Synchronous degassing patterns of the neighbouring volcanoes Llaima and Villarrica in south-central Chile: the influence of tidal forces.

Bredemeyer, Stefan and Hansteen, Thor H. (2014) Synchronous degassing patterns of the neighbouring volcanoes Llaima and Villarrica in south-central Chile: the influence of tidal forces. International Journal of Earth Sciences, 103 (7). pp. 1999-2012. DOI 10.1007/s00531-014-1029-2.

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Abstract

The neighbouring volcanoes Villarrica and Llaima are two of the most active volcanoes in Chile and both currently degas continuously. We present a semi-continuous time series of SO2 fluxes for Villarrica and Llaima volcanoes. The time series was obtained using five scanning Mini-Differential Optical Absorption Spectrometers (Mini-DOAS, UV spectrometers) over 6 months (13 February to 31 July 2010) and is based on 6,829 scans for Villarrica and 7,165 scans for Llaima. Statistical analyses of the SO2 flux time series reveal a periodicity of degassing maxima about every 7 days, and further a conspicuous synchronicity of the degassing maxima and minima between the two volcanoes. Intra-day variations in SO2 fluxes also show a striking correlation between Villarrica and Llaima. All these patterns correlate well with the trend of the modelled solid Earth tide curves, where the 7-day degassing maxima correspond with both the fortnightly tidal maxima and minima. The intra-day degassing peaks mostly correlate well with the periods of maximum deformation rates during the diurnal tidal cycle, and further with semidiurnal minima in atmospheric pressure, a phenomenon we refer to as “the tidal pump”. As there is little time lag between the tidal action and the changes in degassing rates, we infer that degassing at both volcanoes is controlled by conduit convection, involving physical separation between gas and magma at comparatively shallow levels. Variations in daily degassing rates were up to a factor of ca. 12 and 10 for Villarrica and Llaima, respectively, without any noticeable changes in the periodicity. We thus suggest that the described cyclic variations must be taken into account for all comparable volcanoes when using gas monitoring as a tool for volcanic hazard mitigation.

Document Type: Article
Additional Information: Erratum: DOI 10.1007/s00531-014-1037-2 - WOS:000343216700017
Keywords: Villarrica · Llaima · Volcano monitoring · SO2 flux · Earth tides
Research affiliation: OceanRep > SFB 574 > PAM
OceanRep > SFB 574
OceanRep > GEOMAR > FB4 Dynamics of the Ocean Floor > FB4-MUHS Magmatic and Hydrothermal Systems
Refereed: Yes
Open Access Journal?: No
DOI etc.: 10.1007/s00531-014-1029-2
ISSN: 1437-3254
Projects: SFB574
Contribution Number:
ProjectNumber
SFB 574262
Date Deposited: 21 Jul 2014 11:51
Last Modified: 23 May 2017 08:58
URI: http://oceanrep.geomar.de/id/eprint/25304

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