EGU2020-19479, updated on 12 Jun 2020
https://doi.org/10.5194/egusphere-egu2020-19479
EGU General Assembly 2020
© Author(s) 2020. This work is distributed under
the Creative Commons Attribution 4.0 License.

Environmental factors controlling diffuse CO2 emission rates from Cumbre Vieja Volcano, La Palma, Canary Islands

Victoria Leal1, Germán D. Padilla1,2, Gladys V. Melián1,2,3, Alba Martin-Lorenzo1,2, Fátima Rodríguez1, Eleazar Padrón1,2,3, María Asensio-Ramos1, Pedro A. Hernández1,2,3, and Nemesio M. Pérez1,2,3
Victoria Leal et al.
  • 1Instituto Volcanológico de Canarias (INVOLCAN), 38240 La Laguna, Tenerife, Canary Islands, Spain (vleal@iter.es)
  • 2Instituto Tecnológico y de Energías Renovables (ITER), 38611 Granadilla de Abona, Tenerife, Canary Islands, Spain
  • 3Agencia Insular de la Energía de Tenerife (AIET), 38611 Granadilla de Abona, Tenerife, Canary Islands, Spain.

La Palma Island (708.3 km2) is located at the north-western end of the Canarian Archipelago and is one of the youngest island (~2.0My). During the last 123 ka, volcanic activity has taken place exclusively at the southern part of the island, where Cumbre Vieja volcano, the most active basaltic volcano in the Canaries, has been constructed. Seven historical eruptions have occurred at Cumbre Vieja, been Teneguía the last one (1971). On 7-14 of October 2017 and 10-15 November 2018, two intense seismic swarms occurred beneath Cumbre Vieja. In order to monitor the volcanic activity at Cumbre Vieja, main efforts have been focused on diffuse degassing studies since visible volcanic emissions are absent at the surface environment of this volcano. Diffuse CO2 emissions have been monitored at Cumbre Vieja since 1997 in a yearly basis, with a higher frequency since the start of intense seismic swarms until August, 2019. At each survey, 600 sampling sites are selected for soil CO2 efflux measurements performed in situ following the accumulation chamber method. Spatial distribution maps are constructed following the sequential Gaussian simulation (sGs) procedure and, to quantify the CO2 emission from the studied area, 100 simulations are performed for each survey. At each sampling site, soil gas samples were collected at 40cm depth. Isotopic analysis of C in the CO2 of selected soil gas samples (10% of the total) was performed to discriminate the origin of the CO2. Between 2001 and 2017, the estimated diffuse CO2 emission rate released to the atmosphere from Cumbre Vieja volcano has ranged between 320 to 1,544 td-1. After October 2017 seismic swarms, diffuse CO2 emission rates were estimated on a nearly daily basis, showing three increasing trends from 800td-1 up to 3,251td-1, 2,850td-1 and 1,904td-1, respectively. With the aim to filter out the effects of rainfall on the measured CO2 efflux time series, a decorrelation pluviometric data analysis was performed. We found that a moving average of sixty days of the averaged rainfalls of six pluviometers on the studied area explained 49.4% of variability of diffuse CO2 emission. The first peak on diffuse CO2 emission remained after filtering, with a highest value of 2,020td-1, when the time series had a non linear behaviour and the two seismic swarms occurred. Highest value of the second peak was 1,495td-1 whereas the third peak practically disappears after filtering, due to the high influence with rainfall. Isotopic analysis of soil C-CO2 showed enrichments in volcanic-hydrothermal CO2 before the two mean peaks of filtered soil CO2 emission time series. We found seismological and geochemical evidences that these swarms were linked to a deep-seated magmatic intrusion. We hypothesize that the October 2017 seismic swarms were produced by an upward magma migration from an ephemeral magmatic reservoir located in the upper mantle (about 25 km depth), toward another reservoir located close to the Moho beneath Cumbre Vieja (12-15 km). The consequent depressurization of the magma batch was the source of the volatiles observed at the surface, with a delay of few weeks for CO2.

How to cite: Leal, V., Padilla, G. D., Melián, G. V., Martin-Lorenzo, A., Rodríguez, F., Padrón, E., Asensio-Ramos, M., Hernández, P. A., and Pérez, N. M.: Environmental factors controlling diffuse CO2 emission rates from Cumbre Vieja Volcano, La Palma, Canary Islands, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-19479, https://doi.org/10.5194/egusphere-egu2020-19479, 2020