IGP's Observatorio Volcanologico de Arequipa (IGP-OVA) reported that on 1 February at 1559 a gas-and-ash plume from Ubinas rose 0.5-2 km above the crater and drifted E and SE. A photo showed ash from the plume falling onto the flanks. The event was accompanied by increased seismicity for several hours. At 2027 on 7 February a large volcano-tectonic earthquake occurred under the volcano at a depth of 9 km. Bluish gas emissions were sporadic during 8-11 February.

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)