Observatorio Vulcanológico del INGEMMET (OVI) reported that during 28-29 May ash emissions at Ubinas continued; gas-and-ash plumes rose 0.6-2.5 km above the crater and drifted ESE. Ashfall was reported in various towns downwind of the plumes, including Querapi (4 km S), Ubinas (6.5 km SSE), Escacha, Chojata, San Miguel, and Tonohaya. The Buenos Aires VAAC reported that seismicity fluctuated during 2-3 June. Satellite and webcam images as well as pilot observations indicated continuous emission of gas and ash that rose to altitudes of 6.7-10.7 km (22,000-35,000 ft) a.s.l. and drifted NE, E, and SE.

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