10 mai 2013 ( dernière mise à jour : 29 novembre 2018 )
Project Objectives : To model the quantity and composition of volcanic gases as a function of the petrology of the magma at depth and the eruptive regime. We will achieve this by modeling the chemical kinetics of degassing in volcanic conduits by using a combination of experimental, field, and numerical approaches.
Project Partners : Institut des Sciences de la Terre d’Orléans (ISTO) • Cambridge University.
Status : Closed (2008-2012).
|Sampling of the flanks of Llaima. Every few decades, Llaima displays violent Strombolian activity with concurrent emission of lava flow that can reach tens of kilometres around the volcano. Numerical simulations of how the magma flows and stalls in the volcanic conduit can help in understanding these cycles of activity. The simulations need to be tightly constrained by accurate field measurements|
Outcomes : In 1991, Pinatubo, a volcano in the Philippines, produced an eruption that was puzzling to volcanologists around the world. The sulfur dioxide (SO2) emitted by the large eruption was far greater in volume than could have possibly been generated from the magma expelled. This divergence, it appears, is not specific to Pinatubo, but is a common feature of volcanoes worldwide. Clearly, a new set of tools was needed to evaluate the quantity and composition of volcanic gases as a function of the type of magma at depth and the eruptive system. DEMONS, a multi-disciplinary project that evaluates how gases are generated during volcanic eruptions, responded to that need by building just such a toolbox.
One of the main achievements of the DEMONS project is to show that changes in gas composition at active volcanoes can be interpreted in terms of how magma flows in the volcano interior. This conclusion provides an explanation for the divergence, first noted at Pinatubo, between gases emitted during an eruption and the gases stored in the deep magma. The research team used a combination of experiments, mathematical models, and field expeditions. All these methods were focused on the remarkable lava lake located at the summit of Erebus volcano in Antarctica. No less than five field seasons at Erebus yielded an exceptional dataset on gas chemistry and lava lake activity. It was found that the composition of the gas emitted by the lava lake changes instantly when large explosions occur in the lake. The measured gas compositions were analyzed using a new generation of thermodynamic models. It turns out that explosions depend on how fast the magma is ascending below the lake. It is the first time that such a link between gas chemistry and how magma flows at depth can be firmly established.
Focusing on how magma flows beneath volcanoes, the DEMONS team found that magma chambers can be reawakened much faster than previously thought. Team members updated a theoretical model of magma chambers and tested it on data from the 1991 eruption of Pinatubo. Conventional theories had vastly underestimated the volcano’s reawakening time, estimating it would take hundreds of years when in reality it took two months. The new model made a significant leap in precision by estimating a reawakening time of 20 to 80 days, very close to the real value.
Volcanic eruptions are driven by small gas bubbles that transform magma into foam, much like champagne in a bottle suddenly uncorked. To understand how these bubbles generate volcanic gases, the DEMONS team performed laboratory experiments recreating such foamy magmas. Using techniques coming from medical imagery, they obtained 3D images of bubbles showing surprising mechanisms. Some bubbles, for instance, form elegant mushroom-shaped pairs just before coalescing. Such observations yielded new laws explaining how the millions of bubbles contained in a cubic centimeter of magma behave. Such laws are essential to link bubbles and volcanic gases.
|Three-dimensional image (0.4 mm wide) of an experimental sample showing gas bubbles (red) suspended in magma (transparent). The high temperature, high pressure experiment on natural lavas replicated how magma degases in a volcanic conduit. Coalescence laws can be retrieved from 3D measurements, which are then used to model how gas bubbles form long chains and let their gas escape. This phenomenon, although occurring at a very small scale, conditions the outcome of a volcanic eruption : gas escape allows for gentle effusion of lava instead of the violent explosion caused by the brutal expansion of the gas trapped in bubbles|
What else than volcanic gases can be in all these magmatic bubbles ? The study of the unique kind of particles emitted by a volcano when it erupts in the sea, several thousands of meters deep, proved that bubbles can also be made of vaporized seawater. The research team recreated these volcanic particles by simply pouring molten glass into a water tank. It turns out that seawater creates bubbles that are very similar to those generated by volcanic gases. It is rare that natural processes as complex as underwater volcanic explosion are reproduced in the laboratory with such deceptively simple methods.
