Schematic illustrating the conditions under which some travertine forms in Yellowstone caldera

Schematic illustrating the conditions under which some travertine forms in Yellowstone caldera. Increased surficial weathering of glacial till and sediment during wet climate conditions causes greater infiltration of travertine ingredients (Ca²⁺, Mg²⁺, HCO₃^-) into thermal waters at the edges of Upper Geyser Basin (thin blue and yellow arrows) result in travertine deposition in those areas. Deeper sourced, hotter thermal water upflow continues in the center of Upper Geyser Basin and prevents travertine from forming in that area at any time (thick orange dashed arrows). Travertine deposits at Morning Glory and Hillside Springs are shown in pink.