A diagram and a graph showing how ocean island eruptions are much more likely to exhibit SO2 degassing and deformation.
(a) Basaltic volcanic eruptions during the satellite era (2005-2020) classified by tectonic type (island arc vs. ocean island) and by whether volcanic deformation and/or SO2 degassing were observed during the eruption. Ocean island eruptions are much more likely to exhibit SO2 degassing and deformation. (b) For the subset of largest recorded eruptions (erupted volume > 105 m3 or Volcanic Explosivity Index > 4), columns are color-coded to show whether satellites observed degassing only (orange), deformation only (yellow), degassing and deformation (red), or no detection (pink). Again, ocean island basalt eruption are much more likely to exhibit SO2 degassing and ground deformation. Credit: Yip et al. [2022], Figure 8
Editors’ Highlights are summaries of recent papers by AGU’s journal editors.
Source: Geochemistry, Geophysics, Geosystems

In a new study, Yip et al. [2022] compile observations of all subaerial basaltic eruptions since 2005, a period when satellite coverage has been sufficient to test whether each eruption exhibited degassing of magmatic SO2 (a readily-observed proxy for the more abundant magmatic gases H2O and CO2) and whether each eruption was associated with deformation (inflation or deflation) of the ground surface. They find that volatile-rich eruptions, which tend to occur at arc volcanoes, are (surprisingly) much less likely to be accompanied by ground deformation. By contrast, relatively volatile-poor eruptions at ocean island volcanoes are much more likely to show ground deformation.

The authors develop a thermodynamic model of magma degassing and physical properties that emphasizes the role of bubbles in increasing the compressibility of the magma plumbing system, which leads to a surprising new theory and prediction for whether ground deformation will occur. Bubble-rich plumbing systems, they find, are more compressible, and this has the effect of strongly suppressing the stresses that leads to ground deformation.

Citation: Yip, S. T. H., Biggs, J., Edmonds, M., Liggins, P., & Shorttle, O. (2022). Contrasting volcanic deformation in arc and ocean island settings due to exsolution of magmatic water. Geochemistry, Geophysics, Geosystems, 23, e2022GC010387. https://doi.org/10.1029/2022GC010387

—Paul Asimow, Editor, Geochemistry, Geophysics, Geosystems

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