The Human Side of Science: Edison and Tesla, Watson and Crick, and Other Personal Stories behind Science's Big Ideas (2016)
Chapter 8: Alfred Wegener Stands His Ground about Continental Drift
My husband recently made me try on a bikini. A bikini is not so much as a garment as a cloth-based reminder that your parts have been migrating all these years. My waist, I realized that day in the dressing room, has completely disappeared beneath my rib cage, which now rests directly on my hips. I'm exhibiting continental drift in reverse.
—Mary Roach, American humor and popular science writer1
Maps are fascinating, little ones, big ones, ones that are a challenge to fold, whatever. Both of us (AW and CW) have been map guys for a long time, and we've got plenty of company. The best maps are the ones that show the whole world.
World map. From Wikimedia Commons, user Saperaud~commonswiki.
The creator of the first modern atlas was the Flemish cartographer Abraham Ortelius (1527–1598), who started as a map engraver and illuminator, but with encouragement from the eminent cartographer Gerardus Mercator (1512–1594), Ortelius became a full-fledged geographer. After extensive travel and consultation with many other geographers, he issued the first collection of maps of the entire world in 1570, called an atlas, and published by Mercator. He continued to update this work, the last and most complete one being issued in 1597.
Even though this atlas was created prior to the Scientific Revolution of the later 1600s, Ortelius's world map was in itself a substantial observation. So, in the scientific method sense, Ortelius was a keen observer. And yet, mere observation wasn't enough for him. Look at the map again.
It's hard not to form a hypothesis similar to what Ortelius made in his book Thesaurus Geographicus (The Geographic Thesaurus): the Americas were “torn away from Europe and Africa…by earthquakes and floods.”2 Ortelius then continued: “The vestiges of the rupture reveal themselves, if someone brings forward a map of the world and considers carefully the coasts of the three [continents].”3
World map jigsaw puzzles intended for tots have occasioned many grown-ups (and kids, too) to arrive at a similar conjecture when they fit South America's east coast to Africa's west coast with such ease.
Over the next three hundred years or more, many others shared Ortelius's surmise to varying degrees, but let's skip ahead to 1912 to look at someone who stated this hypothesis much more strongly and gave it a name by doing so: continental drift. Meteorologist Alfred Wegener really stirred up a hornet's nest.
Alfred Wegener (1880–1930). From Wikimedia Commons, user Woudloper.
Alfred Wegener was born in Berlin in 1880, the youngest of five children. His father, Richard, was a theologian and taught classical languages at a local gymnasium. Alfred was first in his gymnasium class, then studied physics, meteorology, and astronomy in Berlin, Heidelberg, and Innsbruck. Although his 1905 PhD was in astronomy, he maintained a strong interest in meteorology and climatology. He worked with his older brother Kurt and carried out meteorological measurements, once setting a world's record in 1906 for continuous balloon flight of fifty-two and a half hours aloft. During the same year, Wegener participated in the first of his expeditions to Greenland, making more meteorological measurements. After his return, he became a lecturer in meteorology, applied astronomy, and cosmic physics at the University of Marburg. While there, he wrote a book titled Thermodynamik der Atmosphäre(Thermodynamics of the Atmosphere), that became a standard textbook.
In late 1911, Wegener happened across a scientific paper listing identical fossils of plants and animals on opposite sides of the Atlantic Ocean. After a bit of a search, he found many other similar cases of matching plants and animals. The standard explanation for these similarities was that in the past there were land bridges between continents, but that these bridges were now sunken below the ocean. It seemed far simpler to Wegener that the continents were once joined but had moved apart. Wegener found additional evidence for his hypothesis: some large-scale geological formations from separate continents matched closely, and fossils of tropical plants were found on Arctic islands.
Wegener first mentioned his “continental drift” hypothesis in lectures in 1912. He published a book titled Die Entstehung der Kontinente und Ozeane (The Origin of Continents and Oceans), which gave much more detail about his ideas in 1915. The hypothesis conjectured that about three hundred million years ago, all the lands were joined in a single supercontinent, called Pangea (Greek for “all lands”). The continents then moved across the face of the earth gradually, with the oceans filling in the spaces between them.
Wegener's goal in publicizing his theory was to begin a thorough, open discussion of the possibilities, rather than simple acceptance of a radical new theory. But that was not to be the case.
Continental drift. From the US Geological Survey.
