Helium-3 emission from Nevado Del Ruiz Volcano, Colombia

High helium‐3/helium‐4 ratios, up to 6.6Ratm (6.6 times the atmospheric ratio of 1.40 × 10−6) were observed in nine samples of gases and hot waters from seven sites located around the volcano Nevado del Ruiz, Colombia. The values of the ratio decrease with distance from the crater. Such a tendency coincides well with the pattern first reported from the volcano Ontake, central Japan, and suggests a general signature of helium isotope ratios around individual volcanoes. The corrected helium‐3/helium‐4 ratios at one gas vent sampled twice over six months increased. This is interpreted to mean that the mantle contribution of helium may have increased with time.