Vincent Grafhorst / Minden / Crater of active volcano at twilight, Erta Ale, Danakil Depression, Ethiopia

Vincent Grafhorst / Man looking into crater at night, Mount Nyiragongo, Virunga National Park, Democratic Republic of the Congo

Vincent Grafhorst / Lava in volcanic crater, Mount Nyiragongo, Virunga National Park, Democratic Republic of the Congo

Doug Perrine / Molten lava lake in Halemaumau Crater, a pit crater in the summit caldera of Kilauea Volcano, Hawaii Volcanoes National Park, Hawaii.

Tui De Roy / Fissure eruption of Chico Volcano into 9km diameter caldera. Sierra Negra volcano, Isabela Island, Galapagos, Ecuador. October 2005.

Tui De Roy / People watching the Fissure eruption of Chico volcano into 9km diameter caldera. Sierra Negra volcano, Isabela Island, Galapagos, Ecuador. October 2005.

Tui De Roy / Volcanic caldera - caldera lake steaming after eruption. Fernandina Island, Galapagos, Ecuador.

D. Parer & E. Parer-Cook / Volcanic caldera, Daphne Island, Galapagos Islands, Ecuador

Igor Shpilenok,Igor Shpilenok / Kamchatka Brown Bear (Ursus arctos beringianus) recently risen from hibernation in the caldera of the Uzon Volcano. Kronotsky Zapovednik Nature Reserve, Kamchatka Peninsula, Russian Far East, April.

Tui De Roy / Volcan Alcedo giant tortoises (Chelonoidis nigra vandenburghi) wallowing in rain pools on caldera floor, possibly for thermoregulation or detering parasites, with sulphur fumaroles in background, Alce...

Martin Gabriel / Mountain ridges of Caldera de Taburiente silhouetted through clouds. View from Roque de los Muchachos, La Palma Island, Canary Islands, Spain, February.

Oriol Alamany / Rano Kau Volcano crater with lagoon and Motu islets in the sea, Easter Island, Pacific ocean, November 2004