Report on Ubinas (Peru) — 2 April-8 April 2014
Smithsonian / US Geological Survey Weekly Volcanic Activity Report,
2 April-8 April 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, 2 April-8 April 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's Observatorio Volcanologico de Arequipa (IGP-OVA) reported that during 29 March-2 April seismicity at Ubinas increased significantly. The increase began at 1000 on 29 March with energetic tremor (indicating magma ascent and degassing) and small explosions. On 2 April harmonic tremor was detected. Gas-and-ash plumes rose 0.9-2.2 km above the crater and drifted SE and E. Minor ashfall was reported in Tonohaya (7 km SSE), San Miguel, and Ubinas (6.5 km SSE). Based on webcam views, the Buenos Aires VAAC reported that on 3 April gas-and-steam plumes possibly containing ash rose 6.1-7.3 km (20,000-24,000 ft) a.s.l. and dissipated around the crater. IGP-OVA noted that on 4 April there were 23 explosions detected; ash plumes drifted S and SE. During 5-7 April explosions generated ash plumes that rose as high as 2 km and drifted S and SW. During 7-8 April explosions also ejected incandescent fragments, up to 20 cm in diameter, no more than 1 km away. Ash plumes rose as high as 3 km.
Geological Summary. 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.