See the eerie glacier caves carved by Mount St. Helens’s fiery breath

After the 1980 eruption, a glacier formed in the shadows inside the crater. Scientists—and our photographer—have explored its icy depths.

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Scientist Andreas Pflitsch of Germany's Ruhr University, Bochum deploys a smoke flare in a glacier cave called Mothera in the crater of Mount St. Helens. The smoke will help reveal how such caves are sculpted by hot gases escaping from fumaroles—open vents in the volcano's crust. Pflitsch has also studied the hot winds that rush through subway systems.

See the eerie glacier caves carved by Mount St. Helens’s fiery breath

After the 1980 eruption, a glacier formed in the shadows inside the crater. Scientists—and our photographer—have explored its icy depths.

When photographer Eric Guth drops into Godzilla Cave, he slips into a world of ice built by fire.

Its creation began exactly 40 years ago, on May 18, 1980, the day Mount St. Helens exploded in the Cascade Range in Washington state. The eruption shaved 1,314 feet off the mountaintop. The force sent billions of tons of wet earth rushing down the North Fork Toutle River. A plume of ash shot 15 miles high, at 300 miles per hour. All that heat and pressure left behind a hole, a massive dark crater trapped in shadows at more than 6,200 feet—a brand new factory for snow and ice.

Shielded from sun much of the year, this horseshoe-shaped depression gave rise, as winter snows accumulated beyond the capacity of summers to melt them, to a young glacier. It’s now 660 feet thick, half a square mile in area, and growing. It’s pockmarked by glistening caves: As the volcano belches out its heat, gassy fumaroles melt vertical shafts, dome-shaped amphitheaters, and horizontal passageways through the overlying ice.

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From 2004 to 2008 the volcano was active once again, adding large fresh spines of rock to the lava dome at the center of the crater. The dome splits the glacier into two arms that flow north toward the edge of the crater. Spirit Lake lies beyond.

For several years, a team of scientists and Guth have explored this sculpted universe.

The researchers are mapping the extensive glacier caves and studying life among these frigid walls and vented heat. They’ve found mushrooms, flowers, and moss in steam-soaked soils, and microorganisms under the ice. They’ve found conifer seedlings, dropped by birds or blown in by winds; the seeds lay dormant in moving ice for months or years, until the caves furnished the warmth they needed to germinate. For a short while, at least, the seedlings grow bizarrely fast, straining through the darkness in a doomed search for light.

“It’s exhilarating,” Guth told me recently. “When we get to the farthest reaches of a cave, it’s pretty amazing to think we’re the first people who’ve ever been here.”

They might turn out to be the last. Like many parts of Mount St. Helens National Volcanic Monument, the entire crater is off-limits except to those with research permits—to protect this fragile environment, yes, but also because it’s dangerous. The explorers enter on ropes with gas monitors on their harnesses. Guth has nearly been pinned by a boulder; once, after bad weather kept a helicopter from ferrying them out, he and other team members had to spend the night in a cave.

And these caves, like almost everything at St. Helens, are fleeting, impermanent things.

Eddy Cartaya, a cave rescue expert and U.S. Forest Service law enforcement officer who led these expeditions, has also explored ice caves on the summit of Mount Rainier and on Oregon’s Mount Hood. But he’s partial to the shifting world of St. Helens—a world, he says, of “geology in hyperdrive.”

“There are very few places that are literally moving beneath your feet with new material coming up out of the earth,” Cartaya says. “It is the most dynamic landscape I’ve ever witnessed and utterly amazing.”

Nothing stays the same

In the spring of 2005, around the 25th anniversary of the eruption, I drove from my home in Seattle to St. Helens’ Johnston Ridge Observatory, which looks out over the crater. The previous year the volcano had been spitting and rumbling as it entered a period of rebuilding. A scientist from the U.S. Geological Survey showed me a rock he’d recently hauled from the crater. Just weeks earlier it had still been fluid—part of a molten stream of magma pushing its way up from miles below the earth. The steady flow had started anew that winter.

In just a few months, a small new dome pushing up from inside the crater had grown 350 feet. As the glacier filled in around it and deepened, it made room for bigger caves.

“We usually think of mountains as these permanent fixtures,” says ecologist Eric Wagner, author of the new book After the Blast: The Ecological Recovery of Mount St. Helens. But most of what remains of St. Helens is younger than the pyramids of Egypt. It erupts every 140 years or so, taking and feeding life around it.

One researcher told Wagner that the first year after the 1980 blast had been one of ecological anarchy—plants and animals straining to get by with scant resources in enormous fields of ash and rubble. “It was kind of a mad scramble,” Wagner said. But over time, thin layers of ash boost water retention and add nutrients to soils. Long ago the Pacific Northwest’s rich and diverse Douglas fir forests sprang up through such layers of ash, remnants of the guts of St. Helens, blasted into the air during past eruptions.

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Explorers take in the unexpected vastness of Crevasse Cave for the first time.

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Holding a photo that shows the eastern and western branches of Crater Glacier flowing around the central lava dome, a ranger explains the cycle of destruction and recovery that has taken place at Mount St. Helens since it erupted in 1980.

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Crater Glacier is the youngest, fastest-moving body of ice in the lower 48 states of the U.S.—and one that continues to grow. The walls of the north-facing crater shade it for much of the year and occasionally drop rocks onto its surface.

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The view south from Coldwater Peak offers a commanding view of the Mount St. Helens crater and of the 1980 blast zone.

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Scientist and surveyor Neil Marchington rappels towards backcountry guide Jared Smith and the entrance of Godzilla Cave, which Smith discovered in 2013.

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Water melting off the ceiling of Crevasse Cave drips onto the floor, where it refreezes and is sculpted by winds into unusual shapes. The contrast between cold ice and heat from the fumaroles creates pressure gradients that drive winds in the glacier caves.

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Lead surveyor Scott Linn sketches details during the first survey of Crevasse Cave. The team has since switched to digital mapping methods.

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Eddy Cartaya and other team members, including photographer Guth, leave a glacier cave they have just been forced to spend the night in. The day before, low cloud cover had kept a helicopter from landing to pick them up for the journey home. Fortunately the team had sleeping bags, stoves, and other survival gear along.

Forty years after the last one, the species that existed before the blast have come back—but not in the same numbers or in the same places. This cauldron of ice and fire hasn’t recovered. It’s still busy becoming something new.

“It’s a fascinating, complicated, beautiful, frustrating landscape that we’re really just lucky to get to see,” Wagner says.