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In 2011, a pair of Oregon cavers discovered the largest known glacier cave system in the lower 48 states, just a few hours from Portland. On the Northwest face of Mt. Hood, a hole in the mouth of the Sandy Glacier leads into more than a mile of caves and tunnels inside the ice itself.
Armed with wet suits and ice screws and a Norwegian cave rescue telephone, Brent McGregor and Eddy Cartaya have systematically mapped the Snow Dragon Cave system. They have spent more than 300 hours underneath the ice; motivated by the rare opportunity to explore a place no one has ever seen before and by the extraordinary beauty of the caves.
Few glacier caves have been extensively explored. Mountaineers have typically viewed them as dangerous and have focused on bagging peaks, and many cavers lack the mountaineering skills required to maneuver on glacier ice. Cartaya and McGregor are among just a handful of skilled cavers worldwide who have chosen to explore these hard to reach places.
Many explored glacier caves are in remote parts of Alaska, Greenland, Russia, and the Himalaya. It’s exceptionally rare to have a glacier cave in our backyard- and accessible to a film crew.
Small seasonal openings and caves form underneath most glaciers that experience some seasonal surface melting. Cracks and moulins carry water down into the glacier, and pressurized water builds up underneath the glacier and carves the ice.
In a glacier made of thick ice, pressure squeezes openings in the ice shut in the winter as water flow decreases. But the Sandy Glacier has retreated 40 percent over the last century and the ice is getting thin. That thin glacial ice cannot squeeze openings shut in the winter, resulting in a permanent cave system. The caves allow warm air to move up underneath the glacier, speeding up the melting process.
By completing a precise survey of the height and width of the glacier caves as they grow bigger each year, Cartaya and McGregor are documenting a new aspect of glacial retreat and melting. Climate scientists have used lidar studies, ice surveys, and photo documentation to measure the impact of the warming climate on glaciers in the Northwest. But until Cartaya and McGregor, no one has gathered data on ice loss underneath and inside of a glacier.
History suggests that the appearance of large glacier caves on the Sandy Glacier in Mt. Hood are a sign that the glacier itself may be stagnating and dying.
For most of the 20th century, the Paradise Ice Caves on Mt. Rainer were the national park’s most popular tourist attraction. Today those caves and the entire lower section of the Paradise Glacier have melted away.
The formation and the destruction of these ice caves provide a dramatic visual way for us to tell the story of glacial retreat and loss in the Cascades as a result of climate change.
Thin Ice: Exploring Mount Hood’s Glacier Caves