At the start of the tour
Welcome to Upper Geyser Basin
Welcome to the Upper Geyser Basin in Yellowstone National Park. Within a single square mile around you there are about one hundred and fifty geysers, and hundreds of hot springs, steam vents and other thermal features. Yellowstone has more geysers than anywhere else on Earth.
Long before it was a park, this was a homeland. Twenty-seven Tribes today have ancestral and modern ties to Yellowstone, and people have hunted, gathered and traveled through this country for more than eleven thousand years.
Today's walk goes from Old Faithful, over the river to Geyser Hill, then along the Firehole River to Morning Glory Pool. It's about two miles one way, on boardwalks and a paved trail. I'll tell a story at each stop and stay quiet in between.
One thing first, because it matters here more than anywhere. Stay on the boardwalk. The ground beside it can be a thin crust over scalding water, and more than twenty people have died from burns after entering or falling into Yellowstone's hot springs. Don't touch the water or its runoff, and keep children close. Pets aren't allowed on the boardwalks. If you meet wildlife, give bison and elk at least twenty-five yards, and bears and wolves at least a hundred. Bison have injured more people in Yellowstone than any other animal.
Point 1 · At the stop
Old Faithful
This is Old Faithful. It isn't the biggest geyser in the park, or the most regular, but it erupts more often than any other large geyser here, and it's about as predictable as it was a century ago. Members of the Washburn Expedition named it in 1870 for its consistent performance.
An eruption usually lasts between a minute and a half and five minutes. The column reaches anywhere from about a hundred feet to more than a hundred and eighty, and averages around a hundred and thirty. Each eruption throws out roughly thirty-seven hundred to eighty-four hundred gallons of water, at about two hundred and three degrees Fahrenheit at the vent.
How long is the wait? Lately the typical gap has been around an hour and forty minutes, though it can be quite a bit shorter. Rangers use the length of each eruption to forecast the next one: a long eruption releases more water and heat, so the geyser needs longer to recharge. When the visitor center is open, the prediction is posted there and in the park's app. I won't guess it for you.
Those gaps have grown longer over the years, partly from changes underground and from earthquakes like the one at Hebgen Lake in 1959. Old Faithful could even stop someday. It has before.
History, on the way there
On the way: Beehive Geyser and Geyser Hill
Now for Geyser Hill. Before we look at any one geyser, here's how they all work.
It starts as rain and snow. The water seeps deep underground, where Yellowstone's magma system heats it. Down there, the weight of the water and rock above keeps it from boiling, so it gets far hotter than boiling water at the surface. A geyser has a tight spot in its plumbing, usually near the surface. Steam forms and expands below it until it lifts water out of the vent. That releases the pressure, the superheated water flashes into a violent boil, and the eruption is on. It ends when the water runs out or the system cools, and then the geyser slowly refills.
Point 2 · At the stop
Beehive Geyser and Geyser Hill
This is Geyser Hill, one of the busiest patches of ground in the basin. The vents and pools along this boardwalk are many separate geysers and springs, each with its own habits.
Beehive Geyser has a narrow cone that works like the nozzle of a hose. When Beehive erupts, the water shoots up a hundred and fifty to two hundred feet, for four or five minutes. It's irregular: sometimes about once a day, sometimes weeks apart. If you catch it, you're lucky.
A little further on is the Lion Group: four geysers, Lion, Lioness, Big Cub and Little Cub, all connected underground. Lion has the biggest cone and the biggest eruptions, and it got its name from the deep roar and sudden gushes of steam that often come before it goes.
It's tempting to step off for a closer look. Please don't. The crust here can be thinner than it looks.
History, on the way there
On the way: Castle Geyser
Before Castle Geyser, a story about who was here first, and a myth that lasted far too long.
People have used this country for thousands of years: hunting, fishing, gathering plants, quarrying obsidian, and using the hot waters for ceremony and medicine. Some families of the Tukudika, a name that means eaters of the mountain sheep, stayed inside today's park all year. They softened bighorn sheep horn in hot water from the thermal areas and shaped it into bows that were prized in trade.
After Yellowstone became a national park in 1872, Superintendent P. W. Norris wanted Native people removed, believing they would keep tourists away. A story grew up alongside that removal: that Native people feared the geysers and stayed away. The Park Service now calls it a myth. More than nineteen hundred archeological sites have been found in the park, with only about three percent of it surveyed. And a Crow man named Hunts-to-Die, born before the park existed, described the geysers as places of helpful, kindly spirits.
These basins were never empty. They were part of someone's home, and for many people they still are.
