An American geophysicist from Princeton University, Hess made important contributions to the theory of plate tectonics. He devised the concept of sea-floor spreading (see also dietz, robert sinclair), and discovered and named guyots. His Essay In Geopoetry (1960, 1962) was an attempt to link the features of the sea floor in a common hypothesis, in which he proposed that the continents move passively on rafts or rigid plates.