Skip to main content

Thank you for visiting You are using a browser version with limited support for CSS. To obtain the best experience, we recommend you use a more up to date browser (or turn off compatibility mode in Internet Explorer). In the meantime, to ensure continued support, we are displaying the site without styles and JavaScript.

A compositional tipping point governing the mobilization and eruption style of rhyolitic magma


The most viscous volcanic melts and the largest explosive eruptions1 on our planet consist of calcalkaline rhyolites2,3. These eruptions have the potential to influence global climate4. The eruptive products are commonly very crystal-poor and highly degassed, yet the magma is mostly stored as crystal mushes containing small amounts of interstitial melt with elevated water content5. It is unclear how magma mushes are mobilized to create large batches of eruptible crystal-free magma. Further, rhyolitic eruptions6,7,8 can switch repeatedly between effusive and explosive eruption styles and this transition is difficult to attribute to the rheological effects of water content or crystallinity9,10. Here we measure the viscosity of a series of melts spanning the compositional range of the Yellowstone volcanic system and find that in a narrow compositional zone, melt viscosity increases by up to two orders of magnitude. These viscosity variations are not predicted by current viscosity models11,12 and result from melt structure reorganization, as confirmed by Raman spectroscopy. We identify a critical compositional tipping point, independently documented in the global geochemical record of rhyolites, at which rhyolitic melts fluidize or stiffen and that clearly separates effusive from explosive deposits worldwide. This correlation between melt structure, viscosity and eruptive behaviour holds despite the variable water content and other parameters, such as temperature, that are inherent in natural eruptions. Thermodynamic modelling demonstrates how the observed subtle compositional changes that result in fluidization or stiffening of the melt can be induced by crystal growth from the melt or variation in oxygen fugacity. However, the rheological effects of water and crystal content alone cannot explain the correlation between composition and eruptive style. We conclude that the composition of calcalkaline rhyolites is decisive in determining the mobilization and eruption dynamics of Earth’s largest volcanic systems, resulting in a better understanding of how the melt structure controls volcanic processes.

Access options

Rent or Buy article

Get time limited or full article access on ReadCube.


All prices are NET prices.

Figure 1: Viscosity measurements of samples at 850 °C.
Figure 2: Measured viscosity at 850 °C for samples F, J and L characterized by increasing FeO content.
Figure 3: Thermodynamic modelling results of magma crystallization at varying and pressure.
Figure 4: Summary plot of RAI versus K# for all experimental samples along with 40 natural rhyolitic systems and their eruptive styles.


  1. 1

    Bryan, S. E. et al. The largest volcanic eruptions on Earth. Earth Sci. Rev. 102, 207–229 (2010)

    ADS  Google Scholar 

  2. 2

    Friedman, I., Long, W. & Smith, R. L. Viscosity and water content of rhyolite glass. J. Geophys. Res. 68, 6523–6535 (1963)

    ADS  CAS  Google Scholar 

  3. 3

    Shaw, H. R. Viscosities of magmatic silicate liquids: an empirical method of prediction. Am. J. Sci. 272, 870–893 (1972)

    ADS  CAS  Google Scholar 

  4. 4

    Robock, A. et al. Did the Toba volcanic eruption of ~74 ka B.P. produce widespread glaciation? J. Geophys. Res. Atmos. 114, D10107 (2009)

    ADS  Google Scholar 

  5. 5

    Bachmann, O. & Bergantz, G. W. On the origin of crystal-poor rhyolites: extracted from batholithic crystal mushes. J. Petrol. 45, 1565–1582 (2004)

    ADS  CAS  Google Scholar 

  6. 6

    Christiansen, R. L. The Quaternary and Pliocene Yellowstone plateau volcanic field of Wyoming, Idaho, and Montana. U. S. Geol. Surv. Prof. Pap. 729-G, 145 (2001)

    Google Scholar 

  7. 7

    Castro, J. M., Manga, M. & Cashman, K. V. Dynamics of obsidian flows inferred from microstructures: insights from microlite preferred orientations. Earth Planet. Sci. Lett. 199, 211–226 (2002)

    ADS  CAS  Google Scholar 

  8. 8

    Carn, S. A. et al. The unexpected awakening of Chaitén volcano, Chile. Eos 90, 205–206 (2009)

    ADS  Google Scholar 

  9. 9

    Cabrera, A., Weinberg, R. F. & Wright, H. M. N. Magma fracturing and degassing associated with obsidian formation: the explosive-effusive transition. J. Volcanol. Geotherm. Res. 298, 71–84 (2015)

    ADS  CAS  Google Scholar 

  10. 10

    Befus, K. S. & Gardner, J. E. Magma storage and evolution of the most recent effusive and explosive eruptions from Yellowstone Caldera. Contrib. Mineral. Petrol. 171, 30 (2016)

    ADS  Google Scholar 

  11. 11

    Hui, H. J. & Zhang, Y. Toward a general viscosity equation for natural anhydrous and hydrous silicate melts. Geochim. Cosmochim. Acta 71, 403–416 (2007)

    ADS  CAS  Google Scholar 

  12. 12

    Giordano, D., Russell, J. K. & Dingwell, D. B. Viscosity of magmatic liquids: a model. Earth Planet. Sci. Lett. 271, 123–134 (2008)

