Following the seismic swarms that marked La Cumbre Vieja on the
island of La Palma, in the Canary Islands, between 7 and 14 October, INVOLCAN (Instituto Volcanologico de Canarias) have increased the monitoring since last week with new seismic installations.
On Sunday and Monday, an alkaline trap network consisting of 21 geochemical observing stations was set up (map location opposite) to monitor the diffuse carbon dioxide flux.
A recent article by TV La Palma recalls that surveillance of the Cumbre Vieja is not new, the operations date from 1997.
Among the precursor geochemical signals, INVOLCAN pinpoints the detection of significant changes in the diffuse emission of hydrogen in the atmosphere,
During the 2001/03 campaign, the average diffuse emission value of hydrogen was 2.5 kg per day; this average value rose to 16.6 kg / day during the period 2013-2017, reaching 36 kg / day in June 2017 ... the precursor signals were observed about 4 years before the recording of the recent seismic survey marking the Cumbre Vieja.
Other parameters corroborate these measurements: the geochemical He / CO2 and H2 / CO2 ratios in the soil atmosphere of the Cumbre Vieja also reflect an increase since 2013.
Moreover, the different values of the carbon-13 isotope in the measured atmospheric carbon dioxide show that these emissions contain a greater proportion of deep origin volcanic gases.
Since 2007, the carbon dioxide / hydrogen sulphide ratio values are relatively higher than previously.
These observations reflect the importance of geochemical monitoring of volcanic gases, visible on the surface in plumes and fumaroles, but also invisible to the human eye, in diffuse gaseous emanations.
Sources: INVOLCAN, ITER, IGN Spain & TV La Palma