All about the Grand Prismatic Spring in Yellowstone


The Grand Prismatic Spring in Yellowstone National Park

Along with Old Faithful and the Grand Canyon of the Yellowstone, one of the things you MUST see in Yellowstone is the Grand Prismatic Spring. In this article I’ll cover everything you need to know about it.

What is the Grand Prismatic Spring?

The Grand Prismatic Spring is the largest hot spring in Yellowstone and the third largest in the world. It is over 300 feet long, 200 feet wide, and 100 feet deep. It gets its name from the colorful edges — resembling a light prism — with blue, green, yellow, orange, and red color rings.

It’s a hot spring

The Grand Prismatic is a hot spring. In Yellowstone there are five kinds of geothermal features: hot springs, geysers, fumaroles, mud pots, and travertine terraces. They are all closely related — mostly having to do with water being heated underground and working its way to the surface.

The big difference between a hot spring and a geyser is the plumbing. Geysers have a constriction, or a bottle neck, causing the water to get trapped, build pressure, and explode!

Hot springs don’t have the constriction. So hot water rises to the top, cools, and returns to the bottom. The water circulates freely.

Some hot springs used to be geysers, but something happened to alter the constriction, like an earthquake or a massive eruption.

It’s BIG

There are only two bigger hot springs in the world: Frying Pan Lake in New Zealand and Boiling Lake in Dominica. The Grand Prismatic is 370 feet in diameter and over 120 feet deep.

At Yellowstone it’s common to walk around on boardwalks and look down into deep blue hot springs. There are several gorgeous springs.

Grand Prismatic is a little different because you can’t get close enough to look down into it. Rather, it’s more like you’re looking out over a steaming pond or mountain lake. In fact, in the early days it was also called Prismatic Lake or Emerald Lake.

For that reason, some people don’t seem too impressed by it. It is hard to take it all in. It’s why you need to see it from next to the spring and from above (see below).

It’s colorful

It’s named Prismatic because it has the colors of the light prism. The colors are actually millions of tiny organisms called thermophiles (“thermo” = heat; “phile” = lover).

These organisms can ONLY live in hot temperatures — until it gets too hot even for them. The temperature will determine which organisms can survive, and therefore what colors we see.

The center of the hot spring is a deep blue — it’s too hot for any organisms to survive. As the water moves towards the edges and flows out of the hot spring, it cools, changing the colors from green to yellow to orange to red to brown.

When you see it from the higher viewpoint, it looks like a big eye. Almost like Sauron in Lord of the Rings — but not as spooky. It’s the one hot spring to rule them all!

How to see it

There are two ways to see it: next to it and from above.

Next to it

It has its own parking lot: the Grand Prismatic Spring parking lot. You’ll walk on the bridge crossing the Firehole River and continue on the boardwalk. It makes a loop around the Midway Geyser Basin, and continues along the edge of the Grand Prismatic for a while.

Above it

Drive south to the next parking lot: Fairy Falls. Take the Fairy Falls hike. The Fairy Falls hike is about 5.5 miles round trip, but you only need to walk the first .5 miles before turning left to the Grand Prismatic Spring Overlook. Walk another .3 miles and you’ll arrive at a viewing station.

This viewpoint has exploded in popularity lately. In fact, it wasn’t even an official viewpoint until 2017. When I visited in 2014, I asked a park ranger about the viewpoint. She pretended not to know what I was talking about.

Why? Because at the time, it was just a hillside that people scrambled up to the top. There wasn’t a trail! The whole hillside was being trampled. I admit I did some scrambling to get this view.

Grand Prismatic before the official viewpoint

With all the demand, the park finally put in a trail and an overlook station in 2017.

Where is it?

It’s located in the Midway Geyser Basin. This is located between Madison Junction and Old Faithful.

This general area of the park is composed of (from North to South): Lower Geyser Basin, Midway Geyser Basin, and Upper Geyser Basin.

Notice they are named after their elevation, not their direction. So Upper Geyser Basin (which contains Old Faithful) is the lowest on the map.

Midway is the smallest of the basins. It contains:

  • Grand Prismatic. Obviously the star of the basin.
  • Excelsior Geyser. This is almost as large as Grand Prismatic. See below.
  • Opal Pool & Turquoise Pool. Nice hot springs in their own right. They suffer from a comparison problem. It’s hard to stand out in your neighborhood when your neighbors have mansions.

There are other features that are considered part of Midway Geyser Basin, but there aren’t trails and they aren’t anything to note.

A Yellowstone Visitor

Like Florida Man, Yellowstone Visitor is always up to something bizarre.

In 2014, the National Park Service banned drones from all national parks. 

Just two months later, a tourist from Netherlands crashed his drone into the Grand Prismatic Spring. Oops. 

The park service was very concerned it could damage the colors of the spring, something that happened to Morning Glory spring after people threw debris in it over the years. 

The park service looked at all sorts of options to retrieve the drone. They tried to find it by analyzing helicopter images (being careful not to fly directly over it in the event of a crash), using high-powered binoculars, and asking witnesses where it entered the spring. All to no avail.

With other springs, they use a long robotic arm to remove debris, but the Prismatic is too big for the robotic arm. They thought about using a remote-controlled submarine, but they feared the submarine would malfunction and would also get lost in the spring.

So, the drone still sits at the bottom.

The tourist was fined over $3,000.  

Excelsior Geyser 

Imagine the huge Grand Prismatic as a geyser — that’s basically what Excelsior Geyser used to be. 

It’s almost the size of Grand Prismatic, and it used to erupt in massive explosions that were 300 feet wide and 300 feet tall! Imagine! 

This geyser became famous after the park was created in the late 1800s, as the explosions were unlike anything ever seen. 

Unfortunately, the geyser eruptions slowed down, and it became dormant by 1900. Since it really isn’t a geyser anymore, it’s called Excelsior Geyser Crater. 

Englishman Rudyard Kipling visited Yellowstone in the late 1800s and called this area “Hell’s Half Acre,” and the name stuck for a long time. Every once in a while someone uses that name today. 

Remarkably, there is one known photo of this geyser erupting. In 1888, Frank Jay Haynes snapped a photo of this event. 

Excelsior Geyser — when it was a geyser

Haynes wasn’t just a visitor; he was the official park photographer! He knew all the ins and outs of Yellowstone. 

He sold his photo as a postcard for years. He also included the image in his Haynes Guide to Yellowstone, which he produced every year from 1880-1921, when he died.  When he died, Mount Haynes was named in his honor. 

I’ve read through one of his guides, and it was a real joy to read about what the park was like over 100 years ago (surprisingly different). 

I’ve created my own guide to Yellowstone, and I’ve used his covers as inspiration for my cover. 

Unfortunately my guide doesn’t include a photo of Excelsior Geyser erupting, but it does include a step-by-step plan for getting the most of your Yellowstone vacation. 

Yellowstone is a big and complicated place to see. I simplify it in my itinerary/guide so you don’t have to do a ton of research. 

I’ve been visiting Yellowstone for over 30 years and I’ve even I’ve had many frustrating trips because the park is so big. If you don’t have a plan, you’ll wander around inefficiently.

Use my guide and LOVE your trip to Yellowstone.

I’m also working on a companion audio guide to help you learn about and enjoy the park as you visit.

Thanks for reading this article. I hoped it help you plan your trip. We also have more resources on our YouTube channel.

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