Imperial Geyser

Imperial Geyser is a backcountry geyser at the west end of Lower Geyser Basin, reached by continuing along the Fairy Falls trail beyond the waterfall. Its vent erupts from a blue pool edged by orange-red microbial mats. If you want a second close-up thermal feature after the falls, this is the reason to keep walking.

From Fairy Falls, Spray and Imperial geysers are another 0.6 mile along the trail; returning the same way adds 1.2 miles to your hike. Two trailheads serve the route: the end of Fountain Flat Drive and the Fairy Falls Parking Lot, about a mile south of Midway Geyser Basin. Parking is very limited at both. Pets aren't allowed, and the thermal ground off the maintained path can be unstable, so stay on the trail.

Imperial's first definitive activity report came in August 1927, when a jet reached about 25 feet every few seconds. Activity intensified in 1928, with eruptions approaching 100 feet and lasting hours, separated by long quiet spells. Eruptions stopped in 1929. A new vent opened at the pool's edge in 1966. When the geyser is active, its bursts and pauses each last tens of seconds, so expect a changing rhythm rather than a timed show.

The pool's blue center is neutral to alkaline, like nearby Grand Prismatic Spring, while mudpots along its margin are acidic. That sharp change in chemistry reflects the complicated underground routes that bring steam and water to the surface. For a photo, try to fit the blue center, orange-red edge, and vent into one wide frame; steam can hide parts of the pool between bursts.

The geyser was named in 1929, after its first dramatic years. Visiting members of the National Editorial Association chose “Imperial Geyser” from 17 proposals suggested by artist and scientist William Henry Holmes. “Columbia Geyser” tied in the vote but ultimately lost.