The Firehole River is located in northwestern Wyoming, and is one of the two major tributaries of the Madison River. It flows north approximately 21 miles from its source in Madison Lake on the Continental Divide to join the Gibbon River at Madison Junction in Yellowstone National Park. It is part of the Missouri River system. The Firehole River flows through several significant geyser basins in the park to include the Upper Geyser Basin, which contains the world-famous geyser Old Faithful. The river was named by early trappers for the steam that makes it appear to be smoking as if on fire. Firehole River has been a fishing mecca since the late 19th century and is known today for its excellent fly fishing. Wikipedia
Mammoth Hot Springs is a large complex of hot springs on a hill of travertine in Yellowstone National Park adjacent to Fort Yellowstone and the Mammoth Hot Springs Historic District. It was created over thousands of years as hot water from the spring cooled and deposited calcium carbonate (over two tons flow into Mammoth each day in a solution). Because of the huge amount of geothermal vents, travertine flourishes. Terraces are made of crystallized calcium carbonate. The hot water that feeds Mammoth comes from Norris Geyser Basin. Algae living in the warm pools have tinted the travertine shades of brown, orange, red, and green. Wikipedia
