Report on Guagua Pichincha (Ecuador) — 14 January-20 January 2004
Smithsonian / US Geological Survey Weekly Volcanic Activity Report, 14 January-20 January 2004
Managing Editor: Gari Mayberry
Please cite this report as:
Global Volcanism Program, 2004. Report on Guagua Pichincha (Ecuador). In: Mayberry, G (ed.), Weekly Volcanic Activity Report, 14 January-20 January 2004. Smithsonian Institution and US Geological Survey.
0.171°S, 78.598°W; summit elev. 4784 m
All times are local (unless otherwise noted)
During the afternoon of 7 January, strong rains occurred at Guagua Pichincha and a series of seismic signals attributed to rockfalls and lahars were recorded. A visit to the area by IG scientists on 13 January confirmed that a lahar traveled down the NNE wall of the volcano's crater. In addition, there were small fractures in the SE sector of the volcano and in the crater. IG noted that this activity does not indicate a change in volcanic activity at Guagua Pichincha.
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.