Great Fountain Geyser is one of the largest and most dramatic geysers at Yellowstone National Park. Its "cone" is actually a set of sinter terraces over 100 feet wide -- most, but not all of it is pictured above. The crater at the center, where eruptions take place, is over 10 feet in diameter. It erupts approximately every 10 to 12 hours, with water reaching heights over 100 feet; unfortunately, we arrived between eruptions and didn't have time to wait.

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