    ADS  CAS  Google Scholar 

  13. 13

    Mysen, B. O. & Toplis, M. J. Structural behavior of Al3+ in peralkaline, metaluminous, and peraluminous silicate melts and glasses at ambient pressure. Am. Mineral. 92, 933–946 (2007)

    ADS  CAS  Google Scholar 

  14. 14

    Le Losq, C. & Neuville, D. R. Effect of the Na/K mixing on the structure and the rheology of tectosilicate silica-rich melts. Chem. Geol. 346, 57–71 (2013)

    ADS  CAS  Google Scholar 

  15. 15

    Morgavi, D. et al. The Grizzly Lake Complex (Yellowstone Volcano, USA): mixing between basalt and rhyolite unravelled by microanalysis and X-ray microtomography. Lithos 260, 457–474 (2016)

    ADS  CAS  Google Scholar 

  16. 16

    Vazquez, J. A., Kyriazis, S. F., Reid, M. R., Sehler, R. C. & Ramos, F. C. Thermochemical evolution of young rhyolites at Yellowstone: evidence for a cooling but periodically replenished postcaldera magma reservoir. J. Volcanol. Geotherm. Res. 188, 186–196 (2009)

    ADS  CAS  Google Scholar 

  17. 17

    Girard, G. & Stix, J. Rapid extraction of discrete magma batches from a large differentiating magma chamber: the Central Plateau Member rhyolites, Yellowstone caldera, Wyoming. Contrib. Mineral. Petrol. 160, 441–465 (2010)

    ADS  CAS  Google Scholar 

  18. 18

    Wiesmaier, S. et al. Bimodality of lavas in the Teide-Pico Viejo succession in Tenerife—the role of crustal melting in the origin of recent phonolites. J. Petrol. 53, 2465–2495 (2012)

    ADS  CAS  Google Scholar 

  19. 19

    Bachmann, O., Deering, C. D., Lipman, P. W. & Plummer, C. Building zoned ignimbrites by recycling silicic cumulates: insight from the 1,000km3 Carpenter Ridge tuff, CO. Contrib. Mineral. Petrol. 167, 1025 (2014)

    ADS  Google Scholar 

  20. 20

    Ellis, B. S., Bachmann, O. & Wolff, J. A. Cumulate fragments in silicic ignimbrites: the case of the Snake River Plain. Geology 42, 431–434 (2014)

    ADS  Google Scholar 

  21. 21

    Stelten, M. E., Cooper, K. M., Vazquez, J. A., Calvert, A. T. & Glessner, J. J. G. Mechanisms and timescales of generating eruptible rhyolitic magmas at Yellowstone caldera from zircon and sanidine geochronology and geochemistry. J. Petrol. 56, 1607–1642 (2015)

    ADS  CAS  Google Scholar 

  22. 22

    Wolff, J. A. et al. Remelting of cumulates as a process for producing chemical zoning in silicic tuffs: a comparison of cool, wet and hot, dry rhyolitic magma systems. Lithos 236–237, 275–286 (2015)

    ADS  Google Scholar 

  23. 23

    Gaillard, F., Scaillet, B. & Pichavant, M. Kinetics of iron oxidation-reduction in hydrous silicic melts. Am. Mineral. 87, 829–837 (2002)

    ADS  CAS  Google Scholar 

  24. 24

    Gualda, G. A. R., Ghiorso, M. S., Lemons, R. V. & Carley, T. L. Rhyolite-MELTS: a modified calibration of MELTS optimized for silica-rich, fluid-bearing magmatic systems. J. Petrol. 53, 875–890 (2012)

    ADS  CAS  Google Scholar 

  25. 25

    Barone, G. et al. Nanoscale surface modification of Mt. Etna volcanic ashes. Geochim. Cosmochim. Acta 174, 70–84 (2016)

    ADS  CAS  Google Scholar 

  26. 26

    Mujin, M. & Nakamura, M. A nanolite record of eruption style transition. Geology 42, 611–614 (2014)

    ADS  CAS  Google Scholar 

  27. 27

    Kremers, S. et al. Shallow magma-mingling-driven Strombolian eruptions at Mt Yasur volcano, Vanuatu. Geophys. Res. Lett. 39, L21304 (2012)

    ADS  Google Scholar 

  28. 28

    Eichelberger, J. C., Carrigan, C. R., Westrich, H. R. & Price, R. H. Non-explosive silicic volcanism. Nature 323, 598–602 (1986)

    ADS  CAS  Google Scholar 

  29. 29

    Gonnermann, H. M. & Manga, M. Explosive volcanism may not be an inevitable consequence of magma fragmentation. Nature 426, 432–435 (2003)

    ADS  CAS  PubMed  Google Scholar 

  30. 30

    Gardner, J. E., Llewellin, E. W., Watkins, J. M. & Befus, K. S. Formation of obsidian pyroclasts by sintering of ash particles in the volcanic conduit. Earth Planet. Sci. Lett. 459, 252–263 (2017)

    ADS  CAS  Google Scholar 

  31. 31

    Pouchou, J.-L. & Pichoir, F. in Electron Probe Quantitation SE-4 (eds Heinrich, K. F. J. & Newbury, D. ) 31–75 (Springer, 1991)

