BackgroundVolcán Mojanda's geologic history is complex:
Remnants of an earlier stratovolcano edifice composed of andesitic lava flows underlies the present-day Mojanda edifice. The earlier volcano collapsed leaving a caldera, inside which a new smaller andesitic stratovolcano, Mojanda, was built. Mojanda consists mainly of basic andesite lava flows, scoria flow deposits and a thick summit series of vitric breccias. Mojanda's summit cone was destroyed by phreatoplinian eruptions which left a small summit caldera, containing 2 lakes.
The andesitic-to-rhyolitic Fuya Fuya volcano was constructed contemporaneously with Mojanda immediately to the west. Fuya Fuya had 2 major rhyolitic plinian eruptions, which might have been associated with the formation of a caldera, which occurred less than 165,000 years ago and left a large horseshoe-shaped caldera open to the west.
This collapse can be compared to Mount St. Helens 1980 debris avalanche. It removed a large part of Fuya Fuya and the western part of Mojanda volcano. The resulting avalanche was accompanied by large pyroclastic flows.
After this event, Fuya Fuya entered a more effusive eruptive phase and built a new cone and dacitic lava domes inside its caldera, including the San Bartolo cone. The youngest domes of Fuya Fuya are unglaciated and could be loess than 10,000 years old.
- Smithsonian / GVP volcano information
- Robin et al (2009) "Evolution of the late Pleistocene Mojanda–Fuya Fuya volcanic complex (Ecuador), by progressive adakitic involvement in mantle magma sources", Bull Volc., Volume 71, Number 3, 233-25
See also: Sentinel hub | Landsat 8