This summer one of Yellowstone’s thermal features had a moment. Headlines featuring the word explosion will do that. 

At the end of July, Black Diamond Pool in Biscuit Basin didn’t just erupt. It exploded. Something happened in the unstable ground below it or maybe within the plumbing system that feeds and drains it, causing it to fling steam, hot water, and rocks with enough force to destroy a nearby boardwalk—a boardwalk filled with people doing what people go to Yellowstone to do: see what there is to see, which was not an explosion. 

Because people have reached out to me with questions about the explosion, I’ve done a little research. Here’s what I’ve learned. 

How often does this happen?  

According to Yellowstone geologists, who know more about the park’s geysers than I do, explosions aren’t all that uncommon. Small-scale explosions happen regularly—as in once or twice a year. Large-scale explosions happen rarely, as in very few were named.

This was a large-scale explosion. So was the 1989 event that changed the face of the previously entree’ shaped Porkchop Geyser, located at Norris’s Back Basin, and the late 1880s one that shaped my husband’s favorite thermal feature, Midway’s Excelsior Geyser Crater. Here’s a little more about Excelsior–and why my husband likes it so much:  

Bordered on three sides by bleached bluffs, Excelsior Geyser Crater’s shroud of steam occasionally rolls back, revealing a pool so rich and clear it calls to mind a travel poster for a tropical sea—so much so that, each time I pass by, I’m beset with a disquieting temptation to dive in. This, combined with its massive outflow cascading down the slope to the Firehole River, captured Jaime’s attention from the beginning. Back in the 1880s, Excelsior erupted regularly with a magnitude befitting the size of its crater but, because things are always changing beneath the surface, it slipped into dormancy by the end of the century. One hundred years later, it roused from its slumber for two days of frequent eruptions. Not only does Jaime hope this will happen again, his wish is to drop everything, drive west, and arrive in time to see it. Excelsior’s blend of water, beauty, immensity, history, and mystery may well have meant love at first sight—at least for Jaime. 1

Why did this happen? 

Geysers are not static. They, their surroundings, and the plumbing systems that feed and drain them change. Some people promote the idea that changes to Yellowstone’s thermal areas have something to do with the end of the world. Not so. 

Simply put, there is always more going on below the surface than the eruptions and bubbling we see above. Heat from the magma chamber warms—to varying degrees—water that has seeped into below-ground reservoirs. Some water just heats up and some superheats (meaning to heat beyond the boiling point), builds up pressure, and eventually forces its way to the surface in what we call an eruption. 

For some reason, water in the hydrothermal plumbing system under Black Diamond Pool flashed to steam. I am far from a scientist, but my understanding is that when liquid water turns to steam, it expands. A lot. So, when the water “flashed,” it rapidly created a great deal of pressure underground, pressure that was looking for a place to escape, which it did, with a great deal of force. 

Hence the explosion. 

Was the explosion dangerous? 

Yes, for a variety of reasons. The explosion was a mix of water in the form of liquid and steam, along with mud and debris in the form of rocks ranging from the size of a grapefruit to three feet wide and hundreds of pounds. 2 The boardwalk near the geyser was destroyed. Here are some specifics about what was dangerous and what wasn’t.

• flying and falling rock: dangerous. 
• hot water and steam: dangerous. 
• acidity of the water: not dangerous. (Black Diamond’s water is not acidic, although some of Yellowstone’s thermal features are acidic enough to eat through footwear.)
• running off the boardwalk: dangerous. (The ground that covers thermal areas is very thin and there is no way to visually determine if the path you choose will support you.)

Is Yellowstone safe? 

This is the big question. With its roads, hotels, restaurants, parking lots, post offices, and medical clinics, Yellowstone has all the trappings of civilization—to the point that some say it should be closed. But it isn’t closed. It hosts over 4 million visitors each year. And the visitors strolling along the boardwalk seeing what there was to see, were not expecting to experience an explosion. No one was. There was no warning. 

That’s what makes this a big question. Yellowstone, like Aslan, isn’t tame. We’re wise to remember that the wild in wilderness is ready to break out even in spaces with elements that are familiar and safe-looking. We’re wiser yet to remember that even the landscape of our actual, everyday lives is not as tame as it appears on the surface.

Russell Moore’s words are true. “In many ways the more tranquil you feel, the more endangered you are.” We have an enemy, and what’s true on the trail is true in life: It’s best to be alert and aware, with our minds prepared for action in all places, both the obviously wild and the seemingly safe.  

take heart & happy trails ~ Natalie 🥾

1 Taken from my upcoming book, Waking Up in the Wilderness: A Yellowstone Journey. It’s written by me, available in October, and I’m just a little excited to share it with you. If you are someone who has questions about explosions in places like Yellowstone or learns about walking by faith from spending time in creation (or if you know someone who does), it may be a good next read.

2 The photos of the explosion come from the USGS site, where they share public domain photos.