The more recent islands, Isabela and Fernandina, are still in the process of formation,
the most recent volcanic eruption being registered in 2009.
Thus Isla San Cristobal, the nearest to the mainland, is approximately four million years old and composed of eroded, rounded cones,
while Isla Fernandina dates at less than 7000 years
and is considered to be one of the most active volcanoes in the world.