Yellowstone Park's thermal activities are the best-known and most popular features of its vast landscape. Who would not be curious to see the gigantic, rare and violent eruption of Steamboat Geyser? The cataclysmic earthquakes that have happened once or twice in recent history fascinate everyone, despite the obvious dangers of actually being caught in one.
The punctual eruptions of Old Faithful are tamer, with crowded bleacher seats in front of the National Park Information Center as everyone waits for the steam and hot water to begin to spout. The dozens of smaller but equally extraordinary geysers in the nearby geyser field require around a 90 minute walk along carefully designed boardwalks. I know the timing, because Old Faithful was just erupting when we began our walk, and we saw it go off again as we were returning.
Hot springs, boiling pools, colorful heat-tolerant algae, accretions of limestone from hard water gushing out of the ground, and many other thermal features are abundant throughout the park. At the end of Yellowstone Lake, there's even a geyser just under the surface of the water, and many just beside the shore. Scrubby wildflowers and grasses grow right in the running hot water, and elk and other animals graze near steaming pools. It's all fascinating.
If you want a geology lesson, I'm afraid you won't get it here, though I learned a great deal in 3 days of exploring various hot spring and geyser basins and reading the useful labels and explanations supplied by the Park Service.
The following hot spring photos I've selected just because I like the way they look.
Fishing Cone: the underwater geyser near Yellowstone Lake
Mammouth Hot Springs Limestone Formations
Tomorrow: the geysers.