The thermal features of Yellowstone were truly a fascinating testimony to God's creativity. It was mind-boggling to think of everything going on underneath the surface to result in such strange and widely-varied manifestations on the surface. Some features are calm and placid, while others are roiling incessantly. Mud pots might be thin or thick. Pools could be deep blue, sky blue, emerald green, or even brown. The thermophilic bacteria living around the pools color the borders brown or orange or white depending on temperature. Geysers might be a constant bubble or an infrequent high-powered jet-- and it's all just hot water!
One of the most interesting aspects of the thermal features is the constant change that is taking place. Even Old Faithful isn't erupting quite as often or as predictably as it used to, due at least in part to an earthquake several years ago. There was one place where a boardwalk had been rerouted because a new feature had popped up that was superheating the path. A sign told the story of a geyser that had been continuously spouting until something stopped it up. Pressure built up so much that it unexpectedly exploded, throwing rocks 200 feet away and startling the seven park visitors nearby! Now that geyser is just a quiet spring.
A small geyser that erupts almost constantly.
A thin, fast-boiling mud pot.
A quietly boiling mud pot.
The steaming runoff from Excelsior Geyser flowing into the Firehole River.
Looking over Excelsior Geyser. Excelsior is currently dormant, but when it erupted, it was one of the very biggest geysers. Its large crater and still-continuous flow of water bear witness to this!
Some of these blue pools seemed like something out of a fairy tale.
There was a great array of different formations created by the mineral deposits from the water. Some of them reminded me of what you see in caves. The coloring here is from bacteria.
Anemone Geyser was interesting because we could easily see the different phases of an eruption: filling...
...and draining away.
In the upper right of this picture, you can see an old path. Obviously, this spring just flowed right over it! We never did figure out exactly why some springs form terraces as seen below.
This was our favorite mud pot. Most of the ones we saw were fairly thin, so they just boiled like water. This one was very thick, so when it boiled it threw clumps of mud several feet into the air. Note the circled white spots! The boardwalk in the background was roped off with a sign that said, "Closed due to hot flying mud." We didn't need much convincing; the walk behind the sign was covered with white mud spots. It made a most interesting sound.
Another mud pot.
I found these bubbles peculiar because they just stayed and stayed and hardly ever popped.
This picturesque-looking lake is about as acidic as battery acid-- not a good place to go wading!
This is Dragon's Mouth Spring, and it was easy to see why it got its name. The actual spring is quite a ways back in that cave, so the sound of the water reverberates and is amplified in the cave, making an extraordinary assortment of thumps and bellows. Combined with the continuous spurts of steam and the disturbance in the water, it looked like the ideal location to see a dragon!