skip all navigation
skip banner links
skip primary navigation

Volcanic record of the West Antarctic Ice Sheet


There is intense scientific interest in the history, dynamics and future of the West Antarctic Ice Sheet because it is the world's only remaining marine ice sheet and is considered by many to be inherently unstable and prone to catastrophic collapse and melting (e.g. Hollin, 1962; Hughes, 1973; Mercer, 1978; MacAyeal, 1992; Binschadler, 1995). If the WAIS were to collapse, global sea level would rise by 6 meters. The stability of the WAIS is a function of some balance between external sea level and climate and internal controls of marine ice-sheet and ice-stream dynamics (Alley and Whillans, 1991; MacAyeal, 1992; Bentley, 1997). Ultimately, accurate predictions of future ice-sheet stability and behavior will require numerical models, based on an understanding of the physical dynamics of the present ice sheet and tested by geological constraints on past ice-sheet configurations.

One approach to providing geological constraints on the age of the West Antarctic Ice Sheet is through direct dating and geochemical correlation of englacial tephra layers within the ice sheet.  The stratigraphy and morphology of many West Antarctic englacial tephra layers suggests that the layers were deposited on snow at the time of the volcanic eruption, and were incorporated into the ice with little reworking or mixing, indicating that the age of the tephra layer is truly representative of the age of the surrounding ice.

Several West Antarctic englacial tephra site exist. Mt. Waesche is located at between 1900-2000 meters elevation in a blue ice field on the south side of the volcano, and displays a complex, deformed stratigraphy. A second important site, Mt. Moulton, is located at 2800 meters elevation of the summit ridge of the extinct chain or The tephra layers at Mt. Waesche are dominantly either coarse and basanitic, probably of local derivation, or fine and trachytic, mainly derived from West Antarctic volcanoes Mt. Berlin or Mt. Takahe. Several new, locally-derived englacial tephra layers were found at Mt. Takahe during the 1998/99 field season.  Although displaying boudin-shaped features, the thicker tephra layers at Mt. Waesche appear relatively undeformed, whereas some of the thinner, intercalated layers are strongly isoclinally folded. Three tephra layers at Mt. Waesche have been geochemically correlated with layers found at Mt. Moulton. The correlative layers have ages of between 15 and 27 ka, 27±2 ka, and between 106 and 119 ka, consistent with apparent stratigraphic order.  A single tephra layer at Mt. Waesche has been directly dated using 40Ar/39Ar, and yields an apparent age of 117±7 ka. Although there are tephra layers that seem stratigraphically below the 117±7 ka layer, they appear to represent an overturned repetition of some part of the upper section. Hence, there is no evidence for ice significantly older

More information about the Mt. Moulton site is available on a separate page.


