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Report on Ubinas (Peru) — 29 March-4 April 2006

Smithsonian / US Geological Survey Weekly Volcanic Activity Report, 29 March-4 April 2006
Managing Editor: Sally Kuhn Sennert

Please cite this report as:

Global Volcanism Program, 2006. Report on Ubinas (Peru). In: Sennert, S K (ed.), Weekly Volcanic Activity Report, 29 March-4 April 2006. Smithsonian Institution and US Geological Survey.

Volcano Profile |  Weekly Report (29 March-4 April 2006)


Ubinas

Peru

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

All times are local (unless otherwise noted)


Increased fumarolic activity occurred at Ubinas during the end of March. A Universidad de San Agustin scientist who visited the volcano on 31 March found strong steam-and-ash emissions occurring. Also, leaves of nearby crops were burned and a sound similar to a jet engine emanated from the vent area.

Geologic Background. A small, 1.4-km-wide caldera cuts the top of Ubinas, PerĂº'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.

Sources: US Geological Survey Volcano Disaster Assistance Program (VDAP), Victor Aguilar, Universidad de San Agustin, PerĂº