IG reported that although cloud cover often prevented observations of Reventador, during 30 June and 2, 4, and 9-12 July ash emissions were seen. In the afternoon of 30 June, a diffuse ash plume was visible rising from the summit. Activity increased on 2 July when 41 explosions were recorded, as well as 27 long-period earthquakes and 15 episodes of tremor associated with emissions. A 2-km-high gas-and-ash plume was observed rising from the summit on the morning of 2 July that drifted SE and later that night an explosion was heard. The IG reported that SOTE (Sistema de Oleoducto Transecuatoriano) personnel heard explosions during the morning of 8 July. The next morning, SOTE personnel noted that the summit was clear and a gas-and-ash plume was rising from the summit up to 2 km above the crater rim. Diffuse ash plumes were also noted on 10 and 11 July that reached 1.5 km above the crater and drifted NW.

The seismic network detected the highest number of explosion signatures during 2-5 July when 34-45 events per day were detected. Up to 12 episodes of harmonic tremor per day occurred during 4 and 5 July. The highest number of long-period earthquakes occurred during 10-11 July: 90 events per day. Tremor signatures associated with emissions had a wide range during this reporting period (0-28 per day), but typically numbered less than 15 per day.

Geological Summary. Volcán El 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 stratovolcano has 4-km-wide avalanche scarp open to the E formed by edifice collapse. A young, unvegetated, cone rises from the amphitheater floor to a height comparable to the rim. It has been the source of numerous lava flows as well as explosive eruptions visible from Quito, about 90 km ESE. Frequent lahars in this region of heavy rainfall have left extensive deposits on the scarp slope. The largest recorded 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.

Source: Instituto Geofísico-Escuela Politécnica Nacional (IG-EPN)