    Google Scholar 

  32. 32

    Shapiro, L. M. & Brannock, W. W. Rapid analysis of silicate rocks. Geol. Surv. Bull. C 1036, 295–318 (1956)

    Google Scholar 

  33. 33

    Giuli, G. et al. XAS determination of the Fe local environment and oxidation state in phonolite glasses. Am. Mineral. 96, 631–636 (2011)

    ADS  CAS  Google Scholar 

  34. 34

    Dingwell, D. B. Viscosity–temperature relationships in the system Na2Si2O5–Na4Al2O5 . Geochim. Cosmochim. Acta 50, 1261–1265 (1986)

    ADS  CAS  Google Scholar 

  35. 35

    Dingwell, D. B. Shear viscosities of ferrosilicate liquids. Am. Mineral. 74, 1038–1044 (1989)

    CAS  Google Scholar 

  36. 36

    Dingwell, D. B. & Virgo, D. Viscosities of melts in the Na2O–FeO–Fe2O3–SiO2 system and factors controlling relative viscosities of fully polymerized silicate melts. Geochim. Cosmochim. Acta 52, 395–403 (1988)

    ADS  CAS  Google Scholar 

  37. 37

    Mysen, B. O. & Virgo, D. Influence of pressure, temperature, and bulk composition on melt structures in the system NaAlSi2O6–NaFe3 + Si2O6 . Am. J. Sci. 278, 1307–1322 (1978)

    ADS  CAS  Google Scholar 

  38. 38

    Dingwell, D. B. & Virgo, D. The effect of oxidation state on the viscosity of melts in the system Na2O–FeO–Fe2O3–SiO2 . Geochim. Cosmochim. Acta 51, 195–205 (1987)

    ADS  CAS  Google Scholar 

  39. 39

    Dingwell, D. B. Redox viscometry of some Fe-bearing silicate melts. Am. Mineral. 76, 1560–1562 (1991)

    CAS  Google Scholar 

  40. 40

    Pocklington, H. C. Rough measurement of high viscosities. Math. Proc. Camb. Phil. Soc. 36, 507–508 (1940)

    ADS  CAS  Google Scholar 

  41. 41

    Tobolsky, A. V. & Taylor, R. B. Viscoelastic properties of a simple organic glass. J. Phys. Chem. 67, 2439–2442 (1963)

    CAS  Google Scholar 

  42. 42

    Scarfe, C. M. Melt at one atmosphere viscosity of a pantellerite. Can. Mineral. 15, 185–189 (1977)

    Google Scholar 

  43. 43

    Stevenson, R. J., Bagdassarov, N. S., Dingwell, D. B. & Romano, C. The influence of trace amounts of water on the viscosity of rhyolites. Bull. Volcanol. 60, 89–97 (1998)

    ADS  Google Scholar 

  44. 44

    Di Genova, D. et al. The rheology of peralkaline rhyolites from Pantelleria Island. J. Volcanol. Geotherm. Res. 249, 201–216 (2013)

    ADS  CAS  Google Scholar 

  45. 45

    Watt, S. F. L., Pyle, D. M. & Mather, T. A. Evidence of mid- to late-Holocene explosive rhyolitic eruptions from Chaitén volcano, Chile. Andean Geol. 40, 216–226 (2013)

    Google Scholar 

  46. 46

    Di Genova, D. et al. Approximate chemical analysis of volcanic glasses using Raman spectroscopy. J. Raman Spectrosc. 46, 1235–1244 (2015)

    ADS  CAS  PubMed  PubMed Central  Google Scholar 

  47. 47

    Di Genova, D. et al. Raman spectra of Martian glass analogues: a tool to approximate their chemical composition. J. Geophys. Res. Planets 121, 740–752 (2016)

    ADS  CAS  PubMed  PubMed Central  Google Scholar 

  48. 48

    Di Genova, D., Hess, K.-U., Chevrel, M. O. & Dingwell, D. B. Models for the estimation of Fe3+/Fetot. ratio in terrestrial and extra-terrestrial alkali- and iron-rich silicate glasses using Raman spectroscopy. Am. Mineral. 101, 943–952 (2016)

    ADS  Google Scholar 

  49. 49

    Tauxe, L. Essentials of Paleomagnetism Ch. 3, 33–46 (Univ. California Press, 2010)

    Google Scholar 

  50. 50

    Dunlop, D. J. Superparamagnetic and single-domain threshold sizes in magnetite. J. Geophys. Res. 78, 1780–1793 (1973)

    ADS  Google Scholar 

  51. 51

    Lafuente, B., Downs, R. T., Yang, H. & Stone, N. The power of databases: the RRUFF project. In Highlights in Mineralogical Crystallography (eds Armbruster, T. & Danisi, R. M. ) 1–30 (De Gruyter, 2015)

  52. 52

    Dunlop, D. J. Theory and application of the Day plot (Mrs/Ms versus Hcr/Hc). 1. Theoretical curves and tests using titanomagnetite data. J. Geophys. Res. Solid Earth 107, 1–22 (2002)

