The hot water that feeds Mammoth comes from Norris Geyser Basin after traveling underground via a fault line that runs through limestone and roughly parallel to the Norris-to-Mammoth road. The limestone from rock formations along the fault is the source of the calcium carbonate. Shallow circulation along this corridor allows Norris' superheated water to slightly cool before surfacing at Mammoth, generally at about 80 °C (170 °F). Algae living in the warm pools have tinted the travertine shades of brown, orange, red, and green.