Report on Cayambe (Ecuador) — 14 December-20 December 2016
Smithsonian / US Geological Survey Weekly Volcanic Activity Report, 14 December-20 December 2016
Managing Editor: Sally Kuhn Sennert
Please cite this report as:
Global Volcanism Program, 2016. Report on Cayambe (Ecuador). In: Sennert, S K (ed.), Weekly Volcanic Activity Report, 14 December-20 December 2016. Smithsonian Institution and US Geological Survey.
0.029°N, 77.986°W; summit elev. 5790 m
All times are local (unless otherwise noted)
IG reported that a seismic swarm detected at Cayambe on 5 June was characterized by an increase in the number of volcano-tectonic events. The swarm occurred near an active fault system, NE of the volcano. The seismic activity progressively declined to baseline levels during August. A minor increase was again observed in September, with events migrating to locations underneath the volcano, and then became more pronounced in November. Anomalously large-magnitude earthquakes occurred on 14 November (M 3.3) and on 27 November (M 3.6). Another swarm was also detected on 27 November. Seismicity continued above baseline levels through 2 December. In addition, climbers reported an increase in a sulfur odor.
On 13 December IG noted that during the previous week there was an average of 68 earthquakes/day, mainly volcano-tectonic events and some long-period signals. A M3 event located at a depth of 7 km below the summit was recorded on 8 December. Climbers continued to report an increase in a sulfur odor, and also the presence of new cracks in the glacier near the summit.
Geologic Background. The massive compound andesitic-dacitic Cayambe stratovolcano is located on the isolated western edge of the Cordillera Real, east of the Inter-Andean Valley. The volcano, whose southern flank lies astride the equator, is capped by extensive glaciers, which descend to 4200 m on the eastern Amazonian side. The modern Nevado Cayambe, constructed to the east of older Pleistocene volcanic complexes, contains two summit lava domes located about 1.5 km apart, the western of which is the highest. Several other lava domes on the upper flanks have been the source of pyroclastic flows that reached the lower flanks. A prominent Holocene pyroclastic cone on the lower E flank, La Virgen, fed thick andesitic lava flows that traveled about 10 km E. Nevado Cayambe was recently discovered to have produced frequent explosive eruptions beginning about 4000 years ago, and to have had a single historical eruption during 1785-86.