    Google Scholar 

  53. 53

    Tauxe, L., Mullender, T. A. T. & Pick, T. Potbellies, wasp-waists, and superparamagnetism in magnetic hysteresis. J. Geophys. Res. 101, 571–583 (1996)

    ADS  Google Scholar 

  54. 54

    Tauxe, L., Bertram, H. N. & Seberino, C. Physical interpretation of hysteresis loops: micromagnetic modelling of fine particle magnetite. Geochem. Geophys. Geosyst. 3, 1–22 (2002)

    Google Scholar 

  55. 55

    Butler, R. F. & Banerjee, S. K. Theoretical single-domain grain size range in magnetite and titanomagnetite. J. Geophys. Res. 80, 4049 (1975)

    ADS  CAS  Google Scholar 

  56. 56

    Pullaiah, G., Irving, E., Buchan, K. L. & Dunlop, D. J. Magnetization changes caused by burial and uplift. Earth Planet. Sci. Lett. 28, 133–143 (1975)

    ADS  Google Scholar 

  57. 57

    Liebske, C., Behrens, H., Holtz, F. & Lange, R. A. The influence of pressure and composition on the viscosity of andesitic melts. Geochim. Cosmochim. Acta 67, 473–485 (2003)

    ADS  CAS  Google Scholar 

  58. 58

    Di Genova, D., Romano, C., Giordano, D. & Alletti, M. Heat capacity, configurational heat capacity and fragility of hydrous magmas. Geochim. Cosmochim. Acta 142, 314–333 (2014)

    ADS  CAS  Google Scholar 

  59. 59

    Bouhifd, M. A., Whittington, A., Withers, C. & Richet, P. Heat capacities of hydrous silicate glasses and liquids. Chem. Geol. 346, 125–134 (2013)

    ADS  CAS  Google Scholar 

  60. 60

    Chevrel, M. O., Baratoux, D., Hess, K.-U. & Dingwell, D. B. Viscous flow behavior of tholeiitic and alkaline Fe-rich martian basalts. Geochim. Cosmochim. Acta 124, 348–365 (2014)

    ADS  CAS  Google Scholar 

  61. 61

    Stevenson, R. J., Dingwell, D. B., Webb, S. L. & Bagdassarov, N. S. The equivalence of enthalpy and shear stress relaxation in rhyolitic obsidians and quantification of the liquid-glass transition in volcanic processes. J. Volcanol. Geotherm. Res. 68, 297–306 (1995)

    ADS  CAS  Google Scholar 

  62. 62

    Philpotts, A. R & Ague, J. J. Principles of Igneous and Metamorphic Petrology Ch. 11 (Cambridge Univ. Press, 2009)

  63. 63

    Kolzenburg, S., Giordano, D., Cimarelli, C. & Dingwell, D. B. In situ thermal characterization of cooling/crystallizing lavas during rheology measurements and implications for lava flow emplacement. Geochim. Cosmochim. Acta 195, 244–258 (2016)

    ADS  CAS  Google Scholar 

  64. 64

    Kolzenburg, S., Giordano, D., Thordarson, T., Höskuldsson, A. & Dingwell, D. B. The rheological evolution of the 2014/2015 eruption at Holuhraun, central Iceland. Bull. Volcanol. 79, 45 (2017)

    ADS  Google Scholar 

  65. 65

    Kolzenburg, S. & Russell, J. K. Welding of pyroclastic conduit infill: a mechanism for cyclical explosive eruptions. J. Geophys. Res. Solid Earth 119, 5305–5323 (2014)

    ADS  Google Scholar 

  66. 66

    Perkins, M. E., Nash, W. P., Brown, F. H. & Fleck, R. J. Fallout tuffs of Trapper Creek, Idaho—a record of Miocene explosive volcanism in the Snake River Plain volcanic province. Geol. Soc. Am. Bull. 107, 1484–1506 (1995)

    ADS  CAS  Google Scholar 

  67. 67

    Perkins, M. E. & Nash, B. P. Explosive silicic volcanism of the Yellowstone hotspot: the ash fall tuff record. Geol. Soc. Am. Bull. 114, 367–381 (2002)

    ADS  CAS  Google Scholar 

  68. 68

    Nash, B. P. & Perkins, M. E. Neogene fallout tuffs from the Yellowstone hotspot in the Columbia Plateau region, Oregon, Washington and Idaho, USA. PLoS One 7, 1–13 (2012)

    Google Scholar 

  69. 69

    Girard, G. & Stix, J. Magma recharge and crystal mush rejuvenation associated with early post-collapse Upper Basin Member rhyolites, Yellowstone caldera, Wyoming. J. Petrol. 50, 2095–2125 (2009)

    ADS  CAS  Google Scholar 

  70. 70

    Ellis, B. S. et al. Groundmass crystallisation and cooling rates of lava-like ignimbrites: the Grey’s Landing ignimbrite, southern Idaho, USA. Bull. Volcanol. 77, 87 (2015)

    ADS  Google Scholar 

  71. 71

    Ellis, B. S. et al. Petrologic constraints on the development of a large-volume, high temperature, silicic magma system: The Twin Falls eruptive centre, central Snake River Plain. Lithos 120, 475–489 (2010)

