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Report on Ubinas (Peru) — 21 May-27 May 2008

Smithsonian / US Geological Survey Weekly Volcanic Activity Report, 21 May-27 May 2008
Managing Editor: Sally Kuhn Sennert

Please cite this report as:

Global Volcanism Program, 2008. Report on Ubinas (Peru). In: Sennert, S K (ed.), Weekly Volcanic Activity Report, 21 May-27 May 2008. Smithsonian Institution and US Geological Survey.

Volcano Profile |  Weekly Report (21 May-27 May 2008)


Ubinas

Peru

16.355°S, 70.903°W; summit elev. 5672 m

All times are local (unless otherwise noted)


Based on SIGMET reports, the Buenos Aires VAAC reported that during 22-24 May ash plumes from Ubinas rose to altitudes of 4.9-7.9 km (16,000 and 26,000 ft) a.s.l. and drifted S, E, NE, and SE. On 26 May, a pilot reported that a plume rose to an altitude of km (18,000 ft) a.s.l. and drifted SSE. The plume was also identified on satellite imagery.

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 PerĂº. 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.

Source: Buenos Aires Volcanic Ash Advisory Center (VAAC)