Report on Reventador (Ecuador) — 30 October-5 November 2002
Smithsonian / US Geological Survey Weekly Volcanic Activity Report, 30 October-5 November 2002
Managing Editor: Gari Mayberry
Please cite this report as:
Global Volcanism Program, 2002. Report on Reventador (Ecuador). In: Mayberry, G (ed.), Weekly Volcanic Activity Report, 30 October-5 November 2002. Smithsonian Institution and US Geological Survey.
0.077°S, 77.656°W; summit elev. 3562 m
All times are local (unless otherwise noted)
After 26 years with no explosive activity, a large eruption began at Reventador on 3 November that sent pyroclastic flows down the volcano's flanks. Based on seismic data and observations made by people near Reventador, IG reported that the first pyroclastic flows produced from the eruption occurred on the 3rd around 0900. Then, during 1000-1900 continuous tremor was recorded that may have been associated with continuous ash emissions and small explosions. Between 2000 on the 3rd and 0100 on the 4th, there was an increase in the amount and intensity of the tremor. After 0100 the activity level decreased, but a pulse of activity occurred between 0200 and 0300. A new cycle of activity began during 0700-0800. Small-to-moderate explosions occurred during the day and small pyroclastic flows descended the volcano's flanks. On the morning of the 5th explosive sounds were not heard, no ash fell in towns near the volcano, and meteorological clouds obscured Reventador. In addition, seismicity was low, but some small earthquakes and low-amplitude volcanic tremor occurred.
According to the Washington VAAC, the first eruption on 3 November produced an ash cloud that reached a height of ~16.8 km a.s.l. Subsequent explosions generated more ash clouds and satellite imagery showed discrete ash clouds on the 5th; a thin area of ash at ~16.8 km a.s.l. was located over S Colombia and N Brazil moving E, and a thicker ash cloud drifted W over the Pacific Ocean towards the Galapagos Islands at a height of ~10.7 km. In addition, a nearly stationary area of ash was observed over the Pacific Ocean off the coast of Ecuador at a height of ~9.1 km a.s.l.
According to OCHA, pyroclastic flows on the 3rd reached the Baeza-Lumbaqui highway, blocking inter-city traffic. Ash fell in the towns of Baeza, Cayambe, Yaruqui, El Quinche, Tumbaco, Pifo, Sangoqui, and Quito, Ecuador's capital ~70 km W of Reventador. Quito was paralyzed by ash fall; schools and businesses were closed, residents were told to remain indoors, and all operations at the Mariscal Sucre airport in Quito were suspended. The approximately 3,000 people living in towns at the base of the volcano were evacuated and no deaths or injuries were attributed to volcanic activity.
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.