How ice caves form in Root Glacier, Wrangell-St. Elias National Park

Glaciers are "rivers of ice" that keep moving and changing. Along the eastern edge of Root Glacier, near the Kennecott Mines National Historic Landmark in Wrangell-St. Elias National Park and Preserve, Alaska, many ice caves commonly form. The National Park Service's visual information specialist for the park wrote this short explainer.

Ice cave entrance on Root Glacier. NPS photo.

How an ice cave forms

An ice cave starts when water flows into and through a glacier. The opening is where the water enters, and the flow melts a tunnel through the ice. Water that enters from the glacier's surface usually forms a moulin, a vertical hole leading down into the ice, which can't be reached without advanced climbing gear and skills. But when creeks enter a glacier along a lateral (side) moraine, the warm creek water makes a cavity that grows into a cave. It has a glacier ice roof over a floor of ice, sediment or bedrock.

Ice cave entrance and stream on Root Glacier. NPS photo.

Be geohazard aware

Ice caves are inherently dangerous. Ice or rocks can fall from the ceiling, the cave can collapse, and it can flood. The Park Service advises wearing the proper equipment and going with an experienced guide when traveling on a glacier to look for ice caves, since glaciers have hazardous crevasses (cracks), rockfall and icefall, moulins and thin ice bridges over holes.

Root Glacier above and below

Root Glacier and Mount Blackburn. NPS photo.

Water flowing through an ice cave. NPS photo.

Sources

• National Park Service, "Glacier Ice Caves on Root and Kennicott Glaciers within Wrangell-St. Elias National Park and Preserve" (https://www.nps.gov/articles/000/glacier-ice-caves-on-root-and-kennicott-glaciers-within-wrangell-st-elias-national-park-and-preserve.htm), by the park's visual information specialist. The photographers' names in the credits are left out.
• National Park Service's page; rewritten in hubnx's own words.