TEMPORAL VARIATION OF THE HAWAIIAN PLUME FLUX

The magnitude of the Hawaiian swell, which surrounds the Hawaiian volcanic chain, does not decline monotonically and smoothly with distance along the chain. The observed undulations are interpreted here as reflecting past variations in the buoyancy flux of the Hawaiian plume, rather than the monotonic thermal decline of the swell with age, as has been inferred previously. This interpretation is supported by seismic evidence that indicates there has been little thinning of the lithosphere, which, it is shown, further implies that the time scale for thermal subsidence will be very long. The largest change in flux was an increase in the plume flux by more than a factor of two about 25-30 Myr ago. The size of the volcanic edifices shows a broad correlation with the variations in the swell, supporting this interpretation.