Islands in the Sea of Cortez (aka the Gulf of California) - like much of Baja California - have a volcanic origin, made of multiple layers of ash and tephra plus occasional lava flows.
Erosion along the coastlines exposes these layers, with the varying colors showing the changes in chemistry of the magma in successive generations,
Isla San Esteban is an uninhabited island on which landing is permitted; while walking through the desert one can find several species of lizards endemic to this island.
Isla San Pedro Mártir was once used as a quano mine; it is now a UNESCO World Heritage Site. Surrounded by cliffs, it hosts a large population of sea birds and sea lions.
Keywords:Isla San Pedro Mártir, Islas San Esteban