A Hike to the Periodic Spring on Swift Creek, Afton, Wyoming

 

It was the most unusual sound. Instead of the usual sounds of water cascading over the rocks it seemed like a machine was inside the earth causing the sound of the water to rise and then lower. It kind of reminded me of the sound a piston makes as it cycles through a slow revolution, but that isn’t exactly right either.

Our friend Big Mark arrived from Texas, and so after doing some house stuff we decided to make the short drive to Afton and hike the trail to the periodic spring. The spring is one of the largest known and the hike promised to be a good test of our stamina at higher elevation.

We were all apprehensive after spending so much time at the Gulf Coast, heck Mark lives in Corpus Christi, so we started slowly up the trail, not really planning on getting there but all hoping none the less. Renita was still suffering from her bronchitous and had thought about staying at the truck, but she changed her mind and headed up the trail.

So we took it real easy and stopped to look at the rocks. Being rock hounders we agreed to not pick up any samples until we returned down the gravel trail. Mark and I are both geologists and so it was kind of like old times on a geology field trip as we approached each rock face and hunted for fossils.

Soon Renita pointed out, leave it to a retired coal miner, (ok she was in the office but she did work at a coal mine), some white inclusions that turned out to be recrystallized fossil coral. Really pretty neat but it had lost much of its original structures so we moved on up the trail.

Mark pointed out some crinoid stems and we both agreed that the rock was probably Mississippian in age, (Paleozoic). The trail was really almost a road as it had been made to build the water supply for the town of Afton and so it was really well constructed and pretty easy.

About a mile upstream we reached the water diversion structure and from it we could see where the water came of of the side of the mountain. Now the spring is a periodic spring because it varies in discharge but we couldn’t see it happening as the spring runoff  had increased the springs flow, and the description had told us that the best time to hike was late summer or early fall.

Crossing the footbridge we headed up a steep canyon, formed perhaps from a fault, and the dipping rock layers told of some pretty massive structural geology. The angle of the trail increased and I for one had to pause for a bit as I could feel that I was at elevation.

An old avalanche had buried the trail and so we stopped for some images, with the spring in the background. Using my geology hammer as an ice axe I was able to kick steps into the firmly packed snow and securely climb the rest of the way to the outpouring waters.

Looking down I waved Renita and Mark off from trying to cross the snow, one slip and it could be an unwelcomed slide to the rocks and the creek below. So I reached the spring and here the trail had actually been cemented.

Not only that but the mouth of the spring had been covered, probably to stop idiots from throwing rocks into the water and disrupting the flow. I spied some really black jasper, with white inclusions and picked up a couple of pieces. Maybe I will make some cabochons from them as a reminder of the day.

Carefully retracing my steps I shared my finds with my companions and so we headed back down the path. Mark pointed out some horsetail reeds and I told him that we should also look for sedges, (horsetail is round and sedges have a triangular shaped, sedges have edges).

A water ouzel flew by and it soon waded into the fast moving stream disappearing entirely as it hunted for aquatic insects. We had all seen them before but your first water ouzel,) American Dipper), is always a special welcome back to the mountains.

A muskrat swam downstream and we passed a small cascade, which reminded me of the drive down to Seward. It was on a much smaller scale but it was still a pretty cascade. Mark found a really nice coral fossil and so the rocks have started to pile up, and that’s how it should be.

Too soon we reached the truck and headed back down the narrow and potholed gravel road. We talked of the hike and how it really was a nice pleasant time, time well spent. It’s definitely something that we will recommend to our other friends. Clear skies.