On 31 July and 3-5 August the Buenos Aires VAAC reported continuous emission of light ash from Ubinas. On 30 July INGEMMET reportedsteam-and-gas plumes that rose 500-1100 m above the summit. On 31 July INGEMMET reported an eruption column rose to 3 km (9,800 ft) a.s.l. and drifted NW. On 1 and 3 August gas-and-ash emission rose 200-1200 m above the crater and drifted W.

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: Buenos Aires Volcanic Ash Advisory Center (VAAC), Instituto Geológico Minero y Metalúrgico (INGEMMET)