Report on Reventador (Ecuador) — January 1976
Natural Science Event Bulletin, vol. 1, no. 4 (January 1976)
Managing Editor: David Squires.
Reventador (Ecuador) Explosive eruption begins on 4 January; lava flows enter the jungle
Please cite this report as:
Global Volcanism Program, 1976. Report on Reventador (Ecuador) (Squires, D., ed.). Natural Science Event Bulletin, 1:4. Smithsonian Institution. https://doi.org/10.5479/si.GVP.NSEB197601-352010.
0.077°S, 77.656°W; summit elev. 3562 m
All times are local (unless otherwise noted)
An explosive eruption began during the early morning of 4 January. At dawn an ash column 1 km high was observed. Fine ash was carried W and SW over the Andes, dusting Quito through 10 January. Bombs blown 100 m vertically from the crater were large enough to be seen by the naked eye from a distance of 3 km. Strange seismic signatures, detected 90 km away (at Quito) and attributed to Reventador, began at 0115 on 4 January and continued until 0900 on 9 January. A portable seismograph 10 km from the cone measured continuous harmonic tremor.
Two lava flows descended from the breached crater and divided into three lobes at the base of the cone. During the first 40 hours flows traveled approximately 1.5 km E at 37 m/hour. By 9 January the three lobes had traveled 2.5 km and were advancing approximately 5 m/hour over lahar deposits and jungle. As of 27 January the lava flows had stopped, but infrequent explosive activity, including nuées ardentes, was continuing. The continual ash column had terminated by 25 January. The flows were a black basaltic andesite with olivine, augite, hypersthene, and oxyhornblende.
Reventador had similar eruptions in July 1972 and November 1973. When last visited before the current eruption, on 10 December 1975, it was producing a large steam column.
Further Reference. Hall, M.L., 1980, El Reventador, Ecuador: un volcán activo de los Andes Septentrionales: Revista Politécnica, v. 5, no. 2, p. 123-136.
Geologic Background. Reventador is the most frequently active of a chain of Ecuadorian volcanoes in the Cordillera Real, well east of the principal volcanic axis. The forested, dominantly andesitic Volcán El Reventador stratovolcano rises to 3562 m above the jungles of the western Amazon basin. A 4-km-wide caldera widely breached to the east was formed by edifice collapse and is partially filled by a young, unvegetated stratovolcano that rises about 1300 m above the caldera floor to a height comparable to the caldera rim. It has been the source of numerous lava flows as well as explosive eruptions that were visible from Quito in historical time. Frequent lahars in this region of heavy rainfall have constructed a debris plain on the eastern floor of the caldera. The largest historical eruption took place in 2002, producing a 17-km-high eruption column, pyroclastic flows that traveled up to 8 km, and lava flows from summit and flank vents.
Information Contacts: M. Hall, Escuela Politécnica, Quito.