Instituto Geofísico del Perú (IGP) and Instituto Geológico Minero y Metalúrgico (INGEMMET) reported that the eruption at Ubinas continued during 19-25 July. According to IGP there were 46 volcano-tectonic earthquakes indicating rock fracturing and 122 long-period earthquakes signifying the movement of gas and magma recorded by the seismic network during 17-23 July. In addition, there were seven seismic signals associated with major explosive events, and 9-14 hours of seismic signals related to ash emissions.

Both IGP and INGEMMET reported a few notable explosions and ash plumes during the week. At 0530 on 20 July an explosion produced an ash plume that rose 3-4.5 km above the crater rim and drifted W and SW. Another explosion the next day, at 0922 on 21 July, produced an ash-and-gas plume that rose 5 km above the crater rim. Ashfall was reported in Querapi (4.5 km SE), Ubinas (6.5 km SSE), Tonohaya (7 km SSE), Anascapa (11 km SE), Sacohaya, San Miguel (10 km SE), Escacha, Huatagua (14 km SE), Huarina, Escacha (9 km SE), Matalaque (17 km SSE), Logén, Santa Lucía de Salinas, and Salinas de Moche. An explosion at 1323 on 22 July generated an ash plume that rose 5.5 km and drifted NE, E, and SE. 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)