When a slab avalanche slides a short distance and breaks down into deeper weak layers forming a stair-step pattern on the bed surface.
When multiple weak layers exist in the snowpack, often a smaller, shallower avalanche will travel a few feet to a few yards and the added weight and stress will trigger a deeper weak layer, which results in a much larger and more dangerous avalanche. These types of avalanches can be especially dangerous to people because the following scenario: First, the person who triggers the smaller avalanche will ride the first slide down. As the smaller avalanche descends, it triggers a deeper avalanche. By the time the deeper avalanche picks up speed and descends to the bottom, the victim has stopped at the bottom of the slope and the secondary, larger avalanche will pile debris on top of the victim, often burying them very deeply with no hope of a live recovery.
When you deal with a snowpack that has the potential to step down into deeper weak layers, it’s important to notch back your level of exposure because of the dangerous consequences.