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Report on Ubinas (Peru) — 16 September-22 September 2015


Ubinas

Smithsonian Institution / US Geological Survey
Weekly Volcanic Activity Report, 16 September-22 September 2015
Managing Editor: Sally Sennert.

Please cite this report as:

Global Volcanism Program, 2015. Report on Ubinas (Peru) (Sennert, S, ed.). Weekly Volcanic Activity Report, 16 September-22 September 2015. Smithsonian Institution and US Geological Survey.

Weekly Report (16 September-22 September 2015)

Ubinas

Peru

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

All times are local (unless otherwise noted)


Instituto Geofísico del Perú (IGP) Observatorio Volcanológico del Sur (OVS) reported that long-period and volcano-tectonic events were at low levels at Ubinas during 15-21 September. Sporadic steam-and-gas plumes rose 600 m. Seismicity (hybrid and long-period events) increased during 20-21 September. An explosion on 21 September at 0914 produced ash plumes that rose 1.7 km and drifted S; ash emission continued until about 0800 the next day. Ashfall was reported in Querapi (4.5 km SE), Ubinas (6.5 km SSE), Tonohaya (7 km SSE), Anascapa (11 km SE), Sacohaya, and San Miguel (10 km SE).

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: Instituto Geofísico del Perú (IGP)