| What it is | Thin glaze of ice on rock |
| Danger | Near-invisible, very slick |
| Too thin to | Climb on with tools |
| Difficulty | Intermediate (hazard) |
From the French verglas, meaning glaze ice.
Verglas is a thin, often nearly invisible coating of ice that forms on rock when rain or melting snow freezes onto a cold surface. It makes rock treacherously slick and is too thin to climb on with tools, turning easy terrain into a serious hazard. Verglas is a notorious feature of alpine and winter conditions.
The word is French for glaze ice.
Why it’s dangerous
Near-invisible and frictionless, it can turn easy rock into a slip hazard — a real objective hazard, worsened by exposure.
Dealing with it
Usually avoid or wait it out; it’s too thin for ice technique.
Frequently asked questions
What is verglas?
Verglas is a thin film of clear ice that forms when rain, drizzle, or meltwater freezes onto cold rock. It can be almost invisible, coating holds and ledges with a slick glaze that's far too thin to climb on with ice tools or crampons.
Why is verglas dangerous?
Because it's hard to see and removes nearly all friction, verglas can turn easy rock or a casual ledge into a place where you slip without warning. It's a classic cause of alpine slips and falls, especially in early morning, autumn, and thawing-then-freezing conditions.
How do you deal with verglas?
Often the best response is to avoid affected terrain or wait for the sun to clear it, since it's too thin to climb. Where you must cross it, extreme care, sometimes crampons on rock (dry-tooling style), and protecting the section help — but verglas is mostly a hazard to respect and avoid.
Sources
- Alpine conditions — American Alpine Club