Grand Prismatic Spring, the largest of the geothermal pools in Yellowstone National Park, is 90 m across. The hot pool lies at the top of a broad, low mound formed by deposition of silica at its margins. Overflow channels radiate away from the pool. The colorful rings around the hot-spring pool are formed by algae and other organisms that are temperature dependent. The highest temperature organisms (70-73 degrees Centigrade) are white. Lower-temperature organisms grade to light yellow, orange, red, and then dark green.

Copyrighted photo by Katia and Maurice Krafft, 1984.

Copyrighted image used with permission. All Rights Reserved. Contact photographer for any usage requests.

Yellowstone