Norris Geyser Basin, located in the northwest quadrant of Yellowstone National Park, is one of the most active hydrothermal regions in the park and contains rare types of geysers within a geologically active earthquake area. The basin is located near the intersection of three major ground faults, helping to create the conditions for Norris’s significant geothermal activity. It’s outside the huge Yellowstone Caldera, the basin that remains after a titanic volcanic eruption 631,000 years ago, but within another 2.1-million-year-old caldera.
Nancy and I spent nearly all of Friday, Sept. 12, 2025, at Norris Geyser Basin. Named after Philetus W. Norris, the second superintendent of Yellowstone National Park, the geyser basin has two decidedly different trails: a short 3/4-mile (1.2 km) loop through the Porcelain Basin, and a longer 1.5-mile (2.4 km) loop with stops at geothermal features in the Back Basin. Both geyser basins are at an elevation of about 7,600 feet (2,316 m). Both trails involve the use of many boardwalks to keep visitors from walking too close to the heated features, and the ground is very thin in many spots and bad things would happen if someone broke through (and bad things do happen when someone decides to ignore the rules). I’ll write a posting detailing the Porcelain Basin later; for now, here are some of the sights to see and smell at Norris’s Back Basin, which includes the world’s tallest active geyser.
Before we get started though, let’s review hydrothermal features. Yellowstone National Park’s hydrothermal features are created by magma, which is partially molten rock, remarkably close to the park’s surface. Water, either from snowmelt or rain, percolates downward through faults and fractures in the earth’s surface and then, after making contact with the hot rock formation, rises back toward the surface and collects in open channels that serve as the hydrothermal features’ water supplies.
Geysers, perhaps the most familiar type of hydrothermal feature, form if the channel has a constriction of some type that pressurizes the water. Temperatures in the superheated and pressurized water below the constriction create steadily amounts of steam, which is eventually pushed through the constriction and an instantaneous drop in water pressure below the steam creates an eruption. These events can be fairly predictable, as in the case of Yellowstone’s Old Faithful, or irregular, with intervals between eruptions lasting unpredictable numbers of days, weeks, or even longer.
If a channel doesn’t have a pressurizing constriction, a hot spring is formed as superheated water comes to the earth’s surface, cools somewhat, and is replaced by hotter water beneath it.
The hottest hydrothermal features in Yellowstone National Park, fumaroles, are steam vents in which channel systems have little access to water, and whatever does reach the surface is immediately converted to steam with a temperature greater than that of water’s boiling point (212 degrees F, or 100 degrees C, at sea level).
Finally, mudpots are created when rock around a hydrothermal feature is converted, by acid, into clay. When it mixes with water, the clay forms mud of different colors and viscosities. Gases in the feature bubble up through the mud to make interesting sights, sounds, and smells.
All hydrothermal features are susceptible to changing environmental conditions. If access to water is changed, or the fissures around a feature are altered because of seismic activity, the feature’s activity could change dramatically or even cease altogether. Many geysers, for instance, that were active in years past are now quiet.
The first stop on the Back Basin Loop is this very pretty 27-foot-deep pool, Emerald Spring. The color of a particular hot spring can help determine what minerals that spring contains. Water in a relatively mineral-free clear blue spring, for instance, absorbs all of the colors of sunlight except for blue. Emerald Spring contains significant deposits of the mineral sulfur, the yellow color of which combines with the reflected blue sunlight to create this beautiful shade of green. The temperature of the water in this spring is close to the boiling point, ensuring that only the most heat-tolerant microorganisms, or thermophiles, can survive in this environment. There’s plenty of sulfur in this spring, which is used by some thermophiles as a source of energy. The byproducts from the sulfur’s usage in turn are used by other thermophiles, resulting in a kind of recycling process that creates something like thermophile interdependence.Next up is the world’s tallest active hydrothermal feature, Steamboat Geyser. Although there was a lot of steam evident, Steamboat Geyser on the day of our visit was relatively quiet with just a few intermittent spurts of water measuring a few feet high. When it goes, though, Steamboat really goes: it is capable of shooting steam and water up to 300 feet (91 m) into the air. That’s the distance of a football field. Prior to 1904, Steamboat was not the tallest geyser in the world. That honor belonged to a geothermal feature in New Zealand, Waimangu Geyser, which shot water a mind-blowing 1,600 feet (488 m) into the air. A landslide changed the water table around Waimangu, however, and it hasn’t erupted since.
