Glaciers are magnificent natural structures, dense sheets of ice that can stretch for miles and be a few yards to thousands of feet thick. It’s no wonder many adventurous travelers put hiking one high on their bucket list. But while glaciers may seem like stable, non-threatening slabs of solid terrain perfect for exploration, they can in fact be far from it.
Just head to one of North America’s most popular glaciers–the Athabasca Glacier in Alberta, Canada–and listen for guides to yell at solo wanderers, warning of unseen threats to their safety. That’s because under their feet, there could be a world of hidden hazards, including crevasses and icy rivers, and one wrong step could land explorers in the hospital–or worse. So if you’re headed to hoof it on a glacier, don’t even consider taking a stroll on the surface without hiring a guide if you don’t have extensive training and experience.
Glacier science
While glaciers may seem to be sheets of ice as dense and stable as concrete, that couldn’t be further from the truth. In fact, glaciers are living, breathing things, explains Maria Intxaustegi, a mountaineering guide and member of the expedition team on Lindblad National Geographic Expedition ships, including those that sail to Antarctica where glaciers abound. Meaning they are far from static structures, but are constantly shifting and moving, changing, receding and growing.
“Glacier terrain is a highly dynamic landscape and without proper awareness and methods to route find and mitigate the challenging terrain it is beyond most people’s abilities,” agrees Tim Patterson, a certified guide with the Association of Canadian Mountain Guides (ACMG) and founder of Zuc’min Guiding, which operates in partnership with IceWalks in British Columbia and Alberta, Canada.
Glaciers are shaped by centuries of snow compacting and turning to ice. Many sprout from one large continental mass called an ice sheet in a veritable river of frozen liquid that flows down valleys, usually between peaks, all the weight of frozen water succumbing to gravity and running downward and out. Those fingers of ice, also called tributaries, eventually terminate, often at a water line or a stretch of ground where the ice simply peters out, though other types of glaciers like cirque and hanging glaciers that exist in natural bowls in the landscape tend not to have a traditional terminus.
And much like a typical river, over even a single year glaciers can change, grow and shrink dramatically. Annual precipitation in the form of snow adds to their size while factors like warming temperatures cause them to melt and shrink. A balance of both keeps them stable.
Unfortunately, most glaciers around the world are rapidly retreating instead of growing as a result of climate change. But however they’re moving, they slowly creep over rocks, sediment, even water, and change the landscape as they scrape slowly forward or back. But it’s not just the rock beneath that is altered by moving ice; the glacier itself moves, shifts, and opens up. But not just on the surface; beneath is where the real dangers lie.
Beware of sneaky crevasses
Possibly the most dangerous feature glaciers possess as a result of their natural movement is crevasses, stress fractures in the ice that crack and open up as a result of shifting ice. As a glacier ebbs and flows, ice sliding on rock causes friction, which can weaken the ice and open gaps in the structure. These can be a few inches deep to a few kilometers deep, Intxaustegi explains. And they can mean injury or death in seconds if you fall into one. The worst part: they can be covered by thin layers of snow or ice, making them invisible from the surface if you don’t know what you’re looking for.
“They hide so well,” Intxaustegi says. Even well-trained individuals can miss them if they’re not careful. What’s worse, a crevasse only needs to be a few feet deep to result in broken bones or other serious injuries, she continues.
That means understanding the science of snow and ice and understanding when it looks solid but is hiding a crevasse. When and how to travel on ice takes lots of education, but also experience, Patterson says.
Not that crevasses are all that lurk beneath the surface.
Glacial mills
Water features known as millwells or moulin (also called glacial mills) form where surface water exploits a weakness in the ice and makes a circular, vertical shaft that connects to streams beneath the glacier that eventually flow to the terminus or the end of the ice—known as the toe or leading edge. These under-ice waterways can be as narrow as a few inches in diameter, meaning if you end up in one, it could result in serious injury or death.
What’s more, “Water features like millwells change depending on water flows and sometimes create holes that were not visible only days before,” Patterson states. So even if you’ve been on a guided hike a month or a year before, on the exact same glacier you could still be completely unaware of what worlds exist underneath your feet.
Patterson recalls a story of a friend and mentor who got a closer look at one than he bargained for. The individual was a park ranger at the time and slipped into a glacial mill on the Saskatchewan Glacier in the 1970s. He then slid down an under-ice waterway for several minutes before–extremely luckily–getting spit out alive at the outflow lake some 220 yards from where he fell in.
Other hazards
In addition to crevasses and millwells, there are plenty of other hazards you may encounter on your way to a glacier. Patterson says rockfalls, flooding, ice falls, and highly technical terrain can all pose extreme risks to explorers who may underestimate the perils of wilderness landscapes.
Find your glacier guide
But all of this doesn’t mean you should avoid glacier-based adventures. On the contrary, in many glacier-rich destinations, guides and guide companies abound. To find a reputable company that knows plenty about how and when to travel on the ice, check for guide’s certifications and experience in glaciated terrain, specifically glacier travel and crevasse rescue training.
These individuals can not only guide you safely over the ice, but take you to places that you wouldn’t have found on your own, educate you about the landscape, and share meaningful histories as you explore. Whatever you do, go with someone who knows. And come back safe and alive.
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