Boiling rivers

By José Moutinho from Leça da Palmeira, Portugal (Boiling RiverUploaded by JotaCartas) [CC BY 2.0], via Wikimedia Commons

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Boiling River section of Gardner River near Mammoth Hot Springs, Yellowstone National Park, created where a large hot spring enters the Gardner River, allowing the hot and cool waters to mix into a temperature comfortable enough to bathe in.

Boiling River section of Gardner River near Mammoth Hot Springs, Yellowstone National Park
By Jo Suderman [Public domain], via Wikimedia Commons

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Located in a forest region called Mayantuyacu in Peru, the boiling river, which is guarded by a shaman, flows hot — between 120 and 196 degrees Fahrenheit — for almost 4 miles.