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Abstract

Nevado del Huila Volcano (VNH), the highest volcano of the colombian Andes (5360m) has be en relatively inactive for a long time, may be since prehistoric times because there is no historical record of volcanic activity. This continental margin volcano zone belongs to the volcanic ridge associated to the subduction of the Nazca Plate beneath the South American Plate. VNH has been generally classified as stratovolcano with predominant effusive activity. However the recent discovery of new pyroclastic deposits identified by the authors, suggest that VNH had more than one explosive episode in past time. The lavas ofVNH are typical andesites of active continental margin, belonging to calcoalcaline series. Only a few of the these lavas are slightly tholeitic, all of them have a clear subalcaline tendency (Na20 + K20 < 8%) with a high to medium K20 contents varying between 7,5 - 3%.