Two distinct trends for cooling of the oceanic lithosphere

Abstract

Cooling and contraction of the oceanic lithosphere with age is reasonably well described by simple thermal models. Both ‘plate’ models1–4 and ‘half-space’ models5–7 give similar results up to ages of 50–70 Myr but predict quite different behaviour for sea floor depth, heat flow and other parameters in old basins. Tests of thermal models have been mainly based on topography data3,8,9 which are biased by anomalous shallow regions. Altimeter-equipped satellites offer a new type of observable quantity—geoid height data—which can also constrain lithospheric cooling models10. We present here new observational constraints on the thermal cooling models of the oceanic lithosphere, based on analysis of geoid data over the whole Pacific Ocean. We find that the data closely follow the behaviour predicted by plate models and that they suggest the existence of two distinct cooling regimes, one for sea floor ages ≲30 Myr, the other for ages >30 Myr.