Helium-3 Emission Related to Volcanic Activity

The helium-3/helium-4 ratio in bubbling gases from ten hot springs located around Mount Ontake, an active volcano in central Japan, ranges from 1.71 R atm (1.71 times the atmospheric ratio of 1.40 × 10 -6 ) to 6.15 R atm . The value of the ratio decreases with distance from the central cone of the volcano. Such a tendency may be a characteristic of helium-3 emission in volcanic areas and suggests more primitive helium-3 is carried with fluid flowing through a conduit during volcanic activity.