Chapter 3

Moving on with Morgan at Princeton


“When I moved to Princeton in 1968 I was a little concerned about how Jason might react,” notes McKenzie, “but he was fine.” When Tanya AtwaterTanya AtwaterTanya Atwater (1942-present) is an American geophysicist and marine geologist who specialises in plate tectonics, in particular the plate tectonic history of the San Andreas Fault and western North America. She gained her PhD in 1972 in Marine Geophysics from Scripps Institution of Oceanography. She held posts at the Massachusetts Institute of Technology and University of California, Santa Barbara (UCSB). She is currently Emeritus Professor of Geological Sciences at UCSB. visited Princeton, she, Morgan and McKenzie discussed what happens where three plates meet, without drawing any conclusions. Back in Cambridge in the autumn, McKenzie made sense of it. “I woke up with the answer,” he says. “I wrote it down but did not see why it was the answer until I worked on it with Jason Morgan. It’s a kinematic thing.” At the time people thought that changes in plate configurations reflected changes in plate velocities – and that needed a driving mechanism that could change quickly and in a small space. “It wasn’t a change in the motions of the plates, but a change in the pair of plates involved, so you no longer had to work out how the convection pattern changed so quickly.”

Photocopy of figure from Mason & Raff, “Magnetic Survey off the west coast of North America”, Geological Society of America Bulletin, 72: 1260 (1961), which has been annotated by Tanya Atwater in relation to the research into the paper McKenzie, D & W J Morgan, “The evolution of triple junctions”, Nature, 224: 125-133, (1969).