It's something that every freerider should know, but often it's forgotten thanks to stoke or other reasons. A glacier isn't static but is slowly but surely moving. Like a river of ice. A crevasse could move a couple of meters and be on a different location compared to last season. They made a timelapse in the National Parc of the Ecrins in France, where you can actually the glacier and the crevasses moving.
Update your knowledge
The knowledge you had last season about the location of the crevasses, well, that need to be updated. Before you know it, you fall through a snow bridge and fall into the crevasse. This man lived to tell the tale, but not everybody is that fortunate. Our advice: always ride off-piste with a mountain guide when you're on a glacier.