Snow-covered rock crevasses are a difficult-to-discern hazard you may encounter during snow travel. You will often encounter these hazards in snow-covered rock gardens or over/through rock outcrop areas. Careful research of your terrain before your trip, in snow-free conditions, may help you to identify and avoid these areas. Google Maps may be a good tool to see where these rock gardens and outcrops exist on your proposed route. Using your poles to probe as you travel may also help. Be prepared to self-rescue and partner rescue with the tools you carry and knowledge of extraction techniques. When dealing with hazards like these your best bet is to retreat/backtrack to the solid terrain that you already safely crossed and reassess your options.
The following three-photo series from John Platt shows experienced climbers avoiding a cornice. However, they also soon discovered they were crossing an area with snow-covered rock crevasses, large enough to fall into.