  1. Dunbar, N.W., 2003, From Africa to Antarctica: Adventures in Living and Working in Remote Deserts: Women in Polar Regions Meeting, Columbus OH, Oct. 9-10.
  2. Dunbar, N. W., R. P. Esser, W. C. McIntosh, G. A. Zielinski, and P. R. Kyle, 1998. Englacial tephra layers in West Antarctica: Implications for the history of the West Antarctic Ice Sheet. 4th Annual West Antarctic Ice Sheet Workshop. ABSTRACT
  3. Dunbar, N. W., R. P. Esser, and W. C. McIntosh, 1998, Englacial tephra layers in West Antarctica: Implications for the history of the West Antarctic Ice Sheet: Antarctic Journal of the U.S., v. XXXIII- Review 1998.
  4. Dunbar, N. W., R. P. Esser, W. C. McIntosh, P. R. Kyle, and G. A. Zielinski, 1997, Englacial tephra layers in the East and West Antarctic ice sheets: Indicators of glacial flow patterns on ice sheet margins: EOS, Transactions of the American Geophysical Union, v. 78, p. F250 ABSTRACT.
  5. Dunbar, N.W., Kurbatov, A., Zielinski, G., McIntosh, W.C., Price, P.B., and Bay, R.C., 2003, Volcanic ash records in the Siple Dome Ice Core: West Antarctic Ice Shelf 2003 Research Meeting.
  6. Dunbar, N.W., Kurbatov, A., Zielinski, G., McIntosh, W.C., Price, P.B., and Bay, R.C., 2004, Volcanic ash records in the Siple Dome Ice Core: Siple Dome Principal Investigator Meeting, Reno, NV, Feb. 24, 2003. Download Powerpoint
  7. Dunbar, N. W., W. McIntosh, R. Esser, T. Wilch, and G. Zielinski, 1998, Direct dating and geochemical correlations of englacial tephra layers at two sites in West Antarctica: Proceedings of the West Antarctic Ice Sheet Meeting Chapman Conference, Sept. 13-18, 1998, p. 18-19. ABSTRACT
  8. Dunbar, N.W., McIntosh, W.C., and Esser, R.P., 2008, Physical setting and tephrochronology of the summit caldera ice record at Mount Moulton, West Antarctica: Geological Society of America Bulletin, v. 120, p. 796-812. See abstact
  9. Dunbar, N.W., McIntosh, W.C., V., K.A., and Wilch, T.I., 2007, Integrated tephrochronology of the West Antarctic region; implications for a potential tephra record in the West Antarctic ice sheet (WAIS) Divide ice core, in Cooper, A., and Raymond, C., eds., Tenth international symposium on Antarctic earth sciences; Antarctica; a keystone in a changing world, U. S. Geological Survey. Extended abstract
  10. DUNBAR, N., G. ZIELINSKI, and D. VOISINS, 2003, Tephra layers in the Siple and Taylor Dome Ice Cores, Antarctica: Correlations and Sources. Journal of Geophysical Research,108, 2374-2385. See abstract
  11. ESSER, R., KYLE, P.R. and DUNBAR, N., 1999. 40Ar/39Ar chronology of the Pleiades Volcanic Centre, Northern Victoria Land, Antarctica: A potential source of late-pleistocene englacial tephra layers, 8th International Symposium on Antarctic Earth Science, Victoria University of Wellington, New Zealand, pp. 100.  
  12. HAWLEY, R. L., E. D. WADDINGTON, D. L. MORSE, N. W. DUNBAR, and G. A. ZIELINSKI, 2002, Dating firn cores by vertical strain measurements: Journal of Glaciology, V. 48, p410-406
  13. Kurbatov, A., Dunbar, N.W., Zielinski, G., Mayewski, P., Curran, M., Morgan, V., and van Ommen, T., 2003, Evaluation of Tephra Found in the Law Dome Ice Core, East Antarctica: EOS Transactions of the American Geophysical Union.
  14. Kurbatov, A.V., Zielinski, G.A., Dunbar, N.W., Mayewski, P.A., Meyerson, E.A., Sneed, S.B., and Taylor, K.C., 2006, A 12,000 year record of explosive volcanism in the Siple Dome Ice Core, West Antarctica: Journal of Geophysical Research-Atmospheres, v. 111, p. D12307. See abstract
  15. McIntosh, W.C. and Wilch, T.I., 1995b. Late Pleistocene (223-125 ka) Plinian eruptions in Marie Byrd Land: Potential time horizons in West Antarctic ice cores. VII International Symposium of Antarctic Earth Sciences, Siena, Italy. P. 261.
  16. Wilch, T.I., McIntosh W.C., and Dunbar, N.W., (1999) Late Quaternary volcanic activity in Marie Byrd Land: potential 40Ar/39Ar -dated time horizons in future West Antarctic ice and marine cores, Geol. Soc. Am. Bull., 111, 1563-1580. ABSTRACT
  17. ZIELINSKI., N. DUNBAR, A. KURBATOV, AND D. VOISINS, 2001, Holocene volcanic records in the Siple Dome Ice Core: EOS, Transactions of the American Geophysical Union, v. 82, p. F1408.
  18. Zielinksi, G., and N. Dunbar, 1998, Volcanic Record from the Siple and Taylor Domes, Antarctica: WAISCORES Meeting, Sept. 10, 1998.

Any opinions, findings and conclusions or recomendations expressed in this material are those of the author(s) and do not necessarily reflect the views of the National Science Foundation (NSF)

Return to HOME