Six of the volcanoes are still active (1 on Fernandina and 5 on Isabela). The most recent explosion was in Volcan La Cumbre (Fernandina Island) in February 2009.
The type of volcanic make up characterizes the island's look. Most of the Galapagos Islands were made from a single volcanic cone creating a high point of the island with gentle slopes and a flat coastline. Española (the oldest of the chain) and Fernandina (the youngest in the chain) with their single volcanic cone are typical of most of the islands known as a shield volcano.
Shield volcanoes are formed from a build of fluid lava flows. As the flow emits from the central vent it pours out in all directions creating a broad, gently sloping cone of flat, domical shape. The profile is said to resemble a warrior's shield giving these volcanoes their name. The volcanoes build up slowly the result of thousands of fluid basalt lava flows.
The lava cools into thin layers, which continues to accumulate for years, eventually giving the volcano its height. Shield volcanoes make up some of the largest volcanoes in the world including Mauna Loa in Hawaii, which rises 28,000 feet above the ocean floor. Isabela the largest island of the Galapagos Archipelago was created from the fusion of 6 shield volcanoes.