Islands in the South Atlantic Ocean, about midway between South America and Africa; Ascension Island lies 700 nm northwest of Saint Helena; Tristan da Cunha lies 2,300 nm southwest of Saint Helena

Africa

Saint Helena Island 122 sq km; Ascension Island 88 sq km; Tristan da Cunha island group 98 sq km

Slightly more than twice the size of Washington, DC

Tropical marine; mild, tempered by trade winds

Tropical marine; mild, semi-arid

Temperate marine; mild, tempered by trade winds (tends to be cooler than Saint Helena)

The islands of this group result from volcanic activity associated with the Atlantic Mid-Ocean Ridge

Rugged, volcanic; small scattered plateaus and plains

Surface covered by lava flows and cinder cones of 44 dormant volcanoes; ground rises to the east

Sheer cliffs line the coastline of the nearly circular island; the flanks of the central volcanic peak are deeply dissected; narrow coastal plain lies between The Peak and the coastal cliffs

Queen Mary's Peak on Tristan da Cunha 2,060 m; Green Mountain on Ascension Island 859 m; Mount Actaeon on Saint Helena Island 818 m

Active volcanism on Tristan da Cunha

The island volcanoes of Tristan da Cunha (elev. 2,060 m) and Nightingale Island (elev. 365 m) experience volcanic activity; Tristan da Cunha erupted in 1962 and Nightingale in 2004

Saint Helena harbors at least 40 species of plants unknown elsewhere in the world; Ascension is a breeding ground for sea turtles and sooty terns; Queen Mary's Peak on Tristan da Cunha is the highest island mountain in the South Atlantic and a prominent landmark on the sea lanes around southern Africa