Report on Sangay (Ecuador) — 3 July-9 July 2019
Smithsonian / US Geological Survey Weekly Volcanic Activity Report, 3 July-9 July 2019
Managing Editor: Sally Kuhn Sennert
Please cite this report as:
Global Volcanism Program, 2019. Report on Sangay (Ecuador). In: Sennert, S K (ed.), Weekly Volcanic Activity Report, 3 July-9 July 2019. 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 that a new eruption at Sangay began on 7 May and was continuing as of 3 July. Activity was concentrated at two eruptive centers: the Central Crater and the Ñuñurcu dome (located 190 m SSE of Central Crater). Sporadic explosions at Central Crater produced ash plumes that rose as high as 1.1 km above the crater rim and drifted W and SW. The Ñuñurcu dome fed at least three lava flows that traveled down the SE flank. Collapses of the lava-flow fronts generated small pyroclastic flows and numerous block flows that traveled as far as 3,888 m elevation. Staff of the Parque Nacional Sangay observed atypical sedimentation consisting of volcanic material at the confluence of the Upano River and its tributary, the Volcán River, 23 km SE of the summit. Areas of steaming in the Volcán River were possibly from hot blocks originating from the volcano. Residents of Macas (42 km SSE) reported increased turbidity in the Upano from pyroclastic material.
Geologic Background. 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.