According to a pilot report, the Buenos Aires VAAC reported that an ash plume from Ubinas on 24 May reached an altitude of 6.7 km (22,000 ft) a.s.l. and drifted E. On 25 May, an ash plume reached an altitude of 7 km (23,000 ft) a.s.l. and drifted NW. On 30 May, an ash plume visible on satellite imagery reached an altitude of 7.9 km (26,000 ft) a.s.l. and drifted E.

Buenos Aires Volcanic Ash Advisory Center

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.

Source: Buenos Aires Volcanic Ash Advisory Center (VAAC)