Eric Baccega / Dallol hot spring with salt concretions coloured by sulphur, potassium and iron, Dallol Volcano, Danakil Depression, Ethiopia, March 2015.

Thomas Marent / Japanese Macaque (Macaca fuscata) mother and young in hot spring with juveniles grooming, Jigokudani, Nagano, Japan

Floris van Breugel / A hot spring in the West Thumb Geyser Basin, Yellowstone National Park, Wyoming. The colors are a result of thermophilic bacteria living in the hot springs. December 2010.

Mark MacEwen / Japanese macaque (Macaca fuscata) relaxing in hot spring in Jigokudani, Yaenkoen, Nagano, Japan, February.

Mark MacEwen / Japanese macaque (Macaca fuscata) sleeping at hot spring in Jigokudani, Yaenkoen, Nagano, Japan, February.

Anup Shah / Japanese Macaque (Macaca fuscata) baby sitting on the edge of thermal hotspring pool. Jigokudani Yean-Koen National Park, Japan, February.

Fiona Rogers / Japanese Macaque (Macaca fuscata) pair grooming in a geothermal spring, Jigokudani Monkey Park, Japan

Fiona Rogers / Japanese Macaque (Macaca fuscata) baby in a geothermal spring, Jigokudani Monkey Park, Japan

Fiona Rogers / Japanese Macaque (Macaca fuscata) baby sucking its toe in a geothermal spring, Jigokudani Monkey Park, Japan

Kirkendall-Spring / Travertine limestone terraces of Mammoth Hot Springs in Yellowstone National Park, Wyoming, USA, June 2013.

Denis-Huot,Denis-Huot / Lesser flamingo (Phoeniconaias minor) aerial view of flock and geyser, Bogoria Game Reserve, Kenya

Diane McAllister / Japanese Macaques (Macaca fuscata) enjoy time soaking and grooming in the hot spring in Jigokudani, Japan.