Resumo

LONDONO B., John Makario. RADON AND CO₂ EMISSIONS IN DIFFERENT GEOLOGICAL ENVIRONMENTS AS A TOOL FOR MONITORING VOLCANIC AND SEISMIC ACTIVITY IN CENTRAL PART OF COLOMBIARADON AND CO₂ EMISSIONS IN DIFFERENT GEOLOGICAL ENVIRONMENTS AS A TOOL FOR MONITORING VOLCANIC AND SEISMIC ACTIVITY IN CENTRAL PART OF COLOMBIA. bol.geol. [online]. 2009, vol.31, n.2, pp.83-95. ISSN 0120-0283.

²²²Rn (radon) and CO₂ emissions in soil has been measured during a lapse time of several years in three different geological environments at the central part of Colombia, namely Nevado del Ruiz Volcano (NRV), an active volcanic area, Coffee Axes (CA), an active tectonic zone, and Cerro Machín Volcano (CMV), a zone starting a volcanic reactivation process, in order to compare levels of emissions and to monitoring volcanic and seismic activity. Three networks were deployed, with a total of 16 stations. NRV zone showed the highest values of radon emission, followed by CMV and finally CA. Temporal changes of radon and CO₂ emissions were detected for CA and CMV, related with seismic activity. Although NRV showed stability during the studied period, in agreement with steady tendency in radon emissions, high levels of radon emission were detected. This could be related with the level of activity of NRV, which is still in an active stage, and probably there is a delay effect on its activity, implying a future increase in its activity. For CMV, some temporal changes were detected too, associated probably with the increase in activity of this volcano. ²²²Rn/CO₂ ratios were calculated for several stations. Ratios were similar for the three zones, and temporal changes in that ratio were associated with seismicity at NRV, AC and CMV. Regular measurements of radon and CO₂ emissions is a good tool for monitoring volcanic and seismic activity in this region. A base line of data is an important initial step to understand the phenomena; therefore, it is necessary to continue with the program of regular measurements in this region.

Palavras-chave : Radon gas; CO₂; seismicity; volcano; volcanic activity; prognostic.

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