All this laboratory work does not mean that the researchers remained indoors. Besides Antarctica, they collected data on volcanoes around the world, from Chile to the Caribbean Islands. An unexpected volcanic eruption at Chaiten volcano, Chile, on May 1, 2008, triggered a series of rapid discoveries. Soon after the eruption, a team member collected fresh lava fragments in the devastated town nearby. His analyses showed that the viscous magma feeding the eruption reached the surface at about one meter per second. This unprecedented ascent speed left only two days between the first earthquakes felt by the residents and the eruption that ended 8000 years of dormancy.
The toolbox provided by the DEMONS project is a decisive step so that the vast numbers of gas measurements collected from year to year are exploited to their full potential. These advances will, in time, contribute towards a better forecasting of volcanic eruptions.
|Lava dome extrusion at Soufrière Hills. The dome has been growing since 1995, and periodically collapses on the ruins of Plymouth, a city situated on the west flank of the volcano. Although growth can stop for months at a time, the 200 metre high dome is almost continuously degassing.|
Alletti, M., Burgisser, A., Scaillet, B., & Oppenheimer, C. (2014). Chloride partitioning and solubility in hydrous phonolites from Erebus volcano : A contribution towards a multi-component degassing model. GeoResJ, 3–4, 27–45.
Bouvet De Maisonneuve, C., Dungan, M. A., Bachmann, O., & Burgisser, A. (2013). Petrological Insights into Shifts in Eruptive Styles at Volcan Llaima (Chile). Journal of Petrology, 54(2), 393–420. https://doi.org/10.1093/petrology/egs073
Burgisser A. A semi-empirical method to calculate the permeability of homogeneously fluidized pyroclastic material Journal of Volcanology and Geothermal Research 2012
Burgisser A., Bergantz, G.W. A rapid mechanism to remobilize and homogenize highly crystalline magma bodies Nature 2011
Burgisser, A., Alletti, M., & Scaillet, B. (2015). Simulating the behavior of volatiles belonging to the C-O-H-S system in silicate melts under magmatic conditions with the software D-Compress. Computers & Geosciences, 79, 1–14.
Burgisser, A., Chevalier, L., Gardner, J. E., & Castro, J. M. (2017). The percolation threshold and permeability evolution of ascending magmas. Earth and Planetary Science Letters, 470, 37–47. https://doi.org/10.1016/j.epsl.2017.04.023
Burgisser, A., Oppenheimer, C., Alletti, M., Kyle, P.R., Scaillet, B., Carroll, M.R. Backward tracking of gas chemistry measurements at Erebus volcano Geochemistry, Geophysics, Geosystems 2012
Burgisser. A., Arbaret L, Druitt TH, Giachetti, T. Pre-explosive conduit conditions of the 1997 Vulcanian explosions at Soufrière Hills Volcano, Montserrat : II. Overpressure and depth distributions Journal of Volcanology and Geothermal Research 2010
Caricchi, L., Pommier, A., Pistone, M., Castro, J., Burgisser, A., Perugini, D. Strain-induced magma degassing : Insights from simple shear experiments on bubble bearing melts Bulletin of Volcanology 2011
Castro, J., Dingwell, D. Rapid ascent of rhyolitic magma at Chaiten volcano, Chile, Nature 2009
Castro, J.M., Burgisser, A., Schipper, C.I., and Mancini, S. Mechanisms of bubble coalescence in silicic magmas Bulletin of Volcanology 2012
Degruyter W., Burgisser A., Bachmann O., Malaspinas O. Synchrotron X-ray microtomography and lattice Boltzmann simulations of gas flow through volcanic pumices Geosphere 2010
Forestier-Coste, L., Mancini, S. A Finite Volume Preserving Scheme on Nonuniform Meshes and for Multidimensional Coalescence, SIAM J. Sci. Computing, 2012.
