Alfred Wegener History of Geology

Alfred Wegener

History of Geology
James S. Aber

Born: 1880, Berlin, Germany.

Died: 1930, Greenland Ice Sheet.

Abstract

Alfred Wegener was an accomplished German natural scientist in the fields of meteorology, astronomy, and geology. He was also a skilled balloonist and participated in three scientific expeditions to Greenland. His primary research interest was in the relatively new field of meteorology. He held several academic or research positions in Germany before taking the Chair of meteorology and geophysics at the University of Graz in Austria in 1924. Wegener's most noteable scientific contribution was a unified theory for the origin of continents. His mobilist idea of drifting continents contrasted sharply with the contemporary view of fixed continents and a rigid, shrinking earth.

Wegener first presented his theory of continental drift in 1912 at a meeting of the German Geological Association. In 1915, he published his evidence and conclusions in a now classic book, Die entstehung der kontinente und ozeane (The origin of continents and oceans). Wegener proposed that all modern continents were once assembled together in a supercontinent he named Pangaea. Pangaea, he thought, had existed since the beginning of the earth and had begun breaking apart during the Mesozoic. He believed tidal forces were responsible for breaking up Pangaea and causing the continents to drift.

Wegener's theory of continental drift was generally criticized on both geophysical and geological grounds. However, post-World War II oceanographic evidence and development of plate tectonic theory in the 1960s have vindicated Wegener's basic conclusion that modern continents are drifted fragments of Pangaea.

Introduction

Wegener was an accomplished natural scientist in meteorology, astronomy and geology. He was a Greenland explorer and balloonist. He developed the hypothesis of drifting continents, a presursor to modern plate tectonics, but was not generally accepted until half a century later. Wegener was the son of an evangelical minister. He studied at the universities of Heidelberg, Innsbruck, and Berlin. He earned a Ph.D. in astronomy and was fascinated also by the new science of meteorology. In order to learn more about the atmosphere, he practiced the use of kites and balloons. He became a successful balloonist, in fact, and with his brother Kurt set a world record flight for balloon endurance of 52 hours. He also learned to ski and skate; he had ambition to explore the Arctic.

Wegener was selected to serve as the meteorologist on a Danish expedition to northeastern Greenland. Upon his return to Germany, he was appointed a junior lecturer in meteorology at the University of Marburg, where he wrote an important work on thermodynamics of the atmosphere. In 1912, he participated in another expedition to Greenland, which was the longest crossing of the ice cap to date. In 1913, he married Else Köppen, the daughter of famous meteorologist, W.P. Köppen. His life was interrupted for several years by World War I, in which he served as a junior officer.

After the war, Wegener succeeded his father-in-law as director of meteorological research at the Department of Marine Observatory, Hamburg. He was not well received. In 1924, he became chair of meteorology and geophysics at the University of Graz, Austria, where he found colleagues more receptive to his research efforts. In effect, Wegener was rejected in his own country. He died (of heart attack?) while leading a third expedition to Greenland at age 50.

Major Work

Wegener's most notable scientific contribution was his hypothesis of continental drifting, which he first presented in 1912 at a meeting of the German Geological Association. In 1915 he published his evidence and conclusions in a now classic book--Die Entstehung der Kontinente und Ozeane (The origin of continents and oceans). This work was completely contrary to contemporary views of the day.

Early 20th century geologists viewed continents as fixed features that could rise and fall, but not move sideways. Slow shrinking of the Earth was considered to be the cause of mountain building. Connections of former land bridges and seaways could explain all stratigraphy and distributions of fossils. This was essentially the Atlantis myth of appearing and disappearing continents. Wegener noted several inconsistencies.

1. 
   Close geographic fit of South America and Africa--like a torn newspaper.
   
2. 
   Narrow mountain belts restricted to continental margins.
   
3. 
   Isostasy of crust at two levels--oceanic and continental.
   
4. 
   Distribution of certain fossils, such as Mesosaurus.
   
5. 
   Distribution of ancient climatic indicators does not make sense.
   

A unified hypothesis for origin of the continents was Wegener's attempt to explain this situation. Eduard Suess had earlier proposed the existence of Gondwana(land), which was a megacontinent that included all modern southern continents (S. America, Africa/Arabia, India, Australia, and Antarctica). Wegener went one step further and proposed that all continents had once been joined in a supercontinent he named Pangaea (meaning all land). Pangaea, he thought, had existed from the primordial earth until the Mesozoic, when it began to break up. Wegener at first considered mantle convection as a possible driving mechanism, but later rejected that in favor of tidal force as the cause for Pangaea's breakup and continental drift.

