English: Fountain Paintpots is located in the Fountain Group of Yellowstone's Lower Geyser Basin. Paintpots, or mudpots, are hot pools of thin to thick muddy material consisting of clay-sized grains of clay minerals mixed with varying amounts of water. Rising gases result in bursting bubbles of mud at the surface. The clay forms by chemical weathering of rhyolite lava, a common lithology in the Yellowstone Hotspot area. When rising hydrogen sulfide gas (H2S), exsolved from subsurface magma, reaches the top of the water table, oxidation occurs and sulfuric acid forms (H2SO4). The sulfuric acid reacts with the rhyolite, forming various clay minerals. Mudpots in Yellowstone tend to have thin mud in boreal spring and early summer and boiling-type bubbles appear at the surface. In boreal late summer and autumn, the mud is thick, which alters the bubble surfacing and bubble bursting behavior of rising gases. Fountain Paintpots has various delicate shades of pinks, grays, yellows, and orangish-browns. The non-gray colors are from a variety of disseminated iron oxide species.

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For a video of Fountain Paintpots, see:

www.youtube.com/watch?v=U0LAnamO2eg