    ADS  CAS  Google Scholar 

  72. 72

    Rowe, M. C., Ellis, B. S. & Lindeberg, A. Quantifying crystallization and devitrification of rhyolites by means of X-ray diffraction and electron microprobe analysis. Am. Mineral. 97, 1685–1699 (2012)

    ADS  CAS  Google Scholar 

  73. 73

    Cathey, H. E. & Nash, B. P. The Cougar Point tuff: implications for thermochemical zonation and longevity of high-temperature, large-volume silicic magmas of the Miocene Yellowstone hotspot. J. Petrol. 45, 27–58 (2004)

    ADS  CAS  Google Scholar 

  74. 74

    Bolte, T., Holtz, F., Almeev, R. & Nash, B. P. The Blacktail Creek tuff: an analytical and experimental study of rhyolites from the Heise volcanic field, Yellowstone hotspot system. Contrib. Mineral. Petrol. 169, 15 (2015)

    ADS  Google Scholar 

  75. 75

    Clay, P. L. et al. Textural characterization, major and volatile element quantification and Ar-Ar systematics of spherulites in the Rocche Rosse obsidian flow, Lipari, Aeolian Islands: a temperature continuum growth model. Contrib. Mineral. Petrol. 165, 373–395 (2013)

    ADS  CAS  Google Scholar 

  76. 76

    de Rosa, R. & Sheridan, M. F. Evidence for magma mixing in the surge deposits of the Monte Guardia sequence, Lipari. J. Volcanol. Geotherm. Res. 17, 313–328 (1983)

    ADS  CAS  Google Scholar 

  77. 77

    de Rosa, R., Donato, P., Gioncada, A., Masetti, M. & Santacroce, R. The Monte Guardia eruption (Lipari, Aeolian Islands): an example of a reversely zoned magma mixing sequence. Bull. Volcanol. 65, 530–543 (2003)

    ADS  Google Scholar 

  78. 78

    Pallister, J. S. et al. The Chaitén rhyolite lava dome: eruption sequence, lava dome volumes, rapid effusion rates and source of the rhyolite magma. Andean Geol. 40, 277–294 (2013)

    Google Scholar 

  79. 79

    Castro, J. M. & Dingwell, D. B. Rapid ascent of rhyolitic magma at Chaitén volcano, Chile. Nature 461, 780–783 (2009)

    ADS  CAS  PubMed  Google Scholar 

  80. 80

    Folkes, C. B., de Silva, S. L., Wright, H. M. & Cas, R. Geochemical homogeneity of a long-lived, large silicic system; evidence from the Cerro Galán caldera, NW Argentina. Bull. Volcanol. 73, 1455–1486 (2011)

    ADS  Google Scholar 

  81. 81

    Piochi, M. et al. Constraining the recent plumbing system of Vulcano (Aeolian Arc, Italy) by textural, petrological, and fractal analysis: the 1739 A.D. Pietre Cotte lava flow. Geochem. Geophys. Geosyst. 10, Q01009 (2009)

    ADS  Google Scholar 

  82. 82

    Befus, K. S., Zinke, R. W., Jordan, J. S., Manga, M. & Gardner, J. E. Pre-eruptive storage conditions and eruption dynamics of a small rhyolite dome: Douglas Knob, Yellowstone volcanic field, USA. Bull. Volcanol. 76, 808 (2014)

    ADS  Google Scholar 

  83. 83

    Castro, J. M. et al. Storage and eruption of near-liquidus rhyolite magma at Cordon Caulle, Chile. Bull. Volcanol. 75, 702 (2013)

    ADS  Google Scholar 

  84. 84

    Alloway, B. V., Pearce, N. J. G., Villarosa, G., Outes, V. & Moreno, P. I. Multiple melt bodies fed the AD 2011 eruption of Puyehue-Cordón Caulle, Chile. Sci. Rep. 5, 17589 (2015)

    ADS  CAS  PubMed  PubMed Central  Google Scholar 

  85. 85

    Fytikas, M. et al. Volcanology and petrology of volcanic products from the island of Milos and neighbouring islets. J. Volcanol. Geotherm. Res. 28, 297–317 (1986)

    ADS  CAS  Google Scholar 

  86. 86

    Gertisser, R ., Preece, K . & Keller, J. The Plinian Lower Pumice 2 eruption, Santorini, Greece: magma evolution and volatile behaviour. J. Volcanol. Geotherm. Res. 186, 387–406 (2009)

    ADS  CAS  Google Scholar 

  87. 87

    Michaud, V., Clocchiatti, R. & Sbrana, S. The Minoan and post-Minoan eruptions, Santorini (Greece), in the light of melt inclusions: chlorine and sulphur behaviour. J. Volcanol. Geotherm. Res. 99, 195–214 (2000)

    ADS  CAS  Google Scholar 

  88. 88

    Heiken, G. Plinian-type eruptions in the Medicine Lake Highland, California, and the nature of the underlying magma. J. Volcanol. Geotherm. Res. 4, 375–402 (1978)

    ADS  Google Scholar 

  89. 89

    Eichelberger, J. C. Origin of andesite and dacite: evidence of mixing at Glass Mountain in California and at other circum-Pacific volcanoes. Bull. Geol. Soc. Am. 86, 1381–1391 (1975)

