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Eruption cyclicity at silicic volcanoes potentially caused by magmatic gas waves


This article has been updated


Eruptions at active silicic volcanoes are often cyclical. For example, at the Soufrière Hills volcano in Montserrat1, Mount Pinatubo in the Philippines2, and Sakurajima in Japan3, episodes of intense activity alternate with repose intervals over periods between several hours and a day. Abrupt changes in eruption rates have been explained with the motion of a plug of magma that alternatively sticks or slides along the wall of the volcanic conduit4,5. However, it is unclear how the static friction that prevents the plug from sliding is periodically overcome. Here we use two-phase flow equations to model a gas-rich, viscous magma ascending through a volcanic conduit. Our analyses indicate that magma compaction yields ascending waves comprised of low- and high-porosity bands. However, magma ascent to lower pressures also causes gas expansion. We find that the competition between magma compaction and gas expansion naturally selects pressurized gas waves with specific periods. At the surface, these waves can induce cyclical eruptive behaviour with periods between 1 and 100 hours, which compares well to the observations from Soufrière Hills, Mount Pinatubo and Sakurajima. We find that the period is insensitive to volcano structure, but increases weakly with magma viscosity. We conclude that observations of a shift to a longer eruption cycle imply an increase in magma viscosity and thereby enhanced volcanic hazard.

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Figure 1: Observed cyclicity at two different silicic volcanoes.
Figure 2: Alternation between gas-rich and degassed magma layers.
Figure 3: Dominant wavelength of the perturbation predicted by the theory.
Figure 4: Gas fraction and overpressure profiles obtained from numerical calculations.

Change history

  • 06 September 2013

    In the version of this Letter originally published online, the published online date should have read '5 September 2013'. This has been corrected in the PDF and HTML versions of the Letter.


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The authors thank A. Burgisser whose comments helped improve the manuscript. This work was supported by Campus Spatial Paris Diderot and European Research Council Advanced Grant VOLDIES number 228064.

Author information




C.M. conceived the original model, C.M., Y.R. and D.B. developed the physical and mathematical model, Y.R. and C.M. developed the numerical model, and R.S.J.S. and C.M. made links between the model and the observations. C.M. was the lead author but all authors contributed to the writing of the paper.

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Correspondence to Chloé Michaut.

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The authors declare no competing financial interests.

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Michaut, C., Ricard, Y., Bercovici, D. et al. Eruption cyclicity at silicic volcanoes potentially caused by magmatic gas waves. Nature Geosci 6, 856–860 (2013).

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