Key takeaways
- A snow bridge is a span of snow over a crevasse that can hide the gap entirely.
- Strength varies wildly — some hold a team, others collapse under one person.
- Bridges are weaker when warm/soft (afternoon) and stronger when cold/frozen (early).
- Cross them roped as a team, probing ahead and assessing the bridge before committing.
This is general educational information, not glacier-travel training. Take a course before traveling on glaciers.
What a snow bridge is
A snow bridge is a span of snow across the opening of a crevasse, often concealing the gap entirely so the glacier surface looks continuous and solid. They form from wind-deposited and accumulated snow drifting over the crevasse, and they’re a defining hazard of glacier travel.
Why they’re dangerous
The danger is their unpredictable, hidden strength. A snow bridge might easily hold a roped team — or collapse under a single climber, dropping them into the crevasse. And bridges weaken as they warm through the day, so one that’s solid at dawn can fail by afternoon.
Approaching a dip in the snow that signals a buried crevasse, a roped team stops, probes the snow bridge with an ice axe to judge its thickness, finds a firm spot, and crosses one at a time perpendicular to the gap — moving early while the snow is still frozen and strong.
How to cross safely
Travel roped as a team so a collapse can be arrested, probe ahead to assess the bridge and find hidden edges, cross perpendicular at the strongest point, manage spacing and weight, and favor cold morning conditions. When in doubt, route around. Snow bridges also span the bergschrund at a glacier’s head.
The bottom line
A snow bridge is the glacier's hidden trap — a span of snow over a crevasse that can look like solid ground but vary from rock-solid to fatally fragile. Because you often can't see the gap beneath, glacier travelers rope up, probe ahead, cross at the strongest point in cold conditions, and respect that a bridge solid at dawn may collapse by afternoon.
Frequently asked questions
What is a snow bridge?
A snow bridge is a span of snow that forms across the top of a crevasse, often hiding the gap completely so the surface looks continuous and solid. They form from wind-blown and accumulated snow drifting over the opening, and they're a defining hazard of glacier travel because they can conceal deadly crevasses.
Why are snow bridges dangerous?
Because their strength is unpredictable and often invisible from the surface. A snow bridge might easily hold a roped team, or it might collapse under the weight of a single climber, dropping them into the crevasse below. Bridges also weaken as they warm and soften through the day, so one that's solid at dawn may fail by afternoon.
How do you safely cross a snow bridge?
Travel roped as a team so a collapse can be arrested, probe ahead with an ice axe or pole to assess the bridge and locate hidden crevasse edges, cross perpendicular to the crevasse at the bridge's strongest point, distribute weight (and spacing) carefully, and prefer the cold, firm conditions of early morning. When in doubt, find a better crossing or route around.
Sources
- Glacier travel & crevasse safety — American Alpine Club
- Glacier travel — The Mountaineers