Instituto Geofísico del Perú (IGP) Observatorio Volcanológico del Sur (OVS) reported that during 7-13 July seismic activity declined. Volcano-tectonic earthquakes continued to decrease and the rate of long-period events slightly increased as compared to the previous week. The number of hybrid events decreased, and tremor associated with emissions was greatly reduced. Explosions were observed on 9 and 11 July, producing ash plumes that drifted NE, E, and S. Ash emissions were observed on other days as well.

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)