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Report on Ubinas (Peru) — 27 August-2 September 2008


Ubinas

Smithsonian Institution / US Geological Survey
Weekly Volcanic Activity Report, 27 August-2 September 2008
Managing Editor: Sally Sennert.

Please cite this report as:

Global Volcanism Program, 2008. Report on Ubinas (Peru) (Sennert, S, ed.). Weekly Volcanic Activity Report, 27 August-2 September 2008. Smithsonian Institution and US Geological Survey.

Weekly Report (27 August-2 September 2008)

Ubinas

Peru

16.345°S, 70.8972°W; summit elev. 5608 m

All times are local (unless otherwise noted)


Based on SIGMET reports, analysis of satellite imagery, and pilot observations, the Buenos Aires VAAC reported that during 26-27 August and on 2 September continuous ash plumes from Ubinas rose to altitudes of 5.5-6.1 km (18,000-20,000 ft) a.s.l. Plumes drifted N on 27 August and S on 2 September.

Geological Summary. The truncated appearance of Ubinas, Perú's most active volcano, is a result of a 1.4-km-wide crater at the summit. 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°. The steep-walled, 150-m-deep summit crater 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 from about 1,000 years ago. Holocene lava flows are visible on the flanks, but activity documented since the 16th century has consisted of intermittent minor-to-moderate explosive eruptions.

Source: Buenos Aires Volcanic Ash Advisory Center (VAAC)