Periodic Spring
Periodic Spring Trail, Afton, WY
Afton, WY
A cold mountain spring that pulses on and off like a slow heartbeat, one of only a handful of rhythmic springs on Earth.
Periodic Spring is one of the strangest and rarest natural wonders in Wyoming, a cold mountain spring that does not flow steadily but pulses, surging strong, then fading, then nearly stopping, on a regular cycle, like a slow heartbeat in the rock. It is one of only a handful of true rhythmic springs known in the world.
The spring sits up a forested canyon in the Salt River Range east of Afton, reached by a scenic gravel road and a hike. When conditions are right, usually in the lower flows of late summer and fall, visitors can stand and watch the water build to a rush, ease off, and go quiet again, over and over, a rhythm nature keeps entirely on its own.
What Guests Love
- Watching a cold spring surge, ebb, and stop on a natural cycle
- The scenic canyon hike through forest to reach it
- The rarity of a genuine rhythmic spring, one of just a few worldwide
- The peaceful, green Star Valley setting below the mountains
Worth Knowing
- The spring pulses most reliably in late summer and fall when flow is lower; in high water it may run steadily
- It takes a drive up a gravel canyon road and then a hike to reach, so allow time and wear good shoes
- The water is very cold mountain spring water, and the canyon can be cool even in summer
- The canyon road is usually snowed in during winter, so the spring is a warm-season visit
Details
Afton, WY
Learn about Periodic Spring
A spring that keeps a rhythm
Most springs simply flow, but Periodic Spring pulses on a cycle, its flow rising and falling and sometimes stopping altogether before surging back. When the timing is right, a full cycle plays out over a matter of minutes, so patient visitors can watch it happen again and again.
This behavior is most pronounced when the overall flow is lower, typically in late summer and autumn. During spring runoff and high water, the spring may run more steadily and the rhythm can be hard to see, so the season matters for catching the spring at its most remarkable.
How the pulse is thought to work
The leading explanation is that the spring is fed through a natural siphon deep in the limestone of the mountain. Water collects in a hidden chamber until it rises high enough to spill over into a looping channel, which then siphons the chamber empty in a rush, until the chamber refills and the cycle repeats.
This kind of self-emptying siphon, hidden in the soluble rock, is very rare, which is why so few rhythmic springs exist. The exact plumbing inside the mountain cannot be seen, so some mystery remains, but the siphon idea neatly explains the surge-and-pause rhythm visitors witness at the surface.
The hike up the canyon
Reaching the spring is part of the experience. A gravel road climbs a canyon in the Salt River Range from near Afton, and from the road's end a trail leads up through forest along a rushing creek to the spring itself, set against the rock at the head of the walk.
The canyon is cool and green, shaded by conifers, with the creek for company, making the hike a pleasant outing in its own right. The spring emerges from the mountainside as the source of that very creek, so the water pulsing before you goes on to feed the whole canyon below.
Star Valley, wildlife, and seasons
Below the canyon lies Star Valley, a broad green farming valley along the Salt River near the Idaho border, ringed by mountains and dotted with small towns like Afton, known for its great elkhorn arch. The valley is a peaceful, scenic base for a visit.
The canyon and surrounding range hold moose, deer, elk, and mountain birds, and the forest is quiet and cool even in high summer. The road up the canyon is generally passable only in the warmer months, so the spring is a late-summer and fall destination, exactly when its rhythmic pulse is easiest to see.
Closest Boutels
The closest Boutel™ stays, so you can turn this stop into an overnight. Each is an independently owned, editorially selected place to stay.
Things to Do Near Afton
Afton
About 6 miles west
A Star Valley town famous for the world's largest elkhorn arch spanning its main street.
Salt River Range
Around the spring
Forested mountains with hiking, fishing, and wildlife above the green valley.
Star Valley
Below the canyon
A broad, scenic farming valley along the Salt River near the Idaho line.