I think, in that scenario, it'd depend on what was happening that went into that Athletics roll. Are they trying to jump across? Is that the only way to get across the crevasse? Because I think at my table a player who tries to jump across a crevasse and fails to do so just... falls the 700 feet and dies, so they're trained to not try to do that if they don't have to. Presumably they could throw something across to use as an anchor -- lasso a rock or something, I dunno -- or construct a temporary bridge, or go around to somewhere easier. And if I, as the DM, know the crevasse is 700' deep and that it's a long way to the other side, I'm going to have to communicate that in a way that makes them make intelligent decisions, because I don't want to be responsible for my player thinking it's a trivial jump when it's not. There have to be multiple ways to get across that ravine, and if there aren't there's gotta be a reason why.