Seismic images of hotspots and mantle plumes

A novel global tomography approach has been used to study the deep structure and dynamics of hotspots and mantle plumes. Prominent plumelike slow anomalies are detected under hotspot regions from the crust down to the core-mantle boundary (CMB). Most of the hotspots in South Pacific and Africa are located above the slow anomalies in the lower mantle down to the CMB, suggesting that the mantle plumes under those hotspots may originate from the CMB. The Hawaiian and Iceland plumes are also found to originate from the CMB. However, there may be some small-scaled, weak plumes originating from the transition zone or middle mantle depths. The slow anomalies under hotspots usually do not show a vertical pillar shape, which suggests that plumes are not fixed in the mantle but can be deflected by the mantle winds. As a consequence, hotspots are not fixed but can wander on the Earth’s surface, as evidenced by the recent geomagnetic and numeric modeling studies.