Not sure how far I'll get witht his right now, but here goes...It wasn't an established part of the fiction as nobody had yet interacted with it, but was it on the DM's map? Or was the complex even pre-mapped at all? (if not, you're so far away from anything I can relate to you might as well be speaking Russian of Swahili or some other language I don't know a word of).
My terminology might be more Fail Sideways in this case, but this all seems like normal run-of-play stuff where someone hit what amounts to a chute trap and has to find their way back to the party via some dangers. But, a bit more info (or clarification) needed:
1. Was the trap (for such it is) already on the DM's map or did it suddenly spring into existence at the moment you needed to come up with a failure result? If pre-present, see next question. If spur-of-the-moment, the you're into "GM Force" territory...probably not in a bad way, but it's there.
2. If the trap was a pre-planned thing, then (to cover what some others might be thinking) was there some warning given of it so the party knew to be careful? If not, you're into "gotcha" territory, which I personally have no issue with but others - for whatever reason - do.
Going to chunk all of this together.
1) The move that triggered the encounter with the snow-bridge-covered crevasse hazard was the group move "Undertake a Perilous Journey:"
When you travel through hostile territory, choose one member of the party to act as trailblazer, one to scout ahead, and one to be quartermaster. Each character with a job to do rolls+Wis. ✴On a 10+:
- the quartermaster reduces the number of rations required by one
- the trailblazer reduces the amount of time it takes to reach your destination (the GM will say by how much)
- the scout will spot any trouble quick enough to let you get the drop on it
This is just a conflict resolution move for when the group is striking out through dangerous lands toward a known destination. If they're just exploring parts unknown or ranging toward an unfamiliar destination, UaPJ would not be triggered. Maybe consider the move as a different, mundane analogue to 1e Teleport. If things go awry, they go awry in a truly interesting and dynamic way that leads to unforeseen events which can snowball, thus fundamentally changing the trajectory of play. That is what happened here.
The scout role was outright failed by their goblin henchmen who were assigned to it (RIP poor Exel and Xanob

). This triggered a hard move by me. That move would have been:
Use a monster, danger, or location move
If the scout role would have been a 7-9, I would have just made a soft move. If I decided to go with the same sort of deal, the move would have been:
Reveal an unwelcome truth
In the conversation of play, I probably would have said something like:
"The endless expanse of white has stretched out before you for the last days' travel. The blizzard, though still ominous and looming, flanks you in an eerie, dead stall to the east. To date, the goblin brothers have guided you away from the lairs of nesting Wyverns, Perytons, and navigated around the dangerous terrain of this glacial wasteland.
On the final leg of the journey, the land perpetually rises and falls, fraught with boulders and sharp rocks signalling the approach of your destination. The elevating earth ascends angrily toward the White Dragon's domain and the entrance to the Coldlands beyond. In the distance, you can see the great open cavern, cut naturally into the bottom of the mountainside's face. Earthmaw.
A silly spectacle, the small goblin driver stands up and points, beginning to celebrate. A reminder of the killjoy nature of this dangerous land that is clearly out to kill you, the moment he does so a terrible sound begins beneath you. When the sound of cracking ice begins and snow collapses in an accelerating, jagged line in front of the awkwardly rigged sleds, terror turns his celebrations into a shriek. The lead wolf's forelegs are lost to sight as the beast faceplants then backs abruptly as the cracking, gravelly yawn of a glacial crevasse threatens to swallow you whole...
What do you do?"
Instead, a 6- means the back of the sled falls straight into the crevasse, hanging mid-air with the PCs/hirelings desperately clinging to it, with just the team of sled wolfs losing the battle to keep everything from being swallowed. Everyone but the Elven Arcane Duelist made it out (the situation snowballed for him, but he did manage to save a dog and one of the goblin brothers...I think Exel, before the crevasse and the frozen river claimed him).
2) Very much unlike B/X or a 5e or 1e hexcrawl, here is one of DW's most important GMing principles:
Draw maps, leave blanks
Dungeon World exists mostly in the imaginations of the people playing it; maps help everyone stay on the same page. You won’t always be drawing them yourself, but any time there’s a new location described make sure it gets added to a map.
When you draw a map don’t try to make it complete. Leave room for the unknown. As you play you’ll get more ideas and the players will give you inspiration to work with. Let the maps expand and change.
The only thing that was on the map at this point was:
a) Giliad's Rest at the base of these mountains.
b) The blocked pass that leads to the highlands.
c) A secret tunnel that leads through dangerous caverns, but empties out in the lowlands - added to the map by successful PC move.
d) World's End Bluff and the settlement of World's End (where the PCs were coming from before their journey).
e) The Glacial Wastes (basically the rest of the highlands.
f) Averandox's Glacier (the Ancient Blizzard Dragon's lair) - added to map by successful PC move.
g) Earthmaw (the Hobgoblin kingdom) - added to map by successful PC move.
h) The Coldlands (the true highlands of this mountainous realm high above the tree line).
So lets put that together then. The PCs are Undertaking a Perilous Journey across a hostile, glacial expanse. The possible dangers they could face due to Trailblazer failure are stuff like:
* Weather Takes a Turn
* Lost
Quartermaster is stuff like:
* Water is discovered to be tainted or poisonous
* 1d4 rations are lost due to spoilage or over-consumption
* Someone gets food poisoning and becomes
shaky or
sick
* Nearby Danger is attracted by food
Scout is stuff like:
* Exposure
* Ambush
* Hazard (here we go!)
The players' agency when it comes to an UaPJ move is (a) to trigger it at all, (b) the decision of where they are striking out to, (c) who is taking what role (which feeds into PC build), (d) any strategic moves they can/do make beforehand to ensure that the dangers I can deploy would be further constrained (this could be the deployment of Adventuring Gear such as a map to ensure they can't get lost or some sort of scent that repels a certain predator...or a divination ability that yields portents of the future).
It isn't like hexcrawling or B/X dungeon crawling where you're mapping out a locale and spending exploration turns (listening, searching, 10 ft poling, stealthing, arcane eye-ing, etc) to avoid sequential dangers or make sequential discoveries on a granular map.
DW definitely has more granular interaction (social, exploration, combat) than the transitional journey mechanics, but that is how they function.
So I hope it is clear what the players' agency is in this situation (all of (a) through (d) directly above), what the system's say is (the UaPJ mechanics), and what the GM's role is (follow the game's principles and rules, and on a 6-, follow the fiction and fill their lives with a danger of immediate and severe consequence; such as an immediate hazard event on the failed Scout roll).
So then, I hope that makes a little more clear procedurally how things work themselves out.
That is a lot of "stuff." Let's start with/focus on this and then we can move on.