Instituto Geofísico del Perú (IGP) Observatorio Volcanológico del Sur (OVS) reported that during 19-26 May long-period earthquakes continued at the same rate while volcano-tectonic and hybrid events increased. Overall the dominant signal was spasmodic tremor associated with ash-and-steam emissions. While conducting fieldwork during 19-22 May, OVS staff observed persistent water vapor, gas, and ash emissions that rose 400 m. At 1051 and 1213 on 24 May ash plumes rose as high as 1.2 km and drifted NE and E.

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: Instituto Geofísico del Perú (IGP)