    CAS  Google Scholar 

  90. 90

    Foresta Martin, F. et al. New insights into the provenance of the obsidian fragments of the island of Ustica (Palermo, Sicily). Archaeometry 59, 435–454 (2016)

    Google Scholar 

  91. 91

    Rosen, S. A., Tykot, R. H. & Gottesman, M. Long distance trinket trade: Early Bronze Age obsidian from the Negev. J. Archaeol. Sci. 32, 775–784 (2005)

    Google Scholar 

  92. 92

    Shackley, M. S. Geologic origin of the source of Bearhead Rhyolite (Paliza Canyon) obsidian, Jemez Mountains, Northern New Mexico. New Mex. Geol. 38, 52–65 (2016)

    Google Scholar 

  93. 93

    Ulrich, T. & Kamber, B. S. Natural obsidian glass as an external accuracy reference material in laser ablation-inductively coupled plasma-mass spectrometry. Geostand. Geoanal. Res. 37, 169–188 (2013)

    ADS  CAS  Google Scholar 

  94. 94

    Pe-Piper, G. & Moulton, B. Magma evolution in the Pliocene-Pleistocene succession of Kos, South Aegean arc (Greece). Lithos 106, 110–124 (2008)

    ADS  CAS  Google Scholar 

  95. 95

    Dunbar, N. W., Hervig, R. L. & Kyle, P. R. Determination of pre-eruptive H2O, F and Cl contents of silicic magmas using melt inclusions: examples from Taupo volcanic center, New Zealand. Bull. Volcanol. 51, 177–184 (1989)

    ADS  Google Scholar 

  96. 96

    Stokes, S. & Lowe, D. J. Discriminant function analysis of late Quaternary tephras from five volcanoes in New Zealand using glass shard major element chemistry. Quat. Res. 30, 270–283 (1992)

    Google Scholar 

  97. 97

    Bindeman, I. N. & Valley, J. W. Low-δ18O rhyolites from Yellowstone: magmatic evolution based on analyses of zircons and individual phenocrysts. J. Petrol. 42, 1491–1517 (2001)

    ADS  CAS  Google Scholar 

  98. 98

    Chamberlain, K. J., Morgan, D. J. & Wilson, C. J. N. Timescales of mixing and mobilisation in the Bishop Tuff magma body: perspectives from diffusion chronometry. Contrib. Mineral. Petrol. 168, 1034 (2014)

    ADS  Google Scholar 

  99. 99

    Hildreth, W. & Wilson, C. J. N. Compositional zoning of the bishop tuff. J. Petrol. 48, 951–999 (2007)

    ADS  CAS  Google Scholar 

  100. 100

    Watt, S. F. L., Pyle, D. M., Mather, T. A., Martin, R. S. & Matthews, N. E. Fallout and distribution of volcanic ash over Argentina following the May 2008 explosive eruption of Chaitén, Chile. J. Geophys. Res. 114, B04207 (2009)

    ADS  Google Scholar 

  101. 101

    Hammer, J. E., Cashman, K. V., Hoblitt, R. P. & Newman, S. Degassing and microlite crystallization during pre-climactic events of the 1991 eruption of Mt Pinatubo, Philippines. Bull. Volcanol. 60, 355–380 (1999)

    ADS  Google Scholar 

  102. 102

    Leonard, G. S., Cole, J. W., Nairn, I. A. & Self, S. Basalt triggering of the c. AD 1305 Kaharoa rhyolite eruption, Tarawera volcanic complex, New Zealand. J. Volcanol. Geotherm. Res. 115, 461–486 (2002)

    ADS  CAS  Google Scholar 

  103. 103

    Arce, J. L., Cervantes, K. E., Macíias, J. L. & Mora, J. C. The 12.1 ka Middle Toluca Pumice: a dacitic Plinian-subplinian eruption of Nevado de Toluca in Central Mexico. J. Volcanol. Geotherm. Res. 147, 125–143 (2005)

    ADS  CAS  Google Scholar 

  104. 104

    Scaillet, B. & Evans, B. W. The 15 June 1991 eruption of Mount Pinatubo. I. Phase equilibria and pre-eruption P-T-fO2-fH2O conditions of the dacite magma. J. Petrol. 40, 381–411 (1999)

    ADS  CAS  Google Scholar 

  105. 105

    Walter, R. C., Hart, W. K. & Westgate, J. A. Petrogenesis of a basalt-rhyolite tephra from the west-central Afar, Ethiopia. Contrib. Mineral. Petrol. 95, 462–480 (1987)

    ADS  CAS  Google Scholar 

  106. 106

    Selbekk, R. S. & Trønnes, R. G. The 1362 AD Öræfajökull eruption, Iceland: petrology and geochemistry of large-volume homogeneous rhyolite. J. Volcanol. Geotherm. Res. 160, 42–58 (2007)

    ADS  CAS  Google Scholar 

  107. 107

    Palais, J. M. & Sigurdsson, H. Petrologic evidence of volatile emissions from major historic and pre-historic volcanic eruptions. Understanding Clim. Change 52, 31–53 (1989)

    Google Scholar 

  108. 108

    Sharma, K., Self, S., Blake, S., Thordarson, T. & Larsen, G. The AD 1362 Öræfajökull eruption, S.E. Iceland: physical volcanology and volatile release. J. Volcanol. Geotherm. Res. 178, 719–739 (2008)

