Bulletin of Volcanology

, Volume 70, Issue 4, pp 495–506 | Cite as

Imprints of sub-glacial volcanic activity on a glacier surface—SAR study of Katla volcano, Iceland

  • K. ScharrerEmail author
  • O. Spieler
  • Ch. Mayer
  • U. Münzer
Research Article


The Katla central volcano, covered by the fourth largest Icelandic glacier Mýrdalsjökull, is among the most dangerous and active volcanoes in Iceland. Due to the ice cover, several indicators of its volcanic activity can only be identified indirectly. We analysed a total of 30 synthetic aperture radar (SAR) images with special focus on identifying circular and linear depressions in the glacier surface. Such features are indicative of sub-glacial geothermal heat sources and the adjacent sub-glacial tunnel (melt water drainage) system. The time series comprises images from five different SAR sensors (ERS-1, ERS-2, JERS-1/SAR, RADARSAT and ENVISAT-ASAR) covering a time period of 12 years, starting in 1994. Individual SAR scenes only partly map the glacier surface morphology due to the environmental influences on the SAR backscatter intensity. Thus, only surface features detectable in several SAR scenes at the same location were considered and merged to form an overall picture of the surface morphology of Mýrdalsjökull and its modification by sub-glacial volcanic activity between 1994 and 2006. Twenty permanent and 4 semi-permanent ice cauldrons could be identified on the surface of Mýrdalsjökull indicating geothermally active areas in the underlying caldera. An analysis of their size was not possible due to the indistinct outline in the SAR images. The spatial distribution of the geothermally active areas led to a new, piecemeal caldera model of Katla volcano. All cauldrons are connected to tunnel systems for melt water drainage. More than 100 km of the sub-glacial drainage system could be identified under the Mýrdalsjökull in the SAR time series. It has been found that the tunnel systems are not in agreement with estimated water divides. Our results allow improved assessment of areas of potential Jökulhlaup hazard accompanying a sub-glacial eruption.


SAR remote sensing Ice–volcano interactions Sub-glacial drainage system Caldera formation Iceland Mýrdalsjökull Katla 



We would like to thank ESA, NASDA and CSA for the provision of the SAR data in the course of the following projects: ENVISAT ID 142, ESA; ERS AO.2 D116, ESA; JERS-1 ID J-0410, NASDA; RADARSAT ADRO #517, CSA. This research was made possible by the Bavarian Research Foundation (DPA 37/04). Sincere thanks are given to this institution.

This paper was improved substantially following the comments of the reviewers P. Mouginis-Mark and H. Björnsson.


