During 3-9 September IGP reported that the eruption of Ubinas was continuing. During 3-4 and 9 September, steam plumes from fumaroles occasionally rose from the summit. Seismicity was generally low but dominated by tremor. Two exhalations of ash were observed on 5 September, the first at 0858 generated an ash plume up to 1,000 m above the summit which dispersed S. The second plume occurred at 1327 and dispersed ash 500 m above the summit that dispersed N.

A total of five explosions were detected on 8 September, the strongest occurred at 0850 and produced a 1,200 m plume; the second explosion expelled ash to heights between 1,300 and 1,900 m; ashfall was noted in areas S.

The Buenos Aires VAAC reported Aviation Color Code Orange on 8 and 9 September when visible images revealed a narrow plume of steam and ash drifting SE. By 0400 on 9 September, the emissions contained water vapor, gas, and light ash, and reached an altitude of 7,300 m (24,000 ft) a.s.l..

Geological Summary. The truncated appearance of Ubinas, Perú's most active volcano, is a result of a 1.4-km-wide crater at the summit. It is the northernmost of three young volcanoes located along a regional structural lineament about 50 km behind the main volcanic front. The growth and destruction of Ubinas I was followed by construction of Ubinas II beginning in the mid-Pleistocene. The upper slopes of the andesitic-to-rhyolitic Ubinas II stratovolcano are composed primarily of andesitic and trachyandesitic lava flows and steepen to nearly 45°. The steep-walled, 150-m-deep summit crater contains an ash cone with a 500-m-wide funnel-shaped vent that is 200 m deep. Debris-avalanche deposits from the collapse of the SE flank about 3,700 years ago extend 10 km from the volcano. Widespread Plinian pumice-fall deposits include one from about 1,000 years ago. Holocene lava flows are visible on the flanks, but activity documented since the 16th century has consisted of intermittent minor-to-moderate explosive eruptions.

Sources: Instituto Geofísico del Perú (IGP), Buenos Aires Volcanic Ash Advisory Center (VAAC)