Paper No. 3
Presentation Time: 8:40 AM


NULLO, Francisco, Buenos Aires, 1004, Argentina, RISSO, Corina, Departamento de Geologia, Universidad de Buenos Aires, Ciudad Universitaria, Buenos Aires, 1002, Argentina and NÉMETH, Károly, Massey University, CS-INR, Massey University, CS-INR, Palmerston North, 20459, New Zealand,

Villa La Angostura is a small town in the Neuquén province, Argentina just 45 km to the SE from the Puyehue-Cordón Caulle volcanic Complex (PCCVC), which produced a fissure eruption the 4th of June, 2011. During the most explosive phase of the eruption the VEI was estimated from 3 to 4. PCCVC produced a vulcanian-to-plinian style ryolithic eruption with an estimated plume height of 10.7-13.7 km above the crater level, and drifted an eruption plume to the ESE over the Argentine territory. The PCCVC is a 750 km long NW-SE-trending late-Pleistocene to Holocene basaltic-to-rhyolitic volcanic chain SE of Ranco lake in Chile (40º 32´ SL; 72º 7´ WL). Ash covered more than 19.694.455 ha in Rio Negro and 4.685.695 ha. in Neuquén provinces in Argentina in a thicnkess of 30 to 0.3 cm from proximal to distal areas (INTA, 2011). As a result of the fallout of ash native forest, grass lands, Alpine streams and lakes were coverd by about 30 cm/mm thick monotonous grey ash in the vicinity of Villa La Angostura, that was quickly remobilized by wind action as well as rain falls to trigger local debris flows and extended mudflows creating mud flats in areas where streams enterred to low-lying regions commonly associated with agricultural and sheep breeding activities. Shortly a month after the eruption, the National Park Agency and the Tourism Ministry of Argentina begun the restoration of the park area to re-establish pre-erutpion conditions and allow to open the park to visitors as quickly as possible to regain economy loss the eruption caused. The ash were transported to various depocenters aided by local authorities. Intensive cleaning took place including washing facilities of rest areas and trails, vegetation, foot pathes and part of the town. The ash were covered locally by natural vegetation in order to fix the ash for further remobilisation. It took about 5 months to restore the original scenario involving 5 different agencies across the broad sectors of the National Park. The time, energy and financial input for this lengthy clean up process highlight the significant economic impact on tourism and local economy from distant fine-ash producing eruptions damping ash of few mm-thick over a high altitude - high wind area where ash can easily remobilized by aeolian and fluvial processes.