Grand Prismatic Spring is a highlight of any visit to Yellowstone National Park! The largest hot spring in the park the deep blue pool is surrounded by yellow and orange algae. This is a spot you want to make sure and take time to visit.
Grand Prismatic Spring - Yellowstone National Park
Grand Prismatic Spring is approximately 370 feet in diameter and more than 121 feet in depth. It is the third-largest hot spring in the world and the largest in the United States.
This epic thermal feature is larger than a football field!
One thing to know about Grand Prismatic Spring is it is CRAZY POPULAR and BUSY!!! If you arrive at mid-day or on a weekend you can expect the parking lot to be crowded and super busy.
You will want to plan an hour or two at a minimum for exploring this area. If you get done sooner you will have more time for exploring Old Faithful, Fountain Paint Pot, Firehole Lake Drive, or any of the other attractions in the park.
It is worth noting that the signs on the road say Midway Geyser Basin, not Grand Prismatic Spring so it can be really easy to miss that this epic spot is part of the geyser basin.
Make sure you do not touch the hot spring waters or really any thermal feature in the park! The waters of the Grand Prismatic Spring run at an average of 160ºF.
The rainbow colors around the spring change by season depending on the weather and water temperature. In the summer the pool is vibrant with yellow, orange, and greens. In the winter the colors can be a more muted brown and orange.
Make sure to plan time to see the entire Midway Geyser Basin including Excelsior Geyser, Opal Pool, and Turquoise Pool.
What is the best time to visit Grand Prismatic Spring?
The best time really depends on if you really want to get epic photos or really want to escape the crowds as much as possible.
Grand Prismatic Spring is crazy popular and busy pretty much ALL DAY!
For photography, the best time to visit is in the middle of the day on a bright sunny day when the pool is clear and not covered in steam. This is also one of the most popular times of day so you will want to be prepared for parking issues.
If you have seen super vibrant pics of Grand Prismatic Spring and want to get the same photo make sure you plan enough time for conditions.
Many times the steam coming off of Grand Prismatic Spring can get clouded in and the views are not what you may be hoping for.
The photos you are seeing were taken in the absolutely perfect sunny, no steam, weather that does happen but not all the time.
In the morning Grand Prismatic is often covered in steam due to the ambient air being colder than the pools.
Please note drones are not allowed within Yellowstone National Park.
Where is Grand Prismatic Spring?
Midway Geyser Basin is on the Lower Loop Road approximately 10.5 miles south of Madison on the west side of the road.
Don't miss Excelsior Geyser along the same boardwalk.
How to get to Grand Prismatic Spring
Grand Prismatic Spring is located off the Yellowstone loop road. You will see signs for Midway Geyser Basin.
Grand Prismatic Spring Overlook
Grand Prismatic Spring Overlook provides an epic sweeping view of Grand Prismatic and the surrounding area.
Trail Length - The trail is .6 miles and has a 105-foot elevation gain.
Grand Prismatic Spring Overlook Parking/Trailhead - Park 1 mile (1.6 km) south of Midway Geyser Basin at the Fairy Falls Parking Lot.
Overlook things to know - The trail does not open until May due to bear management.
Parking is super limited so you will want to be prepared to wait for a parking spot.
Pets are not allowed on the trail.
The Grand Prismatic Overlook Trail is an easy to difficult hike depending on the hiker’s physical abilities.
This is due to the incline of the hike and the trail material. The trail is made of black sand/gravel. It makes it difficult to walk this trail.
Especially for people with knee, back, or other health conditions. The hike passes by the Midway Geyser Basin giving you a beautiful view.
You will make your way up the incline as it winds up and makes its way to the top. This rough hike is definitely worth the view when you arrive and see the breathtaking Grand Prismatic Springs from above.
How was the Grand Prismatic Spring formed?
Yellowstone is full of hydrothermal hot springs (nature’s jacuzzi tubs) where water is continually rising causing fractures in the surface of the earth.
Different from a geyser (ie: Old Faithful) hot springs do not have obstructions near the surface causing them to erupt.
Instead, a hot spring is similar to a jacuzzi, where hot water travels up to the top and cools as it reaches the surface - causing that water to sink and be replaced by hotter water from below.
However, unlike your average jacuzzi, Grand Prismatic sits on a bed of rhyolitic rock, which is a colored variation of volcanic rock with high silica content.
