Milan Radisics / Aerial shot of rootless cones or pseudocraters, formed by steam explosions as flowing hot lava crosses over a wet surface, South Iceland, August 2018.

Morley Read / Aerial timelapse rising over misty cloudforest covering the slopes of Sumaco Volcano, with a water filled crater lake in foreground, Napo Province, Ecuador, 2018. (non-ex)

Derek Galon / High altitude Boeri Lake in old volcano crater, Morne Trois Pitons National Park, Dominica, West Indies, Windward Islands.

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

Guy Edwardes / Quilota Crater Lake, Cotopaxi Province, Ecuador, September 2010.

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

Nick Turner / Crater lake with reflections of clouds in the water, Queen Elizabeth National Park, Uganda, January 2009.

Inaki Relanzon / Volcanic eruption, Eyjafjallajokull, near the Myrdalsjokull glacier, South Iceland, april 2010.

Inaki Relanzon / Volcanic eruption, Eyjafjallajokull, near the Myrdalsjokull glacier, South Iceland, april 2010.

Inaki Relanzon / Volcanic eruption, Eyjafjallajokull, near the Myrdalsjokull glacier, South Iceland, april 2010.

Yva Momatiuk & John Eastcott / Volcanic Ubehebe Crater, Death Valley National Park, California

Pete Oxford / Bartolome Island a landscape of lava and ash, Galapagos Islands, Ecuador

Anup Shah / Aerial view inside crater of Mt Longohot, Mount Longonot NP, Kenya

Tui De Roy / Galapagos Land Iguana (Conolophus subcristatus) female searching for descent route into 1, 000 meter active caldera to nest, Fernandina Island, Galapagos Islands, Ecuador

Tui De Roy / Galapagos Hawk (Buteo galapagoensis) overlooking 1000 meter deep active caldera, Fernandina Island, Galapagos Islands, Ecuador

Tui De Roy / Galapagos Giant Tortoise (Chelonoidis nigra) large male on caldera rim, Alcedo Volcano, Isabella Island, Galapagos Islands, Ecuador

Tui De Roy / Cerro Azul caldera with lake and tufa cone at 5,900 feet, Cerro Azul Volcano, Isabella Island, Galapagos Islands, Ecuador

Tui De Roy / Galapagos Giant Tortoise (Chelonoidis nigra) group wallowing in seasonal pool on caldera rim, Alcedo Volcano, Isabella Island, Galapagos Islands, Ecuador

Tui De Roy / Galapagos Giant Tortoise (Chelonoidis nigra) group wallowing in seasonal pond on caldera rim, Alcedo Volcano, Isabella Island, Galapagos Islands, Ecuador

Morley Read / Aerial shot descending towards Wawa Sumaco crater lake, with Sumaco Volcano in background, rainbow and pristine cloudforest, Napo Province, Ecuador, 2018. (non-ex)

Morley Read / Rising aerial shot ascending out of the forest at dawn, revealing Sumaco Volcano and Laguna Wawa Sumaco crater lake, Napo Province, Ecuador, 2018. (non-ex)

Morley Read / Timelapse of Sumaco Volcano, with montane rainforest and Laguna Wawa Sumaco crater lake in foreground, Orellana Province, Ecuador, 2018. (non-ex)

Morley Read / Aerial view of Laguna Wawa Sumaco volcanic crater lake at dawn, with mist blowing through the pristine montane rainforest, Sumaco Volcano, Orellana Province, Ecuador, 2018. (non-ex)

Morley Read / Aerial shot ascending to view Sumaco Volcano and Laguna Wawa Sumaco volcanic crater lake, Orellana Province, Ecuador, 2018. (non-ex)

Espen Bergersen / Berserkjahraun is a 4000-year-old lava field situated on the Snaefellsnes peninsula, Grakula Scoria crater, Iceland, October.

Espen Bergersen / Berserkjahraun, a 4000-year-old lava field situated on the Snaefellsnes peninsula, Grakula Scoria Crater, Iceland, October 2017

Espen Bergersen / Berserkjahraun, a 4000-year-old lava field situated on the Snaefellsnes peninsula, Raudkula Scoria crater. Iceland, October 2017

Espen Bergersen / Berserkjahraun, a 4000-year-old lava field situated, Snaefellsnes peninsula.Raudkula Scoria Crater. Iceland, October 2017

Claudio Contreras / Teddy-bear cholla (Cylindropuntia bigelovii) in El Elegante volcano crater. El Pinacate Biosphere Reserve, northwest Mexico.

Milan Radisics / Aerial shot of rootless cones or pseudocraters, formed by steam explosions as flowing hot lava crosses over a wet surface, South Iceland, August 2018.

Milan Radisics / Aerial shot of rootless cones or pseudocraters, formed by steam explosions as flowing hot lava crosses over a wet surface, South Iceland, August 2018.