    ADS  CAS  Google Scholar 

  109. 109

    Macdonald, R. et al. The1875 eruption of Askja volcano, Iceland: combined fractional crystallization and selective contamination in the generation of rhyolitic magma. Mineral. Mag. 51, 183–202 (1987)

    CAS  Google Scholar 

  110. 110

    Gunnarsson, B., Marsh, B. D. & Taylor, H. P. Generation of Icelandic rhyolites: silicic lavas from the Torfajokull central volcano. J. Volcanol. Geotherm. Res. 83, 1–45 (1998)

    ADS  CAS  Google Scholar 

  111. 111

    Tuffen, H. & Castro, J. M. The emplacement of an obsidian dyke through thin ice: Hrafntinnuhryggur, Krafla Iceland. J. Volcanol. Geotherm. Res. 185, 352–366 (2009)

    ADS  CAS  Google Scholar 

  112. 112

    Macías, J. L. et al. A 550-year-old Plinian eruption at El Chichón Volcano, Chiapas, Mexico: explosive volcanism linked to reheating of the magma reservoir. J. Geophys. Res. B 108, ECV3-1–18 (2003)

    Google Scholar 

  113. 113

    Sparks, R. S. J., Wilson, L. & Sigurdsson, H. The pyroclastic deposits of the 1875 eruption of Askja, Iceland. Phil. Trans. R. Soc. Lond. A 299, 242–272 (1981)

    ADS  Google Scholar 

  114. 114

    Baker, P. E., Buckley, F. & Holland, J. G. Petrology and chemistry of Easter Island. Contrib. Mineral. Petrol. 44, 85–100 (1974)

    ADS  CAS  Google Scholar 

  115. 115

    Edmonds, M., Pyle, D. & Oppenheimer, C. A model for degassing at the Soufriere Hill Volcano, Montserrat, West Indies, based on geochemical data. Earth Planet. Sci. Lett. 186, 159–173 (2001)

    ADS  CAS  Google Scholar 

  116. 116

    Rango, T., Colombani, N., Mastrocicco, M., Bianchini, G. & Beccaluva, L. Column elution experiments on volcanic ash: geochemical implications for the main Ethiopian rift waters. Wat. Air Soil Pollut. 208, 221–233 (2010)

    ADS  CAS  Google Scholar 

  117. 117

    Manley, C. R. Morphology and maturation of melt inclusions in quartz phenocrysts from the Badlands rhyolite lava flow, southwestern Idaho. Am. Mineral. 81, 158–168 (1996)

    ADS  CAS  Google Scholar 

  118. 118

    Higgins, M. W. Petrology of Newberry volcano, Central Oregon. Bull. Geol. Soc. Am. 84, 455–488 (1973)

    CAS  Google Scholar 

  119. 119

    Stevenson, R. J., Hodder, A. P. W. & Briggs, R. M. Rheological estimates of rhyolite lava flows from the Okataina volcanic centre, New Zealand. N. Z. J. Geol. Geophys. 37, 211 (1994)

    CAS  Google Scholar 

  120. 120

    Kolzenburg, S., Russell, J. K. & Kennedy, L. A. Energetics of glass fragmentation: experiments on synthetic and natural glasses. Geochem. Geophys. Geosyst. 14, 4936–4951 (2013)

    ADS  Google Scholar 

  121. 121

    Albert, P. G. et al. Marine-continental tephra correlations: Volcanic glass geochemistry from the Marsili Basin and the Aeolian Islands, Southern Tyrrhenian Sea, Italy. J. Volcanol. Geotherm. Res. 229, 74–94 (2012)

    ADS  Google Scholar 

  122. 122

    Singer, B. S. et al. Eruptive history, geochronology, and magmatic evolution of the Puyehue-Cordón Caulle volcanic complex, Chile. Bull. Geol. Soc. Am. 120, 599–618 (2008)

    CAS  Google Scholar 

  123. 123

    Kuehn, S. C. & Foit, F. F. Jr. Silicic tephras of Newberry Volcano. In What’s New at Newberry Volcano, Oregon: Guidebook for the Friends of the Pleistocene Eighth Annual Pacific Northwest Cell Field Trip (eds Jensen, R. A. & Chitwood, L. A. ) 135–163 (2000)

  124. 124

    Schipper, C. I. et al. Cristobalite in the 2011–2012 Cordón Caulle eruption (Chile). Bull. Volcanol. 77, 34 (2015)

    ADS  Google Scholar 

  125. 125

    Stevenson, R. J., Dingwell, D. B., Webb, S. L. & Bagdassarov, N. S. The equivalence of enthalpy and shear stress relaxation in rhyolitic obsidian and quantification of the liquid-glass transition in volcanic process. J. Volcanol. Geotherm. Res. 68, 297–306 (1995)

    ADS  CAS  Google Scholar 

Download references


This study was supported by a European Research Council Advanced Grant to D.B.D. on ‘Explosive volcanism in the Earth system: experimental insights’ (EVOKES, grant number 247076). E.D. was supported by DFG grant ED 1757/1-1. We thank M. Kaliwoda and R. Hochleitner for Raman measurements at the Mineralogical State Collection Munich (SNSB). In addition, we thank H. W. Lohringer, D. Mueller, and A. Wimmer for assistance during the sample preparation, microprobe analyses and iron titration. Scientific discussions with M. Diez, D. Morgavi and C. M. P. De Campos were greatly appreciated. D.D.G. thanks C. Chelle-Michou and J. Lourenço for their assistance with R programming and H. Mader for comments and suggestions.

