TTE92

Monitoreo de gases volcánicos: análisis de emisiones de dióxido de azufre…

ABSTRACT

The Láscar volcano, located in the Central Andes, is the most active volcanic system

in northern Chile. Its activity began before the last glacial period (40-50 ka) and continues to

this day with minor explosions every 2-3 years. As the main character, Láscar presents

constant degassing at its summit, therefore, to understand its origin and current fluctuation,

an analysis of sulfur dioxide (SO 2 ) emissions was performed, with data measured during four

years (2017-2021) by DOAS instrument of the Volcanological Observatory of the Southern

Andes (OVDAS).

The SO2 emissions database, associated with wind speed and the number of

measurements made by the instrument, were analyzed according to the type of activity and

volcanic alert presented by the volcano during the study period. From this, three periods of

interest were identified: (1) pre-yellow alert: August 2017 to February 2018, (2) yellow alert:

March to August 2018, and (3) post-yellow alert: September 2018 to August 2021; which

conclude a state of passive degassing fluctuating between 275 to 1.142 t/d of SO 2 . However,

from the graphs made, an oscillatory pattern was identified with maximum amplitude during

the austral winter, increase in measurements without detecting SO 2 , and anomalies above

2.000 t/d of SO 2 , which when linked to other precursor parameters of volcanic activity (height

of the outgassing column, surface thermal volcanic activity, and the number of seismic events

type Volcano-Tectonic Long-Period and Screw type) allowed generating a comprehensive

multi-parametric analysis. Thus, it was identified that hydrothermal activity, seasonal

change, and magma ascent dynamics influence volcanic SO 2 emission, generating three

degassing patterns: (1) Low SO 2 volcanic-hydrothermal degassing, (2) SO 2 emissions

influenced by wind velocity, and (3) SO 2 emissions in response to magmatic activity.

In summary, the eruptive activity of the Láscar volcano identified during March 2018

and March 2019, would start with a deep seismic activity to then develop shallow volcanic

activity where SO 2 amounts above 2.429 t/d are emitted. Therefore, it is demonstrated that

SO 2 monitoring, when complemented with other parameters, allows us to get a little closer

to the understanding of volcanic behavior.

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