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Ice–volcano interaction of the 1996 Gjálp subglacial eruption, Vatnajökull, Iceland


Volcanic eruptions under glaciers can cause dangerous floods and lahars1,2,3 and create hyaloclastite (fragmented glassy rock) mountains4,5,6,7,8. But processes such as the rate of heat transfer between ice and magma, edifice formation, and the response of the surrounding glacier are poorly understood, because of the lack of data. Here we present observations from the fissure eruption at Vatnajökull ice cap, Iceland, in October 1996. In the 13 days of the eruption 3 km3 of ice were melted and the erupted magma fragmented into glass forming a hyaloclastite ridge 6–7 km long and 200–300 m high under 500–750 m of ice. Meltwater of temperatures of 15–20 °C flowed along a narrow channel at the glacier bed into the Grímsvötn subglacial lake for five weeks, before draining in a sudden flood, or jökulhlaup. Subsidence and crevassing of the ice cap occurred over the eruptive fissure and the meltwater path, whereas elsewhere the glacier surface remained intact, suggesting that subglacial eruptions do not trigger widespread basal sliding in warm-based glaciers.

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Figure 1: Map of the northwest part of Vatnajökull showing the location of the 1996 eruptive fissure (solid line, in box), midway between the s.
Figure 2: Top, development of ice cauldrons at the eruption site.
Figure 3: Ice melting and heat transfer rate from 1 October 1996 until 3 January 1997.
Figure 4: Schematic sections showing how the eruption penetrated the ice cap, through a narrow chimney through the ice.

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  1. Major, J. J. & Newhall, C. H. Snow and ice perturbation during historical volcanic eruptions and the formation of lahars and floods. Bull. Volc. 15, 1–27 (1989).

    ADS  Google Scholar 

  2. Lowe, D. R. et al. Lahars initiated by the 13 November 1985 eruption of Nevado del Ruiz, Colombia. Nature 324, 51–53 (1986).

    Article  ADS  Google Scholar 

  3. Thorarinsson, S. Vötnin strið (Menningarsjóður, Reykjavík, (1974)).

    Google Scholar 

  4. LeMasurier, W. E. in Volcanoes of the Antarctic Plate and Southern Oceans (eds LeMasurier, W. E. & Thomson, J. W.) 1–17 (AGU, Antarctic Research Series 48, (1990)).

    Google Scholar 

  5. Mathews, W. H. “Tuyas”, flat-topped volcanoes in northern British Columbia. Am. J. Sci. 245, 560–570 (1947).

    Article  ADS  Google Scholar 

  6. Kjartansson, G. Árnesingasaga (Árnesingafélagið, Reykjavík, (1943)).

    Google Scholar 

  7. van Bemmelen, R. W. et al. Tablemountains of Northern Iceland (Brill, Leiden, (1955)).

    Google Scholar 

  8. Jones, J. G. Intraglacial volcanoes of the Laugarvatn region, south-west Iceland—I. Q. J. Geol. Soc. Lond. 124, 197–211 (1969).

    Article  Google Scholar 

  9. Smellie, J. L. & Skilling, I. P. Products of subglacial volcanic eruptions under different ice thicknesses: two examples from Antarctica. Sedim. Geol. 91, 115–129 (1994).

    Article  ADS  Google Scholar 

  10. Werner, R., Schminke, H. U. & Sigvaldason, G. Anew model for the evolution of table mountains: volcanological and petrological evidence from Herdubreid and Herdubreidartögl volcanoes (Iceland). Geol. Rundsch. 85, 390–397 (1996).

    Article  ADS  CAS  Google Scholar 

  11. Jakobsson, S. P. On the consolidation and palagonitization of the tephra of the Surtsey volcanic island, Iceland. Surtsey Research Progress Rep. VI, 121–128 (Surtsey Research Society, Reykjavik, (1972)).

    Google Scholar 

  12. Jakobsson, S. P. Environmental factors controlling the palagonitization of the Surtsey tephra, Iceland. Bull. Geol. Soc. Denmark 27, 91–105 (1978).

