Yellowstone National Park’s biggest draws are its famous geothermal and hydrothermal features. The geysers, hot springs, fumaroles, and mud pots throughout the park make it a must-visit attraction in the United States. Some of its features are very well-known and draw large crowds, while others bubble or steam away in relative obscurity. It’s estimated that there are 10,000 thermal features in the national park so it’s almost impossible to see them all on a vacation, but you’ll definitely want to add at least a few of these onto your Yellowstone itinerary.
What kind of geothermal features are there at Yellowstone?
Yellowstone is home to a variety of geothermal/hydrothermal features. The dramatic features are created by magma deep within the earth heating ground water. Depending on the cracks and pathways through the rock below the surface, these features take on different forms. All of them are fascinating and unlike anything you’re likely to see in your everyday life.
Geysers are the stars of the show and certainly the most dramatic of Yellowstone’s hydrothermal features. In a geyser’s “plumbing” deep underground, the pressure prevents superheated water from boiling. Eventually a buildup of gases relieves that pressure and allows the water to boil rapidly sending it launching up into the air, sometimes to great heights. Yellowstone contains the tallest active geyser in the world – Steamboat Geyser in the Norris Geyser Basin – but you’ll also find plenty of smaller, less dramatic ones. Several of the active geysers have eruptions that can be predicted with a relatively small margin of error, so it’s recommended to check status boards at the visitor center and/or the Yellowstone app for current predictions.
Hot springs are some of the most breathtaking hydrothermal features in Yellowstone, though they’re certainly less dramatic than geysers. Hot springs lack the constrictions in their plumbing that prevent the superheated water from rising so the water is allowed to circulate without the explosive eruptions. Some of them appear to be boiling though this is typically the churning of escaping gases rather than actually boiling water. Others, like the famous Grand Prismatic Spring, look completely still and serene. Many of Yellowstone’s hot springs have distinctive coloring due to microorganisms that live in their waters.
Mud pots are also closely related to hot springs, but these tend to be more acidic with less water involved. Microorganisms living inside convert the escaping sulfuric gases into sulfuric acid which then dissolves the rock. When it mixes with the water, it gives the appearance of chalky, boiling mud. Some of Yellowstone’s mud pots have a ph equivalent to battery acid.
Found mainly in the Mammoth Hot Springs area, these hydrothermal features have a distinctive terraced look that’s formed by dissolved limestone that’s brought to the surface by the thermal waters. As the water flows away or evaporates, the minerals are deposited and form the travertine rock that gives the terraces their unique appearance.
Fumaroles are often overlooked because they lack the dramatic eruptions of geysers or beautiful colors of hot springs, but they’re actually the hottest hydrothermal features present in Yellowstone. Their high heat and limited water supply causes all of the water to boil into steam before it reaches the surface. As a visitor, you’ll see steam pouring out of a hole, sometimes accompanied by a roaring sound.
Geothermal areas of Yellowstone
Though there are some hydrothermal features in the backcountry, may of the most spectacular ones are easily accessible off of park roads. Due to the fragile nature of the surfaces in these hot spots, most of the thermal areas have paved pathways or boardwalks that make it easy to explore. Note that stepping off of these marked paths can be dangerous to you and damaging to the protected areas so use caution when walking and keep a close eye on kids.
This section features the main geothermal areas that are accessible off of the main park roads. Though you’ll find plenty of hydrothermal features in the backcountry, most visitors stick to the well-marked pathways at these areas.
Upper Geyser Basin
Home to Yellowstone’s most famous attraction, Old Faithful, Upper Geyser basin contains numerous thermal features and is surrounded by one of the most well-developed areas of the park. With numerous restaurants to pick from and Yellowstone’s most famous lodging, it’s an ideal place to visit whether you’re spending the night or just want to grab lunch. Most visitors come to see Old Faithful, but it would be a shame to skip the rest of Upper Geyser Basin as it’s home to the highest concentration of hydrothermal features in the park. The main walkway is approximately 5 miles round trip.
Along the trails, you’ll find countless hot springs and four other geysers that park staff can predict within a margin of error. Grand Geyser has an impressive eruption that can send water higher than Old Faithful from its pool. Riverside Geyser has a unique eruption that sends water spouting over the Firehole River. Castle Geyser has a very unique cone that looks more like an old fortress.
If you’re looking for hot springs, you’ll find dozens along the winding pathways. Morning Glory Pool is one of my favorites with its delicate sloping edges and beautiful colors. It’s one of the farthest spots from the visitor center on foot, but it’s well worth the walk.
If you want to stay near Upper Geyser Basin, book a cabin at the Old Faithful Lodge.
This small area is part of the Upper Geyser Basin, but is accessed separately with its own parking area. Its name comes from biscuit-shaped deposits that used to surround one of the hot springs. These “biscuits” are no longer visible due to an eruption in the 1950s that blew them all away, but the name remains. The basin is home to a collection of small pools and geysers along a .6-mile trail.
Black Sand Basin
This small hydrothermal area is also part of Upper Geyser Basin and is named due to the bits of black obsidian sand in the area. It’s home to several large hot springs, including beautiful Rainbow Pool. Two small geysers with irregular but fairly short intervals between eruptions can be viewed right from the parking lot, which makes this one of the easiest places in Yellowstone to spot a geyser eruption if you’re not able to do a lot of walking. If you venture through the whole basin, the trail is only half a mile.
Norris Geyser Basin
Norris is the hottest part of the park, and the high temperatures make it especially active. Here you’ll find Steamboat Geyser, the tallest active one in the world. Unfortunately, its eruptions are not predictable so seeing it in action will be a major stroke of luck. It can go months or even years without erupting, but in 2018 it roared back to life and has been having major eruptions much more often than any known period in its past.