Here’s the thing about Steamboat that’s really wacky: its eruptions are extraordinarily erratic. In the nearly 30 years between 1990 and 2017, Steamboat erupted 12 times (including one interval between eruptions that lasted almost 9 years). Between March 15, 2018, and May 7, 2023, a little over five years, the geyser erupted 165 times. We visited in mid-September 2025, and Steamboat’s last major eruption had occurred on April 14 – five months earlier. Before then, it erupted on Feb. 2, 2025, a little over two months earlier. In all of 2024, Steamboat erupted six times. Nature is chaotic sometimes, and it’s beautiful. Note the huge desolated treeless area in the photo above. The geyser’s eruptions, helped by prevailing southerly winds, caused that destruction.
Cistern Spring is located downhill from Steamboat Geyser – I didn’t measure the elevation change, but it’s at least 50 feet lower, and the boardwalk trail has a couple of switchbacks. However, Cistern Spring is connected underground to Steamboat because it empties completely whenever the larger geyser erupts. The brown, green, and orange colors in Cistern Spring are created by different species of thermophiles. The dead trees around the spring were killed by the silica in Cistern Spring’s water: conditions around the spring were once healthy enough for the trees to germinate, grow, and mature, but then the conditions changed. We saw that a lot all over Yellowstone National Park: big areas of trees that had been killed by changing hydrothermal features.This feature has one of the best names in the Back Basin. It’s Black PitSpring, and it started off about half a century ago as a group of steam vents. Water now continuously bubbles with very small eruptions at its surface.Here’s a closeup, using a telephoto lens, of the little eruptions from Black Pit Spring. It’s a pretty mesmerizing hydrothermal feature, with a great variety of colors (not so much black, though).This is Echinus (pr. e-KI-nus) Geyser, perhaps my favorite feature in the basin. It is named for its mineral deposits, which apparently look the spins of sea urchins (neither Nancy nor I are overly familiar with echinoderms like sea urchins, but we didn’t see anything that resembled sea urchin spines). The red color is due to high concentrations of iron oxide (rust) in the feature. Echinus’s eruptions, which can reach 60 feet in the air, are unpredictable and are now months and even years apart. From 1878 to 1948, the geyser rarely erupted but then moved to periods of relative high activity alternating with dormancy. Prior to 1998, it was on an eruption schedule of about every half-hour to 90 minutes. The scientists believe that something happened underground in 1998 to affect the geyser’s water source. For now, it’s a fairly large and very pretty pool of water (see the guy emerging from the trees on the boardwalk just right of center for scale).This photo was taken on the other side of the geyser from where the previous photo was taken, i.e. just to the right of the guy on the boardwalk in the photo above. Echinus Geyser is a beautifully complex hydrothermal feature, even if we can’t make out the sea-urchin-ish spines.Here’s one of the reasons why Echinus Geyser appeals to me so much: these are terrace formations on the geyser’s southwest side where water leaves the geyser. I took this photo at about the same spot as the photo above, but used my telephoto lens again. These terrace mats are formed by unthinkably large numbers of a microorganism called Archaea (pr. aar-KEE-ah), which is a an immense domain of life that precedes kingdoms (you remember, from high-school biology, the memory aid “Kings Play Chess On Fine Green Sand,” or Kingdom, Phylum, Class, Order, Family, Genus, Species; domain is a step above kingdom). Water coming from the geyser is 176.5 degrees F (80.3 degrees C), and has a pH of 3.3 to 3.6 – it’s nearly as acidic as vinegar. At this point in the terracing, the temperature drops to between 140 and 160 degrees F (60 to 71 degrees C). Archaea absolutely love this hot and acidic water, and survive on the energy produced by iron oxidizing in the geyser’s water then bind together to build these ridges, pools, and ripples. Archaea are very common in nature: different types are found everywhere on the planet, including other features in Yellowstone National