Unlike glaciers (i.e. Mt. Rainier, Mt. Hood) that I've climbed and skied on and which are moving downhill by gravity, these glaciers appear to be more like flat ice fields. The movement of glaciers downhill is what causes the huge crevasses to open and winter snow can then form a bridge that conceals the crevasse. This glacier appears to be relatively flat and I would guess doesn't move or change as dramatically. The guides are probably well aware of where the danger areas are and lead the visitors away from them.