Abstract
We carried out subliquidus viscosity measurement on the 1707 basalt of Fuji volcano, utilizing an atmosphere-controlled furnace with viscometer, which allow temporal sampling during the run. Liquidus temperature of the basalt is 1227°C, and the viscosity of magma changed from 52 Pa sec at 1230°C to 1950 Pa sec at 1130°C. The crystallinity varied from 0 to 24 %. We analyzed the glass, plagioclase and olivine (only at 1130°C), and calculated the melt viscosity at each temperature. Melt viscosity does not vary due to counterbalancing of temperature decrease and decrease of plagioclase component in the melt. Relative viscosity (bulk viscosity/melt viscosity) increased to 14 at 1130°C, which is 3.9 times larger than the commonly used Einstein-Roscoe-Marsh equation.
