Where is the Grand Prismatic Spring?
Quick answer
The Grand Prismatic Spring is in Yellowstone National Park, in the US state of Wyoming, in the United States. It’s the largest hot spring in the US and the third-largest in the world, about 110 m (370 ft) across. Its rainbow rings of blue, green, yellow, orange and red come from heat-loving microbes living in the water.
Key facts
- Location
- Midway Geyser Basin, Yellowstone National Park, Wyoming, USA
- Diameter
- About 110 m (370 ft)
- Depth
- About 50 m (160 ft)
- Water temperature
- About 70 °C (160 °F) at the center
Why the rainbow colors?
| Color | Cause |
|---|---|
| Deep blue center | Very hot, clean water that scatters blue light, like the sky; see why the sky is blue |
| Green and yellow | Microbial mats that survive slightly cooler water |
| Orange and red | Microbes with pigments that protect them from sunlight, in the coolest edges |
These microbes, mostly bacteria and archaea, are called thermophiles, “heat lovers.” See which organisms lack a nucleus. Colors shift with the seasons as the microbes change.
Yellowstone: a supervolcano
Yellowstone sits above a huge volcanic hotspot. Heat from magma deep below powers more than 10,000 hydrothermal features:
| Feature | Famous example |
|---|---|
| Geysers | Old Faithful, erupting roughly every 60–110 minutes |
| Hot springs | Grand Prismatic Spring |
| Mud pots | Fountain Paint Pot |
| Travertine terraces | Mammoth Hot Springs |
Yellowstone contains about half of the world’s active geysers.
America’s first national park
Yellowstone became the world’s first national park in 1872. It covers parts of Wyoming, Montana and Idaho. For the biggest US park, see the largest national park in the US.
Seeing it safely
- The best views are from the Grand Prismatic Overlook on the Fairy Falls Trail, which looks down on the full rainbow.
- A boardwalk runs beside the spring. Visitors must stay on it: the ground can be thin crust over boiling water, and people have been seriously injured by stepping off.
- In cooler weather, steam may hide the colors; sunny summer afternoons are best.
Similar hot-spring mineral terraces exist in Turkey; see the Pamukkale terraces.
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