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Report on Ubinas (Peru) — 5 July-11 July 2023


Smithsonian Institution / US Geological Survey
Weekly Volcanic Activity Report, 5 July-11 July 2023
Managing Editor: Sally Sennert.

Please cite this report as:

Global Volcanism Program, 2023. Report on Ubinas (Peru) (Sennert, S, ed.). Weekly Volcanic Activity Report, 5 July-11 July 2023. Smithsonian Institution and US Geological Survey.

Weekly Report (5 July-11 July 2023)



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

All times are local (unless otherwise noted)

IGP and INGEMMET reported that the eruption at Ubinas continued during 5-12 July. According to IGP there were 67 volcano-tectonic earthquakes indicating rock fracturing and 47 long-period earthquakes signifying the movement of gas and magma recorded during 5-9 July. A period of continuous ash-and-gas emissions was visible on 5 July with the plumes drifting more than 10 km SE and E. The Washington VAAC reported that ash plumes and periodic puffs of ash rose 5.5-9.1 km (18,000-30,000 ft) a.s.l. and drifted N and NE. On 6 July explosions recorded at 0747 and 2330 produced ash-and-gas plumes that rose as high as 3.5 km above the crater rim and drifted within 30 km NW, NE, SE, and S. According to the VAAC the explosion at 0747 produced a plume of ash and gas that rose to 9.1 km a.s.l., drifted SW, and gradually dissipated, while a lower-altitude plume at 7.6 km (25,000 ft) a.s.l. drifted NE. Gobierno Regional de Moquegua declared a state of emergency for districts in the Moquegua region, along with Coalaque Chojata, Icuña, Lloque, Matalaque (17 km SE), Ubinas, and Yunga of the General Sánchez Cerro province, to be in effect for 60 days.

On 7 July the VAAC reported that at 0320 an ash plume rose to 7.3 km (24,000 ft) a.s.l. and drifted E. At 0900 and 1520 steam plumes with diffuse ash rose to 6.7 km (22,000 ft) a.s.l. and drifted SE. Diffuse gas emissions were visible in satellite images drifting SE at 2120. Very small ash puffs visible in satellite and webcam images at 0920 and 1520 on 8 July rose as high as 6.4 km (21,000 ft) a.s.l. and drifted SE. INGEMMET reported that during 9-11 July sulfur dioxide emissions were low at 300 tons per day. Gas-and-steam plumes rose 150-400 m and drifted S. The Alert Level remained at Orange (the third level on a four-color scale) and the public was warned to stay 4 km away from the crater.

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.

Sources: Instituto Geofísico del Perú (IGP), Instituto Geológico Minero y Metalúrgico (INGEMMET), Gobierno Regional de Moquegua, Washington Volcanic Ash Advisory Center (VAAC)