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. A small, 1.4-km-wide caldera cuts the top of Ubinas, Perú's most active volcano, giving it a truncated appearance. 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 degrees. The steep-walled, 150-m-deep summit caldera 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 of Holocene age about 1,000 years ago. Holocene lava flows are visible on the flanks, but historical activity, documented since the 16th century, has consisted of intermittent minor-to-moderate explosive eruptions.

Source: Instituto Geofísico del Perú (IGP)