Periodic Spring

I could discern some very low noted booming which alarmed me. Was there a rock fall? 

Almost imperceptibly the water in the cascade seemed to slow. I didn’t believe my senses at first and kept looking to confirm what I was seeing. Then it was obvious the water had simply run out, stopped, there was no more. While the last of the flow bounced happily down the rocks to the bottom of the cascade.

Then a rushing pneumatic hiss like an exhale or sneeze from above us. Mollie startled and looked down at me. I called her to me in my own alarm to get her nearer to me and away from the sound. 

Then a great roar of noise followed and a torrent of white water issued forth from the narrow base at the back of the limestone slot. It had spontaneously burst from the earth where only wet mossy rocks were before. The water continued as if from a fire hose and danced and cascaded down the bottom of the steep declivity as any creek would. 

Way up where Mollie had been there had not been any trace of running water the whole time we had stood there. I assumed the spring issued from somewhere between us.

Earlier, we had followed a narrow trail up the slot of limestone. The cliffs and trees leered down on us making me aware that any rockfall could carom in such a way as to make it impossible not to be struck. The sense of danger enhanced by an official sign informing us we had proceeded past the maintained portion of the path and putting in mind all manner of hazards; trips, rockfalls, landslides. 

Halfway up the steepest section I had stopped and Mollie stopped much further up and we waited. Not knowing what to expect. And now we knew. 

The whole experience was unsettling. It was profoundly unnatural. It was a sublime experience. And it would repeat again in ten to twenty minute intervals. 

Earlier in the day we were traveling on the western-most edge of Wyoming. Needing a place to stay we saw a campground sign for Swift Creek Canyon. We kept driving up a spectacular narrow limestone canyon and were finally halted by some construction work at a trail head. There was a vault toilet and one picnic bench and space to park. Weird, a single-site campground, I thought. (The actual campground has been closed for years.)

It was getting dark, especially as the valley was quite narrow so as to not admit much light. A quick dinner of hamburger for me and a meaty pouch for Mollie. We had some daylight left and Mollie was pestering me for our evening walk so we strapped on the bear spray and headed up the closed road. I was aware there were a couple trails here but didn’t pay much more attention than that. And this is how we accidentally found the Periodic Spring. 

The Periodic Spring is an oddity of nature, geology, and hydrology as to baffle the mind. Also called a cold geyser as it issues forth at regular intervals. They work, it is hypothesized, by a spring continuously feeding a large chamber while an outlet such as a fissure begins near the bottom of the chamber then travels up some distance before descending again and exiting the side of the cliff face. 

Water slowly fills the chamber from the spring until the chamber is full and the water is forced up the outlet and down again. This forms a siphon and the water is then drawn through the outlet through this siphon. If the rate of flow through the siphon is faster than the spring that feeds the chamber then the chamber will be emptied and the siphon with be stopped. At least until the chamber fills again.

It is a marvel that such a thing should exist in nature. There are perhaps ten in the whole world and this is one of the biggest examples.

There is another periodic action on Swift Creek I noticed during our visit. As we drove up the canyon to our campsite, the water went from clear to milky to red colored at intervals. I couldn’t understand what I was seeing. 

It became clearer and less muddy on our walk up to Periodic Spring. At one point a side canyon had recently had a large avalanche that evidently inundated the canyon and the road. This had been repaired and the river eroded its way through the rock soil and gravel to reach something like its original bed. 

The strata this avalanche originated from was a dark red sandstone or clay evident in the debris pile. Down this side canyon a thin stream of deeply red water admitted and joined the main river stream. 

The next morning from our camp a few hundred yards below this avalanche site I noticed suddenly the entire stream went from what was a clear mountain stream to one that was deep dark red colored. Later it began to run clear again. The avalanche channel must be flaking off red soil occasionally to be washed down in greater and lesser amounts. 

Or maybe up there somewhere is another periodic spring…