GEOMORPHOLOGICAL AND GEOLOGICAL SURVEY, AND SPOT REMOTE-SENSING OF THE CURRENT ACTIVITY OF NEVADO SABANCAYA-STRATOVOLCANO (SOUTH PERU) - ASSESSMENT FOR HAZARD-ZONE MAPPING

The May 28, 1990, eruption of Nevado Sabancaya volcano (Central Andean Volcanic Zone, south Peru) ended a dormant stage of about 200 year du ration. This ice-clad stratovolcano still poses a threat to about 3500 0 people and to cultivated land in the Rio Colca and Siguas valleys. T he volcanic hazards appraisal is based on remote sensing using 5 SPOT images collected during 1990, on geological and geomorphological surve y of the summit volcano, and on calculation of parameters for tephra d ispersal and pyroclastic flowage. Nevado Sabancaya is potentially haza rdous because it was active 200 years ago, and because it is still ice -clad despite its three years of recent activity. In addition, recent tephra-fall deposits on similar volcanoes in this area point to the oc currence of Plinian eruptions during the past 500 years. The mapped ha zard-zones for tephra fallout, pyroclastic flows, lahars, and potentia lly catastrophic events are portrayed according to three types of beha viour: moderate-magnitude vulcanian activity (e.g. June 1990-December 1993), violent explosive activity, and a potentially paroxysmal Plinia n event.