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Blue streak

Yellowstone National Park’s Hydrothermal Features

Geysers, Hot Springs, Travertine Terraces, Mudpots and Fumaroles at
Mammoth Hot Springs, Roaring Mountain, Norris Geyser Basin, Old Faithful and Sulphur Caldron.

Yellowstone National Park has the world’s largest collection of geysers — over 300 — and about half of the worlds hydrothermal features — approximately 10,000!

These many thermal features are indicative of the fact that the park sits on an active volcano with one of the world’s largest calderas measuring 45 by 30 miles (72 by 48 km).
Hot springs frequently display colors resulting from light refraction, suspended minerals and billions of microscopic organisms thriving in water too hot for most other types of life. Researchers at Montana State University and Brandenburg University of Applied Sciences in Germany have created a simple mathematical model based on optical measurements that explains the stunning colors.
Geysers are similar to hot springs but have constrictions in the fractures that allow heated water to move to the surface. When the pressure increases enough the water escapes violently.
Fumaroles are vent holes where water vapor and other gasses are expelled from the ground — sometimes so forcefully that a roaring sound is heard and the earth trembles.
Mudpots form where acidic hot springs have a limited water supply. Microorganisms using hydrogen sulfide as an energy source, convert it to sulfuric acid which breaks down rock into clay. Gasses escaping through the hot, wet clay mud cause it to bubble.

Hydrothermal Feature Pictures


Mammoth Hot Springs

Located in the northwest corner of the park, Mammoth Hot Springs Historic District has the first major thermal feature you will encounter if you enter from the park’s north entrance at Gardiner, Montana. Mammoth Hot Springs Terraces — on a hill of travertine created over thousands of years by mineral-laden hot water — continues to build day-by-day and tier-by-tier.

A 37 foot tall column of rock

A 37 ft (11 m) hot spring cone, named Liberty Cap in 1871 by the Hayden Survey party because of
its resemblance to peaked caps worn during the French Revolution, stands at the base of the terraces.
Fort Yellowstone, a National Historic Landmark with the Horace Albright Visitor Center and Museum in
the old bachelors’officers quarters, the Yellowstone Main Post Office (also on the National Register of Historic Places)
and the Mammoth Hot Springs Hotel & Cabins are all located here.


Orange and white travertine on a hill

The National Park Service has constructed wood pathways on and around the Mammoth Hot Springs Terraces
for visitors to safely view the formation. The Liberty Cap in the top photo is just out of sight at the bottom of the hill
in this photo. We are about half way to the top.


Wet orange travertine terraces
As the water cools and evaporates travertine, a sedimentary rock formed by the precipitation of carbonate minerals, is formed.
Large quantities of limestone deposited beneath the park millions of years ago by vast seas are being brought to the surface.


Terraces and the top of the hill of travertine
Hydrothermal activity at Mammoth Hot Springs frequently varies, sometimes hourly, so it may look quite different on the next visit.


Close up view at the top of an active terrace at Mammoth Hot Springs
The terrace in the last 4 photos is known as Minerva Terrace, currently one of the most active areas at Mammoth Hot Springs.
There are many other examples of travertine terraces around the world.


Steam rising from water surrounded by colorful ragged edges
Colors in the thermal features at Yellowstone are caused by living creatures — pigmented bacteria and their response to sunlight.


Dead trees in travertine
Jupiter Terrace, another section of the mountain, was formed by Jupiter Spring which flowed abundantly in 1923 but had become dormant for several years by 1998. As the terrace grew hot mineral water streamed downhill burying grass and trees. When flooded by hot spring water the trees absorbed calcium carbide. Now “rock solid,” the dead trees can stand for decades.


Roaring Mountain

Roaring Mountain, just off the Grand Loop Road between Mammoth Hot Springs and Norris Geyser Basin,
is a nearly barren hillside of steaming fumaroles. In the 1800’s the roaring sound they made was often heard as much as four miles away. Today it is more of a hiss, but like other hydrothermal features in Yellowstone National Park it could change again at any time.
Numerous steam vents on a bare, gray mountain side.\
Fumaroles are different from other thermal features in the park in that the underground plumbing system is nearly dry.
What little water there is bursts into steam and is forcibly expelled — fumaroles are also known as steam vents.


Close up view of several steam vents on a barren hillside.
A close up (telephoto shot) of the barren hillside and several fumaroles at Roaring Mountain.
Escaping hydrogen sulfide gas, heated by the steam, nourishes microscopic organisms called Sulfolobus acidocaldarious.
Billions of these thermophiles help convert the gas to sulfuric acid which dissolves rock into clay wearing away the mountain.


Norris Geyser Basin

Norris Geyser Basin — the hottest, oldest and most dynamic of Yellowstone’s thermal areas — is, like Mammoth Hot Springs and Roaring Mountain, outside the Yellowstone Caldera but closer to the edge.
Steamboat Geyser, the world’s tallest, is here along with many other geysers, pools, vents and fumaroles.
The Norris Geyser Basin Museum, a National Historic Landmark, and Yellowstone Association bookstore are near the entrance to the basin’s thermal features while the Museum of the National Park Ranger is at the entrance to nearby Norris Campground.
People on a wooden boardwalk through a large barren basin with steam vents and hot springs
Porcelain Basin (photos above and below) is one of two major areas at Norris. It is barren of trees with features that can change daily because of frequent disturbances from seismic activity and water fluctuations. The fumarole to the front left above is known as Black Growler Steam Vent and is quite loud — likely similar to what Roaring Mountain sounded like years ago.


