Old Faithful

Old Faithful is not the tallest geyser in Yellowstone, nor the most powerful — that distinction belongs to the erratic Steamboat Geyser. What makes it extraordinary is its punctuality. The cone sits in the Upper Geyser Basin beside the Firehole River, and roughly every hour and a half it clears its throat with a few splashes before hurling a column of boiling water skyward, on average about 145 feet (44 m), for anything between a minute and a half and five minutes. It was the first geyser in the park to receive a name, given by members of the Washburn–Langford–Doane Expedition who walked into the basin on 18 September 1870 and saw it erupt before anything else.

The reliability is a matter of plumbing. Old Faithful appears to be isolated from the other thermal features of the basin, so its cycle is not disturbed by neighbours stealing its water and heat. Since 1938 observers have known that the length of one eruption predicts the wait for the next: a short play of under two and a half minutes is followed by a pause of around an hour, a long one by roughly an hour and a half. Earthquakes have nudged the rhythm over the decades — the 1983 Borah Peak quake in Idaho noticeably stretched the intervals — but the rule still holds well enough for rangers to post the next eruption to within about ten minutes. Probes lowered into the vent between 1983 and 1994 found water at around 244 °F (118 °C) some 72 feet down, and filmed steam and fog churning in the narrow conduit.

The best moments are the ones around the eruption rather than the peak itself: the steam drifting in cold morning air, the hush of a crowd on the semicircular boardwalk, and the white plume lit sideways at sunset. In the park's early years travellers used the geyser as a laundry, dropping clothes into the vent to be washed by the next eruption. The geyser, together with the log-built Old Faithful Inn nearby, forms the Old Faithful Historic District, and the boardwalks continue from here past dozens of other hot springs and geysers of the Upper Geyser Basin.

Getting there

Old Faithful lies deep inside Yellowstone National Park in Wyoming. The nearest sizeable town is Rexburg, Idaho, about 104 km away; the closest airport is Yellowstone Airport (WYS) near West Yellowstone, about 34 km by straight line. Park roads lead to the Old Faithful area, where the Old Faithful Visitor Education Center posts predicted eruption times (they are also shown at the lodges and in the park's app); the viewing area is less than a quarter of a mile from the center.