    Google Scholar 

  13. Jakobsson, S. P. & Moore, J. G. Hydrothermal minerals and alteration rates at Surtsey volcano, Iceland. Geol. Soc. Am. Bull. 97, 648–659 (1986).

    Article  ADS  CAS  Google Scholar 

  14. Einarsson, P. et al. Center of the Iceland hotspot experiences volcanic unrest. Eos 78, 374–375 (1997).

    Article  ADS  Google Scholar 

  15. Björnsson, H. Subglacial water reservoirs, jökulhlaups and volcanic eruptions. Jökull 25, 1–14 (1975).

    Google Scholar 

  16. Yokoyama, I. Energetics in active volcanos. Tokyo Univ. Earthq. Res. Inst. Bull. 35, 75–97 (1957).

    Google Scholar 

  17. Shimozuru, D. Discussion on the energy partition of volcanic eruption. Bull. Volcanol. 32, 383–394 (1968).

    Article  ADS  Google Scholar 

  18. Charmichael, I. S. E., Turner, F. J. & Verhogen, J. Igneous Petrology 128–130 (McGraw-Hill, New York, (1974)).

    Google Scholar 

  19. Moore, J. G. Mechanism of formation of pillow lava. Am. Sci. 63, 269–277 (1975).

    ADS  Google Scholar 

  20. Bacon, C. R. High temperature heat content and heat capacity of silicate glasses: Experimental determination and a model for calculation. Am. J. Sci. 277, 109–135 (1977).

    Article  ADS  CAS  Google Scholar 

  21. Oddson, B. Rock quality designation and drilling rate correlated with lithology and degree of alteration in volcanic rocks from the 1979 Surtsey drill hole. Surtsey Research Progress Rep. IX, 94–97 (Surtsey Research Society, Reykjavik, (1982)).

    Google Scholar 

  22. Björnsson, H. Hydrology of ice caps in volcanic regions. Soc. Sci. Islandica 45, (Visindafélag Íslendinga, Reykjavik, (1988)).

  23. Gudmundsson, M. T. & Björnsson, H. Eruptions in Grímsvötn, Vatnajökull, Iceland, 1934–1991. Jökull 41, 21–45 (1991).

    Google Scholar 

  24. Blankenship, D. D. et al. Active volcanism beneath the West Antarctic ice sheet and implications for ice-sheet stability. Nature 361, 526–529 (1993).

    Article  ADS  Google Scholar 

  25. Kamb, B. et al. Glacier surge mechanism: 1982–1983 surge of Variegated Glacier, Alaska. Science 227, 469–479 (1985).

    Article  ADS  CAS  Google Scholar 

  26. Björnsson, H. & Einarsson, P. Volcanoes beneath Vatnajökull, Iceland: Evidence from radio echo-sounding, earthquakes and jökulhlaups. Jökull 40, 147–168 (1990).

    Google Scholar 

  27. Björnsson, H., Björnsson, S. & Sigurgeirssoon, Th. Penetration of water into hot rock boundaries of magma at Grímsvötn. Nature 295, 580–581 (1982).

    Article  ADS  Google Scholar 

  28. Gudmundsson, M. T., Björnsson, H. & Pálsson, F. Changes in jökulhlaup sizes in Grímsvötn, Vatnajökull, Iceland, 1934–91, deduced from in-situ measurements of subglacial lake volume. J. Glaciol. 41, 263–272 (1995).

    Article  Google Scholar 

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We thank the Iceland Civil Aviation Authority, especially chief pilot S. Gudbjörnsson, the crews of the helicopters of the Icelandic Coast Guard and J. K. Björnsson of the Iceland Helicopter Service for enthusiastic cooperation during the monitoring of the eruption. F. Pálsson, H. Halldórsson, K. Pálsson, S. Jónsson and P. Símonarson took part in the GPS measurements and members of the Iceland Glaciological Society assisted in fieldwork in June 1997. The figures were prepared by Th. Högnadóttir. A review by D. Blankenship improved the paper.

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Correspondence to Magnú T. Gudmundsson.

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Gudmundsson, M., Sigmundsson, F. & Björnsson, H. Ice–volcano interaction of the 1996 Gjálp subglacial eruption, Vatnajökull, Iceland. Nature 389, 954–957 (1997).

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