Instituto Geofísico del Perú (IGP) Observatorio Volcanológico del Sur (OVS) reported that during 29 April-5 May long-period and tornillo-type earthquakes continued to decrease while volcano-tectonic events increased. Hybrid events were at a low level, however, an increase in the number of events were detected on 29 April. Overall the dominant signal was spasmodic tremor associated with ash-and-steam emissions. Constant steam emissions were visually observed even though cloud cover often prevented observations. Ash emission increased on 1 May, rising as high as 800 m above 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)