Report on Ubinas (Peru) — 20 August-26 August 2014
Smithsonian / US Geological Survey Weekly Volcanic Activity Report, 20 August-26 August 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, 20 August-26 August 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 20-26 August INGEMMET reported that the eruption of Ubinas was continuing. During 20-25 August water vapor, gas, and minor ash plumes rose 200-1800 m above the crater and drifted E, NE, and S. On 21 August an explosion was followed by an ash plume that rose 4.2 km (13,800 ft) above the summit and drifted S and expelled incandescent blocks up to 2 km from the crater, primarily on the S flank. The explosion was heard up to 10 km from the volcano. On 22 August an ash plume rose to 1.8 km (5,900 ft) and drifted E and NE. On 21-22 August ashfall was reported in the towns of Querapi, Ubinas, Escacha, Tonohaya, and Yalahua.
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.