| Abstract: |
We have carried out geochemical surveys in the west area of the newly formed lava dome, Heiseishinzan at Unzen Volcano, from 1999 to 2002. Concentrations of soil air gases of Hg, C02, radon (222Rn) and thoron (220Rn), and gamma-ray intensity were measured within an area approximately 1.5 km NS by 1 km EW west of the dome. Concentration anomalies of soil air Hg and radon and thoron gases were detected in the area near Momijichaya, which is located 1 km west of the dome. Anomalies of gamma-ray intensity were detected in the same area. The location of this anomalous area coincides with the portion of the volcanic conduit interpreted from geophysical methods. |