Abstract

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.

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 1912-13, 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.

Space-shuttle photograph of Greenland. View toward the northern horizon showing the southern and central portions of Greenland. All land and the ice sheet are snow-covered, and sea ice is present along the coast in this winter view. The exploration of Greenland was a major focus in Wegener's life. Space-shuttle photograph STS45-152-104, 3/92. Obtained from the NASA Johnson Space Center.

Portrait of Alfred Wegener in 1912 during an expedition to Greenland. In the public domain; obtained from Wikimedia Commons.

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.

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 and paleoclimatic evidences 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.

Portrait of Alfred Wegener in 1925. In the public domain; obtained from Wikimedia Commons.

Resistance to Wegener's hypothesis

American geology was held in high regard in the early 20th century, and such complete 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 considering 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 global tectonics. In the early twentieth century, 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 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.

State of geological knowledge at beginning of 20th century.

Well Known	Poorly Known
Geology of temperate lowland regions in Europe, North America, South Africa, India, Australia	Geology of tropical, desert, polar, and montane regions in South America, Asia, Greenland, Antarctica, central Africa, Arabia, etc.
Geology of oceanic islands—New Zealand, Hawaii, Iceland, Japan	Geology of all ocean basins
Relative ages of strata and fossils	Absolute ages of strata and fossils
Basic geophysics—magnetism, gravity, earthquakes	Interior structure of the Earth, radioactivity
Physical properties of rocks in near-surface environment	High pressure-temperature rock behavior

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 may be regarded as a forerunner of modern plate tectonics.