Northern Central Andes, Peru	image info
	Volcan Sabancaya
Synonyms: Ampato, Ambato
Location: 15º47'S; 71º51'W
Type: Simple; part of Ambato complex
Summit Elevation: 5967m
Edifice Height: 1600m
Status: Active

Volcan Sabancaya (S) is the youngest component of a complex consisting of three centers; Nevado Hualca Hualca to the north (HH), Sabancaya, and Nevado Ambato (NA) to the south. The edifice is built in the saddle between the two older centers, and consists of extensive flank lava flows (L) which form an apron around the simple cone. Although the upper reaches of the cone are covered by a permanent ice-cap, several short stubby lava flows distributed radially around a youthful summit crater can be discerned.

Between December 1986 and June 1988, a lava dome had grown in the crater and Sabancaya semi-continuously exhibited strong fumarolic activity during which glowing tephra ejections were visible at night. Analysis of TM images acquired in March 1987 and April 1988, showed a change in crater area and shape, but no thermal anomaly. Between the 22nd and 25th June 1988, voluminous steam pulses were emitted every few minutes. Shuttle photography (Mission STS-26 Sept, 1988) showed that the activity of June 1988 had abated and there was no visible sign of activity in the summit crater.

No historic records for this volcano were available in 1988, but since then Peruvian geologists claim to have a record of historic activity dating back some 300 years.

On May 29th 1990, the low level activity (fumarolic) at Sabancaya was interupted by an explosive phase of activity (Norman Banks, Cindy Stein: USGS Vancouver, pers. comm. June, 1990). Periodic loud sonic booms accompanied eruptions throwing ash and "glowing blocks" into the air suggest vulcanian activity. Initially activity was only 2 or 3 time a day but later reports (June 3rd, 1990) indicated explosions every 20 minutes or so, with a strong smell of sulfur, and an increased noise level. The resulting plume streamed NE and ENE with the prevailing winds and was dense to 5 km and ash fall was recorded up to 10 km away.

Sabancaya presents similar, but less severe hazard to Coropuna. About 6000 people live on, near, or along the valleys draining from the complex. Mud and lava flow hazard is obvious, and pyroclastic hazard cannot be ruled out. Mudflows from the north-eastern flank could enter the Majes drainages (which hosts a major canal network resulting from an ogoing irrigation project in the area), while mudflows from the other flanks could enter the south flowing Rio Siguasi. During the 1988 activity cattle died in the areas adjacent to Sabancaya, either directly from poisonous fumes or from eating contaminated foliage (SEAN June 1988). Lavas erupted from vents in the erosional amphitheater on the northern flanks of Hualca Hualca have entered the Rio Majes canyon in the past and dammed it completely - the satellite images show flat-lying lake sediments deposited behind a breached dam, which also forms a prominent nick-point in the canyon profile. Breach of the dam may have caused serious flooding downstream at the time.

de Silva S.L., & Francis, P.W., 1990. Potentially active volcanoes of southern Peru - observations using Landsat Thematic Mapper and Space Shuttle imagery. Bull. Volcanol. 52, 286-301.

Scientific Event Alert Network Bulletin, 1988. V 13, No. 6 p.10-11.