Report on Ubinas (Peru) — 3 September-9 September 2014
Smithsonian / US Geological Survey Weekly Volcanic Activity Report, 3 September-9 September 2014
Managing Editor: Sally Kuhn Sennert
Please cite this report as:
Global Volcanism Program, 2014. Report on Ubinas (Peru). In: Sennert, S K (ed.), Weekly Volcanic Activity Report, 3 September-9 September 2014. Smithsonian Institution and US Geological Survey.
16.355°S, 70.903°W; summit elev. 5672 m
All times are local (unless otherwise noted)
During 3-9 September IGP reported that the eruption of Ubinas was continuing. During 3-4 and 9 September, steam plumes from fumaroles occasionally rose from the summit. Seismicity was generally low but dominated by tremor. Two exhalations of ash were observed on 5 September, the first at 0858 generated an ash plume up to 1,000 m above the summit which dispersed S. The second plume occurred at 1327 and dispersed ash 500 m above the summit that dispersed N.
A total of five explosions were detected on 8 September, the strongest occurred at 0850 and produced a 1,200 m plume; the second explosion expelled ash to heights between 1,300 and 1,900 m; ashfall was noted in areas S.
The Buenos Aires VAAC reported Aviation Color Code Orange on 8 and 9 September when visible images revealed a narrow plume of steam and ash drifting SE. By 0400 on 9 September, the emissions contained water vapor, gas, and light ash, and reached an altitude of 7,300 m (24,000 ft) a.s.l..
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.