Instituto Geofísico del Perú (IGP) reported that the eruption at Ubinas continued at low-to-moderate levels during 10-16 July. During the week there were 80 volcano-tectonic earthquakes indicating rock fracturing and 93 long-period earthquakes signifying the movement of gas and magma. On 16 July there were two seismic signals associated with major explosive events, and 3.6 hours of seismic signals related to ash emissions. Emissions of gas and ash rose to 1.5 km above the summit and drifted as far as 15 km to the E, SE, and S. The Alert Level remained at Orange (the third level on a four-color scale) and the public was warned to stay 4 km away from the crater.

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)