It is believed that Alcedo volcano emerged from the sea approximately 313,000 years ago, based on its sub -aerial volume of 234 km3 and average eruption rate of 1x106 m3 per year. This has produced a volcano that is 1130m high with a caldera that measures 6.1 x 7.4 km. Alcedo volcano is similar to its neighbours to the north, Darwin and to the south, Sierra Negra which also have shallow slopes for the majority of their height. It is also similar to these two in that the depth of the caldera is less than 25% of the height of the volcano. This contrasts with the other major shield volcanoes, Cerro Azul, Wolf on Isabela and Fernandina that have much steeper slopes and have calderas that have a depth which is 40-60% of the sub-aerial height.