"Deep slabs are your basic nightmare. Stability tests like snowpits, explosives and cornice drops are unreliable. They seldom produce "alarm signals" such as collapsing or cracking. They often don't fracture with the first person on the slope but, say, with the third, sixth or tenth person. The only way to manage this kind of hazard is avoidance. All the cagy, old avalanche geeks just stick to slopes less than 30 degrees that are not locally connected to steeper terrain. Simple. Or they choose a safer aspect. Also very simple."