Nature 375, 477 - 479 (08 June 1995); doi:10.1038/375477a0

Ice in the 1994 Rabaul eruption cloud: implications for volcano hazard and atmospheric effects

W. I. Rose^*, D. J. Delene^*, D. J.  Schneider^*, G. J. S. Bluth^*, A. J. Krueger^†, I. Sprod^†, C. McKee^‡, H. L. Davies^§ & G. G. J. Ernst

^* Geological Engineering and Sciences, Michigan Technological University, Houghton, Michigan 49931, USA
^† NASA Goddard Space Flight Center, Greenbelt, Maryland 20771, USA
^‡ Rabaul Volcano Observatory, PO Box 386, Rabaul, Papua New Guinea
^§ University of Papua New Guinea, PO Box 414, University, Papua New Guinea
Department of Geology, University of Bristol, Bristol BS8 1RJ, UK

VOLCANIC clouds are an important natural hazard to aircraft¹, and host chemical reactions that interest both volcanologists^2,3 and atmospheric scientists^4-6. Ice has been suggested as a possible component of eruption clouds⁷, but there has been no direct evidence for its presence. Here we report the detection, using a satellite-borne infrared sensor, of > 2 million tonnes of ice in the cloud produced by the September 1994 eruption of Rabaul volcano, in Papua New Guinea. The cloud also contained relatively low levels of sulphur dioxide (80 50 kilotonnes), compared with other stratospheric eruption clouds. The unusual aspects of this cloud may be related to the entry of sea water into the volcanic vent, and its participation in the eruption column. Past eruptions that occurred in similar (coastal) settings, such as those of Krakatau and Santorini, might have had less effect on the atmosphere than their volume alone would suggest, because the presence of ice may decrease the residence time of ash and sulphur in the atmosphere. In addition, the ability of ice to mask the characteristic spectral signature of volcanic ash will increase the difficulty of designing airborne ash detection systems for aviation safety.

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