An Introduction to Plate Tectonics
Problems with Wegener's Model of Continental Drift
Wegener's model was not accepted by all geologists. Some thought that dispersion by
winds or ocean currents could explain the distribution of fossil species. Other
geologists thought the poles might wander and continents remain stationary. Many
geologists thought Wegener's evidence was insufficient.
The greatest shortcoming, at least in the eyes of American geologists, was the lack
of an adequate mechanism for moving the continents. Wegener proposed that the Earth's
spin caused the continents to move, plowing through the oceanic plate and producing
mountains on their leading edges. Geologists at that time understood enough about the
strength of rocks to know that this was highly unlikely. Wegener's work was largely
unaccepted in the northern hemisphere. In the southern hemisphere, where geologists
were familiar with the rocks that Wegener used to support his hypothesis, continental
drift was generally accepted.
A mechanism to move continents was proposed by Arthur Holmes, Scottish geologist in
1928. He believed heat trapped in the Earth caused convection currents, areas where
fluids beneath the Earth's crust rise, flow laterally, and then fall. The currents
would rise beneath continents, spread laterally, then plunge beneath the oceans.
(Geologists now know that solid rock, not fluids, convect in the mantle).
Unfortunately, Wegener died in 1930 while exploring the Greenland ice cap. He never
had the opportunity to adapt Holmes' ideas to his views of continental drift.
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