Wegener's best evidence was paleoclimatic indicators, and his best reconstruction of Pangaea was for late Paleozoic--Carboniferous and Permian (Schwarzbach 1986). His reconstructions include glaciation around the South Pole, tropical coal belt, and sub-tropical desert belts. In spite of overwhelming geological evidence in support of Pangaea, the idea was not generally accepted. The only strong support came from geologists in the southern hemisphere--the Gondwana region, where the geological evidence for Pangaea is most compeling. However, then as now, southern hemisphere scientists were few in number and well outside the "mainstream" of scientific thinking.

Resistance to Wegener's Hypothesis

Resistance to the hypothesis of continental drift came from two main sources--geophysicists and American geologists. Geophysicists were able to demonstrate that tidal force is far too weak to move continents through a viscous mantle. To accomplish this would require tidal forces so great that the Earth would be torn apart. Without a plausible physical mechanism for continental drift, many people considered the whole idea ridiculous. In 1926, the American Association of Petroleum Geologists (AAPG) held a special symposium on the hypothesis of continental drift. AAPG was and still is one the largest and most influential geological organizations in the world. Nearly every aspect of continental drift was criticized.

American geology was held in high regard in the early 20th century, and such overwhelming rejection of continental drift put an end to serious scientific discussion of the idea for the next four decades. It could be argued that AAPG was not an appropriate body to render a decision on Wegener's ideas. Consider the state of petroleum geology at the time. Oil and gas were produced only from land areas; no offshore oil wells were drilled until after World War II. Petroleum geologists were land-based continental geologists; they had no experience, interest, or appreciation for marine geology of the ocean basins. Furthermore, petroleum geology was (and still is) an applied aspect of the profession. The goal is to find oil and gas, not to understand basic principles of earth history and tectonics. AAPG had no economic incentive to consider the possible implications of continental drift.

Aside from the apparent bias of the AAPG, several other factors may have contributed to the rejection of Wegener's ideas. These factors often come into play whenever a radical new theory is introduced into a mature scientific discipline.

1. 
   Before his time -- Wegener's hypothesis moved ahead of confirming evidence too fast. Many previously unrelated observations were combined into a large theoretical jump. This is contrary to the normal progressive, step-by-step development of science.
   
2. 
   Youthful outsider -- Wegener was a man of many talents, but he had no formal training in geology. Thus, he had no credentials. At the same time, he had no preconceived position to defend or prove. At the beginning of the 20th century, no scientist was recognized until at least age 40; Wegener was in his early thirties when he first proposed continental drift.
   
3. 
   Scientific inertia -- Geology could not remake itself overnight. There was a natural resistance to change, to accepting radical new ideas. Geologists had vested interests in their work and were reluctant to admit past misinterpretations of fundamental significance.
   

With the view of historical analysis, it seems clear that Wegener and continental drift fit a pattern that has been repeated many times in geology as well as other scientific disciplines. As a discipline matures through time, complacency and authority develop, such that new ideas become increasingly difficult to accept. Those who are trained in the discipline "learn" a body of data, facts, methods, and theories which are taken to be literally true. To suggest otherwise may not be in the best interest of a person's reputation and career. Most practitioners of a discipline, thus, have "closed minds" to anything outside the normal dimensions of their work. This was the situation into which Wegener ventured with his hypothesis of continental drift.

Historical Assessment

Hindsight has, of course, vindicated Wegener's basic conclusion that all modern continents are rifted and drifted fragments of Pangaea. Key evidence came from oceanographic studies in the 1950s and '60s. Geologists were forced to accept continental drift as part of plate tectonics, as overwhelming evidence poured in from other disciplines. All this was virtually unknown to Wegener. Consider what was known and not known at the beginning of the 20th century.
Wegener had good information about continental geology for a few regions, but the geology of many continents was poorly known or not even examined in some cases. Essentially nothing was understood about oceanic geology--even the most basic information was lacking for most parts of the world. Radioactivity had only recently been discovered, and its implications for geology and tectonics were barely appreciated. Even the age of the Earth was a subject of much debate, and virtually nothing was known about the deep subsurface of the Earth. In short, Wegener's hypothesis of continental drift was based on fragmentary information with a bias toward the better explored continents. This amounted to only about 10% of the Earth's surface. From this limited data, Wegener made a great mental leap to encompass the whole Earth in a global theory. Few scientists have ever accomplished so much with so little.

For Wegener, continental drift was interesting, but peripheral to his main focus in meteorology and Greenland. He made important contributions in both these subject areas, but continental drift is surely his most significant scientific work. He was not correct about certain aspects, for example the primeval origin of Pangaea or tidal force as the driving mechanism. Nonetheless, he got the basic idea right, and his hypothesis can be regarded as a forerunner of modern plate tectonics.