The Galápagos Islands are an isolated set of volcanoes, consisting of shield volcanoes and lava plateaus, located 1,200 km (746 mi) west of Ecuador. They are driven by the Galápagos hotspot, and are between 4.2 million and 700,000 years of age. The largest island, Isabela, consists of six coalesced shield volcanoes, each delineated by a large summit caldera. Española, the oldest island, and Fernandina, the youngest, are also shield volcanoes, as are most of the other islands in the chain. The Galápagos Islands are perched on a large lava plateau known as the Galápagos Platform, which creates a shallow-water depth of 360 to 900 m (1,181 to 2,953 ft) at the base of the islands, which stretch over a 174 mi (280 km)-long diameter. Since Charles Darwin‘s famous visit to the islands in 1835, over 60 recorded eruptions have occurred in the islands, from six different shield volcanoes. Of the 21 emergent volcanoes, 13 are considered active.
The Galápagos are geologically young for such a big chain, and the pattern of their rift zones follows one of two trends, one north-northwest, and one east–west. The composition of the lavas of the Galápagos shields are strikingly similar to those of the Hawaiian volcanoes. Curiously, they do not form the same volcanic “line” associated with most hotspots. They are not alone in this regard; the Cobb–Eickelberg Seamount chain in the North Pacific is another example of such a delineated chain. In addition, no clear pattern of age is seen between the volcanoes, suggesting a complicated, irregular pattern of creation. How exactly the islands were formed remains a geological mystery, although several theories have been posited.
Wolf Volcano (also known as Mount Whiton), the highest peak in the Galápagos Islands, is situated on Isabela Island and reaches 1,707 m (5,600 ft). It is a shield volcano with a characteristic upturned soup-bowl shape. Inactive for 33 years, the Wolf Volcano erupted May 25, 2015. The volcano is not located near a populated area. The lava is flowing down the volcano’s east and southeast sides, so the pink land iguanas inhabiting the north and west sides have not been endangered.
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 26 June 2018 and ending on 23 Aug 2018.
Alcedo Volcano is one of the six coalescing shield volcanoes that make up Isabela Island. Alcedo, like the other volcanoes in the Galapagos, has been formed as part of the Galapagos hotspot, which is a mantle plume resulting in a hotspot. The volcano is not directly on the hotspot, which is believed to be under the neighbouring island of Fernandina to the west. However, it is still active, with its last eruption in 1993. Due to the remoteness of Alcedo, historical eruptions are not well recorded. An eruption occurred between 1946 and 1960, as determined from variation in photographs. Another eruption in 1954 is now believed to have taken place on neighbouring Sierra Negra. Even the 1993 eruption was not observed at the time and only recorded after an expedition discovered new craters in 1995.