Grand Prismatic Hot Spring in Yellowstone. Photo by Grant Ordelheide

Grand Prismatic Hot Spring in Yellowstone. 

Old Faithful may be more famous, but the Grand Prismatic Hot Spring is the most photographed thermal feature in Yellowstone. That's because of its crazy-bright colors and enormous size.

What Makes the Grand Prismatic so Grand?

Deeper than a 10-Story Building
Extremely hot water travels 121 feet from a crack in the Earth to reach the surface of the spring.

Football Field on Steroids
The third largest spring in the world, the Grand Prismatic is bigger than a football field at 370 feet in diameter. A gridiron is 360 feet long and 160 feet wide.

Rainbow of Colors
The hot spring has bright bands of orange, yellow, and green ring the deep blue waters in the spring. The multicolored layers get their hues from different species of thermophile (heat-loving) bacteria living in the progressively cooler water around the spring. And the deep blue center? That’s because water scatters the blue wavelengths of light more than others, reflecting blues back to our eyes.

A Living Thermometer
What living thing in Yellowstone has helped investigators solve crimes and NASA search for extraterrestrial life on seemingly inhospitable planets? Heat-loving microbes living in the Yellowstone's thermal pools. In 1968, researcher Thomas Brock discovered a microbe living in one of Yellowstone’s extremely hot springs. In the years since, research on Yellowstone’s microbes has led to major medical and scientific advances, including the sequencing of the entire human genome.

A Foreign Object in Grand Prismatic

When a tourist from the Netherlands accidentally—and illegally—flew a drone into the ecologically fragile Grand Prismatic in 2014, the drone disappeared and has never been recovered. Read more about things stuffed down geysers and hot springs.

More Pools and Geysers at Midway Geyser Basin

Directory Sign at Yellowstone's Midway Geyser Basin

Directory Sign at Yellowstone's Midway Geyser Basin.

Yellowstone's Midway Geyser Basin may be small, but it packs a big punch: In addition to Grand Prismatic Spring, see Excelsior Geyser, an enormous geyser crater, Turquoise Pool, and Opal Pool. You can get up close by strolling across the Firehole River and along the short boardwalk that snakes through the thermal area. Be sure to stay on the boardwalk. It is illegal and very dangerous to walk in the geyser basin.

Excelsior Geyser Crater

Runoff from Excelsior Geyser dumping in the Firehole River

Runoff from Excelsior Geyser dumping in the Firehole River

Today, this steaming, bright blue pool is essentially a hot spring. But in its heyday in the late 1800s, Excelsior erupted to heights of about 300 feet. It went dormant for much of the 20th century, only to suddenly erupt for two days in 1985—some of its blasts reached 80 feet in height. Though it’s a quiet pool now, Yellowstone’s constantly changing thermal landscape could revive Excelsior Geyser to its former glory once again.

Getting to the Midway Geyser Basin

Map of the Midway Geyser Basin location from Old Faithful

The Midway Geyser Basin is a short distance north from the Old Faithful area and the west side of the Grand Loop Road. Or, from the West Entrance, drive about 25 miles on the West Entrance Road and Grand Loop Road to the Midway Geyser Basin parking area. Tip: Get there early or late in the day to avoid the tour bus crowds at this justifiably popular spot.


Yellowstone's most famous geyser, Old Faithful at Twilight

8 Best Yellowstone Geyser Basins and Map

A map showing Yellowstone's geyser basins including the Upper Geyser Basin with Old Faithful and Morning Glory Pool, and nearby Grand Prismatic.

Norris Porcelain Basin. Photo by Jeff Vanuga

Norris Geyser Basin - Yellowstone's Hottest, Oldest, Tallest

Norris holds the record for the highest temperature ever recorded in Yellowstone. It has the tallest geyser in the world, and the colors too impress with milky blues, greens, and yellows.

Emerald Spring in the Norris Back Geyser Basin. Photo by Gloria Wadzinski

Extreme Geysers in Yellowstone's Norris Back Basin

At the Norris Back Geyser Basin, you'll see a land of extremes... the tallest, but infrequent geyser, geysers that erupt continuously, springs that have been damaged by man, new geysers, old geysers, and exploding geysers.


Watch Geysers Erupt in Yellowstone

Yellowstone is the largest active geyser field in the world.

Grand Prismatic in Yellowstone National Park

Deaths and Injuries at Yellowstone's Geysers and Hot Springs

The extraordinary natural features that keep Yellowstone such an alluring place can make it perilous.

Yellowstone Old Faithful Geyser

See Old Faithful and 60% of the World's Geysers in Yellowstone's Upper Geyser Basin

See Old Faithful, Castle Geyser, Riverside Geyser and geothermal features of Yellowstone country's steaming vents, erupting geysers and gurgling hot springs.

A woman viewing Morning Glory Pool from the boardwalk

Things Stuffed Down Yellowstone's Geysers

From laundry to couches, soap to horseshoes, Old Faithful and neighboring Yellowstone geysers and hot springs have been a receptacle for more than just water since the park's inception. The latest has been a drone that dived into the Grand Prismatic Hot Spring

Norris Porcelain Geyser Basin. Photo by Gloria Wadzinski

Norris Porcelain Geyser Basin's Milky Colors

Porcelain Basin is named due to the milky color of the mineral deposited here. That whitish-colored mineral is siliceous sinter, also known as geyserite.


Rare Microbes Flourish in Yellowstone National Park Geysers and Hot Springs

The Thermal Biology Institute at Montana State University studies life forms and microbes found in the hot springs and geysers of Yellowstone National Park.