Report on Ubinas (Peru) — 11 April-17 April 2007
Smithsonian / US Geological Survey Weekly Volcanic Activity Report, 11 April-17 April 2007
Managing Editor: Sally Kuhn Sennert
Please cite this report as:
Global Volcanism Program, 2007. Report on Ubinas (Peru). In: Sennert, S K (ed.), Weekly Volcanic Activity Report, 11 April-17 April 2007. 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 a significant meteorological notice (SIGMET), the Buenos Aires VAAC reported that an ash plume from Ubinas rose to altitudes of 5.5-7 km (26,000-27,000 ft) a.s.l. on 10 April and drifted W. INGEMMET reported that on 11 April, emissions of gas and ash produced plumes to altitudes of 6.2-6.4 km (20,000-21,000 ft) a.s.l. and drifted E. Based on an additional SIGMET, the Buenos Aires VAAC reported that an ash plume rose to altitudes of 6.1-6.4 km (20,000-21,000 ft) a.s.l. and drifted SE.
Geologic Background. A small, 1.4-km-wide caldera cuts the top of Ubinas, Peru'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 of Perú. 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 3700 years ago extend 10 km from the volcano. Widespread plinian pumice-fall deposits include one of Holocene age about 1000 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.