Observations of geometry and ages constrain relative motion of Hawaii and Louisville plumes

The classic view of linear island chains as volcanic expressions of interactions between changing plate tectonic motions and fixed mantle plumes has come under renewed scrutiny. In particular, observed paleolatitudes from the Emperor seamounts imply that the Hawaii hotspot was > 5–15° further north during formation of these seamounts and that rapid retardation of its southward migration was the primary agent forming the angular Hawaii–Emperor bend. Supporting this view are predictions from fluid dynamic experiments that suggest the general mantle circulation may displace narrow mantle plumes; consequently the surface locations of hotspots are not fixed and may have varied considerably in the past. However, the locations and ages of available rock samples place fundamental limits on the relative motion between the Hawaii and Louisville hotspots. Here we use such data to estimate empirical age progression curves for separate chains and calculate the continuous variations in hotspot separations through time. While the data are sparse, the inferred inter-hotspot motion for ages > 55 Myr appears significant but the observed relative motion is only about half of what is predicted by mantle dynamics models. To reconcile the observed paleolatitudes with our observed relative motion requires either a larger contemporaneous southward motion of the Louisville hotspot than previously suggested or a moderate component of true polar wander.