Grand Prismatic Spring in Yellowstone National Park: The Largest Hot Spring in USA

Grand Prismatic Spring in Yellowstone National Park: The Largest Hot Spring in USA

Discover the beauty of Midway Geyser Basin. The Grand Prismatic Spring in Yellowstone National Park, the largest hot spring in the Wyoming, USA.
admin |

A trip to Yellowstone National Park is like discovering the most beautiful treasures of nature on the territory of Wyoming. Here you need to examine the Great Prismatic Spring, which symbolizes the park’s spectacular beauty and geothermal power.

Geological History

Yellowstone is a place where hot water vapors rise up, a riot of color beneath your feet. Wyoming’s gemstone is a natural wonder with blue waters and colorful surroundings.

About 2.1 million years ago, our world was the scene of great geologic events. The Yellowstone Caldera was created by a giant volcanic eruption that changed the landscape forever. Fast forward to today, and the Midway Geyser Basin in particular is a testament to these ancient forces.

Yellowstone National Park Grand Prismatic Spring Details
Jason Carter / Sharetheexperience

It starts deep inside the Earth. Rain and snow melt and seep deep into the earth, then are superheated by the Earth’s molten core. It follows a winding path through a maze of cracks and crevices. On its journey, the water functions to carve rocks and collect minerals, especially silica.

Finally, as it triumphantly rises to the surface, it brings these minerals with it and deposits them on the sides of the spring. Over time, these deposits have formed the iconic sinter terraces of the spring. The colors you see – bright reds, oranges, yellows and greens – are the work of microscopic organisms living in this steamy, mineral-rich environment.

What to See at Midway Geyser Basin?

The Midway Geyser Basin is home to several geothermal features, including geysers and fumaroles.

Other important geothermal features include Excelsior Geyser Crater (the largest active geyser crater in the world), Opal Pool, Turquoise Pool.

Yellowstone National Park Grand Prismatic Spring Map
Yellowstone National Park - Grand Prismatic Spring map

Excelsior Geyser

Excelsior Geyser is really impressive to see. One of two large geysers in Yellowstone National Park, it’s the first natural wonder you’ll encounter as you make your way along the wooden platforms.

Once one of the largest geysers in the world, Excelsior is now a hot spring, discharging more than 4,000 gallons (15,142 liters) of boiling water per minute into the Firehole River. The dimensions of the pool are about 61 meters long and 91 meters wide, and the depth can exceed 24 meters.

Yellowstone National Park Grand Prismatic Spring Excelsior Geyser
Excelsior Geyser eruption & crater sixthland / Flickr

Grand Prismatic Spring

This spring is named after the fact that the water is so hot that it evaporates and forms a prism. This spring, which is about 110 meters wide, has a walking path around it so that visitors can see it up close.

Yellowstone National Park Grand Prismatic Spring Close Up
Andrew Parlette
Yellowstone National Park Grand Prismatic Spring Air Look
Eric Henderson

The intense heat of the spring creates an incredible effect around it. The water evaporates so fast that it forms a cloud of steam that can be seen for miles around. The bright colors are created by bacteria living in the hot water. Different colors indicate different temperatures, with blue being the coolest and yellow the hottest.

Why is the Grand Prismatic Spring so colorful?

Located in Yellowstone National Park, Grand Prismatic Spring is not only the third largest spring in the world, but also a place where nature paints the most vibrant rainbows.

This natural wonder, about 50 meters in diameter, gets its breathtaking color palette mainly from heat-loving microorganisms called thermophiles. These small but powerful creatures, invisible to the naked eye, are the true alchemists of the source’s coloration.

For example, cyanobacteria with chlorophyll and carotenoid pigments create green and blue hues reminiscent of those found in a calm blue pool. In contrast, other thermophiles, adapted to slightly cooler waters, produce orange, yellow and red colors that paint the edges of the spring with warm, fiery hues.

Water Temperature: But the formation of Grand Prismatic Spring’s colors is not only about microbes. It is also about water temperature and mineral richness. The center of the spring is known for its extremely hot water, where the temperature can reach around 87°C.

The deep, vivid blue color of the water here is due to the scattering of white light so that only blue wavelengths reach our eyes. As the heated water emanating from the center cools, it creates a hospitable environment for a variety of thermophiles, increasing the attractiveness of the spring.

Mineral Content: Furthermore, the water is full of minerals dissolved from the surrounding rocks. Minerals such as silica, iron, manganese, each enhancing the spring’s vibrant rainbow. For example, iron oxides add a reddish-orange hue to the warm spectrum seen around the spring.

What makes the Grand Prismatic Spring so special?

Grand Prismatic Spring in Yellowstone National Park is the largest hot spring in the USA and the third largest in the world. Visitors are captivated by the vibrant colors created by the colorful bacteria that live in its thermal waters.

Grand Prismatic Spring’s significance has a historical context, first recorded by early European explorers during the Hayden Expedition in 1839. Its location in Yellowstone’s thermal basin, with features such as surrounding geysers and thermal pools, and its proximity to the Firehole River, has made it a central attraction in the park.

The lure of the spring often causes tour buses to park in the immediate area and visitors to marvel at the beauty of this geological treasure.

How can I get the best view of Grand Prismatic Spring?

For a unforgettable view of Grand Prismatic Spring, one of the most iconic hot springs in the USA, a hike to the viewpoint is a must. The trail begins at the conveniently located Fairy Falls Road parking area, just south of the main parking area, about a mile away.

