The Influence of the Activity of the Usu Volcano in 1977 on the Toya Hot Springs, Hokkaido

Abstract

Variations in temperature, water level and chemical composition of the Toya hot springs due to the activity of the Usu double volcano in 1977 were investigated. Following results were obtained in 1978.
Temperatures of hot springs investigated increased gradually during a series of the phreatic explosions that followed on the initial explosions.
The water level of them rised more or less in the area keeped relatively high temperature.
By the variation of chemical composition in water, the hot springs in the Toya area can be divided into two groups ; one is characterized by the increase in both chloride concentration and water temperature ; the othes by the increase in bicarbonate content but the decrease in pH.