Historically active Santa Barbara volcano at the western end of the island is truncated by two calderas. The youngest of these formed about 15,000 years ago.
Comenditic lava domes fill and surround the caldera.
Pico Alto lies north of the fissure zone in the north-central part of the island and contains a Pleistocene caldera largely filled by lava domes and lava flows. Historical eruptions have occurred from Pico Alto, the fissure zone between Pico Alto and Santa Barbara, and from submarine vents west of Santa Barbara. Click on the index link or scroll down to read the reports. All information contained in these reports is preliminary and subject to change. These phenomena were discontinuous but persisted until the night of 23 December when local residents observed orange lights several miles W of Terceira.