Report on Ubinas (Peru) — 18 June-24 June 2014
Smithsonian / US Geological Survey Weekly Volcanic Activity Report, 18 June-24 June 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, 18 June-24 June 2014. Smithsonian Institution and US Geological Survey.
16.355°S, 70.903°W; summit elev. 5672 m
All times are local (unless otherwise noted)
INGEMMET reported intermittent explosions from Ubinas along with continuing daily tremor and long-period earthquales during 18-23 June. Two explosions were noted on 18 June, as were six gas-and-ash emissions that generated diffuse plumes 400-700 m above the summit. Ashfall was reported in Querapi (located 4 km S). On 19 June the seismic network detected two explosions, and gas-and-ash emissions were observed nine times, reaching 300-1,200 m above the crater. Ashfall was reported in the areas of Querapi, Ubinas (6.5 km SSE), Escacha, Tonohaya (7 km SSE), and San Miguel (10 km SE).
No explosions were recorded on 20 June, but seven gas-and-ash emissions were observed (200-500 m above the crater) with the webcamera. On 21 June, six explosions were recorded, with gas-and-ash plumes seen nine times to heights of 500-1,200 m above the crater. Light ashfall was reported in the towns of Ubinas, Lloque, and Yunga. Seismicity on 22 June included one explosion signature. The webcamera captured views of eight gas-and-ash plumes that reached 300-1,000 m above the crater. No explosions were registered on 23 June, although six gas-and-ash plumes were observed with plume heights as high as 1,300 m above the crater.
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.