Cerro Azul is a shield volcano on the south western part of Isabela Island, and is one of the most active in the Galapagos, with its last eruption between May and June 2008. Sierra Negra is a large shield volcano at the southeastern end of Isabela Island that rises to an altitude of 1124 m. It coalesces with the volcanoes Cerro Azul to the west and Alcedo to the north. The volcano is one of the most active in the Galapagos, with the last eruption starting on 22 October 2005, and lasting until 30 October 2005.