Decompression melting occurs near the surface, and they can originate at the 670-km discontinuity or at the core-mantle boundary.
It is believed that there are about 50 of these around the world, and that they are anchored by the topography of the D double prime layer.  Decompression melting occurs near the surface, and they can originate at the 670-km discontinuity or at the core-mantle boundary. The inferred buoyancy flux moving through channels approximately 50 to 100 kilometers wide indicates that they transport less than 10% of the mantle's heat budget. They may be capable of triggering ridge jumps or even major plate rifting.  FTP, name these columns of hot, buoyant material, which can produce hotspots.
It is believed that there are about 50 of these around the world, and that they are anchored by the topography of the D double prime layer.  
mantle plumes (do not accept superplumes or superswells)