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.

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.

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.

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...

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