Ripples of lava frozen in time wrinkle the surface of Pinnacle Rock off the Galápagos’ Bartolome Island. The formation is the eroded remains of a volcanic tower known as a tuff cone. Tuff cones are formed when magma from an inland volcano reaches the sea, sputtering layer upon layer of basalt ash that eventually rises into this monument of nature.

(Photograph shot on assignment for, but not published in, the National Geographic book Majestic Island Worlds, 1986)