Model of the lithosphere with a creep threshold stress

Abstract

Laboratory workers have shown that there is a threshold stress which must be exceeded before diffusion creep is possible, both in metals and in oxide ceramics. Although no data are available for silicate ceramics at low enough stress, it seems likely that a creep threshold stress will be found to be in effect here too. This paper shows that the threshold stress that would be required in the lithosphere to explain bathymetry and gravity observations at the Emperor Seamounts is about 30 MN/m 2 (0.3 kbar) at a depth of 25 km. This value fits in with the laboratory observations, supporting the assumption that the threshold stress observed in metals and oxides is operating in the lithosphere too. This result is of interest in two ways: it may provide additional clues about the physical origin of the creep threshold stress, clues that are not available from laboratory studies alone; and it suggests a view of the lithosphere whose thickness depends not only on the temperature but also on the state of stress in the Earth.