  1. Benn DJ, Evans DJA (1998) Glaciers and glaciation. Arnold, LondonGoogle Scholar
  2. Björnsson H (1975) Subglacial water reservoirs, Jökulhlaups and volcanic eruptions. Jökull 25:1–15Google Scholar
  3. Björnsson H (1988) Hydrology of ice caps in volcanic regions. Societas Scientiarium Islandica 45:1–139Google Scholar
  4. Björnsson H (2002) Subglacial lakes and Jökulhlaups in Iceland. Global Planet Change 35:255–271CrossRefGoogle Scholar
  5. Björnsson H, Pálsson F, Gudmundsson MT (2000) Surface and bedrock topography of the Mýrdalsjökull ice cap, Iceland: the Katla caldera, eruption sites and routes of Jökulhlaups. Jökull 49:29–46Google Scholar
  6. Björnsson H, Rott H, Gudmundsson S, Fischer A, Siegel A, Gudmundsson MT (2001) Glacier–volcano interaction deduced by SAR interferometry. J Glaciol 47:58–70CrossRefGoogle Scholar
  7. Björnsson H, Pálsson F, Sigurdsson O, Flowers GE (2003) Surges of glaciers in Iceland. Ann Glaciol 36:82–90CrossRefGoogle Scholar
  8. Dehn J, Dean K, Engle K (2000) Thermal monitoring of North Pacific volcanoes from space. Geology 28:755–758CrossRefGoogle Scholar
  9. Einarsson P, Brandsdóttir B (2000) Earthquakes in the Mýrdalsjökull area, Iceland, 1978–1985: seasonal correlation and connection with volcanoes. Jökull 49:59–74Google Scholar
  10. Gao J, Yansui L (2001) Application of remote sensing, GIS and GPS in glaciology: a review. Prog Phys Geogr 25:520–540Google Scholar
  11. Gudmundsson GB, Stefansson R (2007) Seismicity beneathMýrdalsjökull and Eyjafjallajökull ice caps, Iceland. Ann Glaciol 45 (in press)Google Scholar
  12. Gudmundsson MT, Högnadóttir T, Kristinsson AB, Gudbjörnsson S (2007) Geothermal activity in the subglacial Katla caldera, Iceland, 1999–2005, studied with radar altimetry. Ann Glaciol 45:66–72CrossRefGoogle Scholar
  13. Harris AJL, Flynn LP, Keszthelyi L, Mouginis-Mark PJ, Rowland SK, Resing JA (1998) Calculation of lava effusion rates from Landsat TM data. Bull Volcanol 60:52–71CrossRefGoogle Scholar
  14. Henderson FM, Lewis AJ (eds) (1998) Principles and application of imaging radar: manual of remote sensing, 3rd edn., vol. 2. Wiley, New YorkGoogle Scholar
  15. Jakobsson SP (1979) Petrology of recent basalts of the eastern volcanic zone, Iceland. Acta Nat Isl 26:1–103Google Scholar
  16. Jaenicke J, Mayer Ch, Scharrer K, Münzer U, Gudmundsson Á (2006) The use of remote sensing data for mass balance studies at Mýrdalsjökull ice cap, Iceland. J Glaciol 52:565–573CrossRefGoogle Scholar
  17. Kjaer KH, Krüger J, van der Meer JJM (2003) What causes till thickness to change over distance? Answers from Mýrdalsjökull, Iceland. Quat Sci Rev 22:1687–1700CrossRefGoogle Scholar
  18. König M, Winther JG, Isaksson E (2001) Measuring snow and glacier ice properties from satellite. Rev Geophys 39:1–27CrossRefGoogle Scholar
  19. Kristmannsdóttir H, Snorrason A., Gislason SR, Haraldsson H, Gunnarsson A, Hauksdottir S, Elefsen SO (2002) Geochemical warning for subglacial eruptions—background and history. In: Snorrason Á, Finnsdóttir HP, Moss ME (eds) The extremes of the extremes: extraordinary floods. Proc. Reykjavík, Iceland Symp. July 2000. IAHS Publ 271:231–236Google Scholar
  20. Lacasse C, Sigurdsson H, Carey SN, Jóhannesson H, Thomas LE, Rogers NW (2006) Bimodal volcanism at the Katla subglacial caldera, Iceland: insight into the geochemistry and petrogenesis of rhyolitic magmas. Bull Volcanol 69:373–399. DOI  10.1007/s00445-006-0082-5 Google Scholar
  21. Larsen G (2000) Holocene eruptions within the Katla volcanic system, south Iceland: characteristics and environmental impact. Jökull 49:1–28Google Scholar
