Chapter 2

Pivotal moment: The History of the Earth’s Crust

“It was quite clear at this conference that everything was going to change”.


BullardBullardMcKenzie’s PhD supervisor, Edward Crisp Bullard (1907 – 1980), was a noted experimental physicist who devised innovative equipment and developed a dynamo theory to model the origin of the Earth’s magnetic field. He was a student of Ernest Rutherford and a pioneer of marine geophysics in the UK. He was head of the Department of Geodesy and Geophysics at Cambridge through the 1960s, noted as a good leader who supported his staff, always managing to find a little money to get a student to a significant conference or to kick-start a new project. suggested that McKenzie (then at ScrippsScrippsScripps Institution of Oceanography, San Diego, California was established to support marine biological research, but from 1908 onwards pioneered geophysical research in the oceans. Teddy Bullard was a frequent visitor and undertook early ocean floor heat flow measurements with Roger Revelle. In 1962 the University of California established the new Institute of Geophysics and Planetary Physics alongside Scripps in La Jolla. ) attend this conference, a small gathering of about 40 invited scientists, on 11-12 November 1966 at NASA’s Goddard Institute for Space Science in New York. It was here that Fred VineFred VineFred Vine (1939-present) started as a graduate student at Madingley Rise in 1962. He worked with Drum Matthews on the magnetic fluctuations recorded in the rocks of the Indian Ocean floor. Fred Vine modelled the linear patterns of normal and reversed magnetism, parallel to the mid ocean ridge and with mirror symmetry across it. They combined Harry Hess’s suggestion of sea floor spreading like a conveyor belt with the newly-discovered sequence of past reversals of the Earth’s magnetic field to produce a simple model of crustal formation at mid ocean ridges. Vine and Matthews published their model – independently discovered by Lawrence Morley at about the same time – in 1963. presented his Princeton data on magnetic anomalies – much better than the Indian Ocean data on which Vine and MatthewsMatthewsDrummond Matthews (1931–1997) was a fellow of Kings College Cambridge when McKenzie was an undergraduate. He was young and involved in College life. Drum was originally a geologist, with a PhD on the petrology of seafloor rocks. He worked extensively at sea, collecting gravity, magnetic and depth data, plus some seabed cores and samples, including on the International Indian Ocean Experiment in 1961-63. He, with Maurice Hill, influenced McKenzie to go into geophysics as a graduate student. Matthews continued in marine geophysics, and was the driving force behind the British Institutes Reflection Profiling Syndicate which obtained the first deep seismic profiles around the UK. had based their paper. Lynn SykesLynn SykesLynn Sykes (1937-present) worked on marine earthquake data, using the Worldwide Standard Seismograph Network, an outcome of the International Geophysical Year 1957-8. This network standardised the responses of seismometers, making possible analysis of the direction of movement on faults in earthquakes. The network also improved earthquake location, showing that most marine quakes took place at plate boundaries. At Lamont, Sykes used this data to demonstrate that Tuzo Wilson’s transform faults existed, by determining the orientation of the first motion on the fault generating the earthquake. also derived slip-vector directions from earthquakes, using the newly-established Worldwide Standard Seismographic Network. And it was here that the plate tectonics paradigm took shape. “It was quite clear at this conference”, says McKenzie, “that everything was going to change”.

Letter from Robert A Phinney, professor of geophysics, Princeton University, New Jersey, USA, concerning the publication of the proceedings of the conference ‘History of the Earth’s Crust’, [held at the Goddard Institute for Space Studies, 10-11 November, 1966], at which McKenzie presented a paper [“The geophysical importance of high-temperature creep”], 25-26 January 1967.