Sight · Yellowstone National Park
A quick look at one of Yellowstone's most acidic hot springs.
Overview
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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
Sulphur Caldron“You're nearing Sulphur Caldron, a quick roadside stop for a restless, pale hot spring. Its water has a pH of about one to two, close to battery acid and among the most acidic in Yellowstone.”
Plays as you drive up to Sulphur Caldron 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
Sulphur Caldron is a roadside hot spring in Yellowstone's Mud Volcano area, just north of Mud Volcano on Grand Loop Road. You can see its restless, pale pool in a short stop; pair it with Mud Volcano if you want a longer look at the area's hot-spring and mudpot features.
NPS calls this one of Yellowstone's most acidic hot springs and gives its pH as about 1–2. That's close to battery acid. Stay on the boardwalks and trails; the hot water can severely burn.
The sulfur is more than the name. Hydrogen sulfide rises from underground, and microbes use it to help make sulfuric acid, which breaks rock down into wet clay around Mud Volcano. That gas also makes the rotten-egg smell.
For a photo, include the churning pool and its white and yellow mineral rim. That contrast shows the basin's character better than filling the frame with water alone.
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
EasyMud Volcano Trail0.6 mi · 1.5 hr · 0.3 mi awayA compact boardwalk loop through bubbling Yellowstone mudpots.
ChallengingMary Mountain–Nez Perce Trail20.2 mi · 10 hr · 4.8 mi awayA full-day traverse from Hayden Valley to Nez Perce Creek.
Sight · 0.3 mi awayMud VolcanoBubbling mud, sulfur air, and Dragon’s Mouth share a short loop.
Sight · 0.8 mi awayHayden Valley Overlook at Yellowstone RiverWide river bends make this a good place to scan for bison.
Picnic area · 0.9 mi awayNez Perce Ford Picnic AreaA quiet lunch break beside the Yellowstone River.
Picnic area · 1.2 mi awayCascade Picnic AreaA useful table break beside the Yellowstone River.
Picnic area · 1.8 mi awayLeHardys Picnic AreaA chance to see cutthroat trout leap upstream in spring.
Sight · 2.8 mi awayLeHardys RapidsWatch the river tumble; spring trout are a bonus.
Sight · 5 mi awayFishing BridgeA quick fish-watching stop at a bridge closed to fishing.Parkwolf’s Yellowstone ranking
The audio tour guide for the drive, plus offline maps, trails, and wildlife heatmaps for when the signal drops.
