Periodic Spring is well named...

and very reliable, surging in 15 minute-long cycles of enormous discharge, then completely shutting down for a similarly long recharging period. This unusual and extremely rare hydrologic phenomenon is the outlet of a confined karst aquifer system hosted in the Madison Limestone. The intermittent spring lays in a deeply recessed canyon near Afton, Wyoming and requires a slow drive on a potholed gravel road and a short hike to reach.

Here is a well presented description of the spring, including an explanation of the mechanism at work: Geology of Wyoming - Periodic Spring.

Closer view of the modified spring orifice under flowing conditions. I recorded a time-lapse video of the spring over several cycles with a GoPro, tripod seen at left, and will post it here in a little bit.

UPDATED 19 September 2023: Here’s the time-lapse video of Periodic Spring through several cycles of discharge and recharge, each about 15 minutes long, shot over about 45 minutes. It’s magic!

Communing with bison...

in the Lamar Valley in the northeastern part of Yellowstone National Park. I spent an entire day observing about 500+ bison in several small herds, only about a tenth of the total estimated population in the park.

The majestic American bison (Bison bison).

The majestic American bison (Bison bison).

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Typical scene in Yellowstone: Always yield to a huge animal with horns when it decides to cross the road.

Typical scene in Yellowstone: Always yield to a huge animal with horns when it decides to cross the road.

Lip-smacking good.

Lip-smacking good.

Time for a dust bath.

Time for a dust bath.

Catching a midday nap.

Catching a midday nap.

Heart Mountain...

is a beautiful and solitary peak (8,123 ft (2,476 m)) located north of Cody, Wyoming, the eroded vestigial remnant of an enormous slide block that was emplaced nearly 50 million years ago. A ~4 km thick sheet of rock about 1,300 square kilometers in area detached from the plateau to the west, sliding rapidly on a 2 degree detachment plane tens of kilometers towards the southeast into the Bighorn and Absaroka Basins. Heart Mountain is technically a klippe, and here’s more information about the largest terrestrial mass movement on Earth.

Sunrise behind Heart Mountain.

Sunrise behind Heart Mountain.

The summit block is composed of Paleozoic-age carbonate rocks, sitting on shale of the Willwood Formation that is 300 million years younger.

The summit block is composed of Paleozoic-age carbonate rocks, sitting on shale of the Willwood Formation that is 300 million years younger.

Moonglow at Devils Tower...

dramatically illuminates the landscape but, unfortunately, the nearly-full orb brightens the night sky so much that the Milky Way vanishes from view.

North side of Devils Tower shot at 2 am MDT from the Joyner Ridge trailhead. That’s Jupiter to the left of the Tower and Saturn above and slightly to the right. Ordinarily the Milky Way would appear in this frame to the right of the Tower but the Moon brightens the sky too much for it to be visible.

North side of Devils Tower shot at 2 am MDT from the Joyner Ridge trailhead. That’s Jupiter to the left of the Tower and Saturn above and slightly to the right. Ordinarily the Milky Way would appear in this frame to the right of the Tower but the Moon brightens the sky too much for it to be visible.

View of south face from Tower Trail, shot at 11 pm MDT and entirely illuminated by moonlight.

View of south face from Tower Trail, shot at 11 pm MDT and entirely illuminated by moonlight.

Star trails shot between 10:30-11:00 pm MDT showing the south face of Devils Tower. The white streaks across the lower part of the image were made by late-night hikers and their flashlights. They never knew I was there! Heh.

Star trails shot between 10:30-11:00 pm MDT showing the south face of Devils Tower. The white streaks across the lower part of the image were made by late-night hikers and their flashlights. They never knew I was there! Heh.

Devils Tower National Monument...

was the focus of yesterday afternoon and evening. It’s a small but magnificent (and the first) National Monument.

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I’ve climbed the ~870 foot (265 meters) high columnar edifice twice, using the classic Durrance Route, just to the right (inside) the shadow line in the center of the image. This fantastic climb was pioneered in 1938 by Jack Durrance and Harrison Butterworth, the second ascent of the Tower.

I’ve climbed the ~870 foot (265 meters) high columnar edifice twice, using the classic Durrance Route, just to the right (inside) the shadow line in the center of the image. This fantastic climb was pioneered in 1938 by Jack Durrance and Harrison Butterworth, the second ascent of the Tower.

Yellowstone National Park...

early last week, during my travels south to Utah.

Geothermal steam during a chilly early morning at Norris Geyser Basin, the hottest part of the caldera.

Geothermal steam during a chilly early morning at Norris Geyser Basin, the hottest part of the caldera.

Norris Geyser Basin painted with various colorful heat-tolerant bacteria.

Gibbon Falls (84 feet (26 m) tall).

Gibbon Falls (84 feet (26 m) tall).

So-called Black Pool at West Thumb.

So-called Black Pool at West Thumb.

Fishing Cone on the shore of Yellowstone Lake at West Thumb. Jim Bridger tells a tall tale here: “When he needed a quick meal, Bridger would catch a trout and reel it in slowly, allowing time for it to cook on the line as it passed through the hot…

Fishing Cone on the shore of Yellowstone Lake at West Thumb. Jim Bridger tells a tall tale here: “When he needed a quick meal, Bridger would catch a trout and reel it in slowly, allowing time for it to cook on the line as it passed through the hot water.”

Grand Prismatic Spring at Midway Geyser Basin. (Click image to enlarge.)

Elk calf slowly nodding off on the warm ground near a geothermal vent.

Elk calf slowly nodding off on the warm ground near a geothermal vent.

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Grand Geyser, in the Upper Geyser Basin, fountaining as high as 200 ft (60 m).

Grand Geyser, in the Upper Geyser Basin, fountaining as high as 200 ft (60 m).

Last but not least, Old Faithful.

Last but not least, Old Faithful.