A hot spring is a spring that is produced by the emergence of geothermally heated groundwater from the Earth's crust. The hot spring pools contain microorganisms known as thermophiles, a type of extremophile. They are organisms that exist in the most unlikely, unlivable, and extreme places, hence their name. The color comes from the way that these thermophiles reflect the light of the sun. There are geothermal hot springs in many locations all over the crust of the earth, but many of these wonderful water bodies are concentrated in the Yellowstone National Park, USA.
# Grand Prismatic Spring, USAThe Grand Prismatic Spring in Yellowstone National Park is the largest hot spring in the United States, and the third largest in the world. It is located in the Midway Geyser Basin. Grand Prismatic Spring was noted by geologists working in the Hayden Geological Survey of 1871, and named by them for its striking coloration. Its colors include blue, green, yellow, orange, gold, red and brown, and recall the rainbow disperson of white light by an optical prism.
# Sapphire Pool, USA Sapphire Pool is located in Biscuit Basin, Yellowstone National Park, Wyoming. The pool, with temperatures over 200°F (93°C), is named for its crystal-clear water and for its resemblance to an Oriental sapphire. The pool changed dramatically after the 1959 earthquake and erupted up to 150 feet (45 m), but stopped by 1968.
# Cistern Spring, USACistern Spring is located in the Yellowstone National Park. It used to be a small gray pool, but in 1966 it transformed into a very active, colorful spring, often overflowing creating terraces of minerals that killed nearby trees such as the ones in the background. The pool is often blue in color, but sometimes it is green, just like in the picture. The underground plumbing of Cistern Spring is linked to the nearby Steamboat Geyser, which when it erupts, is the tallest geyser in the world.
# Crested Pool, USACrested Pool is a hot spring in the Upper Geyser Basin in Yellowstone National Park. The spring is 42 feet (12.8 m) deep. It is named for the crest which surrounds the pool. Although it is considered a spring, Crested Pool sometimes erupts like a geyser.
# Doublet Pool, USADoublet Pool is a hot spring in the Upper Geyser Basin of Yellowstone National Park, Wyoming. This pool is 8 feet (2.4 m) deep and its temperature is approximately 194.4 °F (90.2 °C). Its scalloped edge is made of geyserite. Although geysers rarely occur in Doublet Pool, with only two or three have been seen the pool on the right pulses over the vents about every two hours.
# Champagne Pool, New ZealandChampagne Pool is a prominent geothermal feature within the Waiotapu geothermal area in the North Island of New Zealand. The terrestrial hot spring is located about 30 km (20 mi) southeast of Rotorua and about 50 km (30 mi) northeast of Taupo. The name Champagne Pool is derived from the abundant efflux of carbon dioxide (CO2), similar to a glass of bubbling champagne.