Instituto Geofísico del Perú (IGP) and Instituto Geológico Minero y Metalúrgico (INGEMMET) reported that the eruption at Ubinas continued during 7-13 August. According to IGP a daily average of 102 volcano-tectonic earthquakes indicating rock fracturing and 60 long-period earthquakes signifying the movement of gas and magma. An explosion on 10 August produced an ash plume that rose 2.4 km above the crater rim and drifted 25 km SE and E. Ashfall was reported in Ubinas, Matalaque, and Chojata. INGEMMET noted that sulfur dioxide emissions were at moderate levels during 10-11 and 13-14 August, averaging 2,400-3,700 tons per day. Ash-and-steam plumes rose as high as 800 m and drifted E, SE, S, and W during 13-14 August. 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: Instituto Geofísico del Perú (IGP), Instituto Geológico Minero y Metalúrgico (INGEMMET)