Milan Radisics / Aerial shot of rootless cones or pseudocraters, formed by steam explosions as flowing hot lava crosses over a wet surface, South Iceland, August 2018.

David Fleetham / View across crater of dormant Haleakala / East Maui Volcano. Haleakala National Park, Maui, Hawaii. March 2016.

David Fleetham / Hawai'i silversword (Argyroxiphium sandwicense macrocephalum) covered by an unusual snowfall near crater summit of dormant Haleakala / East Maui Volcano. Haleakala National Park, Maui, Hawaii. Feb...

Doug Perrine / Ohia lehua tree (Metrosideros polymorpha) on edge of caldera with lava lake, Halemaumau Crater, Kilauea Volcano, Hawaii Volcanoes National Park, Hawaii, March 2017.

Doug Perrine / Lava lake hidden the caldera of Halemaumau Crater lights up a plume of steam, sulfur dioxide, and sulfuric acid at dusk, Kilauea Volcano, Hawaii Volcanoes National Park, Hawaii. March 2017.

Doug Perrine / Lava lake hidden the caldera of Halemaumau Crater lights up a plume of steam, sulfur dioxide, and sulfuric acid at dusk, Kilauea Volcano, Hawaii Volcanoes National Park, Hawaii.

Doug Perrine / Ohia lehua tree (Metrosideros polymorpha) with garlands hung in it. At edge of caldera with lava lake, Halemaumau Crater, Kilauea Volcano, Hawaii Volcanoes National Park, Hawaii, March 2017.

Kirkendall-Spring / Lava glowing in the Halema'uma'u Crater viewed from the Jaggar Museum in Volcanoes National Park Hawaii. December 2016.

Kirkendall-Spring / Lava glowing in the Halema'uma'u Crater viewed from the Jaggar Museum in Volcanoes National Park, Hawaii. December 2016.

Kirkendall-Spring / Lava glowing in the Halema'uma'u Crater viewed from the Jaggar Museum in Volcanoes National Park, Hawaii. December 2016.

Vincent Grafhorst / Smoke inside active volcanic crater, Erta Ale, Danakil Depression, Ethiopia

Vincent Grafhorst / Tourists on crater rim of active volcanic crater, Danakil Depression, Ethiopia

Vincent Grafhorst / Lava inside volcanic crater at night, Erta Ale, Danakil Depression, Ethiopia

Vincent Grafhorst / Smoke from volcanic crater at night, Erta Ale, Danakil Depression, Ethiopia

Michel Roggo / Underwater view of Blue Lake, lake in an extinct volcano, Mount Gambier, South Australia, Australia. March 2015. Photographed for The Freshwater Project

Michel Roggo / Underwater view of Blue Lake, lake in an extinct volcano, Mount Gambier, South Australia, Australia. March 2015. Photographed for The Freshwater Project

Michel Roggo / Underwater view of Blue Lake, lake in an extinct volcano, Mount Gambier, South Australia, Australia. March 2015. Photographed for The Freshwater Project

Michel Roggo / Blue Lake, lake in an extinct volcanic maar (a broad volcanic crater) Mount Gambier, South Australia, Australia, March 2015 . Photographed for The Freshwater Project

Michel Roggo / Blue Lake, lake in an extinct volcanic maar (a broad, low-relief volcanic crater) Mount Gambier, South Australia, Australia, March 2015 . Photographed for The Freshwater Project

Michel Roggo / Blue Lake, lake in an extinct volcanic maar (a broad volcanic crater) Mount Gambier, South Australia, Australia, March 2015 . Photographed for The Freshwater Project

Paul Bertner / Volcano at night, Mount Nyiragongo, Virunga National Park, Democratic Republic of the Congo

Christophe Courteau / Timelapse of the lava lake in Nyiragongo Crater at night, Virunga National Park, Democratic Republic of Congo, 2016.

Christophe Courteau / Close-up of the lava lake in Nyiragongo Crater at night, Virunga National Park, Democratic Republic of Congo, 2016.

Frederique Olivier / Panning shot of Ngorongoro Crater from the crater rim, Tanzania.

Jiri Lochman / The rim of the ancient volcanic crater, Border Ranges National Park, Gondwana Rainforest UNESCO Natural World Heritage Site, New South Wales, Australia.

Jiri Lochman / Rim of ancient volcanic crater, Border Ranges National Park, Gondwana Rainforest UNESCO Natural World Heritage Site, New South Wales, Australia.

Doug Perrine / Hot lava fountains at a subduction zone at the edge of a lava lake, covered by plates of partially solidified cooled lava floating on its surface, in a pit within Halemaumau Crater, Kilauea Volcano, H...

Doug Perrine / Molten lava boils at night in a lava lake in a pit below the crater floor of Halemaumau Crater, Kilauea Volcano, Hawaii. Red-orange jagged lines are junctures between plates of hard cooled lava floati...

