Midway Geyser Basin is my next stop on the lower loop road. You can see the stream rising in huge clouds as you approach. There’s a large parking area and even now, in the off season, it’s pretty full. Its hard to imagine what it would be like at the height of the tourist season. A solid wooden bridge crosses the Firehole River. Steaming, boiling water flows down the bank into the river.
Huge billowing clouds of steam blow across the bridge and walkways.
The Boardwalk crosses the Firehole River before zig-zaging first to the right then back to the left always climbing upward. The first hot spring we pass is the Excelsior Geyser Crater. Its the water from this crater that is flowing into the Firehole River. Dumping 4000-4500 gallons of boiling water per minute into the river its not surprising that there are always clouds of steam. Excelsior Geyser used to erupt in a powerful plume from 100-300 ft high but after some particularity powerful eruptions it subsided to the simmering hot spring that it is today. Scientists speculate that those powerful eruptions damaged the internal plumbing ending the more spectacular thermal displays.
Grand Prismatic Spring is the largest hot spring in the United States and the third largest in the world. The vivid colors in the spring are the result of microbial mats around the edges of the mineral-rich water.
The mats produce colors ranging from green to red. In the summer, the mats tend to be orange and red, whereas in the winter the mats are usually dark green. The center of the pool is sterile due to extreme heat. The deep blue color of the water in the center of the pool results from the intrinsic blue color of the water. The effect is strongest in the center of the spring, because of its sterility and depth. Usually the photos you see in magazines are taken from above.
The View From Above
Most photos of the Grand Prismatic Spring are taken looking down. Many are aerial views taken from airplanes or maybe a helicopter. There is also a trail that leads from the Grand Prismatic Spring to Fairy Falls. Along the way there are 2 other geysers and a lookout above the hot spring. The trail is only .5 miles but it climbs 105 ft. I’ve added this hike to my bucket list. For now it was time to leave the clouds and steam of Midway behind and turn for home.