Alfred Wegner (1880- 1930) was a radical pioneer, advancing scientific thinking though thorough research and critical observations. His ideas created a ‘stepping stone’, literally and metaphorically, which brought continents together and progressed ideas of the world in leaps and bounds. However, it was not until after his death that his ideas were accepted by the scientific community.
Right from the start, Wegner was always going to struggle to achieve acceptance of his theories. Being a meteorologist, and not a geologist, meant that many did not appreciate his scientific understanding and did not feel he was qualified to theorise on Earth’s past. Wegner was dogged though. He had an idea and he couldn’t let go of it: that the continents had once all been connected as one super continent, Urkontinent (German for one continent).
It’s easy to see why he came up with this idea. Looking at the edges of the continents they appear like pieces of a puzzle. The Western side of South America fits neatly into the bite out of the east coast of Africa. America and Europe can be slotted together at a bit of an angle. The jigsaw fit of the continents was Wegner’s first piece of evidence to support his theory of Continental Drift, where he proposed the continents were drifting apart and had once been together.
Wegner was a smart man and an excellent scientist. He knew that a simple observation like that would never ensure his theory would be accepted. He needed more evidence. So, the meteorologist turned his hand to palaeontology -the study of fossils. The Mesosaur was the first fossil to assist him with his radical ideas. A freshwater reptile which couldn’t survive in salt water, was found on both sides of the Atlantic, in South America and Africa. There was no way this creature could have swam, and it definitely didn’t fly. This was surely evidence that these land masses were once joined. Further studies into other fossils began to show similar findings, where organisms which had no means of crossing large oceans appeared to have done just that.
Wegner was on mission. He travelled the globe and found further evidence in the rocks. The Appalachian Mountains of the east coast of North America were found to be geologically the same as rocks found on British and Scandinavian coasts. These were later dated and found to be the same age as well. A coincidence? Surely not!
On an expedition to Svalbard in Norway, Wegner found fossils of tropical plants which indicated a much warmer climate in the past. Had Norway once been closer to the equator? Still thinking along these lines, Wegner noted that bituminous coal, which typically forms in tropical forests and swamps, could be found in the northern hemisphere as well as Antarctica, far from where you would expect coal to form now. Travels to Africa and South America delivered more insight. On the rocks he found scratches, known as glacial striations. These are caused when glaciers move over the land. Had these now warm continents once been much colder?
Wegner compiled his evidence in a book, The Origins of Continents and Oceans. However, without a mechanism to explain what caused continents to move, his ideas were still quashed. In his search for further proof, Wegner travelled to the Antarctic and was lost in a blizzard. Wegner died before a mechanism for these continental movements was found, and thus never saw his theory accepted by the scientific community, and with no appreciation of the fantastic research he had pulled together.
It is now widely accepted that the continents did once fit together as one supercontinent (we now call Pangea which is Greek for All Earth). In fact, there is evidence that the continents have come together and pulled apart at least three times in Earth’s history.
However, unlike Wegner’s idea that they “drift” like rubber ducks on a pond, tectonic plates are forced to move slowly, driven by processes within the Earth. Our understanding of these processes is still evolving with time but forms part of the Theory of Plate Tectonics. Most people will have learnt that convection currents within the mantle push the plates apart at mid-ocean ridges, and together at collision or convergent zones (resulting in subduction and/or mountain building, depending on the plates involved). However, more recent ideas, from newer evidence of processes, are that slab-pull, where the subducting edge of a plate drags the rest of the plate downwards is a major driving force of plate tectonics.
One of the most exciting things about Geology is that there is so much still to learn, and so many questions yet to be answered. Theories are still being questioned today, and we need the radical thinkers and Wegner’s of the world to continue to work doggedly to propose answers and gather evidence.
- For more information and activities relating to plate tectonics check out the Year 9 WASP resources.
- For more information about current thinking on the driving force behind plate tectonics read this article by the British Geological Survey.
- For a short video about Alfred Wegner’s Theory, featuring a fun activity, click here.
References: All images from wikicommons