Remote Tristan da Cunha

Remote Tristan da Cunha

Tristan da Cunha, often said to be the most remote inhabited island in the world, is the sort of place where seabirds outnumber people. It is part of an island group in the South Atlantic Ocean situated approximately halfway between the southern tips of South America and Africa. Neighboring volcanic peaks within the group include the smaller, uninhabited Inaccessible Island and the Nightingale Islands.

The OLI-2 (Operational Land Imager-2) on Landsat 9 captured this image of the island group on May 24, 2023. Tristan da Cunha’s highest point, Queen Mary’s Peak, reaches 2,060 meters (6,760 feet) above sea level and displays steep gullies that radiate downward on all sides.

The island’s vegetation is divided into distinct zones related to elevation. Large tussock-forming grasses once covered the island’s coastal fringes, but most of this has become pasture, according to the Royal Botanic Gardens, Kew. Woodlands of Phylica arborea, known as island cape myrtle, cover the volcano’s lower slopes (dark green) and transition into ecosystems that include tree ferns, sphagnum moss, small grasses, bryophytes, and lichens on its upper reaches (light green).

Offshore, underwater forests of giant kelp surround the islands. The kelp, Macrocystis pyrifera, is one of the fastest-growing seaweeds on the planet. Though suspended sediment may be discoloring the water in some areas, signs of kelp forests (green) are visible in several areas immediately offshore. In preparation for an ecological survey of the island’s marine ecosystems, a team of National Geographic researchers used dozens of Landsat 7 and 8 images to locate the likely locations of kelp forests and plan underwater surveys.

About 240 people live in Edinburgh of the Seven Seas, the small town on the northern edge of the island. The main occupations are fishing and farming. Many residents harvest crayfish—sold as Tristan rock lobster—and raise potatoes and livestock. Away from town, thousands of birds, including populations of northern rockhopper penguins, Atlantic yellow-nosed albatross, and broad-billed prion, nest on the small, circular island.

The number of birds might be higher if mice and rats had not found their way to the islands. Likely introduced by sailors in the 1800s, rodent populations have boomed, despite an annual rat hunting competition and holiday. The small mammals are thought to eat large numbers of bird eggs and young birds.

Ecologists have warned that an abundance of oversized mice may even be on the verge of pushing a critically endangered seabird, the Tristan albatross, to the brink of extinction on Gough Island (out of the scene to the southeast). Another notable species on Inaccessible Island is the Inaccessible Island rail, the smallest living flightless bird in the world.

All of the islands are the product of a volcanic hot spot, a type of volcanism that brings magma from deep within Earth’s mantle. Tristan da Cunha, the youngest and largest of the group, formed about 200,000 years ago. It last erupted in October 1961, forcing people on the island to evacuate. Radiometric dating techniques indicate that Nightingale is the oldest of the three main islands, with volcanic rocks ranging from 360,000 to 18 million years old. Inaccessible Island has rocks that range from 1 million to 6 million years old.

NASA Earth Observatory images by Lauren Dauphin, using Landsat data from the U.S. Geological Survey. Story by Adam Voiland.

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