  22. Lipman PW (1997) Subsidence of ash-flow calderas: relation to caldera size and magma-chamber geometry. Bull Volcanol 59:198–218Google Scholar
  23. Lombardo V, Buongiorno MF, Pieri D, Merucci L (2004) Differences in Landsat TM derived lava flow thermal structures during summit and flank eruption at Mount Etna. J Volcanol Geotherm Res 134:15–34CrossRefGoogle Scholar
  24. Malin MC, Evans DL, Elachi C (1978) Imaging radar observations of Askja Caldera, Iceland. Geophys Res Lett 5:931–934Google Scholar
  25. McDonough M, Martin-Kaye PHA (1984) Radargeologic interpretation of Seasat imagery of Iceland. Int J Remote Sens 5:433–450CrossRefGoogle Scholar
  26. Molnia BF, Jones JE (1989) View through ice: are unusual air-borne radar backscatter features from the surface of the Malaspina Glacier, Alaska, expressions of subglacial morphology? EOS Trans AGU 70:701–710CrossRefGoogle Scholar
  27. Molnia BF, Jones JE (1990) Radar remote sensing of glacial features, Malaspina Glacier, Alaska. Am Assoc Pet Geol Bull 74:723Google Scholar
  28. Näslund JO, Hassinen S (1996) Supraglacial sediment accumulations and large englacial water conduits at high elevations in Mýrdalsjökull, Iceland. J Glaciol 42:190–192Google Scholar
  29. Nye JF (1976) Water flow in glaciers: Jökulhlaups, tunnels and veins. J Glaciol 76:181–207Google Scholar
  30. Oppenheimer C (1991) Lava flow cooling estimated from Landsat Thematic Mapper infrared data: the Lonquimay eruption (Chile, 1989). J Geophys Res 96:21865–21878CrossRefGoogle Scholar
  31. Roberts MJ (2005) Jökulhlaups: a reassessment of floodwater flow through glaciers. Rev Geophys 43:RG1002. DOI  10.1029/2003RG000147
  32. Röthlisberger H (1972) Water pressure in intra- and subglacial channels. J Glaciol 62:177–203Google Scholar
  33. Scharrer K, Mayer Ch, Nagler T, Münzer U, Gudmundsson Á (2007) Effects of ash-layers of the 2004 Grímsvötn eruption on SAR backscatter in the accumulation area of Vatnajökull. Ann Glaciol 45:189–196Google Scholar
  34. Sigurdsson O, Zóphoníasson S, Ísleifsson E (2000) The Jökulhlaup from Sólheimajökull, July 18th 1999. Jökull 49:60–75Google Scholar
  35. Soosalu H, Jónsdóttir K, Einarsson P (2006) Seismicity crisis at the Katla volcano, Iceland—signs of a cryptodome? J Volcanol Geotherm Res 153:177–186CrossRefGoogle Scholar
  36. Sturkell E, Sigmundsson F, Einarsson P (2003) Recent unrest and magma movements at Eyjafjallajökull and Katla volcanoes, Iceland. J Geophys Res 108:2369. DOI  10.1029/2001JB000917 Google Scholar
  37. Sturm M, Benson CS (1985) A history of Jökulhlaups from Strandline Lake, Alaska, U.S.A. J Glaciol 31:272–280Google Scholar
  38. Tómasson H (1996) The Jökulhlaup from Katla in 1918. Ann Glaciol 22:249–254Google Scholar
  39. Ulaby FT, Moore RK, Fung AK (1986) Microwave remote sensing active and passive, vol. III. Addison-Wesley, ReadingGoogle Scholar
  40. University of Iceland (2006) Katla monitoring. Cited on 03 Dec 2006
  41. Wingham DJ, Siegert MJ, Shepherd A, Muir AS (2006) Rapid discharge connects Antarctic subglacial lakes. Nature 440:1033–1036. DOI  10.1038/nature04660 CrossRefGoogle Scholar

Copyright information

© Springer-Verlag 2007

Authors and Affiliations

  • K. Scharrer
    • 1
    Email author
  • O. Spieler
    • 2
  • Ch. Mayer
    • 3
  • U. Münzer
    • 1
  1. 1.Section Geology, Department of Earth and Environmental SciencesLudwig-Maximilians-UniversityMunichGermany
  2. 2.Section Mineralogy, Petrology and Geochemistry, Department of Earth and Environmental SciencesLudwig-Maximilians-UniversityMunichGermany
  3. 3.Bavarian Academy of Sciences and Humanities, Commission for GlaciologyMunichGermany

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