Forestier-Coste, L., Mancini, S., Burgisser, A., James, F. Numerical resolution of a mono-disperse model of bubble growth in magmas Applied Mathematical Modelling 2012
Forien M., Arbaret L., Burgisser A., Champallier R Experimental constrains on shear-induced crystal breakage in magmas Journal of Geophysical Research 2011
Giachetti T., Burgisser A., Arbaret L., Druitt T.H., Kelfoun, K. Quantitative textural analysis of Vulcanian pyroclasts (Montserrat) using multi-scale X-ray computed microtomography : comparison with results from 2D image analysis Bulletin of Volcanology 2011
Ilanko, T., Oppenheimer, C., Burgisser, A., & Kyle, P. (2015). Cyclic degassing of Erebus volcano, Antarctica. Bulletin of Volcanology, 77(6), 56. https://doi.org/10.1007/s00445-015-0941-z
Ilanko, T., Oppenheimer, C., Burgisser, A., & Kyle, P. (2015). Transient degassing events at the lava lake of Erebus volcano, Antarctica : Chemistry and mechanisms. GeoResJ, 7, 43–58. https://doi.org/10.1016/j.grj.2015.05.001
Laumonier M., Arbaret L., Burgisser A., Champallier R. Porosity redistribution enhanced by strain localization in crystal-rich magmas Geology 2011
Mancini, S., Forestier-Coste, L., Burgisser, A., James, F., & Castro, J. (2016). An expansion–coalescence model to track gas bubble populations in magmas. Journal of Volcanology and Geothermal Research, 313, 44–58.
Martin, R.S., Ilyinskaya, E., Oppenheimer, C., The enigma of reactive nitrogen in volcanic emissions, Geochimica et Cosmochimica Acta, 2012.
Molina, I., Burgisser, A., & Oppenheimer, C. (2015). A model of the geochemical and physical fluctuations of the lava lake at Erebus volcano, Antarctica. Journal of Volcanology and Geothermal Research, 308, 142–157.
Molina, I., Burgisser, A., Oppenheimer, C. Numerical simulations of convection in crystal-bearing magmas : A case study of the magmatic system at Erebus, Antarctica, Journal of Geophysical Research 2012
Moussallam, Y., Oppenheimer, C., Aiuppa, A., Giudice, G., Moussallam, M., Philip Kyle, P., Hydrogen emissions from Erebus volcano, Antarctica, Bulletin of Volcanology, 2012
Oppenheimer, C., Fischer, T. P., & Scaillet, B. (2014). 4.4 - Volcanic Degassing : Process and Impact. In H. D. Holland & K. K. Turekian (Eds.), Treatise on Geochemistry (Second Edition) (pp. 111–179). Oxford : Elsevier. https://doi.org/10.1016/B978-0-08-095975-7.00304-1
Oppenheimer, C., Moretti, R., Kyle, P., Eschenbacher, A., Lowenstern, J., Hervig, R., Dunbar, N.W. Mantle to surface degassing of alkalic magmas at Erebus volcano, Antarctica Earth and Planetary Science Letters 2011
Oppenheimer, C., Scaillet, B., Martin, R.S., Sulfur degassing from volcanoes : source conditions, surveillance, plume chemistry and impacts Reviews in Mineralogy and Geochemistry, 2011
Peters, N., Oppenheimer, C., & Kyle, P. (2014). Autonomous thermal camera system for monitoring the active lava lake at Erebus volcano, Antarctica. Geoscientific Instrumentation, Methods and Data Systems, 3, 13–20.
Peters, N., Oppenheimer, C., Killingsworth, D. R., Frechette, J., & Kyle, P. (2014). Correlation of cycles in Lava Lake motion and degassing at Erebus Volcano, Antarctica. Geochemistry Geophysics Geosystems, 15, 3244.
Peters, N., Oppenheimer, C., Kyle, P., & Kingsbury, N. (2014). Decadal persistence of cycles in lava lake motion at Erebus volcano, Antarctica. Earth and Planetary Science Letters, 395, 1–12.
Schipper C.I., White J.D.L., Nichols A.R.L., Burgisser A., Hellebrand E., and Murtagh R. Incipient melt segregation as preserved in subaqueous pyroclasts Geology 2012
Schipper, C.I., White, J.D.L., Houghton, B.F. Textural, geochemical, and volatile evidence for a Strombolian-like eruption sequence at Lō`ihi Seamount, Hawai`I Journal of Volcanology and Geothermal Research 2011
Schipper, I.C., Sonder, I., Schmid, A., White, J.D.L., Dürig, T., Zimanowski, B., Büttner, R. Vapour dynamics during magma–water interaction experiments : hydromagmatic origins of submarine volcaniclastic particles (limu o Pele) Geophysical Journal International 2012