Punctuated or sustained? Estimates of the CO2 output of explosive volcanic eruptions
Abstract
Our understanding of the magnitude and nature of volcanic carbon outgassing is becoming more refined. There is now an abundance of observations of CO2 fluxes from passively degassing and effusive erupting volcanoes, as well as from diffuse degassing structures in volcanic regions. Much less well understood, however, is the CO2 output from large, explosive (plinian) eruptions which inject CO2 into the stratosphere and which occur much less frequently. During the satellite era, we have had the opportunity to observe directly a small number of VEI 4 and 5 eruptions, and the associated SO2 loading in the atmosphere. The time-averaged SO2 output from these explosive eruptions is small compared to the SO2 produced during passive degassing and open vent degassing from volcanoes such as Mount Etna (Italy), Bagana (Papua new Guinea) and Ambrym (Vanuatu). CO2 is not easily observed using satellite-based sensors, owing to the difficulty of detection of small volcanic signals over the very large CO2 concentrations in our atmosphere, even for large, explosive eruptions. To understand the CO2 output from explosive eruptions, therefore, we must turn to indirect methods. Here we use melt inclusion data for the products of plinian eruptions to constrain the composition of a pre-eruptive exsolved volatile phase, which allows us to estimate its C/S ratio. We then use a compilation of data for recent explosive eruptions to place contraints on the magnitude of the exsolved volatile phase, based on a) the compressibility of magma reservoirs in the crust inferred from observations of ground displacements and b) the magnitude of the syn-eruptive SO2 gas output. We thus produce estimates of the magnitude of the CO2 output from plinian eruptions, scaled up to potential VEI 7 and 8 eruptions, that is compared to the flux of volcanic CO2 from passive, effusive and diffuse degassing.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2018
- Bibcode:
- 2018AGUFM.V51A..06E
- Keywords:
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- 1030 Geochemical cycles;
- GEOCHEMISTRYDE: 4930 Greenhouse gases;
- PALEOCEANOGRAPHYDE: 8185 Volcanic arcs;
- TECTONOPHYSICSDE: 8408 Volcano/climate interactions;
- VOLCANOLOGYDE: 8412 Reactions and phase equilibria;
- VOLCANOLOGYDE: 8419 Volcano monitoring;
- VOLCANOLOGYDE: 8430 Volcanic gases;
- VOLCANOLOGY