Yellowstone’s thermal fields seem to echo not only life’s first appearance on the planet, but its early development as well: steaming hot water bubbling from the earth bringing forth organisms metabolizing oxygen. Scientists call such organisms aerobic. As water flows from Yellowstone’s hot springs, mats of color appear. These are colonies of bacteria and algae, which eventually host still other living organisms such as delicate, colorful plants. Their ancient ancestors generated the atmosphere we live in. Here, at the bizarre Mud Volcano, the remains of a giant conical mudpot that blew itself up in the 19th century, we see this process still at work. Layer upon layer of plants emerge from the warm mud, dusted with light snow, like sugar on a cake. The horizontal white bands alternate with the red and green bands. Each band of snow serves as a transition point from color to color. The white powdered plants move us through the entire picture, as they reveal the layers of color that lie within them.