The colors of this burning source are partly alive.

In Yellowstone, Grand Prismatic Spring seems surrounded by strips of paint. However, it is a hot spring, whose surroundings host microscopic organisms. Taken individually, they escape the eye; gathered in very large numbers, they make up colored masses visible in the landscape.

These thermophiles live in conditions that would be hostile to many other living beings. Communities vary with temperature: warmer areas include colorless or yellow organisms, while cooler waters may have orange, brown or green hues.

The water also circulates between the depth and the surface: it cools, goes down and gives way to warmer water. This circulation distinguishes the source of a geyser that erupts. What looks like a mineral decoration thus combines two less visible movements: that of water underground and that of life on a microscopic scale.