CSIC - Instituto de Recursos Naturales y Agrobiología de Sevilla (IRNAS)
Abstract
Comunicación oral presentada en el 1st European Meeting on Geomicrobiology of volcanic caves. días 2-3 de marzo de 2023 celebrado en la Casa de la Ciencia-CSIC de SevillaDuring the eruption at Cumbre Vieja ridge (La Palma, Canary Islands, 2021) a radon (222Rn) detector (CORENTIUM Pro alpha particles counter) was emplaced inside the “Las Palomas” lava tube (San Juan eruption, 1949). In addition, a CO2 meter logger was emplaced to determine relationships between the 2021 eruption and radon plus CO2 inner fluxes. There is a geostructural relationship between the 1949 and 2021 eruptions, probably connected by a previous fault, shown the volcanic vents’ alignment trending NW-SE. In October 2021, the radon and CO2 loggers were moved to the upper part of the lava tube, in the San Juan volcanic vent (Llano del Banco hollow dyke). Once the eruption ended (in early 2022) both loggers were placed in one newly formed lava tube, and data will be collected in February 2023. Preliminary results show daily average radon values ranging between 2 - 9 Bq/m3, although sporadic peaks of about 270 and 650 Bq/m3 were recorded related to volcano-tectonic earthquakes and volcanic intensity. In general, basaltic eruptions of alkaline affinity show low radon values due to the low concentration in the magma body of uranium and related chemical elements (Th, Ra, etc.). Geochemical analysis of emitted lavas shows a U concentration of about 1 to 5 ppm (μg/g) and Th 9.5 ppm. Summer values of Rn increased up to 3 KBq/m3, related to the climate conditions instead of volcanic activity.This study was funded by the project CSIC 20223PAL002 “Investigación Geológica de la Erupción de 2021 en Cumbre Vieja” and partially by the project FAMRAD (PID2020-113407RB-I00): Geochemical modeling of seismic prediction from endogenous gas emission (222Rn, CO2, CH4), and earthquakes by using radioactive caves and boreholes in the Alhama de Murcia fault.N
