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

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

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.