Guagua Pichincha is one of Ecuador's most active volcanoes. The stratovolcano is part of a complex that rises immediately west of the capital Quito, at only 8 km distance from the city center. 3 major explosive eruptions have occurred at Guagua Pichincha in the past 2000 years, the most recent one in 1660. An event of similar size today is a major threat to the ca. 2 million city of Quito.
The volcano and the older extinct Rucu Pichincha stratovolcano form a broad volcanic massif 23 km in diameter. Historical activity of the volcano has included large explosive eruptions some of which produced sub-plinian and plinian eruption columns, lava domes. Guagua Pichincha volcano's eruptions frequently produce dangerous pyroclastic flows.
Following a 100 year long interval of being dormant, Guagua Pichincha volcano has entered a new phase of low seismic, phreatic and magmatic activity in 1981.
A lava dome is located at the head of a 6-km-wide breached caldera that formed during a late-Pleistocene slope failure of Guagua Pichincha about 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. Many minor eruptions have occurred since the beginning of the Spanish era at Guagua Pichincha, which is one of Ecuador's most active volcanoes. 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 the west, and affected agricultural activity, causing great economic losses.
Plinian eruptions from Guagua Pichincha
Over the past 2000 years, 3 Plinian eruptions happened at the Guagua Pichincha volcano, in the 1st century AD, in the 10th century, and in AD 1660. The eruptions produced plinian eruption columns of 25-30 km height and left well-defined fallout pumice layers covering the upper slopes of the volcano. The 10th century eruption was the largest, with a VEI of 5.
(C. Robin et al. (2008) "Late Holocene phases of dome growth and Plinian activity at Guagua Pichincha volcano (Ecuador)", Journal of Volcanology and Geothermal Research, 176, pp. 7–15)
