Report on Reventador (Ecuador) — 6 July-12 July 2005
Smithsonian / US Geological Survey Weekly Volcanic Activity Report, 6 July-12 July 2005
Managing Editor: Gari Mayberry
Please cite this report as:
Global Volcanism Program, 2005. Report on Reventador (Ecuador). In: Mayberry, G (ed.), Weekly Volcanic Activity Report, 6 July-12 July 2005. Smithsonian Institution and US Geological Survey.
0.077°S, 77.656°W; summit elev. 3562 m
All times are local (unless otherwise noted)
As of 6 July, harmonic tremor, occasional explosions, and long-period and volcano-tectonic earthquakes continued at Reventador. Strong Strombolian fountaining was observed during the evening and one of the lobes of a lava flow (Lava number 5) was advancing down the caldera wall following the Río Marker. The flow abruptly slowed to ~20 m/day in comparison to flow-front velocities of ~70 m/day during 19-23 June, and ~50 m/day during 23-30 June. Lava number 5 was ~1.2 km from a steep incline, where it could begin to rapidly descend to the alluvial fan where the highway and petroleum pipeline are located.
Based on information from IG, the Washington VAAC reported that an ash plume extended N of the volcano's summit on 11 July. No ash was visible on satellite imagery.
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.