Report on Sangay (Ecuador) — 5 May-11 May 2021
Smithsonian / US Geological Survey Weekly Volcanic Activity Report,
5 May-11 May 2021
Managing Editor: Sally Kuhn Sennert
Please cite this report as:
Global Volcanism Program, 2021. Report on Sangay (Ecuador). In: Sennert, S K (ed.), Weekly Volcanic Activity Report, 5 May-11 May 2021. Smithsonian Institution and US Geological Survey.
2.005°S, 78.341°W; summit elev. 5286 m
All times are local (unless otherwise noted)
IG reported a high level of activity at Sangay during 5-11 May. Seismicity was characterized by 3-28 daily explosions, long-period earthquakes, lahar events, and signals indicating emissions. Weather clouds and rain sometimes prevented visual observations of the volcano, especially during 8-9 May. Based on the Washington VAAC and occasional webcam images, ash plumes were visible during 4-8 and 10 May rising as high as 2 km above the summit and drifting mainly NW, W, and SW. Eruptions during midmorning and again around noon on 7 May produced ash plumes that rose 2.3 km and drifted WSW; higher plumes rose 5.4 km and drifted NW. Notable ashfall was reported in multiple places in the afternoon; in Guamote (40 km WNW), in Riobamba, and Alusí. A lava flow descended the SE flank. Minor amounts of ash fell in parts of the Guayas province in the morning of 8 May. The seismic network recorded lahar signals during 7-10 May.
Geological Summary. The isolated Sangay volcano, located east of the Andean crest, is the southernmost of Ecuador's volcanoes and its most active. The steep-sided, glacier-covered, dominantly andesitic volcano grew within horseshoe-shaped calderas of two previous edifices, which were destroyed by collapse to the east, producing large debris avalanches that reached the Amazonian lowlands. The modern edifice dates back to at least 14,000 years ago. It towers above the tropical jungle on the east side; on the other sides flat plains of ash have been sculpted by heavy rains into steep-walled canyons up to 600 m deep. The earliest report of a historical eruption was in 1628. More or less continuous eruptions were reported from 1728 until 1916, and again from 1934 to the present. The almost constant activity has caused frequent changes to the morphology of the summit crater complex.