Norris Geyser Basin

Closest entrances and distances: 28 miles from West Yellowstone (west) entrance; 26 miles from Gardiner (north) entrance

Even if you’ve visited Yellowstone’s oldest, hottest, and most acidic basin before, you haven’t really seen it: The volatile Norris Geyser Basin ★★ changes constantly as old features go dormant, new geysers force their way from the earth, mineral-laden hot springs plug up old tunnels, and earthquakes scramble up the underground “pipes.” Here, heat-loving microorganisms called thermophiles form intricate mats of yellow, green, red, and black among the superhot features; most of the hot springs and fumaroles (steam vents) have temperatures above the boiling point (199°F/93°C at this elevation). In fact, the park’s hottest geothermal temperature ever recorded, a bit more than 1,000 feet underground here, was a blistering 459°F (237°C).

Norris encompasses two loop trails. The shorter one, a .8-mile figure eight through Porcelain Basin, starts with a grand overlook across the baked-white landscape of steaming pools and vents. Highlights include the 20- to 30-foot-high Constant Geyser (despite the name, it’s not always erupting); pulsing Whirligig Geyser; and the hot spring Congress Pool, which might be a hissing dry vent or a boiling puddle.

Back Basin Loop contains many more features on its 1.5-mile loop trail. The most exciting one is undoubtedly Steamboat Geyser, the world’s tallest at 400 feet. Major eruptions used to be erratic and rare, but the behemoth spouted 32 times in 2018 and kept up the pace in the first half of 2019—so you could get lucky! Echinus Geyser is the biggest known acidic geyser, with a pH approaching vinegar’s. Lately Echinus’s shows have been few and far between. Other geysers, springs, and fumaroles fill out the basin.