Instituto Geofísico del Perú (IGP) reported that during 1-15 June seismicity at Ubinas was characterized by daily averages of 144 events associated with rock fracturing and 73 events associated with fluid movement. Gas, steam, and ash emissions were sometimes visible rising as high as 800 m above the crater rim and drifting mainly E and NE, though ash was not present in the emissions at least during 12-15 June. Sulfur dioxide emissions were minor, averaging 74 tons per day. A total of 23 thermal anomalies were identified in satellite images. Gas-and-steam emissions rose as high as 500 m above the crater rim during 16-17 June. The Alert Level remained at Yellow (the second level on a four-color scale) and the public was warned to stay 2 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)