Interaction of mantle plumes and lithosphere

When plumes impinge the base of the lithosphere, they may cause intraplaplate volcanism. However, the distribution of volcanism critically depends on lithosphere thickness variations, and whether spreading ridges are closeby. We perform numerical models of plumes interacting with imposed surface plate motions and lithosphere of variable thickness. Modelled plume shape is compared with tomographic images; modelled distribution of melts is compared with hotspot tracks. In the case of Tristan, which was studied within SPP SAMPLE, the changing distance between plume and spreading ridge leads to variable amounts and distribution of melt production at different times (Gaßmöller et al., 2016; Figure 1). The influence of plate motions and the Central Indian spreading ridge on the Reunion plume, which was studied as part of the Rhum-Rum project can be seen in the movie on this page created by Eva Bredow. Our numerical models explain the gap in the hotspot track between Maldives and Chagos as caused by a long transform fault along the Central Indian ridge, and the Rodrigues ridge due to plume material flowing to the nearest segment of the spreading ridge, thus confirming a long-standing hypothesis first put up by Jason Morgan in 1978 (Bredow et al, 2017). Further case studies were conducted for Iceland (Steinberger et al., 2017) and Kerguelen (Bredow und Steinberger, in press). The movement of Greenland over the Iceland Plume more than 50 million years ago still causes an increased heat flow, and therefore an increased melting of the Greenland Ice Sheet from below (Rogozhina et al., 2016).