System possesses high degree of polymerization in the liquid state.
4 4- tetrahedra link together to form polymer chains. Net result is that silicate magmas with abundant Fe and Mg have a low degree of polymerization and low viscosity. In contrast, absence of Fe and Mg promotes polymerization and increases viscosity. Oxygens from adjacent water molecules then repel each other. Undercooling Temperature necessary for nucleation and crystallization to begin, Usually below the predicted crystallization temperature.