By Robert Hazen, Ph.D., George Mason University
One of the great scientific revolutions of the 20th century has been plate tectonics, whose central principle is that convection of soft, hot rocks in the Earth’s deep interior causes thin, brittle plates to move at the surface. However, this theory was preceded by another hypothesis called the continental drift theory, proposed by German meteorologist Alfred Wegener in 1912.
Before the Plate Tectonic Theory
Plate tectonics is a transformation in the earth sciences that took place rather swiftly, in just a few short years, and also rather quietly.
In the 1960s, every textbook, every professor, taught that Earth’s oceans and continents are essentially permanent features; the Atlantic, the Pacific were always there, as were the North and South America, Europe, Asia, and Africa.
Yes, indeed, the ocean level may have risen, inundating certain parts of the land; the ocean may have receded, causing larger extents of land and land bridges between the continents; but by and large, the features of the Earth had been unchanged for billions of years.
This is a transcript from the video series The Joy of Science. Watch it now, on Wondrium.
Isostasy: The Principle of Mountain Building
Before the 1960s, it was also conventional wisdom that mountain building is essentially a vertical process. Mountains are raised up, and then come down. The principle that was described in mountain building is called isostasy: it’s basically buoyancy; it’s the principle of an iceberg. If you have an iceberg, you have a deep, lightweight root, and a little bit of the iceberg pops above the surface; that’s the principle of a mountain.
If you have a part of the crust that thickens, perhaps because of sedimentation, you have a deep root; and that whole material floats up and you get a high mountain above it. Isostasy was used to explain the existence of mountains.
Idiosyncratic Geological Processes
Geological processes were also thought to be local and idiosyncratic. Each country, each state had its own geological survey; and rather than matching up the boundaries and seeing the continuity, each state conducted its own investigation. Fossils were a local phenomenon.
There was no point, if you were in one state, to worry about what was going on two or three states farther away. So geologists were rather localized; they were interested in particular regions of the globe.
Earth sciences were similarly fragmented into lots of different disciplines. You had people who studied fossils (paleontologists), but they weren’t particularly interested in volcanoes. The people who studied volcanoes weren’t interested in mining and economic geology. The miners weren’t interested in earthquakes. The structure of the deep interior was considered to be something totally different, and the geophysicists, the seismologists who studied the inner structure really had nothing whatsoever to do with the people who studied the crusts, the oceans, the atmospheres.
Learn more about the Earth’s topography.
The Continental Drift Theory
The German meteorologist Alfred Wegener, who lived from 1880 to 1930, proposed the theory of continental drift in 1912, on the basis of some curious phenomena he had seen in studying geology.
It’s surprising: Wegener was actually a meteorologist, he studied weather patterns; and his principal research had to do with the upper air masses of the Arctic, which seemed to drive many of the weather patterns in Europe.
In a sense, the continental drift theory was sort of a sideline, kind of a hobby for Wegener. Wegener’s theory of continental drift was predicated on several intriguing and powerful observations regarding the match-up of geological features across the Atlantic Ocean. One thing you may have noticed, on a globe or on a map, is that the shape of the continents is rather similar. North America and South America have a coastline on the Atlantic, which is rather similar to the coastline of Europe and Africa.
Wegener noticed this match-up, and said that maybe there was some reason why these two coastlines matched up so closely. In addition, he did a lot of research on specific geological and paleontological phenomena along the two coasts, and he found all sorts of intriguing coincidences of things matching up.
Learn more about the dynamic Earth.
Geological and Paleontological Coincidences
If you go to a place in Wales called St David’s, you find giant trilobites right on the coast, right in the ocean surf. These trilobites are a species called Paradoxides, which occurs in several places around the world; but the ones at St. David’s are quite distinctive. You also find the exact same species, in a very similar location right along the coast, in Boston, Massachusetts. Wegener said they match up, right across the Atlantic.
You also have the great diamond fields in Africa, which, across the Atlantic, match up to the diamond fields in Brazil.
There are other distinctive geological formations that match up across the ocean, as well, and Wegener said, this is more than just a coincidence. Indeed, he said, somehow North America and South America have drifted away from Europe and Africa. The principal objection to Wegener’s novel hypothesis was that it lacked any mechanism for moving an entire continent.
Common Questions about Alfred Wegener and the Continental Drift Theory
Alfred Wegener was a German meteorologist who lived from 1880 to 1930. In 1912, he proposed the continental drift theory on the basis of some curious phenomena he had seen in studying geology.
Alfred Wegener proposed the continental drift theory based on several intriguing and powerful observations regarding the match-up of geological features across the Atlantic Ocean. In addition, he did a lot of research on specific geological and paleontological phenomena along the two coasts, and he found all sorts of intriguing coincidences of things matching up.
Wegener noticed that the distinctive giant trilobites species found in St David, Wales, were exactly the same as the species found in the coastlines of Boston, Massachusetts. For Wagener, this was more than just a coincidence. He believed that somehow North America and South America had drifted away from Europe and Africa.
