Multi-scale observations of the variability of magmatic CO2 emissions, Mammoth Mountain, CA, USA

Jennifer L. Lewicki; George E. Hilley

doi:10.1016/j.jvolgeores.2014.07.011

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Multi-scale observations of the variability of magmatic CO2 emissions, Mammoth Mountain, CA, USA

Jennifer L. Lewicki·George E. Hilley

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Abstract

One of the primary indicators of volcanic unrest at Mammoth Mountain is diffuse emission of magmatic CO 2 , which can effectively track this unrest if its variability in space and time and relationship to near-surface meteorological and hydrologic phenomena versus those occurring at depth beneath the mountain are understood. In June–October 2013, we conducted accumulation chamber soil CO 2 flux surveys and made half-hourly CO 2 flux measurements with automated eddy covariance and accumulation chamber (auto-chamber) instrumentation at the largest area of diffuse CO 2 degassing on Mammoth Mountain (Horseshoe Lake tree kill; HLTK). Estimated CO 2 emission rates for HLTK based on 20 June, 30 July, and 24–25 October soil CO 2 flux surveys were 165, 172, and 231 t d − 1 , respectively. The average (June–October) CO 2 emission rate estimated for this area was 123 t d − 1 based on an inversion of 4527 eddy covariance CO 2 flux measurements and corresponding modeled source weight functions. Average daily eddy covariance and auto-chamber CO 2 fluxes consistently declined over the four-month observation time. Wavelet analysis of auto-chamber CO 2 flux and environmental parameter time series was used to evaluate the periodicity of, and local correlation between these variables in time–frequency space. Overall, CO 2 emissions at HLTK were highly dynamic, displaying short-term (hourly to weekly) temporal variability related to meteorological and hydrologic changes, as well as long-term (monthly to multi-year) variations related to migration of CO 2 -rich magmatic fluids beneath the volcano. Accumulation chamber soil CO 2 flux surveys were also conducted in the four additional areas of diffuse CO 2 degassing on Mammoth Mountain in July–August 2013. Summing CO 2 emission rates for all five areas yielded a total for the mountain of 311 t d − 1 , which may suggest that emissions returned to 1998–2009 levels, following an increase from 2009 to 2011.

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Journal of Volcanology and Geothermal Research Article

Source-reported bounding extent: 37.59° to 37.66° latitude; -119.09° to -119° longitude. This indicates report coverage, not an exact sampling location. View area on OpenStreetMap.

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BibTeX RIS

Jennifer L. Lewicki, George E. Hilley. 2014. Multi-scale observations of the variability of magmatic CO2 emissions, Mammoth Mountain, CA, USA. https://doi.org/10.1016/j.jvolgeores.2014.07.011

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