Report on Ubinas (Peru) — 20 May-26 May 2009
Smithsonian Institution / US Geological Survey
Weekly Volcanic Activity Report, 20 May-26 May 2009
Managing Editor: Sally Sennert.
Please cite this report as:
Global Volcanism Program, 2009. Report on Ubinas (Peru) (Sennert, S, ed.). Weekly Volcanic Activity Report, 20 May-26 May 2009. Smithsonian Institution and US Geological Survey.
16.355°S, 70.903°W; summit elev. 5672 m
All times are local (unless otherwise noted)
Based on SIGMET notices, the Buenos Aires VAAC reported that on 20 May an eruption of Ubinas produced an ash plume that rose to an altitude of 7.3 km (24,000 ft) a.s.l. and drifted NE. Ash was not detected on satellite imagery. According to a news article, two explosions were detected on 25 May. Gas emissions impacted local residents and their fields, prompting residents to request government assistance.
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.