Gorely volcano, tundra plants on slopes, summit crater rims on skyline, Kamchatka, East Siberia, Russia

Crater of Mount Eden with city beyond, Auckland, Central Auckland, North Island, New Zealand, Pacific

Grand Prismatic Spring, Midway Geyser Basin, Yellowstone National Park, UNESCO World Heritage Site, Wyoming, United States of America, North America

The Blue Lake, a natural reservoir and one of three crater lakes at the top of Mt Gambier, an extinct volcano and town in the south east of the state, South Australia, Australia

Grand Prismatic Spring, Midway Geyser Basin, Yellowstone National Park, UNESCO World Heritage Site, Wyoming, United States of America, North America

Excelsior Geyser Crater, Midway Geyser Basin, Yellowstone National Park, UNESCO World Heritage Site, Wyoming, United States of America, North America

Tourists on the boardwalk around the Grand Prismatic Spring, Midway Geyser Basin, Yellowstone National Park, UNESCO World Heritage Site, Wyoming, United States of America, North America

Grand Prismatic Spring and Excelsior Pool behind, Midway Geyser Basin, Yellowstone National Park, UNESCO World Heritage Site, Wyoming, United States of America, North America

Norris Geyser Basin in Yellowstone National Park, USA

Norris Geyser Basin in Yellowstone National Park, USA

Mount Aso, Kumamoto Prefecture, Japan

Kagoshima Prefecture, Japan

Hot spring with steaming turquoise water, Excelsior Geyser Crater, Yellowstone National Park, Wyoming, USA, North America

Hot spring with steaming turquoise water, Excelsior Geyser Crater, Yellowstone National Park, Wyoming, USA, North America

Strokkur Geysir , Laugarvatn, Iceland

Geysir, Hveravellir, Iceland

Hot spring, Yellowstone national park, Wyoming, USA

Excelsior Geyser Crater near Grand Prismatic Spring, Yellowstone National Park.