Rapid response to the Chaiten eruption, Chile, May 2008: ash fallout and impact

David Pyle University of Oxford

Work funded by a NERC Urgency Grant

Collaborators:Sebastian Watt, Tamsin Mather, Naomi Matthews, Blae Quayle, Elspeth Robertson (Oxford); Robert Martin (Cambridge); Costanza Bonadonna (Geneva); Chuck Connor, Alain Volentik (Florida)

Thanks to: Alberto Fierro, British Embassy, Buenos Aires; the Mayor of Esquel, Chubut Province; Gustavo Villarosa, Univ. Bariloche. Talk given to the UK National Centre for Earth Observation Science Meeting, September 2009

Photo: Puntiagudoi volcano (left) and Osorno volcano (right), southern Chile. David Pyle Photo: Chaiten Dome, January 2009. David Pyle

Ash dispersal in volcanic eruptions

How is ash transported during explosive volcanic eruptions?

What is the fate of ash once deposited?

How good are current models of ash transport and deposition?

Can Earth Observation tools provide a rapid impact assessment following explosive eruptions?

Photo: NASA MODIS infra red , May 5 2008

Regional context: volcanism in Southern Chile

Active volcanic arc (~ 1 volcano every 35 km); multiple eruptions over past 10,000 yr

Images: Sebastian Watt; work described in SFL Watt et al , Holocene tephrochronology of the Hualaihue region, Andean southern volcanic zone, southern Chile. Quaternary International (2011, under review) and SFL Watt, PhD thesis, University of Oxford, 2010.

Regional context: volcanism in Southern Chile

Location, structure and stability of edifices controlled by regional tectonics

SFL Watt et al 2009 Bulletin of Volcanology 71, 559-574

Regional context: volcanism in Southern Chile

Eruptions often triggered by major regional earthquakes

SFL Watt et al 2009 Earth and Planetary Science Letters 277, 399-407

Chaiten eruption: May 2008

2008: limited precursory seismicity at a volcano with no known eruptions in ca. 10 kyr

Images: Sebastian Watt, unpublished. Central image – earthquake search from NEIC.

Chaiten eruption: the ash plume crosses Patagonia

May 3, 2008. (MODIS). May 5, 2008. (MODIS).

Terra MODIS (15:15 UT, 6 May) 6 May eruption column; Aqua MODIS (19:15 UT, 6 May)

Satellite images: NASA MODIS Rapid Response TeamSFL Watt et al., Journal of Geophysical Research 114, B04207, 28 April 2009.S Carn et al., EOS Trans AGU, 90 (24), 205-7, 16 June 2009.

Satellite imagery records widespread ash fallout across central Patagonia

SFL Watt et al., Journal of Geophysical Research 114, B04207, 28 April 2009

Chaiten eruption: May 2008

Still cleaning up ash, Futaleufu (January 2009) Lahar damage in Chaiten town, January 2009

Photo: David Pyle Photo: David Pyle

Fieldwork in June 2008 by Seb Watt, Rob Martin and Naomi Matthews

Chaiten eruption: May 2008

Urgency fieldwork: rapid mapping of ash thickness, grainsize at 250 sites.

Area with > 0.1 mm ash ~ 8 x the area of WalesErupted volume ~ 0.07 km3: largest explosive eruption of rhyolite since Katmai

(1912).

Thick fallout deposits near Chaiten volcano (January 2009) reveal eruption stratigraphy

Reworking and

continuing activity

Main ash fallout phase: May 6-8?

Ash fallout: May 3-5?

May 2 – initial phase

Tracking ash deposit preservation: Argentinian lakes and Chilean grasslands (January 2009)

Photos: David Pyle

Field data: new constraints for ash dispersal models; ground-truthing satellite observations

Proximal stratigraphy preserved on a tree stump near Minchinmavida. Photos: David Pyle

F. Alfano et al., Tephra stratigraphy and eruptive volume of the May 2008 Chaiten eruption, Chile. Bulletin of Volcanology (in press), 2011.

Ash fallout across the snow and ice cap of Minchinmavida. Image from Jan 2009

Chaiten eruption: immediate environmental impact?

RS Martin et al 2009 Journal of Volcanology and Geothermal Research 184, 462-472.

Ephemeral lake waters Wild grasses

RS Martin et al., Journal of Volcanology and Geothermal Research 184, 462-472, 20 July 2009.

Chaiten eruption: immediate environmental impact?Correlations of trace element concentrations with ash fallout thickness

across central Patagonia (June 2008)

Chaiten eruption: short lived regional environmental impact

Comparison of grasses in June 2008, and January 2009

RS Martin et al., Journal of Volcanology and Geothermal Research 184, 462-472, 20 July 2009.

Chaiten eruption, 2008

-Once in a decade opportunity to capture details of fresh ash fallout across a continent

- Significant new dataset against which to test and refine ash transport and deposition models

- Case study of a major eruption at a long-dormant volcano in an understudied part of the world

Chaiten Dome, January 2009. Photo: David Pyle