During the week moderate explosive activity produced small ash clouds at Guagua Pichincha. The Washington VAAC reported that one such cloud was visible on GOES-8 imagery at 0956 on 1 November and the IG reported that the ash cloud was near the summit level (~5 km a.s.l.). The IG also reported that seismicity continued after the eruption, suggesting that further explosive activity was possible. Small explosions and seismic activity suggested that dome growth occurred. The volcano is at Alert Level Yellow.

Geological Summary. Guagua Pichincha and the older Pleistocene Rucu Pichincha stratovolcanoes form a broad volcanic massif that rises immediately W of Ecuador's capital city, Quito. A lava dome grew at the head of a 6-km-wide scarp formed during a late-Pleistocene slope failure ~50,000 years ago. Subsequent late-Pleistocene and Holocene eruptions from the central vent consisted of explosive activity with pyroclastic flows accompanied by periodic growth and destruction of the lava dome. Many minor eruptions have been recorded since the mid-1500's; the largest took place in 1660, when ash fell over a 1,000 km radius and accumulated to 30 cm depth in Quito. Pyroclastic flows and surges also occurred, primarily to then W, and affected agricultural activity.

Sources: Washington Volcanic Ash Advisory Center (VAAC), Instituto Geofísico-Escuela Politécnica Nacional (IG)