Dilute PDC´s interacting with a body of water. The Copahue surge

PETRINOVIC, I. A.; MARTI, J; AGUIRRE-DÍAZ, G.; GEYER,A.

Mendoza

Congreso; ISC 2010; 2010

IAS

Known examples of pyroclastic density currents (PDC´s) blowing on water includes the Krakatoa 1883, Mt.Peleé (1902), Santorini 1628 B.C. and the recent examples of Montserrat 1996; 2003. Krakatoa 1883, was particularlyelucidating because the surge, traveled 80 km over the sea until the Sumatra coast. In this case, distal fa -cies decrease in sorting coefficient, median grain size and thickness. Here we present preliminary studies of facieschanging in a dilute PDC because it blow on a lake and deposit inland of the shore line. The flow initiates atthe present active crater of the Copahue volcano, descend by the canyon of Agrio river (12 km), cross over theAgrio lake (2 km) and deposit inland (1.8 km). Preliminary results of distal facies did not reveal significantchanges in particle concentration or sorting or size. Notwithstanding, a conspicuous alternation of ductile and drybed sets indicates both steam-enriched and normal pulses of the surge. Our study is significative to better under -stand the flow dynamics of dilute PDC´s before and after the interaction with a body of water, in particular, therole of steam and particle segregation in the regime of transport and deposit of dilute PDC´s flowing over water.