The Unbelievable True Story of Butte’s Big Pit Tsunami

BUTTE, MT - In the month of September of the year of 1998, something very strange happened in Butte, Montana.

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The Day Butte Made Waves

You may know Butte for a lot of things—its rich mining history, its larger-than-life characters, and, of course, the Berkeley Pit. But did you know that in September of 1998, the pit decided to flip the script and create its own version of a tsunami? Yeah, you read that right.

The Calm Before the Slide

It was just another day in September 1998. The Berkeley Pit, a relic of Butte’s mining past, had been slowly filling with acidic water for years. Nothing seemed particularly out of the ordinary, and there was no ominous music playing in the background (that we're aware of) when Mother Nature had other plans.

The southeastern wall of the pit had been holding back 1.3 million cubic yards of loose alluvium (for those of us who aren’t geologists: basically a whole lot of rocks and dirt), and on that fateful day, gravity decided to make itself known.

When Dirt Meets Water

And then, it happened. Like a slow-motion scene from a movie, the massive wall of loose material began to slip. Bit by bit, then all at once, the southeastern wall collapsed into the pit's lake, causing a 1.3 million cubic yard landslide. How much material is that? Enough to fill over 100 Olympic swimming pools.

As the earth plunged into the toxic waters below, the water level shot up by an incredible three feet. If you’ve ever belly-flopped into a pool, you know that water displacement is no joke.

Surf’s Up

Butte had its very own 20-foot-plus wave that day. The water, displaced by the massive landslide, surged up in a wave tall enough to make any surfer in Montana (admittedly, that’s probably a small group) daydream about catching it.

Of course, the wave didn’t spill out into Uptown Butte or anything quite that dramatic, but the image of a 20-foot wave rippling across the toxic pit water is one for the history books.

The Aftermath: Pit Problems

As cool as a giant wave sounds, the aftermath was less fun and more "uh-oh." The Berkeley Pit is one of the largest Superfund sites in the country, and any significant movement of water brings concerns about contamination and environmental impact. As the alluvium sank to the bottom of the pit, officials closely monitored the situation, worried about what it might mean for water levels and potential overflow.

Thankfully, the wave didn’t breach the pit’s edge, but it left a lasting mark on Butte’s landscape—both literally and in the town’s memory. In the years that followed, the pit’s water levels continued to rise, but nothing quite like the "Great Berkeley Pit Tsunami" has happened since.

Final Splash

In the end, the story of the 1998 Berkeley Pit Tsunami is more than just a quirky historical footnote—it’s a reminder that Butte has always been a place of extremes. From its booming mining days to its quieter but no less fascinating present, this town knows how to make waves. Quite literally, as it turns out.

So, next time you’re standing on the edge of the pit, gazing at the oddly beautiful, metallic-colored waters, just remember: beneath that calm surface, Butte’s got a story to tell.

And who knows—maybe the Berkeley Pit isn’t done surprising us yet.