The trail itself is an easy one-way hike of 1.3 kilometers (0.8 miles) and passes through stunning views of Yellowstone. Once on the trail, you will cross the Firehole River, an integral part of the park’s geothermal ecosystem, whose very name refers to the thermal features in Yellowstone.

Yellowstone National Park Grand Prismatic Spring Overlook
After a short trail to the overlook, you will see this wonderful pool from the viewing platform.Rebecca Latson / Flickr

As you walk, you will enjoy various views of the park. When you arrive at the viewpoint, you will be mesmerized by the view of Grand Prismatic Spring. From this vantage point, you can get a much better view of the spring’s massive size and the vibrant spectrum of colors created by the unique species of bacteria living in its warm, mineral-rich waters.

Yellowstone National Park Fairy Falls Aerial View
Fairy Falls trailGoogle Earth

After experiencing this splendor, if you want to explore a little further, you can continue on to Fairy Falls. If you’ve packed a lunch, the nearby picnic area offers the perfect place to soak up the beauty of Yellowstone.

Opal Pool

The Opal Pool in Yellowstone is a small but fascinating natural wonder. Its most striking feature is its bright blue color, which stands out among shades of green, yellow and orange, thanks to the microbial mats on its edges.

Yellowstone National Park Opal Pool
Opal PoolTashnuva
Yellowstone National Park Turquoise Pool
Turquoise PoolAnak Tok / Flickr

Due to its small size, the Opal Pool is particularly sensitive to seasonal changes. In winter it is usually the first to freeze and the last to thaw, as it does not have enough steam to speed up this process. Usually calm, the Opal Pool can occasionally surprise visitors by erupting as a geyser.

Turquoise Pool

As its name suggests, the Turquoise Pool is known for its vibrant turquoise waters. This pool is surrounded by intricate sinter formations and bright microbial mats that create a striking visual contrast. Its shallower and cooler waters compared to other springs in the area support a variety of thermophile microorganisms.

Tips for visiting Midway Geyser Basin

  • Always use designated paths and boardwalks. Going off the road can be dangerous because the ground around the sources can lead to accidents.
  • The area can be steamy, obstruct vision and pose a risk of burns. The heat can also be a cause of dehydration.
  • The Midway Geyser Basin is home to a variety of wildlife such as elk and bison. Be careful not to disturb these animals by watching them from a safe distance.
  • The views from the basin are breathtaking, so bring a camera. However, be aware that drones are generally not permitted in national parks.
  • Take time to observe where the water comes out of the spring and how it bubbles, showcasing the basin’s dynamic geothermal activity.
  • The basin may be small, but it is a popular destination. Arrive early or late in the day to avoid crowds and find parking more easily.


How Hot is the Grand Prismatic Spring?

This spring is incredibly hot. The temperature in the center of the pool can reach as high as 87°C (189°F). As the water flows outward from the center, the temperature gradually decreases, which supports the life of different types of heat-loving microorganisms. This change in temperature is one of the factors contributing to the vibrant colors seen at the edges of the spring.

Can you swim at Grand Prismatic Spring?

Swimming is prohibited due to the extremely high temperatures and the delicate ecosystem it supports. The National Park Service enforces rules to protect the spring and its unique features, and failure to follow these rules can result in penalties, fines or even criminal charges.

What Happens If You Touch or Swim in Great Prismatic Spring?

Touching or swimming is not only illegal, but also extremely dangerous. Boiling water can cause severe burns and can even be life-threatening. Furthermore, human contact with the spring can damage delicate microbial mats and disrupt the ecosystem, which can affect the appearance and health of the spring. Do not step outside the walkways.

Does Grand Prismatic Spring Smell?

Yes, it has an odor. Often described as a “rotten egg” smell, it is caused by hydrogen sulfide gas produced by certain thermophile microorganisms living in the hot spring. The smell can sometimes be strong and unpleasant, but it is a natural by-product from the unique ecosystem found inside the spring.

Best Times to Visit

Although Grand Prismatic Spring can be visited year-round, the best time to visit for the best view depends on the weather and time of day.

The vibrant colors of the spring are best seen on sunny days, when sunlight can pierce through the steam rising from the hot water. Therefore, visiting between June and September, when the weather is usually clear and warm, increases your chances of seeing the full spectrum of the spring’s colors.

Also, consider visiting in the early morning or late afternoon, when the sun is lower in the sky, reducing the glare on the water surface and making the colors more distinct.

For a quieter experience, opt for the shoulder seasons, such as May or October, when the park is less crowded but the weather conditions are still favorable.

How to Get to Grand Prismatic Spring?

Getting to Grand Prismatic Spring in Yellowstone National Park requires combining several modes of transportation and a bit of preparation, but with the right information, the journey becomes a smooth and enjoyable experience.

The first step to reaching this place is to reach Yellowstone National Park. The park is accessible by car with five entry points: north, northeast, east, south and west.

  • Personal Vehicle: The most popular option is to use your own vehicle or a rental car. This allows you the freedom and flexibility to explore the park at your own pace.
    Guided Tours: Some companies offer guided bus tours that include key stops in the park, including the Great Prismatic Spring. This option allows you to sit back and relax while learning more about the park from knowledgeable guides.

Parking may be limited, especially during peak season. Arriving early in the morning or late in the afternoon can increase your chances of finding a parking space. If the main parking lot is full, additional parking can be found along Grand Loop Road, but be prepared to walk a little longer.



The fascinating color and geological spectacle of the Great Prismatic Spring always succeeds in captivating its visitors. By learning about the scientific explanations and historical context surrounding this phenomenon, you can gain a closer understanding of its beauty.