Abstract

During the winter months of August-September 2003 a small (VEI=0-1) eruption took place at the 9 km long fissure-like Nevados de Chillán Volcanic Complex (36°50'S), that includes Nuevo (formed between 1906 and 1945) and Arrau (formed in the 1973-1986 period) volcanoes. Only the local inhabitants and tourists of the ski resort located at the foothills noted the eruption. From August 29 to September 4, 2003, low-magnitude explosive events occurred and brown-greyish to white gas and ash columns reached up to 400 to 500 m above the crater, rising at periods that lasted for 20 to 25 minutes. After the first week, explosions became more sporadic and occurred at two-three day intervals. Strong prevailing winds from the north dispersed the low-altitude plume to the SSE until the eruption finally stopped by the middle of September. A new compound crater is now present in the saddle between Nuevo and Arrau volcanoes. This 64 m fissure-like double crater is surrounded by an area of intense fumaroles near to Nuevo volcano suggesting the renewal of activity in the complex