The focus of this work is on magmatic convection and its relation to compositional heterogeneity. Magmatic convection is the inevitable response to the cooling magma in crustal magma bodies. yet the melt-dominated source bodies of large silicic ash flow tuffs are compositionally heterogeneous. Numerical experiments and scaling analysis are used to address problems of how compositional heterogeneity forms and persists in convecting magma bodies. Magmatic convection is modeled as double-diffusive convection where heat and a light chemical component (e.g. SiO...