Recent unrest at Peteroa volcano (35° 15’ S). Application of ASTER Imagery

PATRICIA SRUOGA; DAVID SCHONWANDT; SILVIA CASTRO GODOY; M. URAI; L. KAKU

Pucón, Chile

Congreso; IAVCEI General Assembly; 2004

IAVCEI

Peteroa volcano is located in the Southern Andes (35º 15´S 70º 35´W) and belongs to the Azufre-Planchón-Peteroa Volcanic Complex. Holocene activity has been limited and was mainly explosive.The last eruptive events occurred in 1991 and 1998. The 1991 phreatomagmatic eruption caused the eastward dispersion of extremely fine dacitic ash and the opening of two pits within the summit amphitheatre. The 1998 ash-fall episode was of lesser magnitude and since then, volcanic unrest has been detected within the summit area of this remote Andean volcano. Fumarolic activity has been increasing since 1996 with the opening of 5-7 new vents at the western bottom of one of the crater lakes and with diffuse emanations along the crater walls. Two volcanic earthquakes were recorded on 22/12/03 and 17/03/04, which are tentatively related to observed slumping in the area surrounding the oldest pit crater. Volcano monitoring by ASTER data includes Digital Elevation Model (DEM) analysis and absolute temperature evolution of thermal anomalies in crater lakes by Thermal infrared bands (TIR) in night time images. DEM and ortho-rectified images were obtained from ASTER L1Adata prior and after the 10/03/04 seismic event in order to assess major morphological changes.Maximun temperature reaches 32ºC in the crater lake with strongest fumarolic activity. Our data indicate that ASTER remote sensing is a powerful tool to monitor the behavior of Peteroa over time, mainly because it is remote and isolated for most of the year, and in situ measurements are difficult to make.