Report on Ubinas (Peru) — 16 April-22 April 2014
Smithsonian / US Geological Survey Weekly Volcanic Activity Report, 16 April-22 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, 16 April-22 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) and Observatorio Vulcanológico del INGEMMET (OVI) reported that 21 moderate explosions at Ubinas were detected during 11-16 April along with a sharp increase in seismicity; the magnitude and frequency of explosions increased during 14-16 April. Multiple explosions during 16-22 April ejected incandescent tephra, and generated plumes of gas, water vapor, and ash that rose at most 5 km above the crater. Ash fell in multiple areas in almost all directions, but was most concentrated to the S, SW, and W; towns affected included Querapi (4 km S), Ubinas (6.5 km SSE), Sacuaya, Huatagua (14 km SE), Escacha, Quinistaquillas, San Miguel (10 km SE), Tonohaya, and Matalaque. On 18 April at 1836 a significant gas-and-ash emission was accompanied by the ejection of incandescent blocks that landed up to 2 km from the crater. Explosions on 19 and 22 April ejected incandescent tephra, 20-30 cm in diameter, up to 2.5 km away from the crater. Fine ash fell in Omate, 37 km SSW. According to a news article, an evacuation of 4,000 residents was underway, along with nearly 30,000 livestock.
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.