Variations of the Hawaiian hot spot activity revealed by variations in the magma production rate

Abstract

In order to evaluate the activity of the Hawaiian hot spot, we calculate both the magma production rate, associated with volcanism, and the rate of swell formation, characteristic of the plume behavior. Both computations are made along the Emperor‐Hawaii track. Depth anomaly is calculated by correcting the 2′ bathymetry grid of Smith and Sandwell [1997] from thermal subsidence. A new filtering method is then used to separate the topography associated with volcanism and the swell surrounding the hot spot chain. The volume of magma includes the compensating root underlying the volcanoes, computed assuming either an Airy compensation (local) or a flexural root (regional) associated with the volcanic load. Next, the volume corresponding to the swell is calculated between the swell amplitude map and the zero value of the depth anomaly. Temporal variations of both volumes are then computed by the means of 1° × 10° windows translated along the hot spot track. Both volume fluxes are correlated through time and present (1) a general increase in amplitude for the last 30 Ma, indicating an increase in hot spot activity, and (2) short‐wavelength oscillations with a 5 m.y. period, which may reflect the presence of solitary waves in the plume conduit. Contrary to the swell volume flux, the magma production rate estimation is not dependent on the subsidence model and is still valid for the older part of the chain. It is thus the most relevant parameter to describe the temporal variation of the Hawaiian hot spot behavior.