Report on Ubinas (Peru) — 4 September-10 September 2019
Smithsonian / US Geological Survey Weekly Volcanic Activity Report, 4 September-10 September 2019
Managing Editor: Sally Kuhn Sennert
Please cite this report as:
Global Volcanism Program, 2019. Report on Ubinas (Peru). In: Sennert, S K (ed.), Weekly Volcanic Activity Report, 4 September-10 September 2019. Smithsonian Institution and US Geological Survey.
16.355°S, 70.903°W; summit elev. 5672 m
All times are local (unless otherwise noted)
IGP reported that during 3-9 September three volcanic explosions were detected at Ubinas, all producing eruption plumes that rose to heights less than 2.5 km above the crater rim. The largest, and first, was recorded at 1358 on 3 September and produced significant amounts of ash and gas, affecting areas to the S and SE. After the explosions gas-and-steam plumes rose as high as 1 km. The Alert Level remained at Orange (the second highest level on a four-color scale) and the public were warned to stay outside of a 10-km radius.
Geologic Background. 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.