Although there was some support, principally by South African geologist Alexander du Toit, British geologist Arthur Holmes, and Swiss geologist Émile Argand, the major reaction by geologists was swift and almost uniformly hostile. Rollin T. Chamberlin, geology professor at the University of Chicago, said, “Wegener's hypothesis in general is of the footloose type, in that it takes considerable liberty with our globe, and is less bound by restrictions or tied down by awkward, ugly facts than most of its rival theories.” Chamberlain also suggested that “if we are to believe in Wegener's hypothesis we must forget everything which has been learned in the past 70 years and start all over again.” In 1926, a major conference was held by the American Association of Petroleum Geologists to criticize the theory.
Why such outcry? First of all, Wegener wasn't trained as a geologist. He was considered by geologists to be an outsider or even an amateur. The fact that he was German and his writings didn't translate well into other languages didn't help in the time leading up to World War I. In addition, Wegener's idea was often misinterpreted as referring to the fit of the coastlines as opposed to the continental shelf, which is not subject to the same erosion and variation in the hardness or softness of rocks.
A bigger problem was the lack of a mechanism for the drift. What force could account for continents “plowing around in the mantle,” as one critic put it? Wegener had several candidates for this force, but they were quickly demolished by opponents. As Wegener himself put it, “The Newton of drift theory has not yet appeared.”4
In 1930, Wegener died while on his fourth expedition to Greenland. Continental drift theory was quietly swept under the rug, much to the relief of the geologists supporting the more popular notion of an unchanging Earth. Some years later, Arthur Holmes speculated that the driving force was supplied by currents in the mantle, the layer below the crust, but it took physical evidence from an unexpected source to help Wegener's ideas toward acceptance.
SUPPORT FROM AN UNLIKELY SOURCE
Victor Vacquier Sr. (1907–2009) and his family escaped the Russian Civil War by taking a one-horse sleigh across the ice-covered Gulf of Finland to Helsinki in 1920. Eventually immigrating to the United States, Vacquier earned a BS in electrical engineering and an MS in physics both from the University of Wisconsin. While working for Gulf Research in the 1930s, Vacquier invented an instrument for measuring the strength and direction of magnetic fields. This device was called a fluxgate magnetometer and was extremely accurate as well as being light and rugged.
Victor Vacquier Sr. (1907–2009). American Geophysical Union (AGU), courtesy AIP Emilio Segre Visual Archives.
Initially, the fluxgate magnetometer was used for petroleum exploration, but it also saw service in World War II as a submarine detector. After the war, in the International Geophysical Year (1957–1958), Vacquier directed a program from the Scripps Research Institute that used war surplus magnetometers to map the magnetic fields of the rocks on the ocean floor. The result was quite surprising: On either side of the deepest part of the ocean, the magnetic fields in the rocks had an alternating striped pattern. The simplest explanation for this observation was that the ocean floor was spreading, and when molten rock from the mantle below came to the surface, the magnetic ore (magnetite) in the molten rocks aligned itself with the earth's magnetic field at the time. Since the earth's magnetic field is known to have reversed direction at irregular intervals averaging two hundred thousand years, the pattern of reversals was frozen into the rocks on the ocean floor. Since continental drift could well have caused this pattern, Wegener's theory gained strong experimental support.
Magnetic stripes in ocean floor rocks. From the US Geological Survey.
These developments led to a new theory, championed by Canadian geologist J. Tuzo Wilson in 1965, called “plate tectonics” (from the Latin tectonicus, which translates to “pertaining to building,” referring to the earth's crust).
The earth consists of a series of layers, which are, from the outermost to the innermost:
The Crust: a relatively thin, rigid layer made of fairly low-density rock and consisting of about a dozen major plates and many minor ones. The plates move slowly, dragged along by currents in the next layer down and cause volcanoes, earthquakes, and mountain formations as they collide and move apart.
The Mantle: the thickest layer made of higher-density rock that is very hot. At depths below the uppermost mantle, this layer flows quite slowly, like a glacier.
The Outer Core: a hot liquid layer of iron and nickel that is more dense than the mantle and sloshes around because of the earth's rotation.
The Inner Core: the earth's center, made of iron that is too hot and under too much pressure to be liquid.
Earth model. From the US Geological Survey.
The plate tectonics model differs from Wegener's continental drift hypothesis in that the continents don't plow through the mantle; instead, the continents are part of the plates, which ride on the mantle and move because of underlying mantle currents.
So, when you look at that map we discussed earlier, realize that you are looking only at Earth's surface and think about all the activity in its mantle and cores below. And, if your next visit to Earth is a million years from now, your old map will be obsolete.
Used with permission from Sidney Harris.
Used with permission from Sidney Harris.
Used with permission from Sidney Harris.
From the stable perspective of our lovely Planet Earth, let us head to the great beyond, starting with a seemingly well-grounded fellow: Albert Einstein.