Author information




D.D.G. conceptualized the original idea, performed the low-temperature viscosity, calorimetric, Raman spectroscopic measurements, and Rhyolite-MELTS simulations. D.D.G., S.K. and S.W. synthetized the samples and performed the high-temperature viscosity measurements, wrote the original draft paper, finalized the figures, and compiled the database of chemical compositions. E.D. performed the magnetic measurements, wrote the associated text and finalized the figures. D.R.N, K.U.H. and D.B.D. advised on the optimal experimental methods and contributed to producing a final manuscript.

Corresponding author

Correspondence to D. Di Genova.

Ethics declarations

Competing interests

The authors declare no competing financial interests.

Additional information

Reviewer Information Nature thanks M. Manga and Y. Zhang for their contribution to the peer review of this work.

Publisher's note: Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.

Extended data figures and tables

Extended Data Figure 1 High- and low-temperature viscosity measurements of samples investigated in this study.

See Extended Data Table 2 for experimental data and Extended Data Table 1 for sample chemistry.

Extended Data Figure 2 Comparison between measured and calculated viscosities of all samples at 850 °C.

The solid black line is a 1:1 reference line. Symbols are values predicted by the HZ11 (red) and GRD12 (black) models. The red and black dotted lines show linear fits to the model results. The two models generally agree, with the exception of samples J, C and F, which are described better by the HZ model than by the GRD model.

Extended Data Figure 3 Raman spectra of samples F, J and L.

These samples show increasing FeO content. Spectra were acquired before the low-temperature viscosity measurements. The peak at about 670 cm−1 (sample L) indicates the magnetite peak. The FeO content (in wt%) is given in parentheses in the key; see Extended Data Table 1.

Extended Data Figure 4 Magnetic-hysteresis analyses of samples F, J, and L.

These samples show increasing FeO content. (See Extended Data Table 1 for sample chemistry.) a, Hysteresis loops of six sub-samples of samples F and J. M is magnetization. b, Hysteresis loops of ten sub-samples of sample L. c, Hysteresis as in b corrected for a paramagnetic slope calculated using the linear portion of every loop for fields >1.25 T and normalized for the saturation magnetization Ms. The red vertical band indicates all values of B90, calculated for every loop as the field where M/Ms = 0.9. The B90 values are used in d to estimate the size of the magnetic particles as described in Methods.

Extended Data Figure 5 Differential thermal analysis data for samples F, J and L.

These samples show increasing FeO content at a heating or cooling rate of 10 °C min−1 under an argon atmosphere. (FeO content in wt% is given in parentheses in the key; see Extended Data Table 1.) The temperatures given are . Thin lines represent the first heating scans; thick lines represent the second heating scan. The nanolite-bearing sample (L) shows two endothermic peaks during the first heating scan, revealing two distinct amorphous domains (nanolite-free and nanolite-bearing). The lower glass transition temperature (peak at 692.4 °C) represents the nanolite-free amorphous domain. Except for the topmost curve, the curves were shifted along the y axis for clarity.

Extended Data Figure 6 Total alkali versus silica diagram of all effusive and explosive samples plotted in Fig. 4.

Note that the classic total alkali versus silica classification of these samples does not allow us to distinguish between explosive and effusive behaviour. Only through the newly developed RAI can these populations be clearly separated (Fig. 4).

Extended Data Figure 7 Calculated viscosities at the measured Tgpeak.

Data reported in Extended Data Table 1 after ref. 125 (see Methods for further details). The viscosity remains constant over the investigated range of silica content with the exception of sample L. This sample exhibits an extremely high viscosity owing to the iron depletion effect (see main text). The error in the viscosity measurements was estimated to be ±0.05 logarithmic units (see Methods).

Extended Data Table 1 Chemical composition and iron oxidation state of all glasses (in wt%)
Extended Data Table 2 Viscosity measurements of all samples

Related audio

Supplementary information

Supplementary Data

This file contains Supplementary Table 1. (XLSX 93 kb)

Supplementary Data

This file contains Supplementary Table 2. (XLSX 172 kb)

PowerPoint slides

Rights and permissions

Reprints and Permissions

About this article

Verify currency and authenticity via CrossMark

Cite this article

Di Genova, D., Kolzenburg, S., Wiesmaier, S. et al. A compositional tipping point governing the mobilization and eruption style of rhyolitic magma. Nature 552, 235–238 (2017).

Download citation

Further reading


By submitting a comment you agree to abide by our Terms and Community Guidelines. If you find something abusive or that does not comply with our terms or guidelines please flag it as inappropriate.


Quick links

Nature Briefing

Sign up for the Nature Briefing newsletter — what matters in science, free to your inbox daily.

Get the most important science stories of the day, free in your inbox. Sign up for Nature Briefing