Doug Perrine / Molten lava boiling in a lava lake in a pit below the crater floor of Halemaumau Crater, Kilauea Volcano, Hawaii. May 2015.

Nick Upton / Caldera de los Marteles, a large volcanic crater with Canary island sage (Salvia canariensis) and Gran Canaria broom (Teline microphylla) bushes, near Rincon. Gran Canaria UNESCO Biosphere Reserve, Gr...

Nick Upton / Caldera de los Marteles, a large volcanic crater with Canary island sage (Salvia canariensis) and Gran Canaria broom (Teline microphylla) bushes, near Rincon. Gran Canaria UNESCO Biosphere Reserve, Gr...

David Noton / Eldborg volcanic crater with snowclad Hafursfell beyond, Snaefellsnes Peninsula, Iceland, March 2015,

Julian Hume / View of Diamond Crater, Oahu, around 1000 years ago. King Kong finch (Chloridops regiskongi) flying past an Oahu palmcreeper (Ciridops sp) perched. Extinct 1892. Directly behind, an O'ahu O'o (Moho ap...

Christophe Courteau / Salt harvesting system inside the crater, Bunyampaka salt lake, Queen Elizabeth National Park. Uganda

Christophe Courteau / Panoramic view across the Ngorongoro Crater, Tanzania.

Christophe Courteau / Panoramic view across the crater of Ol Doinyo Lengai, known locally as The Mountain of God, Rift Valley, Tanzania. It is still an active volcano.

Eric Baccega / Lava lake at night in the crater of Nyiragongo Volcano, Virunga National Park, North Kivu Province, Democratic Republic of Congo July 2016.

Eric Baccega / Lava lake at night in the crater of Nyiragongo Volcano, Virunga National Park, North Kivu Province, Democratic Republic of Congo July 2016.

Eric Baccega / Steam rising from active lava lake in the crater of Nyiragongo Volcano, Virunga National Park, North Kivu Province, Democratic Republic of Congo, Africa July 2016.

Eric Baccega / Steam rising from active lava lake in the crater of Nyiragongo Volcano, Virunga National Park, North Kivu Province, Democratic Republic of Congo, Africa

Eric Baccega / Lava lake at night in the crater of Nyiragongo Volcano, Virunga National Park, North Kivu Province, Democratic Republic of Congo

Alex Hyde / (Eryngium carlinae) flowering next to the crater rim of Volcano Irazu, 3400 m. Costa Rica

Alex Hyde / (Eryngium carlinae) flowering next to the crater rim of Volcano Irazu, 3400m Costa Rica

Alex Hyde / Vegetaion including huge leaves of (Gunnera insignis) growing next to the crater rim of Volcano Irazu, 3400m Costa Rica

Alex Hyde / (Gaultheria myrsinoides) flowering next to the crater rim of Volcano Irazu, 3400m. Costa Rica

Alex Hyde / (Maianthemum gigas) flowering next to the crater rim of Volcano Irazu, 3400m, Costa Rica

Alex Hyde / (Castilleja irasuensis) flowering next to the crater rim of Volcano Irazu, 3400m. Costa Rica

Vincent Grafhorst / Lava in volcanic crater, 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

Vincent Grafhorst / Lava in volcanic crater, 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

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

Enrique Lopez-Tapia / An armed soldier watching the activity of Erta Ale volcano crater at dawn. Afar Region, Ethiopia, Africa. November 2014.

Enrique Lopez-Tapia / An armed soldier watching activity of Erta Ale volcano crater at dawn. Afar Region, Ethiopia, Africa. November 2014. November 2014.

Kirkendall-Spring / Paved section of the North Crater Trail in Craters Of The Moon National Monument and Preserve, Idaho, USA, June 2015.

Kirkendall-Spring / Syringa (Philadelphus lewisii) blooming along the North Crater Flow Trail with cinder cone fragments in the background, Craters Of The Moon National Monument and Preserve, Idaho, USA, June.

Kirkendall-Spring / Twisted tree trunk at night along the North Crater Flow Trail, Craters Of The Moon National Monument, Idaho, USA, July.

Suzi Eszterhas / Volcanic crater near Lake Myvatn, Northern Iceland, June 2009.

Eric Baccega / Erta Ale Volcano crater glowing at night, Danakil Depression, Ethiopia, March 2015.

Michele Westmorland / View of Twin Craters / Los Gemelos, Santa Cruz Island, Galapagos Islands, January 2012.

Tui De Roy / Galapagos Hawk (Buteo galapagoensis) pair overlooking sulphur fumaroles on caldera rim, Alcedo Volcano, Isabela Island, Galapagos Islands, Ecuador

Suzi Eszterhas / Craters along shore of Myvatn Lake, northern Iceland