No latest activity reported for O'a Caldera.

Below is a summary of eruption dates and Volcanic Explosivity Indices (VEI).

The following references are the sources used for data regarding this volcano. References are linked directly to our volcano data file. Discussion of another volcano or eruption (sometimes far from the one that is the subject of the manuscript) may produce a citation that is not at all apparent from the title. Additional discussion of data sources can be found under Volcano Data Criteria.

Di Paola G M, 1972. The Ethiopian Rift Valley (between 7° 00' and 8° 40' lat north). {Bull Volc}, 36: 517-560

IAVCEI, 1973-80. Post-Miocene Volcanoes of the World. {IAVCEI Data Sheets, Rome: Internatl Assoc Volc Chemistry Earth's Interior}.

Mohr P A, Mitchell J G, Raynolds R G H, 1980. Quaternary volcanism and faulting at O'a caldera, central Ethiopian Rift. {Bull Volc}, 43: 173-190

Mohr P A, Wood C A, 1976. Volcano Spacings and Lithospheric Attenuation in the Eastern Rift of Africa. {Earth Planet Sci Lett}, 33: 126-144

O'a caldera along the central Ethiopian Rift is the country's largest rift-valley caldera. The caldera forms the eastern portion of the 15 x 25 km dumbbell-shaped Lake O'a (also known as Lake Shalla). Formation of the caldera about 240,000 years ago was accompanied by the eruption of two ignimbrite deposits, the first of which was strongly welded. The only post-caldera activity consists of two pyroclastic cones north of the caldera, one silicic and the other basaltic, and a group of tuff rings, spatter cones, and lava flows of Holocene (perhaps as young as prehistorical) age near the SW shore of the lake. These were erupted along the Corbetti-Shalla segment of the Wonji Fault Belt, which extends north from Corbetti caldera. Fumarolic activity continues on all sides of the lake.