 Radiometric dating indicates that Santa Clara is the oldest of the islands, at 5.8 million years old, followed by Robinson Crusoe, 3.8 – 4.2 million years old, and Alexander Selkirk, 1.0 – 2.4 million years old.The seafloor around Juan Fernández Islands is rich in Manganese–Iron nodules, which may be of potential economic interest.The islands have a subtropical Mediterranean climate, moderated by the cold Humboldt Current, which flows northward to the east of the islands, and the southeast trade winds.