Report on Ubinas (Peru) — 9 July-15 July 2014
Smithsonian / US Geological Survey Weekly Volcanic Activity Report, 9 July-15 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, 9 July-15 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)
IGP reported that the eruption of Ubinas was continuing during 12 June-10 July. During 12-30 June six explosions generated plumes 1,400-3,600 m above the crater. Volcanic tremor was associated with ash emissions during 12-21, 25, and 26 June. During 28-29 June more than 1,000 hybrid earthquakes were recorded, but volcano-tectonic earthquakes were scarce. A moderate explosion on 30 June generated an incandescent plume. After more than 50 hours of tremor, a moderate explosion occurred at 0858 on 30 June; the plume reached 1,800 m above the crater and ejected tephra 1,500 m down the NW flank.
During 30 June-10 July IGP detected five, small-sized explosions that generated plumes 400-1,500 m above the crater. Seismicity was also reduced during this period; the greatest number of hybrid earthquakes was registered on 6 July when a swarm of 115 earthquakes occurred.
Geologic Background. 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.