Fountain Paint Pot is the Lower Loop's first boardwalk, an easy half-mile loop through the Lower Geyser Basin that takes most visitors 30 to 45 minutes. It packs all four of Yellowstone's major hydrothermal features into one walk: fumaroles, geysers, hot springs and mudpots. The mudpots give the stop its name, and iron oxides color the acidic mud in shades a painter would recognize. The lot sits on the right for southbound drivers, with vault toilets, and parking runs short between 10 a.m. and 6 p.m., so arriving early or late pays off. Pets are not allowed on the boardwalk, even when carried. Firehole Lake Drive, which leaves the main road opposite this area, is closed to vehicles, so a visitor center is the place to ask about it.
Fountain Paint Pot is on your right in about a quarter mile. Pull in. This is the first real boardwalk of the day, an easy half-mile loop, and thirty to forty-five minutes covers it. Parking is limited, especially from ten in the morning to six at night, and there are vault toilets at the lot. Turn right when you pull out. Stay on the boardwalk, keep children close, and don't let them run. The ground out there can be a thin crust over super-heated water. No pets on the boards either, even carried. You came for the mud. This one loop shows you all four of the park's major hot-water features, steam vents, geysers, hot springs and mudpots, but the mud gets the name. A mudpot works like a double boiler. Surface water pools in a clay-lined hollow, and steam rising from below heats it. Microbes turn hydrogen sulfide gas into sulfuric acid, the acid breaks rock down into clay, and you get a gooey mix with gases gurgling up through it. Iron oxides tint it pink, beige and gray, and there's your paint. Most people assume every spring here is acid that will dissolve whatever falls in. Nearly all the major hot springs and geysers here are neutral or alkaline, including almost all along the Firehole. The mudpots are the acid ones. Out in this basin is a hill called Twin Buttes, a thermal kame, made when glaciers sat over active hot ground, melted from beneath and dropped their debris, and silica-rich water cemented it. Thermal kames are unique to the Yellowstone region. Look down at the trees as you walk. South of the trail stand lodgepoles with white bases, as if they'd pulled on socks. Their roots draw thermal water, silica and minerals build up in the wood, and eventually the trees die. The term for them is bobby socks.
Photo: NPS Photo / Diane Renkin · Public domain