The Upper Geyser Basin has the highest concentration of geothermal features in Yellowstone National Park. This complement of features includes the most famous geyser in the park, Old Faithful Geyser, as well as four other predictable large geysers. One of these large geysers in the area is Castle Geyser which is about 1,400 feet northwest of Old Faithful. Castle Geyser has an interval of approximately 13 hours between major eruptions, but is unpredictable after minor eruptions. The other three predictable geysers are Grand Geyser, Daisy Geyser, and Riverside Geyser. Wikipedia
Crested Pool is a hot spring in the Upper Geyser Basin in Yellowstone National Park. The spring is 42 feet deep. Adjacent to the Old Faithful Inn, the spring is named for the "crest" which surrounds the pool. Although it is considered a spring, Crested Pool sometimes erupts like a geyser. Wikipedia
The Grand Canyon of the Yellowstone is the first large canyon on the Yellowstone River downstream from Yellowstone Falls in Yellowstone National Park in Wyoming. The canyon is approximately 24 miles long, between 800 and 1,200 ft deep and from .25 to .75 mi wide. The colors in the canyon are a result of hydrothermal alteration. The rhyolite in the canyon contains a variety of different iron compounds. Exposure to the elements caused the rocks to change colors. The rocks are oxidizing; in effect, the canyon is rusting. The colors indicate the presence or absence of water in the individual iron compounds. Most of the yellows in the canyon are the result of iron present in the rock rather than, as many people think, sulfur. Wikipedia
