Chapter 3

From continental drift to plate tectonics

“Right from the beginning those of us who were involved knew that we were right. As soon as I saw the slip vectors round the North Pacific and realized that I could describe that by a single pole, for me, that was it. With JasonJasonJason Morgan (1935-present) took his PhD at Princeton where he spent most of his career. His work on plate tectonics, published 1968, focused on magnetic anomaly data, in contrast to McKenzie’s application of fault slip directions; they are fundamentally the same theory. Morgan went on to apply and refine Tuzo Wilson’s ideas about hot spots and mantle plumes, together with mantle convection. I think it was exactly the same. It was so obviously straightforward. The key piece of the story for me was that the plates were rigid. Once somebody pointed that out to you, it was completely obvious. There were all these magnetic anomalies formed by spreading ridges and they hadn’t been deformed since they were formed, so clearly the plates were rigid. Furthermore the earthquakes all lay along the plate boundaries, so there wasn’t really any doubt about all that.”

Artwork for the paper McKenzie, D, “Plate tectonics and continental drift”, Endeavour, 29: 39-44, (1970) showing the location of shallow earthquakes from 1961-1967, which outline the oceanic plates.

In terms of a paradigm shift, we had no understanding of all that before it happened. It was more that suddenly we understood things which we’d never understood before, which made sense. The ways forward were quite obvious…it became like ordinary scientific progression, almost at once.

How did it feel to be in the midst of a paradigm shift?