Alejandro Selkirk Island
, previously known as Isla Más Afuera
, is the second largest and most westernly island of the Juan Fernández Islands
. It is situated 181 km west of Robinson Crusoe Island
In 1966, the Chilean
government renamed Isla Más Afuera to Alejandro Selkirk Island, with Isla Más a Tierra becoming Robinson Crusoe Island. Alexander Selkirk
was a Scottish
sailor who was marooned on Robinson Crusoe Island (then uninhabited) for four years. His survival inspired the novel Robinson Crusoe
There is a former penal settlement on the middle of the east coast, at . About 20 buildings can be made out on detailed satellite images
The settlement was operative from 1909 to 1930. It initially housed 190 criminals. From 1927 to 1930, there were 160 political prisoners on the island.
The island measures 11 km north-south and 6 km east-west, and has an area of 44.6 km². It is densely wooded and very mountainous and is marked by ridges
and numerous deep ravines
lead to a steep-to, rugged coast on the east side of the island off which are tremendous depths. The coastal cliffs
are up to 1,000 meters high. The south, west and north sides of the island have sandy strips of beach which extend 0.1 mile offshore in places. The highest peak, Cerro de Los Inocentes, rises to 1,329 metres
at the of the southwest side of Alejandro Selkirk Island, and at the southwest extremity there is a prominent rock with a hole through it.
Landing is possible near the center of the east shore at Quebrada Sanchez, and at the foot of Quebrada Las Casas ), where there is a boat slip and buildings of the former penal colony. Anchorage can be taken about 0.3 mile ENE of Quebrada Sanchez in depths of 40.2 to 49.4 meters. The ravine is recognized by a white patch on a hill near it. Anchorage can also be taken, in depths of 31.1 to 50 meters, with sand bottom, off Rada de la Colonia.
Dating of the rocks on the island show that it is the youngest of the Juan Fernández Islands at an age between 1 or 2 million years old. Due to its age, the island has had a little erosion.
About 59 km southwest of the island is submerged Sefton Reef almost reaching sea level, and 47 km northwest Yosemite Rock (). Podesta Island reported further west is a phantom island.
The Juan Fernández fur seal is known to have existed during the late-1600s on the island with the population of the seals on Alejandro Selkirk Island and Robinson Crusoe Island believed to be in excess of four million by the late 17th century. A census of 1797 estimated a population 2-3 million fur seals. The species was hunted to near extinction by the 1800s and was thought to be extinct for 100 years until 200 were found on the island in 1965. Since then, the population has grown at a steady rate of 15-20% every year.