Report on Cotopaxi (Ecuador) — 3 June-9 June 2015
Smithsonian / US Geological Survey Weekly Volcanic Activity Report,
3 June-9 June 2015
Managing Editor: Sally Kuhn Sennert
Please cite this report as:
Global Volcanism Program, 2015. Report on Cotopaxi (Ecuador). In: Sennert, S K (ed.), Weekly Volcanic Activity Report, 3 June-9 June 2015. Smithsonian Institution and US Geological Survey.
0.677°S, 78.436°W; summit elev. 5911 m
All times are local (unless otherwise noted)
IG reported that the seismic network at Cotopaxi had detected increases since mid-April; 628 local earthquakes were detected in April and 3,000 events were detected in May. Very-long-period earthquakes were recorded in May, especially during the last week, located in the N and NE parts of the cone at depths of 3 and 14 km. Sulfur dioxide emissions increased on 20 May, possibly from sporadic emissions becoming more continuous, and were 2,500-3,000 tons/day by the end of May. Baseline values were 500 tons/day. Slight inflation was detected by N and NE inclinometers. Crater fumarolic activity increased, with plumes sometimes visible from Quito (55 km N). Climbers indicated a very intense sulfur dioxide odor on the N part of the cone during 22-23 May.
Geological Summary. The symmetrical, glacier-covered, Cotopaxi stratovolcano is Ecuador's most well-known volcano and one of its most active. The steep-sided cone is capped by nested summit craters, the largest of which is about 550 x 800 m in diameter. Deep valleys scoured by lahars radiate from the summit of the andesitic volcano, and large andesitic lava flows extend to its base. The modern edifice has been constructed since a major collapse sometime prior to about 5,000 years ago. Pyroclastic flows (often confused in historical accounts with lava flows) have accompanied many explosive eruptions, and lahars have frequently devastated adjacent valleys. Strong eruptions took place in 1744, 1768, and 1877. Pyroclastic flows descended all sides of the volcano in 1877, and lahars traveled more than 100 km into the Pacific Ocean and western Amazon basin. Smaller eruptions have been frequent since that time.