Chapter 2

Conveyor belts under the sea

In 1963, 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. and Drum MatthewsDrum MatthewsDrummond 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. used magnetic data from the Indian Ocean floor to combine the idea of reversals of the Earth’s magnetic field with Harry HessHarry HessHarry Hess (1906-1969) began his career at Princeton in the 1930s, undertaking submarine gravity experiments with Vening Meinesz. After war service and promotion to an Admiral of the US Navy, he returned to Princeton and his interests in marine geology. His proposal of seafloor spreading and the conveyor belt carrying new ocean crust away from the mid-ocean ridges was influential. He had also worked on the gravity anomalies that became associated with subduction zones, encouraging him to consider mantle convection as a part of plate tectonics. ’s concept of sea floor spreading at mid ocean ridges. They envisaged a conveyor belt model where new ocean crust formed at the ridge is imprinted with the prevailing magnetic field at the time and moves outwards as it gets older. Reversals of the field led to the symmetrical pattern of stripes. Lawrence Morley independently developed the same model at the same time. “The problem for them,” recounts McKenzie, “was that nobody believed in seafloor spreading and almost nobody believed in the reversals of the main field either. So they were taking two things which were controversial and saying that this explained the stripes.”

IMAGE REFERENCE: Figure from: Vine, F. D. and Matthews, D. H. 1963. Magnetic anomalies over oceanic ridges. Nature. 199: 947–949.