what are the three main components of magma what factors control and how the viscosity of magma?
['Magma Composition: Silicate-rich magmas are typically formed at destructive plate boundaries, by partial melting and/or assimilation of crustal rocks (which are richer in silica than the rock of the mantle). ... ', 'Temperature: ... ', 'Volatile Content: ... ', 'Crystal Content: ... ', 'Experiements.']