Chapter 2

Sea floor spreading

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. had in 1962 described a means of generating oceanic crust by volcanism at the mid ocean ridges. He envisaged new crust forming at the ridges and moving away to each side, a process he called sea-floor spreading. His experience in the US Navy had shown him that flat-topped seamounts existed on the deep sea floor; he related them to wave erosion followed by ocean floor subsidence. Hess saw the ridges as related to mantle convection, possibly formed by upwelling currents.

IMAGE REFERENCE: Diagram representing the apparent progressive overlap of ocean sediments on a mid-ocean ridge and the effect of the mantle moving laterally away from the ridge crest, from Hess, Harry “History of Ocean Basins”, published in Engel, et al (eds) ‘Petrological Studies: a volume in honor of A F Buddington’, Geological Society of America, (1962).