マグマ粘性率の理論的背景

—— とくに自由体積と配置エントロピーの役割について ——

抄録

In the past several decades a significant number of research papers has been appeared on the international journals of earth sciences that has referred to the viscous behavior of magmatic silicate melts. It is, obviously, the reflection of importance of viscosity on the magmatic process such as magma generation and volcanic eruption and of importance for the understanding of early history of the Earth.
Contrary to the importance, the theoretical background of viscosity of a magmatic silicate melt has not been understood well.
This review paper is concerned with the introduction to some basic knowledges and two representative theories on the viscosity of magmatic silicate melts. The first part deals with the definition, methods of viscosity measurement and the effects of parameters that govern the viscous behavior. The second part deals with the free volume theory, which was the early theoretical background for the understanding of viscous behavior of a liquid. This theory emphasizes the importance of free space in a magmatic silicate melt. The third part deals with the configurational entropy theory, which is the theory in much fashion in magma science. The characters of this theory are the combination of thermodynamic data with the viscosity, and the emphasis of the number of configurational state attainable in a magmatic silicate melt. This theory succeeded in the quantitative interpretation of the change of viscosity with temperature and chemical composition.