For 10 points, this is what region of the Earth, which resides between the crust and the outer core?
The deepest parts of this region display dramatically reduced viscosity; some have argued to call this region the Bullen layer, rather than the existing name of D'' (D double-prime). It is constantly in the process of shedding potassium, and is rich in olivines. This region's namesake plumes are thought to be the cause of flood basalts as well as hotspots, while the upper portion of this region, which exhibits isostasy is named the aesthenosphere and has the Moho discontinuity as its outer edge. For 10 points, this is what region of the Earth, which resides between the crust and the outer core?
The deepest parts of this region display dramatically reduced viscosity; some have argued to call this region the Bullen layer, rather than the existing name of D''
{mantle}