Grand Prismatic Spring is the largest and one of the most brilliant of Yellowstone’s many colorful hot springs. It massive expanse stretches approximately 200 feet (61m) across. The high temperature of its water—°160 (70°C)—ensures that the spring is often cloaked in steam.

Deep beneath us, magma from an active volcano heats water that rises to the surface through fissures in the rocks. The result is a hot spring that pours almost 500 gallons of hot water each minute into the Firehole River. Minerals dissolved in the hot water are deposited and gradually build the gracefully terraced shoulders of this feature.

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Did You Know?

• Prismatic means brilliantly colored.

• The intense blue color in the center of this hot spring is due to sunlight being scattered by fine particles suspended in the water.

• The yellow, orange, and brown colors encircling the hot spring and lining the runoff channels are caused by thermophiles—heat-loving microorganisms. These microbes contain colorful pigments that allow them to make energy from sunlight and thrive in the harsh conditions of hot springs.

This exhibit made possible by a generous grant to the Yellowstone Park Foundation

Marker can be reached from Grand Loop Road (U.S. 89) 1 mile south of Firehole Lake Drive, on the right when traveling south.

Courtesy hmdb.org

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