In the 1910s and 1920s,
Alfred Wegener, a German meteorologist, suggested that the continents
were once connected, and have since drifted apart. This hypothesis
of continental drift was welcomed by geologists in Europe and
the southern hemisphere, but rejected in America.
Holmes (Britain) and Alexander du Toit (S. Africa) published books
(1929 and 1937, respectively) that encapsulated the fossil and rock
evidence for continental drift, including diagrams that look much
like modern plate tectonics. Figure
1, left (click to zoom in), is similar to one from Holmes' textbook.
In the first half of the
1900s, American geologists operated chiefly by induction, proceeding
to ideas based strictly on observation. They strongly embraced uniformitarianism:
because they saw no current evidence for drifting continents,
they concluded that it didn't happen in the past. These approaches
were so rigid that they could not accept new ideas based on other
By the early 1940s, geologists
in much of the rest of the world accepted, or at least entertained
the idea of, continental drift. American geologists were comparative
isolationists throughout the 1930s, 1940s, and 1950s, rejecting outright
the types of data cited by others.
The conflict between pro-drifters
and anti-drifters remained unresolved partly because the world's seafloors
were almost completely unexplored. Then came WWII and Cold War, and
heavy spending by the U.S. military on research.