Radon emanometry in soil gases and activity in ashes from El Chichon Volcano

Radon (²²²Em) emanation measurements in soil gases are reported in connection with the 1982 eruptions of El Chichón Volcano.²²²Em detection is performed with LR-115 cellulose nitrate track detectors. Results show a general decreasing pattern of²²²Em concentration in soil with time after the eruptions. Activity measurements of radon daughters in ashes show that a large amount of²²²Em and²²⁰Em was released from magma degassing during the eruptions, and that only a fraction of the degassed magma was erupted. An important fluid interaction between the magma chamber and the surrounding sedimentary rock is also suggested.