift. That was an absolute revolution for science. At that time, in the sixties and seventies, it was just as important for science as the topic of “climate” today. All sorts of people went to sea and conducted magnetic measurements to determine the continental drift between the various oceans and understand when and how India, for example, separated from Antarctica.
The new aeromagnetic dataset Riiser-Larsen Sea, Source: Alfred Wegener Institut
Is there is an explanation for how the movements of the plates come about?
We don’t really know the mechanism itself. We know that, due to the high temperatures, the Earth’s mantle is plastic and the continents “float” on it. However, no one has understood yet how the convection cells really function. At the moment there is a lack of resources to carry out systematic investigations on this in the ocean. Or it’s questionable whether we can resolve these deep structures with geophysical methods. There are various models, but they have yet to be substantiated due to a lack of data.
What great questions is your working group at the Alfred Wegener Institute preoccupied with?
In principle, the magnetic field measurements that were carried out to verify continental drift ended at the beginning of the 1980s. The view taken back then was that we know everything. Our working group focuses on gaining a better understanding of the processes in the mantel that boost continental drift. For this purpose we conduct appropriate experiments off the coast of East Greenland, in the Arctic, Antarctic and Namibia. In doing so, we have seen that details of the models of continental drift for the southern continents are erroneous. Particularly the age data and geometry of how especially the continents in the southern hemisphere moved were significantly improved through our measurements in relation to the old models. We take a closer look at the plate tectonics in the Southern Ocean and examine such questions as: why continents break apart at certain spots, what driving forces cause this breaking apart and the extent to which continental drift had impacts on environmental conditions in the past (volcanism, size of the oceans, etc.). What influence did, for instance, the pronounced volcanism in East Greenland and Norway 55 million years ago have on extreme warming of the Earth during this period? In this period Greenland separated from Europe and the North Atlantic started to form.
What technology is applied in this research?
Among other things, we make use of our research aircraft, which are equipped with magnetometers. Even though fundamental physics is still the same as in the fifties, technology has made rapid advances. Whereas measured values used to be read off and entered by hand in a field book, nowadays all of this takes place automatically and much faster in small computer-controlled sensors. When our aircraft flies at 180 kilometres per hour, we can obtain up to 20 measured values a second in order to record the Earth’s magnetic field in detail.
What can a young geoscientist today still learn from Alfred Wegener?
The key is to have a certain doggedness and patience. And I mean doggedness in the positive sense. The attitude that I will stick to this issue and not let myself get thrown off track right away by someone who thinks he knows it all better. You can be wrong sometimes. But this doggedness, this patience and also the financial support to work on a question longer than three years are important. It’s an illusion to believe you can find answers to scientific problems in three years. This applies in particular to basic research that we at the Alfred Wegener Institute carry out. Rapid application and use of the results is frequently not possible. We cannot say when we’ll need this knowledge. The continental drift is a classic example of this. It took nearly 60 years for the idea to be confirmed, but it then led to a fundamental understanding of the global distribution of earthquakes, volcanoes, i.e. the geo-risks for humanity in certain regions, on the one hand, and of the distribution of natural resources, on the on the hand. As a consequence, completely new branches of knowledge and industries came into being.