Report on Ubinas (Peru) — 16 July-22 July 2014
Smithsonian / US Geological Survey Weekly Volcanic Activity Report, 16 July-22 July 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, 16 July-22 July 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 16-22 July INGEMMET and IGP reported that the eruption of Ubinas was continuing with gas-and-ash emissions reported most days. An explosion on 17 July, preceded by several days of banded tremor, generated an eruption column that rose 5 km above the summit and expelled incandescent blocks onto the flanks. More explosions on 19 and 21 produced eruption columns of gas-and-ash; the column on 19 July rose 2.8 km above the summit. Emissions and exhalations on 16, 18, and 22 July of gas-and-ash rose to 200-1800 m above the summit. Eruption columns and emissions drifted mostly E, NE, and SE. There were no significant emissions on 20 July. Ashfall was reported in various towns downwind of the plumes, in the areas of Querapi (4 km S), Ubinas (6.5 km SSE), Tonohaya (7 km SSE), San Miguel (10 km SE), Escacha, Yalahua, Lloque, and Sacuhaya.
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.