In the Porcelain Basin area, head downhill from the parking area to enter a sea of colorful runoff from the many hot springs. Don’t forget to look behind you as the view back up the hill from the boardwalk is one of the most dramatic in any of Yellowstone’s geothermal areas. Aside from the many hot springs, you’ll also find adorably named Whirlagig Geyser here, which has a unique spiral water pattern when it erupts, though this one is not predictable. The trails here are approximately 2 miles long.
Artists’ Paint Pots
This small area features mud pots and small but colorful hot springs. It’s located between the Norris Geyser Basin and Madison Junction. There is a loop trail approximately a mile long that takes you past the thermal features here so you can get an up-close view of the burbling mud pots.
Midway Geyser Basin
Midway Geyser Basin is much smaller than the previous two thermal areas, but it’s home to one of the most famous spots in the park. Grand Prismatic Spring is the largest known hot spring in the world and its rainbow-hued waters are absolutely captivating. The .8-mile boardwalk path here allows you to get a relatively closeup view of it, but to truly appreciate it, check out the Fairy Falls trail which has a new-ish overlook that offers a spectacular aerial view.
You’ll also find a couple smaller hot springs as well as the pool formed by extinct Excelsior Geyser. Once an erupting geyser, it blew its plumbing apart and is now just a large pool emitting towers of steam. It’s particularly impressive in the morning when the cooler air makes the steam look even more dramatic.
Fountain Paint Pots
Similar to the Artists’ Paint Pots further north, this thermal area features several mud pots along the half-mile loop trail. Located in the Lower Geyser Basin – the park’s largest basin – these are some of the easiest features to explore in the area due to their proximity to the main park road. In addition to the mud pots, you’ll also find hot springs and some irregularly erupting geysers in the area.
West Thumb Geyser Basin
West Thumb is a bit unique as it’s located right on the shores of Yellowstone Lake. In fact, some of the thermal features are even located underwater beneath the surface of the lake. There are several smaller hot springs along the mile-long boardwalk here, but the most famous thermal element is Fishing Cone, a small cone filled with hot water that typically pokes just above the surface of the water.
Mud Volcano and Sulfur Cauldron
Mud Volcano isn’t the most famous area of the park – you won’t find powerful geysers or rainbow-colored hot springs here – but it’s fascinating and certainly worth a visit to view its features that seem to belong on another planet. Most of the features along the .6-mile trail are mud pots and acidic pools and a short trail (approximately half a mile) will take you to the highlights.
Dragon’s Mouth Spring is near the parking area and features a hot spring that emerges from a cave. The sounds of roiling waters echoing out of the cave along with the steam escaping make it seem like a dragon really is lurking inside of it. You’ll definitely want to stop and take a good listen.
You’ll also find the titular Mud Volcano, which reportedly erupted shooting mud high into the air until the 1800s, but is now just a pool of bubbling mud. Follow the pathway uphill to visit Sour Lake, a hot spring that looks like a pretty pool, but actually has the pH of battery acid. Yikes.
Across the main road from the Mud Volcano parking area you’ll find Sulfur Cauldron. From the overlook above it, you’ll see the churning hot springs the area is named for. Like previously mentioned Sour Lake, these pools have incredibly acidic waters, comparable to stomach acid. The whole area is – as my fiance said – “pretty metal.”
Mammoth Hot Springs
Located in the northwest corner of the park, Mammoth Hot Springs is an area of travertine terraces formed by hot springs. As the water from the springs evaporates, it deposits calcium carbonate, which makes the beautiful terraces and ridges that make Mammoth famous. Some have a chalky white appearance, while other areas are colored by the microorganisms that live there.
There are 1.75 miles of boardwalk trails looping around the lower portions, where you’ll get up-close views of famous Minerva Terrace among others. The Upper Terrace Drive is a one-way loop approximately 1.5 miles long that takes you up on top of the terraces for aerial views of them. Plan to do the drive early in the day if possible as there is limited parking and traffic can clog up.
If you want to stay near the terraces, book a room at the Mammoth Hot Springs Hotel.
Backcountry hydrothermal features
While Yellowstone’s most famous features are located in the areas we’ve already covered, there are several hydrothermal features that are located in backcountry areas. These are further from the main roads and require a bit more effort to view, but their remoteness means that you’ll also find fewer other visitors crowding around them. On the flip side, you also won’t find boardwalks in these areas, so pay close attention to stay on well-marked trails to avoid potentially deadly falls into thermal features.
Shoshone Geyser Basin
Located along the shores of Shoshone Lake, the second biggest in the park, this geyser basin is also one of the most densely packed with hydrothermal features. If you make the 8+ mile hike to this thermal area, you’ll find more than 80 geysers, plus plenty of hot springs and mud pots. Most access is via the trail to Lone Star Geyser south of the Old Faithful area.
Heart Lake Geyser Basin
Heart Lake is located south of Yellowstone Lake and features a decently sized collection of hot springs and geysers. It’s accessed via a 7.5-mile trail from the main road, passing through forest and along a creek bed. Rustic Geyser is one of the most popular features, erupting with short intervals in between periods of dormancy.
Monument Geyser Basin
This small, little-known geyser basin is one of the more easily accessible backcountry thermal areas. A mile-long trail takes you along the Gibbon River and to this basin with a few pools and former geyser cones. Monument Geyser is a tall, thin cone that occasionally spouts a bit of steam, but no longer erupts.