Estimating remobilization rate of ash deposited during the Puyehue (Southern Andes) eruption in 2011

HALLER MJ; FRUMENTO OA

Flagstaff

Encuentro; Volcanism in the American Southwest; 2012

Yellowstone Volcanic Observatory - USGS

Puyehue - Cordón del Caule volcano in Southern Andes erupted explosively in June 2011 depositing ash over a region of more than 75,000 km2 to the east and southeast of the volcano in the Argentine Patagonian meseta. A minimum of 1.36 km3 of uncompacted tephra was ejected, which is equivalent to 0.29 km3 of solid rock. The thickness of ash ranged from 30 cm in the Andean area to less than 1 mm in the Atlantic coast zone. This deposited ash has been frequently remobilized for months by the wind impacting on the population, transportation, agriculture, livestock and water resources of the region. Modelling approach based on empirical field observations, considers that one third of the fallen ash is fixed by the vegetation or incorporated into the soil by illuviation processes, while two thirds are resuspended by the wind. The climate model allowed us to calculate a monthly average emission rate (catch and remobilization of particles outside the region) 700g/m2, equivalent to 52 x 106 tons/month. Based on these calculations it was estimated that the remobilization of Puyehue volcano ashes and decreasing of the consequent adverse effects would extend for a period of 33 months. Current observations (July 2012) show that during strong wind storms volcanic ash reaches the Atlantic coast.