Instituto Geofísico del Perú (IGP) Observatorio Volcanológico del Sur (OVS) reported that during 9-16 June the number of long-period earthquakes greatly decreased to 62 events/day from 778 events/day the previous week. Volcano-tectonic events continued to occur at a high rate. Periods of constant ash emissions during 9-11 June rose as high as 1.4 km above the crater base and drifted mainly NE, E, and SE. Sporadic pulses of gas and ash on 12 June rose 800 m. A hybrid event was recorded at 1915 on 13 June; six hours later a thermal anomaly was detected by satellite images. Another thermal anomaly was detected on 16 June.

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)