Authors: Thouret, J.C.; Ramírez, J.C.; Gibert-Malengreau, B.; Vargas, C.A.; Naranjo, J.L.; Vandemeulebrouck, J.; Valla, F.; Funk, M.

Source: Annals of Glaciology, Volume 45, Number 1, October 2007 , pp. 115-127(13)

Publisher: International Glaciological Society

Abstract:

The catastrophic lahars triggered by the 13 November 1985 eruption of the ice-clad Nevado del Ruiz volcano, Colombia, demonstrate that the interaction of hot pyroclasts with snow and ice can release 30-50 million m³ of meltwater in 30-90 minutes. The 1985 eruption caused a 16% loss in area and a 9% loss in volume of snow, firn and ice. Turbulent pyroclastic density currents mechanically mixed with snow and produced meltwater at a rate of 0.5-1.6 mm s⁻¹. Laboratory experiments suggest that turbulent, fluidized pyroclastic density currents exert mechanical and thermal scour, thereby efficiently transferring heat from hot pyroclasts to snow. Ice cap loss at Nevado del Ruiz continued between 1985 and 2000, representing a ∼52% decline in area and a ∼30% fall in volume. Ice 60-190 m thick caps the east and southeast summit plateau, whereas an ice field < 30 m thick and devoid of snow is retreating on the north, northeast and west edges. This asymmetrical distribution of ice reflects combined long-term effects of the 1985 eruption and of the post-1985 ice cap retreat. Should volcanic activity resume, steep-sided glaciers can fail and pyroclastic flows and surges can sweep the snowpack and generate mixed avalanches and lahars. Although the potential source of meltwater has decreased since 1985, extensive debris at the ice cap margins can be incorporated to future lahars.

Document Type: Research article

DOI: http://dx.doi.org/10.3189/172756407782282589

Publication date: 2007-10-01

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• The Annals of Glaciology is a peer-reviewed, thematic journal published 2 to 4 times a year by the International Glaciological Society (IGS). Publication frequency is determined and volume/issue numbers assigned by the IGS Council on a year-to-year basis and with a lead time of 3 to 4 years. The Annals of Glaciology is included in the ISI Science Citation Index from volume 50, number 50 onwards.

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