The Boset volcanic complex includes the Boset-Gudda (Great Boset) and Boset-Bericha (Little Boset) composite volcanoes rising above the floor of the Ethiopian Rift valley. Initial basaltic-to-trachytic activity at Gudda followed by rhyolitic effusive and explosive eruptions resulted in the formation of a caldera, a remnant of whose rim is found on the NW flank. Elsewhere, post-caldera activity produced very recent pantelleritic obsidian fissure-fed lava domes and flows that buried the caldera wall. Flank eruptions from fissures parallel to the rift produced voluminous pantelleritic lava flows. Bericha has produced similar very recent obsidian flows and associated pumice flows. Fissures connecting the edifices have erupted basaltic lava flows.