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Mojanda Volcano | John Seach
Ecuador
0.13 N, 78.27 W
summit elevation 4263 m
Stratovolcanoes
Mojanda volcano consists of two active stratovolcanoes (Mojanda and Fuya Fuya) near the town of Otavalo.
Andesitic lava flows form the main part of the base Mojanda volcano. Following caldera collapse, a small andesitic stratovolcano was built, consisting mainly of basic andesite lava flows, scoria flow deposits and a thick summit series of vitric breccias. This cone was partly destroyed by phreatoplinian eruptions which produced a small, summit caldera.
Fuya Fuya grew on the western flank of Mojanda. Its activity began with andesitic and dacitic viscous lava flows and domes and followed with a period of intense pyroclastic activity, during which two voluminous Plinian airfalls of rhyolitic pumice were erupted. Later, the activity of Fuya Fuya became effusive with the building of an intermediate andesitic edifice, the San Bartolo cone.
A Mount St. Helens type collapse event occurred in Fuya Fuya which resulted in the loss of a large part of Fuya Fuya and the western part of Mojanda. This avalanche was accompanied by large pyroclastic flows and was followed by the construction of a dacitic dome complex within the avalanche caldera.
Further reading
Robin, Claude, et al. "Evolution of the late Pleistocene Mojanda–Fuya Fuya volcanic complex (Ecuador), by progressive adakitic involvement in mantle magma sources." Bulletin of volcanology 71.3 (2009): 233-258.
Robin, Claude, et al. "Mojanda volcanic complex (Ecuador): development of two adjacent contemporaneous volcanoes with contrasting eruptive styles and magmatic suites." Journal of South American Earth Sciences 10.5-6 (1997): 345-359.
Mojanda Volcano Eruptions
No recent eruptions, but evidence of large avalanches.