Point 3 · At the stop
Castle Geyser
This is Castle Geyser, with the largest cone in the basin. It may also be the oldest geyser here. The cone is thousands of years old, and it sits on even older platforms. Together they make one of the largest sinter formations in the world.
Sinter is the mineral crust you see all through this basin. Deep underground, hot water dissolves silica out of rhyolite, the volcanic rock beneath Yellowstone. When the water comes up and cools, the silica drops out and coats everything it touches, lining the plumbing and building pools and cones like this one, a thin layer at a time. Where silica-rich water splashes, it can form spiny, bulbous masses called geyserite.
Castle erupts much less often than Old Faithful, usually more than half a day apart, and rangers predict it. An eruption starts with water, often around seventy-five feet high, for about twenty minutes, then a noisy steam phase that can roar for another thirty to forty minutes.
This boardwalk is a short side trip. When you're ready, cross back over the bridge and follow the boardwalk north toward Grand Geyser.
Point 4 · At the stop
Grand Geyser
This is Grand Geyser. The park has long called it the tallest predictable geyser in the world. It's a classic fountain geyser: instead of a steady column from a cone, like Old Faithful, it erupts out of a pool in powerful bursts. A typical eruption has one to four bursts and lasts about nine to twelve minutes, and the tallest bursts can reach around two hundred feet.
Grand usually erupts several hours apart, and its prediction comes with a wide window, about an hour either way. The park predicts six geysers in all, and three of them, Old Faithful, Castle and Grand, are already behind you on this walk.
If a prediction is posted and the time is close, this is a good place to wait. If not, enjoy the pool and the steam, and keep in mind that every one of these eruptions is a prediction the earth doesn't have to keep.
Point 5 · At the stop
Beauty Pool and Chromatic Pool
This is Beauty Pool, with Chromatic Pool just beyond it. When they're at their best, you see rich blue water framed by rings of colored bacteria.
These two pools are connected underground. Every so often, the energy shifts between them: the water level in one drops, while the other rises and overflows. The time between those shifts has ranged from a few weeks to several years, so what you see today may not be what the last visitors saw.
The colorful mats around the edges are living communities, and the hot springs here hold microbes found nowhere else on Earth. That's one more reason to keep hands, feet and everything else out of the water and off the crust.
History, on the way there
On the way: Riverside Geyser
Now for Riverside Geyser. One thing to know about every geyser on this walk: they change. Earthquakes shift their plumbing, and the same silica that builds the cones keeps coating the channels underground. Giant Geyser, back along the boardwalk, can throw water more than two hundred feet high for an hour and a half, and it can also go quiet for years.
Even Old Faithful has gone silent. Scientists working with the Yellowstone Volcano Observatory dated mineralized wood from Old Faithful's own mound. It was lodgepole pine that grew there between about twelve thirty-three and thirteen sixty-two. Lodgepoles don't grow on an active geyser mound, so for more than a century, Old Faithful didn't erupt. Tree rings show a severe, long drought began in the mid-twelve-hundreds, just as those trees took root. Less rain and snow meant less groundwater, and the geyser went still. The researchers suggest longer droughts could make eruptions less frequent in the future.
Point 6 · At the stop
Riverside Geyser
This is Riverside Geyser, on the far bank of the Firehole River. Its cone sits right at the water's edge, and when it erupts, the column arches out over the river, about seventy-five feet high, for around twenty minutes.
Riverside gives a warning. For an hour or two before an eruption, water runs over the edge of its cone. So if you see it overflowing, it may be worth waiting. It's one of the park's six predicted geysers, and it usually erupts about every six hours or a little more.
Even when it's quiet, the cone is worth a look. Like Castle's, it was built from sinter, the silica that hot water leaves behind, one thin layer after another.
Point 7 · At the stop
Morning Glory Pool
Here it is: Morning Glory Pool. For a long time it was hotter, and the orange and yellow bacteria that need cooler water grew only around its edges.
What changed it was people. Over the years, visitors threw thousands of pounds of coins, trash, rocks and even logs into the pool. The debris lodged in its sides and vent and slowed the circulation of hot water, and the pool cooled. Today its average temperature is around one hundred and sixty degrees Fahrenheit, cool enough for those orange and yellow bacteria to spread in toward the center. Natural changes may be cooling it too.
So the most famous pool on this walk is also its clearest lesson: everything here is easier to damage than it looks. Please don't throw anything in, and if you see someone who does, tell a ranger.
That's the end of the tour. The paved trail leads back to Old Faithful, about a mile and a half. Thank you for walking the Upper Geyser Basin with me.