Also unlike Jacuzzis, which are typically plugged into a local power source, Grand Prismatic is warmed by the heat of the magma from deep in the earth.
As this mineral heavy water travels to the surface and heads out of the spring to cool, the sinter, or the white-gray landscape around the spring you see, is beginning to form.
Wait, Where’s the Smell?
If you have been to visit a hot spring before, oftentimes your nose lets you know you are reaching your destination before you can even see the springs.
This is due to sulfur binding with oxygen to form the compound sulfate. Another major difference Grand Prismatic Spring holds versus other hot springs is the absence of that common smell of sulfur (rotten egg) in the air.
This is a lucky coincidence that no hydrogen sulfide gas is present in the air, though it could remain in the water.
How Hot is Grand Prismatic Spring?
188.6 degrees Fahrenheit up to 205 degrees.
Can you swim in the Grand Prismatic Spring?
No!!! No!!! No!!!
I don't know if we can say NO enough about anyone swimming in Grand Prismatic Spring.
The pool is over 188 degrees and will kill you and if it doesn't kill you it is guaranteed to cause 3rd-degree burns in seconds.
While this temp is perfect for budding bacteria, it is very unsafe for humans, causing catastrophic burns, and even death.
Why is Grand Prismatic Spring So Colorful?
Grand Prismatic Springs gets its name because of the rainbow of colors within the pool.
Deep below Yellowstone NP an active volcano magma heats water that rises to the surface through fissures in the earth's crust.
The spring is formed when water emerges from deep cracks in the earth's surface. The water flows upwards into the center of the pool at a high temperature and then cools down as it spreads over the pool.
The rings of temperature create the different colors within the pool. Each temperature zone is inhabited by heat-loving bacteria called thermopiles.
The center of the pool is always a deep blue due to the high temperature of the water creating a sterile environment.
The water is moving so much that the hot spring pours 500 gallons of water every minute into the Firehole River.
No, it’s not your polarized sunglasses causing the… well, grand… display of color at Grand Prismatic Spring, but rather the thermophilic (heat-loving) bacteria who make their homes beneath the bubbling surface.
Grand Prismatic holds the presence of chemotrophs (organisms that use chemicals as a source of energy) mixed with a great deal of phototrophic life.
While a lot of Grand Prismatic’s bacteria is photosynthetic, relying heavily on the sun, there is debate if a chemotrophic bacteria, Aquifex, which is fueled by hydrogen gas, is also present.
Three recognizable cyanobacteria (aquatic photosynthesizing bacteria) have been identified across the scalding temperatures of the spring.
All cyanobacteria use light as their main energy source and are responsible for the greens, oranges, yellows, reds, and browns that you may glimpse while looking at the spring.
Things to Know
There are bathrooms available in the main parking lot. Be prepared for there to be a line!
Make sure to bring water with you for the walk. There is no water available along the boardwalk.
There is no shade along the boardwalk! Be prepared for the sun and weather.
Nearby Yellowstone Attractions
Old Faithful - Old Faithful is just down the road from the Midway Geyser Basin.
Firehole Lake Drive - Check out the Great Fountain Geyser, White Dome Geyser, and Firehole Lake on this beautiful scenic drive.
Biscuit Basin - Check out Black Opal Pool and the Jewel Geyser in Biscuit Basin.
Fountain Paint Pot - Explore the Fountain Paint Pot Trail to check out the Celestine Pool, Jet Geyser, Fountain Geyser, and Clepsydra Geyser.
Firehole Canyon Drive - Check out Firehole Falls and Firehole River Swimming Area on this great scenic drive.
Check out all of the Yellowstone Campgrounds to help plan your time in the park.
Closest Yellowstone Lodging
Additional Yellowstone Resources
Yellowstone Lodging -Check out all of the lodges you can stay in while visiting Yellowstone NP.
Yellowstone Camping - Check out all of the campgrounds available within the park.
Things to do Yellowstone - Check out all of the top things to do in the park.
Yellowstone Facts - Learn more about the unique features in Yellowstone.
Free National Park Days - Check out all of the days the National Park Service waives park entrance fees.
National Parks in Wyoming - Check out all of the parks you can visit while in Wyoming.
Grand Teton Guide - Everything you need to know to plan a great visit to Grand Teton NP