Report on Guagua Pichincha (Ecuador) — 21 March-27 March 2001
Smithsonian / US Geological Survey Weekly Volcanic Activity Report, 21 March-27 March 2001
Managing Editor: Gari Mayberry
Please cite this report as:
Global Volcanism Program, 2001. Report on Guagua Pichincha (Ecuador). In: Mayberry, G (ed.), Weekly Volcanic Activity Report, 21 March-27 March 2001. Smithsonian Institution and US Geological Survey.
0.171°S, 78.598°W; summit elev. 4784 m
All times are local (unless otherwise noted)
The IG reported that during the week of 18-24 March a total of 806 long-period earthquakes were registered. However, 460 of those occurred on the 18th along with a moderate ash emission. Long-period event counts were below 20/day as of 21 March. Visual observations made by the Guards of the Refuge revealed that fumarolic activity increased, with higher steam columns on 18, 22, and 23 March, and a stronger sulfur smell until 22 March. No rockfall sounds were heard. The small number of rockfall signals detected as of 26 March suggests that lava dome 9 is stable. The volcano remained at Alert Level Yellow.
Geologic Background. Guagua Pichincha and the older Pleistocene Rucu Pichincha stratovolcanoes form a broad volcanic massif that rises immediately to the W of Ecuador's capital city, Quito. A lava dome is located at the head of a 6-km-wide breached caldera that formed during a late-Pleistocene slope failure ~50,000 years ago. Subsequent late-Pleistocene and Holocene eruptions from the central vent in the breached caldera consisted of explosive activity with pyroclastic flows accompanied by periodic growth and destruction of the central lava dome. One of Ecuador's most active volcanoes, it is the site of many minor eruptions since the beginning of the Spanish era. The largest historical eruption took place in 1660, when ash fell over a 1000 km radius, accumulating to 30 cm depth in Quito. Pyroclastic flows and surges also occurred, primarily to then W, and affected agricultural activity, causing great economic losses.