Park, and your gut, mouth, and skin are covered in them right now (not the same ones in this picture; remember that Archaea covers a lot of different species, let alone all of the other Kings Playing Chess). It’s extremely likely that when the scientists do find irrefutable evidence of extraterrestrial life, it will be in the form of Archaea or something close to it. This is a view a little further down the boardwalk from Echinus Geyser. That small river of water is flowing northwesterly from the geyser – it’s a pretty desolate landscape in the river bottom, but remember that the river has a pH nearly equal to that of vinegar. Notice also the steam rising from the ground where the river meets the trees in upper left; as the scientists say, this is a geothermally active area, and that is evidence of yet another geothermal feature.This is Porkchop Geyser, so named because of its shape when viewed from above and which only intermittently erupted until 1985 when it started spouting on a continuous basis. Those eruptions wasn’t enough to keep the geyser’s constriction from building up tremendous pressure and four years later, on Sept. 5, 1989, this feature exploded with a violence sufficient to throw large rocks more than 200 feet (61m). Fortunately, the tourists present for this surprise event weren’t injured. Porkchop’s vent hole at times has been the diameter of a garden hose; after the explosion, it’s about 7 feet in diameter. After that event, Porkchop became a gently bubbling hot spring with only occasional – and unpredictable – geyser eruptions.Even if it didn’t erupt while we were there, Veteran Geyser was a lot of fun to listen to. The area in shadow in the lower right corner of the picture is a vent through which Veteran exhaled with what sounded like someone in severe respiratory distress. A couple with whom I’d briefly spoken at Steamboat was here admiring Veteran as well, and, realizing that we were nearing the end of the Back Basin loop, the woman asked what our favorite hydrothermal feature was. I quickly answered with Echinus Geyser, and asked what her favorite was. She said it was Black Pit Spring, but mostly because of the name. I couldn’t disagree with her. In a basin filled with features named Green Dragon Spring, Puff ‘n Stuff Geyser, and Black Hermit Caldron, Black Pit Spring does still manage to stand out.At the time when Yellowstone’s visitors toured via stagecoaches, Minute Geyser erupted every 60 seconds to heights of 40 to 50 feet (12-15 meters). Inexplicably, many of those tourists tossed rocks into one of the geyser’s vents and eventually plugged it. While it continuously spouts water about 3 feet (0.9 meter) now, it’s unknown whether the feature will ever fully erupt again. Signs warning tourists to not throw rocks, coins, or other objects into park’s hydrothermal features were all over Yellowstone. I just can’t wrap my head around why someone would want to do that in the first place.The Back Basin loop trail ends with a short hike up a hillside, resulting in this magnificent view of Norris’s other geyser area, the Porcelain Basin. I’ve got pictures of the features within Porcelain Basin as well, and will post those in the near future.
There are about 25 named features within Back Basin, so this was a look at less than half of what’s there. Walking around any of Yellowstone National Park’s hydrothermal areas gets you really close to all kinds of aspects of our natural world, and it’s easy to think that it’s always looked the way it appears today. But conditions underground, like earthquakes, heat changes, mineral buildup, and more, ensure that these features are anything but timeless: a geyser can become a hot spring (and vice versa), for instance, because of subtle and usually unseen geologic changes.
It was a fun day at Norris’s Back Basin, and one that Nancy and I will appreciate for a long time – especially because the next time we go, it may be significantly different.
Works Consulted
Lynne, Bridget Y. “The Geothermal Guide to Yellowstone National Park.” 2017.
National Park Service. “Norris Geyser Basin Trail Guide.” March 2024.
National Park Service interpretive signage at features throughout Back Basin.
Wikipedia, articles on Archaea, Echinus Geyser, and Steamboat Geyser. Accessed September 2025. If you use Wikipedia, please support it.
Tales of The Goddard 