Sight · Yellowstone National Park
A 66-foot acidic geyser with sea-urchin spines around a red rim.
Overview
Echinus is a roughly 66-foot-wide acidic geyser in Norris Geyser Basin's Back Basin, known as the world's largest acidic geyser. Its broad pool, rust-red rim and silica-coated spines make it stand out among the basin's thermal features. It's a good stop for the color and unusual geology; eruptions are irregular, so don't plan around catching one.
Parkwolf’s verdictWhy stop hereMap
Plan your stop
The highest, rockiest slopes around here are a summer buffet for grizzly bears.
Yellowstone Tour Guide
Parkwolf is a GPS audio tour guide for Yellowstone National Park. As you drive, it chimes in with what’s ahead: hidden gems, upcoming stops, history, geology, and wildlife, right through your car’s speakers.
See the Yellowstone audio tourRecorded for this place
Norris Geyser Basin“You're coming up on the entrance to Norris Geyser Basin, where I'd allow about an hour to explore on foot. For a shorter visit, choose Porcelain Basin, an open sweep of pale ground, blue pools and hissing vents.”
Plays as you drive up to Echinus Geyser in the Parkwolf Yellowstone Tour Guide.
More stories near here in the app
“First time driving through a national park. We used the Yellowstone tour on grand loop Road and it’s just like having a tour guide in your car with you.”
Guide
See it on Back Basin's 1.5-mile loop, a mix of boardwalk and bare ground. The approach from the Norris Museum and Information Station descends a steep, uneven trail, so the whole visit isn't a flat boardwalk stroll. Benches and tiered platforms circle the pool and give you several heights to look from. Back Basin is reached by snowmobile in winter.
Iron oxides color the rim red-orange, and the sharp rocks around the water carry silica deposits. That spiny shape inspired mineralogist Albert Charles Peale to name it after sea urchins during his 1878 visit. Its unusual acidity comes from volcanic gases mixing with neutral water; the diluted acid isn't strong enough to dissolve the geyser's underground plumbing.
Echinus was historically quiet before 1948, then erupted every 40 to 80 minutes during the 1970s. Its activity waned by the early 2000s. The large, multi-level platforms were built for the period when eruptions were frequent and predictable. Don't treat those historic intervals as a current schedule.
From one of the raised platforms, frame the broad pool with its orange-red rim and spiny rocks; the boardwalk and surrounding trees help show its scale. A closer view brings out the sea-urchin-like silica formations. If it erupts while you're there, the higher angle gives the spray room in the frame.
Wildlife
713 sightingsGrizzly BearMost seen around 6 AMSighting map
743 sightingsWolfMost seen around 6 AMSighting map
5,273 sightingsBisonMost seen around 7 AMSighting map
3,258 sightingsElkMost seen around 7 PMSighting map
397 sightingsMooseMost seen around 7 PMSighting map
1,494 sightingsBlack BearMost seen around 7 PMSighting mapSighting maps show where each species has been reported across Yellowstone. Wildlife moves, so no sighting is guaranteed.
Keep exploring
EasyPorcelain Basin Trail1 mi · 45 min · 0.3 mi awayLoop past steaming geysers and vivid runoff in a pale basin.
EasyBack Basin Trail1.5 mi · 1.3 hr · 0.3 mi awayA wooded thermal loop with geysers scattered through the pines.
ModerateSolfatara Creek Trail6.3 mi · 3.5 hr · 1.2 mi awayA long thermal creek walk through forest, meadows, and hot springs
EasyArtists Paintpots Trail1 mi · 45 min · 2.6 mi awayA short loop past bubbling mud and a steep climb.
EasyIce Lake Trail1 mi · 45 min · 3.4 mi awayA short forest walk to the western edge of Ice Lake.
ModerateMonument Geyser Basin Trail2.4 mi · 2 hr · 3.4 mi awayA steep climb from the Gibbon River to a pale thermal basin.
EasyWolf Lake Trail2.4 mi · 1.5 hr · 3.7 mi awayA short waterfall walk through Yellowstone's forest and wet meadows.
Sight · 0.1 mi awaySteamboat GeyserThe world’s tallest active geyser—and you can’t plan its eruptions.
Sight · 0.3 mi awayEmerald SpringSulfur yellow and reflected blue light make this hot spring emerald.
Sight · 0.3 mi awayPorkchop GeyserA quiet pool with a very loud history.
Sight · 0.3 mi awayMinute GeyserA low spout and a cautionary story about visitor damage.
Sight · 0.3 mi awayNorris Geyser Basin Museum and Information StationA 1930 stone and log museum opens onto Norris’s geothermal story.
Sight · 0.4 mi awayPorcelain Basin OverlookA short boardwalk reveals changing colors across a thermal basin.
Picnic area · 0.9 mi awayNorris Meadows Picnic AreaA quieter riverside lunch stop near Norris Basin
Sight · 1.1 mi awayMuseum of the National Park RangerA small log museum traces Yellowstone's ranger profession.Parkwolf’s Yellowstone ranking
The audio tour guide for the drive, plus offline maps, trails, and wildlife heatmaps for when the signal drops.
