Mantle Plumes - Its Not That simple! 

I came across THIS ARTICLE and it looks like one I should read. But I suspect it will take me a long time! So rather than take forever to understand it and try to summarise it, I will let you do that! Best of luck! 

a | Schematic cross section through Earth’s interior, depicting the key components of plume generation and upwelling near, above and along the edges of a large low-shear-velocity province (LLSVP) and near the core–mantle boundary. These LLSVPs might contain localized ultra-low velocity zones (ULVZs) and along their edges subducted material may pile up over hundreds of millions of years. b | Schematic cross section of a plume root showing the entrainment of subducted materials, LLSVP and ULVZ components, and possibly core materials at the edge of a LLSVP and centred above an ULVZ (that might be a unique deep mantle locality containing partial melt).