Report on Ubinas (Peru) — 12 April-18 April 2006
Smithsonian / US Geological Survey Weekly Volcanic Activity Report, 12 April-18 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, 12 April-18 April 2006. Smithsonian Institution and US Geological Survey.
16.355°S, 70.903°W; summit elev. 5672 m
All times are local (unless otherwise noted)
A significant meteorological forecast (SIGMET) was issued on 15 April for an ash cloud from Ubinas at a height of 6.1-7.3 km (20,000-24,000 ft) a.s.l., and later that day for a cloud at 6.1-9.1 km (20,000-30,000 ft) a.s.l. The Aviation Color Code was Red until 16 April when the Buenos Aires VAAC received a report that activity had ceased. According to a news report on 18 April, however, officials urged residents the town of Querapi ~5 km from the volcano to evacuate.
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.