|Travertine terraces at Mammoth Hot Springs.|
Day hikers can walk through one of the world’s largest collection of travertine terraces on the Mammoth Hot Springs boardwalks at Yellowstone National Park.
A series of connected trails cut through the heart of the sprawling hot springs. A 0.8-mile loop allows you to see most of the major features. The best time to visit is late spring through early autumn; the road leading to the hot springs generally is closed December through April.
To reach the site, from the U.S. Hwys. 191/89 intersection near West Yellowstone, take the Grand Loop Road/U.S. Hwy. 89 east and north about 30 miles toward the Montana border. A couple of parking areas can be found off the highway's left/west side with walking paths leading from them into the hot springs area; among the best lots is the one immediately north of the road that turns off the highway to the horse corral.
The trail leaves from the lot's northwest corner. Where the asphalt path gives way to boardwalk, goes left/south. The boardwalk enters a massive stretch of white terrain that is noticeable from an airplane flying over. Fifty hot springs can be found in this area of the park.
The boardwalk passes the Jupiter Terrace with the Main Terrace south and west of it. These hot pools cascading over travertine terraces are a spectacular sight of steaming rocks and skeletal trees. The pools’ temperatures here can reach up to 163 degrees F.
Next, the boardwalk passes a junction heading right/north; continue straight. The oft-photographed Minerva Terrace sits on the trail’s north side.
The terraces exists because a partially molten magma chamber sits far beneath the surface. As rain and snowmelt seeps into the ground, rock warmed by the magma in turn heats the water, which then shoots back upward through fissures.
As the water rises and meets carbon dioxide gas, it forms a weak acid that dissolves limestone buried underground. Upon reaching the surface, the carbon dioxide escapes into the air and leaves behind the calcium carbonate – aka as travertine – that forms the white terraces. More than two tons of calcium carbonate flow daily to the surface at Yellowstone.
At the second junction, take the boardwalk right/north. The Cleopatra Terrace is to the right/west. This part of the boardwalk loops around the Minerva Terrace.
As reaching the topic of the loop, pass the junction heading left/north. The scenic Palette Spring will then appear on the left/north side of the walkway.
Some of the terraces are colored orange, brown, red and even green. This is because of the algae – known as thermophiles – that lives in the warm pools on the surface.
At the next junction, take the stem trail going right; this leads you into the heart of the Minerva Terrace. After taking in the sites, head back to the junction and go straight/southeast.
From there, ignore the other trail junctions as this boardwalk heads back to the asphalt path that leads to your parking lot.
Learn about other great national park day hiking trails in my Best Sights to See at America’s National Parks guidebook.