Report on Guagua Pichincha (Ecuador) — 16 April-22 April 2003
Smithsonian / US Geological Survey Weekly Volcanic Activity Report,
16 April-22 April 2003
Managing Editor: Gari Mayberry
Please cite this report as:
Global Volcanism Program, 2003. Report on Guagua Pichincha (Ecuador). In: Mayberry, G (ed.), Weekly Volcanic Activity Report, 16 April-22 April 2003. 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 indicated that they detected seismic signals from a very minor Guagua Pichincha eruption on 17 April. The volcanologist on duty saw no visual signs of ash, implying that the seismic signals resulted from a very weak eruption with products confined to the summit crater. The IG also noted seeing similar seismic signals sporadically over the previous few days. The signals were thought to result from out-gassing, a class of behavior that if more energetic could generate larger ash clouds of impact to local residents and aviators. The IG also reported several volcano-tectonic earthquakes, seismic signals of rockfalls, and one long-period earthquake.
Geological Summary. 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.