Rapid response to Chaiten eruption provides once in a decade opportunity to refine models of ash dispersal

Sebastian Watt, David Pyle and Tamsin Mather

Figure 1: May 3 2008 AVHRR image of Chaiten’s plume on
3rd May 2008 stretching across Argentina towards the Atlantic coast.

Within two days of the start of the Chaiten eruption it became clear that this was a major event – the largest volcanic eruption globally for nearly 20 years, and the largest explosive eruption of rhyolite for 90 years. We successfully applied for a NERC urgency grant in order to map out the distribution of ash from the eruption.  Using MODIS satellite imagery to guide them, our field team mapped the ash fallout to a deposited thickness of ~ 0.1 mm, and collected samples from over 220 sites across an area of 100,000 square kilometers.  With these field data and samples we were able to make the first scientific assessment of the size and impact of the eruption. Ash fallout on the ground corresponded closely to the areas identified on satellite imagery, allowing us to identify the time sequence of deposition of the different fallout units. Together with the grainsize and other data we have since collected, this will provide a once- in- a- decade opportunity to test and refine the current generation of models of ash dispersal and deposition. This will have a significant impact in terms of improving models of ash fall hazards from explosive eruptions. This work has so far yielded two papers ( Watt et al., 2009; Martin et al., 2009), some press coverage (e.g. NERC’s Planet Earth) and one scientific report ( Carn et al., 2009). Our NERC Urgency Funding was eventually matched by support to international colleagues through both NSF and the University of Geneva.

References

Carn, S.A., J.S. Pallister, L. Lara, J.W. Ewert, S. Watt, A.J. Prata, R.J. Thomas and G. Villarosa, The unexpected awakening of Chaitén volcano, Chile, EOS, Trans. Amer. Geophys. Un., 90, 205-206, 2009.

Martin, R.S., S.F.L. Watt, D.M. Pyle, T.A. Mather, N.E. Matthews, B. Georg, J.A. Day, T. Fairhead, M.L.I. Witt and B.M. Quayle, Environmental effects of ashfall in Argentina from the 2008 Chaitén volcanic eruption, J. Volcanol. Geotherm. Res., 184, 462-472, doi:10.1016/j.jvolgeores.2009.04.010, 2009

Watt, S.F.L., D.M. Pyle, T.A. Mather, R.S. Martin and N.E. Matthews, Fallout and distribution of volcanic ash over Argentina following the May 2008 explosive eruption of Chaitén, Chile, J. Geophys. Res., 114, B04207, doi:10.1029/2008JB006219, 2009.