El Tatio geyser basin on altiplano, boiling pool with algal colour zoning, Atacama Desert, Chile, South America

Boiling mud pool, Namafjall geothermal area, near Lake Myvatn, northeast area, Iceland, Polar Regions

Natural pool of boiling water, geothermal area, Te Puia, Gisborne District, North Island, New Zealand, Pacific

Blisters measuring about 10 cm across in boiling mud pool, Mud volcano, Yellowstone National Park, UNESCO World Heritage Site, Wyoming, United States of America (U.S.A.), North America

Bubbling mud pools and geothermal ground on Krafla mountain near Myvatn, Iceland, Polar Regions

Bubbling mud pools in the geothermal area of Hverir near Myvatn, Northern Iceland, Polar Regions

Bubbling mud pools in the geothermal area of Hverir near Myvatn, Northern Iceland, Polar Regions

Bubbling mud pools in the geothermal area of Hverir near Myvatn, Northern Iceland, Polar Regions

Bubbling mud pools in the geothermal area of Hverir near Myvatn, Northern Iceland, Polar Regions

Strokkur geyser erupting, in the Geysir hot springs area, Haukadalur geothermal area, Southwest Iceland

A blue coloured boiling hot mud pool emanates steam as the sunset colours the sky orange, in Hveraröndor Hverir Geothermal Area at Namaskard Pass, North Iceland.