Society hotspot

[2] Magnetotelluric imaging has found higher conductivity in the upper mantle under the active area southeast of Tahiti consistent with anomalously hot rising material.

[4][5] Evidence for the former model includes magnetotelluric imaging which finds conductivity anomalies of less than 150 kilometres (93 mi) in radius indicating a plume of limited extent[9] and seismic imaging of the transition zone under the Society hotspot which shows a thinned area of less than 500 kilometres (310 mi) implying that the thermal flux from lower to upper mantle is on the scale of a plume rather than a superplume.

[4] Clouard and Bonneville 2001 have argued that certain features of the Society hotspot, such as the lack of an initial flood basalt at the old end of the chain, short-lived volcanic activity,[12] and petrological and geochemical analysis of the lavas which reveals a number of shallow-source components,[13] are inconsistent with the plume model and have proposed a tectonic origin.

According to this model, the Society and other volcanic chains in the south Pacific result from a system of fissures caused by intraplate stresses related to thermal contraction of the lithosphere, subduction-induced flow of the asthenosphere, and changes in the configuration of plate boundaries which have enabled pre-existing melt in the crust and shallow mantle to escape to the surface.

[13][14][15][16] The timing of volcanic activity and orientation of the chain, both of which coincide closely with major alterations in plate boundary configurations and consequent changes in the lithospheric stress field and direction of asthenospheric counterflow, support this model.