Instituto Geofísico del Perú (IGP) reported that the eruption at Ubinas continued during 22-27 August. There were daily averages of 229 volcano-tectonic earthquakes indicating rock fracturing and 54 long-period earthquakes signifying the movement of gas and magma. In addition, seismic signals associated with ash emissions were recorded for an average of eight hours per day, with a maximum of 17 hours on 26 August. An explosion at 1757 on 25 August generated an ash-and-gas plume that rose 4.2 km above the crater rim and drifted up to 25 km in multiple directions. According to the Buenos Aires VAAC diffuse ash-and-gas puffs, both daily and with periods of continuous emissions, reached 6.1-7.3 km (20,000-24,000 ft) a.s.l. (up to 1.6 km above the summit) and drifted multiple directions. 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.

Sources: Buenos Aires Volcanic Ash Advisory Center (VAAC), Instituto Geofísico del Perú (IGP)