Smaller side of the basin with colorful steam vents, blue pools with forest and mountains in the distance.
Most of the water in this basin is at least at or above the boiling point (199°F at this elevation) with the highest temperature
of any geothermal area in Yellowstone recorded here (459°F – 237°C 1,087 ft – 326 m below the surface).


Close up of a vent in Porcelain Basin at Norris
In this close up (telephoto shot) of one of the vents in Porcelain Basin you can see some resemblance to the calcium carbonate buildup that happens at Mammoth Hot Springs but on a smaller scale. The big difference is that temperatures are higher here. Water actually travels underground from Norris to Mammoth giving it time to dissolve more limestone and cool down.


Steam venting from a an area of bare ground surrounded by forest
A second area of Norris Geyser Basin, known as Black Basin, is heavily wooded. More than a dozen geysers, including Steamboat Geyser in the photo above, can be viewed along the 1.5 mile trail of boardwalk and dirt that encircles the area. Steamboat is the world’s tallest active geyser and has infrequent, unpredictable eruptions reaching 300 – 400 feet lasting up to 12 hours.


Old Faithful Area — Upper Geyser Basin

Old Faithful Geyser is the best known of Yellowstone’s hydrothermal features and most popular attraction in the park. Its frequency and regularity — averaging 92 minutes (51 – 120 min.) between eruptions — makes it easy for park visitors to view the event. There are also a large number of other hydrothermal features in the Upper Geyser Basin and many visitors services. Large parking lots accommodate the crowds. There is a visitor center, stores, gas station and Old Faithful Inn, Old Faithful Lodge Cabins and Snow Lodge.
Hundreds of people on a long, curved wooden bleacher
Park visitors waiting to see Old Faithful erupt with the Old Faithful Inn in the background.


Geyser erupting against a blue sky
This is what they came to see — Old Faithful Geyser erupting right on time.
Several trails/boardwalks branch out from here where a large number of other hydrothermal features can be experienced.
Each of the photos below was taken within sight of Old Faithful Geyser and are within a 1 hour walk.


People standing on a boardwalk watch a geyser errupt
Aurum Geyser, like Old Faithful, is a cone-type geyser. Smaller and not as regular, but you can get much closer.



Close up of small geyser
Pump Geyser is another cone-type geyser near the center of Geyser Hill. With very frequent, almost constant small eruptions a stable microbial community has formed in the run-off channel.



A boiling spring with orange and brown overflow into a nearby river
Chinese Spring (aka Chinaman Spring) is so named because of its use in the 1880’s as a clothes boiler resulting in an eruption.
In the top left corner you see the Firehole River which splits the basin and joins the Gibbon River
(Gibbon River Falls picture on my Yellowstone NP photo essay) at Madison Junction to form the Madison River.



Blue water in an odd shaped pool
Just a few feet from China Spring Blue Star Spring has a somewhat star shaped sinter formation around the pool.
Like several other pools in the area the blue color can be deceiving. It looks like cool water but is typically near or even above the boiling point. Blue Star Spring is about 192°F, Chinese Spring in the photo above — 200°F.


A large multi-amoeba shaped hot spring
Doublet Pool is formed by two hot springs together. Detail pictures below.
It is on the other side of the board walk (inside of the loop) from Aurum Geyser shown in a photo above.


Closer view of Doublet Pool edges
You can’t get this close to Doublet Pool so having a telephoto lens or close focusing binoculars is highly advantages.


Detail view of Doublet Pools odd edge shapes
An even more extreme telephoto shot shows multiple levels below the surface (indicating different depths in the past)
and greater detail of the edges and microbial mat.
As mentioned above there are many more hydrothermal features at this location.


Sulphur Caldron

One of the most acidic springs in Yellowstone NP, Sulphur Caldron emits a strong odor. Located on the Grand Loop Road about 4.5 miles north of Fishing Bridge there is a small parking area and a sidewalk to an overlook. The Yellowstone River is nearby.
Steam rising from multiple spots including a large green boiling pool in the foreground
Sulphur Caldron has been described as a “witches brew” with bacteria providing unusual colors in the boiling water.
The crater of an active mudpot is visible just beyond the caldron and steam rises from several more.


Exploding mud bubbles in a steaming mudpot
This steaming mudpot is just a few feet away from Sulphur Caldron.
I had to wait for the wind to blow the steam away (thankfully in the other direction as the sulphur odor was quite strong)
in order to catch this shot of mud bubbles popping — one of my favorite Yellowstone NP hydrothermal feature pictures.


If you liked this you will probably enjoy my photo essays on Yellowstone National Park (Yellowstone intro plus bison, rivers and lakes photos) and the Grand Canyon of the Yellowstone (with spectacular waterfalls).
Visit more National Parks and National Monuments in the US from my National Parks page.

Previous — Grand Canyon of the Yellowstone

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