[IMAGE: Grand Prismatic Spring, by Photograph by Carsten Steger]
![[IMAGE: Grand Prismatic Spring, by Photograph by Carsten Steger]](https://upload.wikimedia.org/wikipedia/commons/thumb/0/0b/Aerial_image_of_Grand_Prismatic_Spring_%28view_from_the_south%29.jpg/1280px-Aerial_image_of_Grand_Prismatic_Spring_%28view_from_the_south%29.jpg){kind=link}
Grand Prismatic Spring
Photograph by Carsten Steger, Natural
Grand Prismatic Spring in Yellowstone National Park is the largest hot spring in the United States — over 100 metres across. From the air, it looks like a giant eye.
Hot water rises from deep underground. The centre is extremely hot and a deep, clear blue. As the water flows outward and cools, different microbes can survive: mats of bacteria and archaea that produce pigments in yellow, orange, red and brown. Each colour marks a different temperature.
The organisms living in Yellowstone's hot springs have been important to science. An enzyme from one of them, Thermus aquaticus, made possible PCR, the technique used to copy DNA in laboratories — including in COVID tests.
Look for
- The deep blue centre, too hot for most life
- Rings of yellow, orange and red
- Streams of colour spreading out like rays