Ubinas is Peru's most active volcano. A small, 1.4-km-wide caldera cuts the top of the volcano. The steep-walled, 150-m-deep summit caldera contains an ash cone with a 500-m-wide and 200 m deep crater Debris-avalanche deposits from the collapse of the SE flank of Ubinas about 3700 years ago extend 10 km from the volcano. Widespread plinian pumice-fall deposits from Ubinas include one of Holocene age about 1000 years ago. Holocene lava flows are visible on the volcano's flanks, but historical activity, documented since the 16th century, has consisted of intermittent minor-to-moderate explosive eruptions.
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Source: abbreviated from Global Volcanism Program information on Ubinas