Book I of John McPhee’s epic geological history Annals of the Former World ends with the rise of the plate tectonics theory in the 1950s and 1960s. Led by Harry Hess, a mineralogist who used his time on an attack transport in World War II to map the ocean floor with a new tool called a Fathometer. One feature he saw, according to McPhee, “were dead volcanoes, spread out around the Pacific bottom like Hershey’s Kisses on a tray” (p. 127). It’s images like this that make Annals so accessible and even a little fun.
As the ocean mapping and seismological monitoring brought in detailed data revealing patterns across the Earth, Hess began to see “that seafloors were spreading away from mid-ocean ridges, where new seafloor was continuously being created in deep cracks” (p. 128). He pulled it all together in an essay called “History of Ocean Basins” and, harkening back to Umbgrove, a Dutch geological writer, described the work as “an essay in geopoetry.” Basically, he was creating a foundation for a theory and that required some suspension of belief. New paradigms require new ways of thinking and they may not always be grounded in current science.
It is hardly likely that all of the numerous assumptions made are correct. Nevertheless it appears to be a useful framework for testing various and sundry groups of hypotheses relating to the oceans. It is hoped that the framework with necessary patching and repair may eventually form the basis for a new and sounder structure (p. 129)
McPhee brings the theory into the present day as he works alongside Kenneth Deffeyes, an oil geologist with whom he spends time in the book. When McPhee asks about geologists who do not accept plate tectonics, Deffeyes seems unphased, with skepticism being a part of the field and science in general:
There are always many ideas in various stages of acceptance. That is how science works. Ideas range from the solidly accepted to the literally half-baked–those in the process of forming, the sorts of things about which people call each other up in the middle of the night. All science involves speculation, and few sciences includes as much speculation as geology (p. 133).
McPhee shows how the scientists set out to fill in the gaps that will either prove or disprove the theory. At one point, Hess sends Deffeyes to test the age of some rocks that, if he were right, would be young. If not, the whole theory would be called into question. This is serious hypothesis testing.
But then, there is a moment when the various threads seem to click and the theory becomes accepted because its explanations seem to make sense. McPhee quotes a marine geologist who was a graduate student at the time: “It is a wondrous thing to have the random facts in one’s head suddenly fall into the slots of an orderly framework. It is like an explosion inside…I think I spend half my time just talking and listening to people from many fields, searching together for how it might all fit together. And when something does fall into place, there is that mental explosion and the wondrous excitement. I think the human brain must love order” (p. 135).